New upstream version 1.0.28upstream/1.0.28

1 files changed, 5624 insertions, 0 deletions

diff --git a/backend/genesys_gl841.cc b/backend/genesys_gl841.cc
new file mode 100644
index 0000000..9e8fc15
--- /dev/null
+++ b/backend/genesys_gl841.cc
@@ -0,0 +1,5624 @@
+/* sane - Scanner Access Now Easy.
+
+   Copyright (C) 2003 Oliver Rauch
+   Copyright (C) 2003, 2004 Henning Meier-Geinitz <henning@meier-geinitz.de>
+   Copyright (C) 2004 Gerhard Jaeger <gerhard@gjaeger.de>
+   Copyright (C) 2004-2013 Stéphane Voltz <stef.dev@free.fr>
+   Copyright (C) 2005 Philipp Schmid <philipp8288@web.de>
+   Copyright (C) 2005-2009 Pierre Willenbrock <pierre@pirsoft.dnsalias.org>
+   Copyright (C) 2006 Laurent Charpentier <laurent_pubs@yahoo.com>
+   Copyright (C) 2010 Chris Berry <s0457957@sms.ed.ac.uk> and Michael Rickmann <mrickma@gwdg.de>
+                 for Plustek Opticbook 3600 support
+
+
+   This file is part of the SANE package.
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+   MA 02111-1307, USA.
+
+   As a special exception, the authors of SANE give permission for
+   additional uses of the libraries contained in this release of SANE.
+
+   The exception is that, if you link a SANE library with other files
+   to produce an executable, this does not by itself cause the
+   resulting executable to be covered by the GNU General Public
+   License.  Your use of that executable is in no way restricted on
+   account of linking the SANE library code into it.
+
+   This exception does not, however, invalidate any other reasons why
+   the executable file might be covered by the GNU General Public
+   License.
+
+   If you submit changes to SANE to the maintainers to be included in
+   a subsequent release, you agree by submitting the changes that
+   those changes may be distributed with this exception intact.
+
+   If you write modifications of your own for SANE, it is your choice
+   whether to permit this exception to apply to your modifications.
+   If you do not wish that, delete this exception notice.
+*/
+
+#define DEBUG_DECLARE_ONLY
+
+#include "genesys_gl841.h"
+
+#include <vector>
+
+/****************************************************************************
+ Low level function
+ ****************************************************************************/
+
+/* ------------------------------------------------------------------------ */
+/*                  Read and write RAM, registers and AFE                   */
+/* ------------------------------------------------------------------------ */
+
+/* Set address for writing data */
+static SANE_Status
+gl841_set_buffer_address_gamma (Genesys_Device * dev, uint32_t addr)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+
+  DBG(DBG_io, "%s: setting address to 0x%05x\n", __func__, addr & 0xfffffff0);
+
+  addr = addr >> 4;
+
+  status = sanei_genesys_write_register (dev, 0x5c, (addr & 0xff));
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed while writing low byte: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  addr = addr >> 8;
+  status = sanei_genesys_write_register (dev, 0x5b, (addr & 0xff));
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed while writing high byte: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  DBG(DBG_io, "%s: completed\n", __func__);
+
+  return status;
+}
+
+/****************************************************************************
+ Mid level functions
+ ****************************************************************************/
+
+static SANE_Bool
+gl841_get_fast_feed_bit (Genesys_Register_Set * regs)
+{
+  GenesysRegister *r = NULL;
+
+  r = sanei_genesys_get_address (regs, 0x02);
+  if (r && (r->value & REG02_FASTFED))
+    return SANE_TRUE;
+  return SANE_FALSE;
+}
+
+static SANE_Bool
+gl841_get_filter_bit (Genesys_Register_Set * regs)
+{
+  GenesysRegister *r = NULL;
+
+  r = sanei_genesys_get_address (regs, 0x04);
+  if (r && (r->value & REG04_FILTER))
+    return SANE_TRUE;
+  return SANE_FALSE;
+}
+
+static SANE_Bool
+gl841_get_lineart_bit (Genesys_Register_Set * regs)
+{
+  GenesysRegister *r = NULL;
+
+  r = sanei_genesys_get_address (regs, 0x04);
+  if (r && (r->value & REG04_LINEART))
+    return SANE_TRUE;
+  return SANE_FALSE;
+}
+
+static SANE_Bool
+gl841_get_bitset_bit (Genesys_Register_Set * regs)
+{
+  GenesysRegister *r = NULL;
+
+  r = sanei_genesys_get_address (regs, 0x04);
+  if (r && (r->value & REG04_BITSET))
+    return SANE_TRUE;
+  return SANE_FALSE;
+}
+
+static SANE_Bool
+gl841_get_gain4_bit (Genesys_Register_Set * regs)
+{
+  GenesysRegister *r = NULL;
+
+  r = sanei_genesys_get_address (regs, 0x06);
+  if (r && (r->value & REG06_GAIN4))
+    return SANE_TRUE;
+  return SANE_FALSE;
+}
+
+static SANE_Bool
+gl841_test_buffer_empty_bit (SANE_Byte val)
+{
+  if (val & REG41_BUFEMPTY)
+    return SANE_TRUE;
+  return SANE_FALSE;
+}
+
+static SANE_Bool
+gl841_test_motor_flag_bit (SANE_Byte val)
+{
+  if (val & REG41_MOTORENB)
+    return SANE_TRUE;
+  return SANE_FALSE;
+}
+
+/** copy sensor specific settings */
+/* *dev  : device infos
+   *regs : registers to be set
+   extended : do extended set up
+   half_ccd: set up for half ccd resolution
+   all registers 08-0B, 10-1D, 52-59 are set up. They shouldn't
+   appear anywhere else but in register_ini
+
+Responsible for signals to CCD/CIS:
+  CCD_CK1X (CK1INV(0x16),CKDIS(0x16),CKTOGGLE(0x18),CKDELAY(0x18),MANUAL1(0x1A),CK1MTGL(0x1C),CK1LOW(0x1D),CK1MAP(0x74,0x75,0x76),CK1NEG(0x7D))
+  CCD_CK2X (CK2INV(0x16),CKDIS(0x16),CKTOGGLE(0x18),CKDELAY(0x18),MANUAL1(0x1A),CK1LOW(0x1D),CK1NEG(0x7D))
+  CCD_CK3X (MANUAL3(0x1A),CK3INV(0x1A),CK3MTGL(0x1C),CK3LOW(0x1D),CK3MAP(0x77,0x78,0x79),CK3NEG(0x7D))
+  CCD_CK4X (MANUAL3(0x1A),CK4INV(0x1A),CK4MTGL(0x1C),CK4LOW(0x1D),CK4MAP(0x7A,0x7B,0x7C),CK4NEG(0x7D))
+  CCD_CPX  (CTRLHI(0x16),CTRLINV(0x16),CTRLDIS(0x16),CPH(0x72),CPL(0x73),CPNEG(0x7D))
+  CCD_RSX  (CTRLHI(0x16),CTRLINV(0x16),CTRLDIS(0x16),RSH(0x70),RSL(0x71),RSNEG(0x7D))
+  CCD_TGX  (TGINV(0x16),TGMODE(0x17),TGW(0x17),EXPR(0x10,0x11),TGSHLD(0x1D))
+  CCD_TGG  (TGINV(0x16),TGMODE(0x17),TGW(0x17),EXPG(0x12,0x13),TGSHLD(0x1D))
+  CCD_TGB  (TGINV(0x16),TGMODE(0x17),TGW(0x17),EXPB(0x14,0x15),TGSHLD(0x1D))
+  LAMP_SW  (EXPR(0x10,0x11),XPA_SEL(0x03),LAMP_PWR(0x03),LAMPTIM(0x03),MTLLAMP(0x04),LAMPPWM(0x29))
+  XPA_SW   (EXPG(0x12,0x13),XPA_SEL(0x03),LAMP_PWR(0x03),LAMPTIM(0x03),MTLLAMP(0x04),LAMPPWM(0x29))
+  LAMP_B   (EXPB(0x14,0x15),LAMP_PWR(0x03))
+
+other registers:
+  CISSET(0x01),CNSET(0x18),DCKSEL(0x18),SCANMOD(0x18),EXPDMY(0x19),LINECLP(0x1A),CKAREA(0x1C),TGTIME(0x1C),LINESEL(0x1E),DUMMY(0x34)
+
+Responsible for signals to AFE:
+  VSMP  (VSMP(0x58),VSMPW(0x58))
+  BSMP  (BSMP(0x59),BSMPW(0x59))
+
+other register settings depending on this:
+  RHI(0x52),RLOW(0x53),GHI(0x54),GLOW(0x55),BHI(0x56),BLOW(0x57),
+
+*/
+static void sanei_gl841_setup_sensor(Genesys_Device * dev, const Genesys_Sensor& sensor,
+                                     Genesys_Register_Set * regs,
+                                     SANE_Bool extended, SANE_Bool half_ccd)
+{
+    DBG(DBG_proc, "%s\n", __func__);
+
+    // that one is tricky at least
+    for (uint16_t addr = 0x08; addr <= 0x0b; ++addr) {
+        regs->set8(0x70 + addr - 0x08, sensor.custom_regs.get_value(addr));
+    }
+
+    // ignore registers in range [0x10..0x16)
+    for (uint16_t addr = 0x16; addr < 0x1e; ++addr) {
+        regs->set8(addr, sensor.custom_regs.get_value(addr));
+    }
+
+    // ignore registers in range [0x5b..0x5e]
+    for (uint16_t addr = 0x52; addr < 0x52 + 9; ++addr) {
+        regs->set8(addr, sensor.custom_regs.get_value(addr));
+    }
+
+  /* don't go any further if no extended setup */
+  if (!extended)
+    return;
+
+  /* todo : add more CCD types if needed */
+  /* we might want to expand the Sensor struct to have these
+     2 kind of settings */
+  if (dev->model->ccd_type == CCD_5345)
+    {
+      if (half_ccd)
+	{
+          GenesysRegister* r;
+	  /* settings for CCD used at half is max resolution */
+	  r = sanei_genesys_get_address (regs, 0x70);
+	  r->value = 0x00;
+	  r = sanei_genesys_get_address (regs, 0x71);
+	  r->value = 0x05;
+	  r = sanei_genesys_get_address (regs, 0x72);
+	  r->value = 0x06;
+	  r = sanei_genesys_get_address (regs, 0x73);
+	  r->value = 0x08;
+	  r = sanei_genesys_get_address (regs, 0x18);
+	  r->value = 0x28;
+	  r = sanei_genesys_get_address (regs, 0x58);
+	  r->value = 0x80 | (r->value & 0x03);	/* VSMP=16 */
+	}
+      else
+	{
+          GenesysRegister* r;
+	  /* swap latch times */
+	  r = sanei_genesys_get_address (regs, 0x18);
+	  r->value = 0x30;
+          regs->set8(0x52, sensor.custom_regs.get_value(0x55));
+          regs->set8(0x53, sensor.custom_regs.get_value(0x56));
+          regs->set8(0x54, sensor.custom_regs.get_value(0x57));
+          regs->set8(0x55, sensor.custom_regs.get_value(0x52));
+          regs->set8(0x56, sensor.custom_regs.get_value(0x53));
+          regs->set8(0x57, sensor.custom_regs.get_value(0x54));
+	  r = sanei_genesys_get_address (regs, 0x58);
+	  r->value = 0x20 | (r->value & 0x03);	/* VSMP=4 */
+	}
+      return;
+    }
+
+  if (dev->model->ccd_type == CCD_HP2300)
+    {
+      /* settings for CCD used at half is max resolution */
+      GenesysRegister* r;
+      if (half_ccd)
+	{
+	  r = sanei_genesys_get_address (regs, 0x70);
+	  r->value = 0x16;
+	  r = sanei_genesys_get_address (regs, 0x71);
+	  r->value = 0x00;
+	  r = sanei_genesys_get_address (regs, 0x72);
+	  r->value = 0x01;
+	  r = sanei_genesys_get_address (regs, 0x73);
+	  r->value = 0x03;
+	  /* manual clock programming */
+	  r = sanei_genesys_get_address (regs, 0x1d);
+	  r->value |= 0x80;
+	}
+      else
+	{
+	  r = sanei_genesys_get_address (regs, 0x70);
+	  r->value = 1;
+	  r = sanei_genesys_get_address (regs, 0x71);
+	  r->value = 3;
+	  r = sanei_genesys_get_address (regs, 0x72);
+	  r->value = 4;
+	  r = sanei_genesys_get_address (regs, 0x73);
+	  r->value = 6;
+	}
+      r = sanei_genesys_get_address (regs, 0x58);
+      r->value = 0x80 | (r->value & 0x03);	/* VSMP=16 */
+      return;
+    }
+}
+
+/** Test if the ASIC works
+ */
+/*TODO: make this functional*/
+static SANE_Status
+sanei_gl841_asic_test (Genesys_Device * dev)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+  uint8_t val;
+  size_t size, verify_size;
+  unsigned int i;
+
+  DBG(DBG_proc, "%s\n", __func__);
+
+  return SANE_STATUS_INVAL;
+
+  /* set and read exposure time, compare if it's the same */
+  status = sanei_genesys_write_register (dev, 0x38, 0xde);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to write register: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  status = sanei_genesys_write_register (dev, 0x39, 0xad);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to write register: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  status = sanei_genesys_read_register (dev, 0x38, &val);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to read register: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+  if (val != 0xde)		/* value of register 0x38 */
+    {
+      DBG(DBG_error, "%s: register contains invalid value\n", __func__);
+      return SANE_STATUS_IO_ERROR;
+    }
+
+  status = sanei_genesys_read_register (dev, 0x39, &val);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to read register: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+  if (val != 0xad)		/* value of register 0x39 */
+    {
+      DBG(DBG_error, "%s: register contains invalid value\n", __func__);
+      return SANE_STATUS_IO_ERROR;
+    }
+
+  /* ram test: */
+  size = 0x40000;
+  verify_size = size + 0x80;
+  /* todo: looks like the read size must be a multiple of 128?
+     otherwise the read doesn't succeed the second time after the scanner has
+     been plugged in. Very strange. */
+
+  std::vector<uint8_t> data(size);
+  std::vector<uint8_t> verify_data(verify_size);
+
+  for (i = 0; i < (size - 1); i += 2)
+    {
+      data[i] = i / 512;
+      data[i + 1] = (i / 2) % 256;
+    }
+
+  status = sanei_genesys_set_buffer_address (dev, 0x0000);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to set buffer address: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+/*  status = sanei_genesys_bulk_write_data(dev, 0x3c, data, size);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to bulk write data: %s\n", __func__, sane_strstatus(status));
+      free (data);
+      free (verify_data);
+      return status;
+      }*/
+
+  status = sanei_genesys_set_buffer_address (dev, 0x0000);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to set buffer address: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  status = sanei_genesys_bulk_read_data(dev, 0x45, verify_data.data(), verify_size);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to bulk read data: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  /* todo: why i + 2 ? */
+  for (i = 0; i < size; i++)
+    {
+      if (verify_data[i] != data[i])
+	{
+	  DBG(DBG_error, "%s: data verification error\n", __func__);
+	  DBG(DBG_info, "0x%.8x: got %.2x %.2x %.2x %.2x, expected %.2x %.2x %.2x %.2x\n",
+	      i,
+	      verify_data[i],
+	      verify_data[i+1],
+	      verify_data[i+2],
+	      verify_data[i+3],
+	      data[i],
+	      data[i+1],
+	      data[i+2],
+	      data[i+3]);
+	  return SANE_STATUS_IO_ERROR;
+	}
+    }
+
+  DBG(DBG_info, "%s: completed\n", __func__);
+
+  return SANE_STATUS_GOOD;
+}
+
+/*
+ * Set all registers LiDE 80 to default values
+ * (function called only once at the beginning)
+ * we are doing a special case to ease development
+ */
+static void
+gl841_init_lide80 (Genesys_Device * dev)
+{
+  uint8_t val;
+
+  INITREG (0x01, 0x82); /* 0x02 = SHDAREA  and no CISSET ! */
+  INITREG (0x02, 0x10);
+  INITREG (0x03, 0x50);
+  INITREG (0x04, 0x02);
+  INITREG (0x05, 0x4c); /* 1200 DPI */
+  INITREG (0x06, 0x38); /* 0x38 scanmod=1, pwrbit, GAIN4 */
+  INITREG (0x07, 0x00);
+  INITREG (0x08, 0x00);
+  INITREG (0x09, 0x11);
+  INITREG (0x0a, 0x00);
+
+  INITREG (0x10, 0x40);
+  INITREG (0x11, 0x00);
+  INITREG (0x12, 0x40);
+  INITREG (0x13, 0x00);
+  INITREG (0x14, 0x40);
+  INITREG (0x15, 0x00);
+  INITREG (0x16, 0x00);
+  INITREG (0x17, 0x01);
+  INITREG (0x18, 0x00);
+  INITREG (0x19, 0x06);
+  INITREG (0x1a, 0x00);
+  INITREG (0x1b, 0x00);
+  INITREG (0x1c, 0x00);
+  INITREG (0x1d, 0x04);
+  INITREG (0x1e, 0x10);
+  INITREG (0x1f, 0x04);
+  INITREG (0x20, 0x02);
+  INITREG (0x21, 0x10);
+  INITREG (0x22, 0x20);
+  INITREG (0x23, 0x20);
+  INITREG (0x24, 0x10);
+  INITREG (0x25, 0x00);
+  INITREG (0x26, 0x00);
+  INITREG (0x27, 0x00);
+
+  INITREG (0x29, 0xff);
+
+  const auto& sensor = sanei_genesys_find_sensor_any(dev);
+  INITREG (0x2c, sensor.optical_res>>8);
+  INITREG (0x2d, sensor.optical_res & 0xff);
+  INITREG (0x2e, 0x80);
+  INITREG (0x2f, 0x80);
+  INITREG (0x30, 0x00);
+  INITREG (0x31, 0x10);
+  INITREG (0x32, 0x15);
+  INITREG (0x33, 0x0e);
+  INITREG (0x34, 0x40);
+  INITREG (0x35, 0x00);
+  INITREG (0x36, 0x2a);
+  INITREG (0x37, 0x30);
+  INITREG (0x38, 0x2a);
+  INITREG (0x39, 0xf8);
+
+  INITREG (0x3d, 0x00);
+  INITREG (0x3e, 0x00);
+  INITREG (0x3f, 0x00);
+
+  INITREG (0x52, 0x03);
+  INITREG (0x53, 0x07);
+  INITREG (0x54, 0x00);
+  INITREG (0x55, 0x00);
+  INITREG (0x56, 0x00);
+  INITREG (0x57, 0x00);
+  INITREG (0x58, 0x29);
+  INITREG (0x59, 0x69);
+  INITREG (0x5a, 0x55);
+
+  INITREG (0x5d, 0x20);
+  INITREG (0x5e, 0x41);
+  INITREG (0x5f, 0x40);
+  INITREG (0x60, 0x00);
+  INITREG (0x61, 0x00);
+  INITREG (0x62, 0x00);
+  INITREG (0x63, 0x00);
+  INITREG (0x64, 0x00);
+  INITREG (0x65, 0x00);
+  INITREG (0x66, 0x00);
+  INITREG (0x67, 0x40);
+  INITREG (0x68, 0x40);
+  INITREG (0x69, 0x20);
+  INITREG (0x6a, 0x20);
+  INITREG (0x6c, dev->gpo.value[0]);
+  INITREG (0x6d, dev->gpo.value[1]);
+  INITREG (0x6e, dev->gpo.enable[0]);
+  INITREG (0x6f, dev->gpo.enable[1]);
+  INITREG (0x70, 0x00);
+  INITREG (0x71, 0x05);
+  INITREG (0x72, 0x07);
+  INITREG (0x73, 0x09);
+  INITREG (0x74, 0x00);
+  INITREG (0x75, 0x01);
+  INITREG (0x76, 0xff);
+  INITREG (0x77, 0x00);
+  INITREG (0x78, 0x0f);
+  INITREG (0x79, 0xf0);
+  INITREG (0x7a, 0xf0);
+  INITREG (0x7b, 0x00);
+  INITREG (0x7c, 0x1e);
+  INITREG (0x7d, 0x11);
+  INITREG (0x7e, 0x00);
+  INITREG (0x7f, 0x50);
+  INITREG (0x80, 0x00);
+  INITREG (0x81, 0x00);
+  INITREG (0x82, 0x0f);
+  INITREG (0x83, 0x00);
+  INITREG (0x84, 0x0e);
+  INITREG (0x85, 0x00);
+  INITREG (0x86, 0x0d);
+  INITREG (0x87, 0x02);
+  INITREG (0x88, 0x00);
+  INITREG (0x89, 0x00);
+
+  /* specific scanner settings, clock and gpio first */
+  sanei_genesys_read_register (dev, REG6B, &val);
+  sanei_genesys_write_register (dev, REG6B, 0x0c);
+  sanei_genesys_write_register (dev, 0x06, 0x10);
+  sanei_genesys_write_register (dev, REG6E, 0x6d);
+  sanei_genesys_write_register (dev, REG6F, 0x80);
+  sanei_genesys_write_register (dev, REG6B, 0x0e);
+  sanei_genesys_read_register (dev, REG6C, &val);
+  sanei_genesys_write_register (dev, REG6C, 0x00);
+  sanei_genesys_read_register (dev, REG6D, &val);
+  sanei_genesys_write_register (dev, REG6D, 0x8f);
+  sanei_genesys_read_register (dev, REG6B, &val);
+  sanei_genesys_write_register (dev, REG6B, 0x0e);
+  sanei_genesys_read_register (dev, REG6B, &val);
+  sanei_genesys_write_register (dev, REG6B, 0x0e);
+  sanei_genesys_read_register (dev, REG6B, &val);
+  sanei_genesys_write_register (dev, REG6B, 0x0a);
+  sanei_genesys_read_register (dev, REG6B, &val);
+  sanei_genesys_write_register (dev, REG6B, 0x02);
+  sanei_genesys_read_register (dev, REG6B, &val);
+  sanei_genesys_write_register (dev, REG6B, 0x06);
+
+  sanei_genesys_write_0x8c (dev, 0x10, 0x94);
+  sanei_genesys_write_register (dev, 0x09, 0x10);
+
+  /* set up GPIO : no address, so no bulk write, doesn't written directly either ? */
+  /*
+  dev->reg.find_reg(0x6c).value = dev->gpo.value[0];
+  dev->reg.find_reg(0x6d).value = dev->gpo.value[1];
+  dev->reg.find_reg(0x6e).value = dev->gpo.enable[0];
+  dev->reg.find_reg(0x6f).value = dev->gpo.enable[1]; */
+
+  // FIXME: the following code originally changed 0x6b, but due to bug the 0x6c register was
+  // effectively changed. The current behavior matches the old code, but should probably be fixed.
+  dev->reg.find_reg(0x6c).value |= REG6B_GPO18;
+  dev->reg.find_reg(0x6c).value &= ~REG6B_GPO17;
+
+  sanei_gl841_setup_sensor(dev, sensor, &dev->reg, 0, 0);
+}
+
+/*
+ * Set all registers to default values
+ * (function called only once at the beginning)
+ */
+static void
+gl841_init_registers (Genesys_Device * dev)
+{
+  int addr;
+
+  DBG(DBG_proc, "%s\n", __func__);
+
+  dev->reg.clear();
+  if (dev->model->model_id == MODEL_CANON_LIDE_80)
+    {
+      gl841_init_lide80(dev);
+      return ;
+    }
+
+    for (addr = 1; addr <= 0x0a; addr++) {
+        dev->reg.init_reg(addr, 0);
+    }
+    for (addr = 0x10; addr <= 0x27; addr++) {
+        dev->reg.init_reg(addr, 0);
+    }
+    dev->reg.init_reg(0x29, 0);
+    for (addr = 0x2c; addr <= 0x39; addr++)
+        dev->reg.init_reg(addr, 0);
+    for (addr = 0x3d; addr <= 0x3f; addr++)
+        dev->reg.init_reg(addr, 0);
+    for (addr = 0x52; addr <= 0x5a; addr++)
+        dev->reg.init_reg(addr, 0);
+    for (addr = 0x5d; addr <= 0x87; addr++)
+        dev->reg.init_reg(addr, 0);
+
+
+    dev->reg.find_reg(0x01).value = 0x20;	/* (enable shading), CCD, color, 1M */
+    if (dev->model->is_cis == SANE_TRUE) {
+        dev->reg.find_reg(0x01).value |= REG01_CISSET;
+    } else {
+        dev->reg.find_reg(0x01).value &= ~REG01_CISSET;
+    }
+
+    dev->reg.find_reg(0x02).value = 0x30 /*0x38 */ ;	/* auto home, one-table-move, full step */
+    dev->reg.find_reg(0x02).value |= REG02_AGOHOME;
+    sanei_genesys_set_motor_power(dev->reg, true);
+    dev->reg.find_reg(0x02).value |= REG02_FASTFED;
+
+    dev->reg.find_reg(0x03).value = 0x1f /*0x17 */ ;	/* lamp on */
+    dev->reg.find_reg(0x03).value |= REG03_AVEENB;
+
+  if (dev->model->ccd_type == CCD_PLUSTEK_3600)  /* AD front end */
+    {
+      dev->reg.find_reg(0x04).value  = (2 << REG04S_AFEMOD) | 0x02;
+    }
+  else /* Wolfson front end */
+    {
+      dev->reg.find_reg(0x04).value |= 1 << REG04S_AFEMOD;
+    }
+
+  const auto& sensor = sanei_genesys_find_sensor_any(dev);
+
+  dev->reg.find_reg(0x05).value = 0x00;	/* disable gamma, 24 clocks/pixel */
+  if (sensor.sensor_pixels < 0x1500)
+    dev->reg.find_reg(0x05).value |= REG05_DPIHW_600;
+  else if (sensor.sensor_pixels < 0x2a80)
+    dev->reg.find_reg(0x05).value |= REG05_DPIHW_1200;
+  else if (sensor.sensor_pixels < 0x5400)
+    dev->reg.find_reg(0x05).value |= REG05_DPIHW_2400;
+  else
+    {
+      dev->reg.find_reg(0x05).value |= REG05_DPIHW_2400;
+      DBG(DBG_warn, "%s: Cannot handle sensor pixel count %d\n", __func__,
+          sensor.sensor_pixels);
+    }
+
+
+  dev->reg.find_reg(0x06).value |= REG06_PWRBIT;
+  dev->reg.find_reg(0x06).value |= REG06_GAIN4;
+
+  /* XP300 CCD needs different clock and clock/pixels values */
+  if (dev->model->ccd_type != CCD_XP300 && dev->model->ccd_type != CCD_DP685
+                                        && dev->model->ccd_type != CCD_PLUSTEK_3600)
+    {
+      dev->reg.find_reg(0x06).value |= 0 << REG06S_SCANMOD;
+      dev->reg.find_reg(0x09).value |= 1 << REG09S_CLKSET;
+    }
+  else
+    {
+      dev->reg.find_reg(0x06).value |= 0x05 << REG06S_SCANMOD; /* 15 clocks/pixel */
+      dev->reg.find_reg(0x09).value = 0; /* 24 MHz CLKSET */
+    }
+
+  dev->reg.find_reg(0x1e).value = 0xf0;	/* watch-dog time */
+
+  dev->reg.find_reg(0x17).value |= 1 << REG17S_TGW;
+
+  dev->reg.find_reg(0x19).value = 0x50;
+
+  dev->reg.find_reg(0x1d).value |= 1 << REG1DS_TGSHLD;
+
+  dev->reg.find_reg(0x1e).value |= 1 << REG1ES_WDTIME;
+
+/*SCANFED*/
+  dev->reg.find_reg(0x1f).value = 0x01;
+
+/*BUFSEL*/
+  dev->reg.find_reg(0x20).value = 0x20;
+
+/*LAMPPWM*/
+  dev->reg.find_reg(0x29).value = 0xff;
+
+/*BWHI*/
+  dev->reg.find_reg(0x2e).value = 0x80;
+
+/*BWLOW*/
+  dev->reg.find_reg(0x2f).value = 0x80;
+
+/*LPERIOD*/
+  dev->reg.find_reg(0x38).value = 0x4f;
+  dev->reg.find_reg(0x39).value = 0xc1;
+
+/*VSMPW*/
+  dev->reg.find_reg(0x58).value |= 3 << REG58S_VSMPW;
+
+/*BSMPW*/
+  dev->reg.find_reg(0x59).value |= 3 << REG59S_BSMPW;
+
+/*RLCSEL*/
+  dev->reg.find_reg(0x5a).value |= REG5A_RLCSEL;
+
+/*STOPTIM*/
+  dev->reg.find_reg(0x5e).value |= 0x2 << REG5ES_STOPTIM;
+
+  sanei_gl841_setup_sensor(dev, sensor, &dev->reg, 0, 0);
+
+  /* set up GPIO */
+  dev->reg.find_reg(0x6c).value = dev->gpo.value[0];
+  dev->reg.find_reg(0x6d).value = dev->gpo.value[1];
+  dev->reg.find_reg(0x6e).value = dev->gpo.enable[0];
+  dev->reg.find_reg(0x6f).value = dev->gpo.enable[1];
+
+  /* TODO there is a switch calling to be written here */
+  if (dev->model->gpo_type == GPO_CANONLIDE35)
+    {
+      dev->reg.find_reg(0x6b).value |= REG6B_GPO18;
+      dev->reg.find_reg(0x6b).value &= ~REG6B_GPO17;
+    }
+
+  if (dev->model->gpo_type == GPO_XP300)
+    {
+      dev->reg.find_reg(0x6b).value |= REG6B_GPO17;
+    }
+
+  if (dev->model->gpo_type == GPO_DP685)
+    {
+      /* REG6B_GPO18 lights on green led */
+      dev->reg.find_reg(0x6b).value |= REG6B_GPO17|REG6B_GPO18;
+    }
+
+  DBG(DBG_proc, "%s complete\n", __func__);
+}
+
+/* Send slope table for motor movement
+   slope_table in machine byte order
+ */
+static SANE_Status
+gl841_send_slope_table (Genesys_Device * dev, int table_nr,
+			      uint16_t * slope_table, int steps)
+{
+  int dpihw;
+  int start_address;
+  SANE_Status status = SANE_STATUS_GOOD;
+  char msg[4000];
+/*#ifdef WORDS_BIGENDIAN*/
+  int i;
+/*#endif*/
+
+  DBG(DBG_proc, "%s (table_nr = %d, steps = %d)\n", __func__, table_nr, steps);
+
+  dpihw = dev->reg.find_reg(0x05).value >> 6;
+
+  if (dpihw == 0)		/* 600 dpi */
+    start_address = 0x08000;
+  else if (dpihw == 1)		/* 1200 dpi */
+    start_address = 0x10000;
+  else if (dpihw == 2)		/* 2400 dpi */
+    start_address = 0x20000;
+  else				/* reserved */
+    return SANE_STATUS_INVAL;
+
+  std::vector<uint8_t> table(steps * 2);
+  for(i = 0; i < steps; i++) {
+      table[i * 2] = slope_table[i] & 0xff;
+      table[i * 2 + 1] = slope_table[i] >> 8;
+  }
+
+  if (DBG_LEVEL >= DBG_io)
+    {
+      sprintf (msg, "write slope %d (%d)=", table_nr, steps);
+      for (i = 0; i < steps; i++)
+	{
+	  sprintf (msg+strlen(msg), ",%d", slope_table[i]);
+	}
+      DBG(DBG_io, "%s: %s\n", __func__, msg);
+    }
+
+  status =
+    sanei_genesys_set_buffer_address (dev, start_address + table_nr * 0x200);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to set buffer address: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  status = sanei_genesys_bulk_write_data(dev, 0x3c, table.data(), steps * 2);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to send slope table: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  DBG(DBG_proc, "%s: completed\n", __func__);
+  return status;
+}
+
+static SANE_Status
+gl841_set_lide80_fe (Genesys_Device * dev, uint8_t set)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+
+  DBGSTART;
+
+  if (set == AFE_INIT)
+    {
+      DBG(DBG_proc, "%s(): setting DAC %u\n", __func__, dev->model->dac_type);
+
+      dev->frontend = dev->frontend_initial;
+
+      /* write them to analog frontend */
+      status = sanei_genesys_fe_write_data(dev, 0x00, dev->frontend.regs.get_value(0x00));
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: writing reg 0x00 failed: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+      status = sanei_genesys_fe_write_data(dev, 0x03, dev->frontend.regs.get_value(0x01));
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: writing reg 0x03 failed: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+      status = sanei_genesys_fe_write_data(dev, 0x06, dev->frontend.regs.get_value(0x02));
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: writing reg 0x06 failed: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+    }
+
+  if (set == AFE_SET)
+    {
+      status = sanei_genesys_fe_write_data(dev, 0x00, dev->frontend.regs.get_value(0x00));
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: writing reg 0x00 failed: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+      status = sanei_genesys_fe_write_data(dev, 0x06, dev->frontend.regs.get_value(0x20));
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: writing offset failed: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+      status = sanei_genesys_fe_write_data(dev, 0x03, dev->frontend.regs.get_value(0x28));
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: writing gain failed: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+    }
+
+  return status;
+  DBGCOMPLETED;
+}
+
+/* Set values of Analog Device type frontend */
+static SANE_Status
+gl841_set_ad_fe (Genesys_Device * dev, uint8_t set)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+  int i;
+
+  /* special case for LiDE 80 analog frontend */
+  if(dev->model->dac_type==DAC_CANONLIDE80)
+    {
+      return gl841_set_lide80_fe(dev, set);
+    }
+
+  DBG(DBG_proc, "%s(): start\n", __func__);
+  if (set == AFE_INIT)
+    {
+      DBG(DBG_proc, "%s(): setting DAC %u\n", __func__, dev->model->dac_type);
+
+      dev->frontend = dev->frontend_initial;
+
+      /* write them to analog frontend */
+      status = sanei_genesys_fe_write_data(dev, 0x00, dev->frontend.regs.get_value(0x00));
+      if (status != SANE_STATUS_GOOD)
+            {
+        DBG(DBG_error, "%s: writing reg 0x00 failed: %s\n", __func__, sane_strstatus(status));
+      	return status;
+            }
+
+      status = sanei_genesys_fe_write_data(dev, 0x01, dev->frontend.regs.get_value(0x01));
+      if (status != SANE_STATUS_GOOD)
+            {
+        DBG(DBG_error, "%s: writing reg 0x01 failed: %s\n", __func__, sane_strstatus(status));
+        return status;
+            }
+
+      for (i = 0; i < 6; i++)
+        {
+    	status =
+    	  sanei_genesys_fe_write_data (dev, 0x02 + i, 0x00);
+    	if (status != SANE_STATUS_GOOD)
+    	  {
+            DBG(DBG_error, "%s: writing sign[%d] failed: %s\n", __func__, 0x02 + i,
+                sane_strstatus(status));
+    	    return status;
+    	  }
+        }
+    }
+  if (set == AFE_SET)
+    {
+      /* write them to analog frontend */
+      status = sanei_genesys_fe_write_data(dev, 0x00, dev->frontend.regs.get_value(0x00));
+      if (status != SANE_STATUS_GOOD)
+            {
+        DBG(DBG_error, "%s: writing reg 0x00 failed: %s\n", __func__, sane_strstatus(status));
+      	return status;
+            }
+
+      status = sanei_genesys_fe_write_data(dev, 0x01, dev->frontend.regs.get_value(0x01));
+      if (status != SANE_STATUS_GOOD)
+            {
+        DBG(DBG_error, "%s: writing reg 0x01 failed: %s\n", __func__, sane_strstatus(status));
+        return status;
+            }
+
+      /* Write fe 0x02 (red gain)*/
+      status = sanei_genesys_fe_write_data(dev, 0x02, dev->frontend.get_gain(0));
+      if (status != SANE_STATUS_GOOD)
+            {
+        DBG(DBG_error, "%s: writing fe 0x02 (gain r) fail: %s\n", __func__, sane_strstatus(status));
+        return status;
+            }
+
+      /* Write fe 0x03 (green gain)*/
+      status = sanei_genesys_fe_write_data(dev, 0x03, dev->frontend.get_gain(1));
+      if (status != SANE_STATUS_GOOD)
+            {
+        DBG(DBG_error, "%s: writing fe 0x03 (gain g) fail: %s\n", __func__, sane_strstatus(status));
+        return status;
+            }
+
+      /* Write fe 0x04 (blue gain)*/
+      status = sanei_genesys_fe_write_data(dev, 0x04, dev->frontend.get_gain(2));
+      if (status != SANE_STATUS_GOOD)
+            {
+        DBG(DBG_error, "%s: writing fe 0x04 (gain b) fail: %s\n", __func__, sane_strstatus(status));
+        return status;
+            }
+
+      /* Write fe 0x05 (red offset)*/
+      status =
+          sanei_genesys_fe_write_data(dev, 0x05, dev->frontend.get_offset(0));
+      if (status != SANE_STATUS_GOOD)
+            {
+        DBG(DBG_error, "%s: write fe 0x05 (offset r) fail: %s\n", __func__, sane_strstatus(status));
+        return status;
+            }
+
+      /* Write fe 0x06 (green offset)*/
+      status =
+          sanei_genesys_fe_write_data(dev, 0x06, dev->frontend.get_offset(1));
+      if (status != SANE_STATUS_GOOD)
+            {
+        DBG(DBG_error, "%s: write fe 0x06 (offset g) fail: %s\n", __func__, sane_strstatus(status));
+        return status;
+            }
+
+      /* Write fe 0x07 (blue offset)*/
+      status =
+          sanei_genesys_fe_write_data(dev, 0x07, dev->frontend.get_offset(2));
+      if (status != SANE_STATUS_GOOD)
+            {
+        DBG(DBG_error, "%s: write fe 0x07 (offset b) fail: %s\n", __func__, sane_strstatus(status));
+        return status;
+            }
+          }
+  DBG(DBG_proc, "%s(): end\n", __func__);
+
+  return status;
+}
+
+/* Set values of analog frontend */
+static SANE_Status
+gl841_set_fe(Genesys_Device * dev, const Genesys_Sensor& sensor, uint8_t set)
+{
+    (void) sensor;
+  SANE_Status status = SANE_STATUS_GOOD;
+  int i;
+
+  DBG(DBG_proc, "%s (%s)\n", __func__,
+      set == AFE_INIT ? "init" : set == AFE_SET ? "set" : set ==
+      AFE_POWER_SAVE ? "powersave" : "huh?");
+
+  /* Analog Device type frontend */
+  if ((dev->reg.find_reg(0x04).value & REG04_FESET) == 0x02)
+    {
+      return gl841_set_ad_fe (dev, set);
+    }
+
+  if ((dev->reg.find_reg(0x04).value & REG04_FESET) != 0x00)
+    {
+      DBG(DBG_proc, "%s(): unsupported frontend type %d\n", __func__,
+          dev->reg.find_reg(0x04).value & REG04_FESET);
+      return SANE_STATUS_UNSUPPORTED;
+    }
+
+  if (set == AFE_INIT)
+    {
+      DBG(DBG_proc, "%s(): setting DAC %u\n", __func__, dev->model->dac_type);
+      dev->frontend = dev->frontend_initial;
+
+      /* reset only done on init */
+      status = sanei_genesys_fe_write_data (dev, 0x04, 0x80);
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: reset fe failed: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+      DBG(DBG_proc, "%s(): frontend reset complete\n", __func__);
+    }
+
+
+  if (set == AFE_POWER_SAVE)
+    {
+      status = sanei_genesys_fe_write_data (dev, 0x01, 0x02);
+      if (status != SANE_STATUS_GOOD) {
+        DBG(DBG_error, "%s: writing data failed: %s\n", __func__, sane_strstatus(status));
+        return status;
+      }
+      return status;
+    }
+
+  /* todo :  base this test on cfg reg3 or a CCD family flag to be created */
+  /*if (dev->model->ccd_type!=CCD_HP2300 && dev->model->ccd_type!=CCD_HP2400) */
+  {
+
+    status = sanei_genesys_fe_write_data(dev, 0x00, dev->frontend.regs.get_value(0x00));
+    if (status != SANE_STATUS_GOOD)
+      {
+        DBG(DBG_error, "%s: writing reg0 failed: %s\n", __func__, sane_strstatus(status));
+	return status;
+      }
+    status = sanei_genesys_fe_write_data(dev, 0x02, dev->frontend.regs.get_value(0x02));
+    if (status != SANE_STATUS_GOOD)
+      {
+        DBG(DBG_error, "%s: writing reg2 failed: %s\n", __func__, sane_strstatus(status));
+	return status;
+      }
+  }
+
+  status = sanei_genesys_fe_write_data(dev, 0x01, dev->frontend.regs.get_value(0x01));
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: writing reg1 failed: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  status = sanei_genesys_fe_write_data(dev, 0x03, dev->frontend.regs.get_value(0x03));
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: writing reg3 failed: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  status = sanei_genesys_fe_write_data (dev, 0x06, dev->frontend.reg2[0]);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: writing reg6 failed: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  status = sanei_genesys_fe_write_data (dev, 0x08, dev->frontend.reg2[1]);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: writing reg8 failed: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  status = sanei_genesys_fe_write_data (dev, 0x09, dev->frontend.reg2[2]);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: writing reg9 failed: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  for (i = 0; i < 3; i++)
+      {
+	status =
+          sanei_genesys_fe_write_data(dev, 0x24 + i, dev->frontend.regs.get_value(0x24 + i));
+	if (status != SANE_STATUS_GOOD)
+	  {
+	    DBG(DBG_error, "%s: writing sign[%d] failed: %s\n", __func__, i,
+		sane_strstatus(status));
+	    return status;
+	  }
+
+	status =
+          sanei_genesys_fe_write_data(dev, 0x28 + i, dev->frontend.get_gain(i));
+	if (status != SANE_STATUS_GOOD)
+	  {
+	    DBG(DBG_error, "%s: writing gain[%d] failed: %s\n", __func__, i,
+		sane_strstatus(status));
+	    return status;
+	  }
+
+	status =
+          sanei_genesys_fe_write_data(dev, 0x20 + i,
+                                       dev->frontend.get_offset(i));
+	if (status != SANE_STATUS_GOOD)
+	  {
+	    DBG(DBG_error, "%s: writing offset[%d] failed: %s\n", __func__, i,
+		sane_strstatus(status));
+	    return status;
+	  }
+      }
+
+
+  DBG(DBG_proc, "%s: completed\n", __func__);
+
+  return SANE_STATUS_GOOD;
+}
+
+#define MOTOR_ACTION_FEED       1
+#define MOTOR_ACTION_GO_HOME    2
+#define MOTOR_ACTION_HOME_FREE  3
+
+/** @brief turn off motor
+ *
+ */
+static SANE_Status
+gl841_init_motor_regs_off(Genesys_Register_Set * reg,
+			  unsigned int scan_lines)
+{
+    unsigned int feedl;
+    GenesysRegister* r;
+
+    DBG(DBG_proc, "%s : scan_lines=%d\n", __func__, scan_lines);
+
+    feedl = 2;
+
+    r = sanei_genesys_get_address (reg, 0x3d);
+    r->value = (feedl >> 16) & 0xf;
+    r = sanei_genesys_get_address (reg, 0x3e);
+    r->value = (feedl >> 8) & 0xff;
+    r = sanei_genesys_get_address (reg, 0x3f);
+    r->value = feedl & 0xff;
+    r = sanei_genesys_get_address (reg, 0x5e);
+    r->value &= ~0xe0;
+
+    r = sanei_genesys_get_address (reg, 0x25);
+    r->value = (scan_lines >> 16) & 0xf;
+    r = sanei_genesys_get_address (reg, 0x26);
+    r->value = (scan_lines >> 8) & 0xff;
+    r = sanei_genesys_get_address (reg, 0x27);
+    r->value = scan_lines & 0xff;
+
+    r = sanei_genesys_get_address (reg, 0x02);
+    r->value &= ~0x01; /*LONGCURV OFF*/
+    r->value &= ~0x80; /*NOT_HOME OFF*/
+
+    r->value &= ~0x10;
+
+    r->value &= ~0x06;
+
+    r->value &= ~0x08;
+
+    r->value &= ~0x20;
+
+    r->value &= ~0x40;
+
+    r = sanei_genesys_get_address (reg, 0x67);
+    r->value = 0x3f;
+
+    r = sanei_genesys_get_address (reg, 0x68);
+    r->value = 0x3f;
+
+    r = sanei_genesys_get_address (reg, REG_STEPNO);
+    r->value = 0;
+
+    r = sanei_genesys_get_address (reg, REG_FASTNO);
+    r->value = 0;
+
+    r = sanei_genesys_get_address (reg, 0x69);
+    r->value = 0;
+
+    r = sanei_genesys_get_address (reg, 0x6a);
+    r->value = 0;
+
+    r = sanei_genesys_get_address (reg, 0x5f);
+    r->value = 0;
+
+
+    DBGCOMPLETED;
+    return SANE_STATUS_GOOD;
+}
+
+/** @brief write motor table frequency
+ * Write motor frequency data table.
+ * @param dev device to set up motor
+ * @param ydpi motor target resolution
+ * @return SANE_STATUS_GOOD on success
+ */
+static SANE_Status gl841_write_freq(Genesys_Device *dev, unsigned int ydpi)
+{
+SANE_Status status = SANE_STATUS_GOOD;
+/**< fast table */
+uint8_t tdefault[] = {0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0x36,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xb6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0xf6,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76,0x18,0x76};
+uint8_t t1200[]    = {0xc7,0x31,0xc7,0x31,0xc7,0x31,0xc7,0x31,0xc7,0x31,0xc7,0x31,0xc7,0x31,0xc7,0x31,0xc0,0x11,0xc0,0x11,0xc0,0x11,0xc0,0x11,0xc0,0x11,0xc0,0x11,0xc0,0x11,0xc0,0x11,0xc7,0xb1,0xc7,0xb1,0xc7,0xb1,0xc7,0xb1,0xc7,0xb1,0xc7,0xb1,0xc7,0xb1,0xc7,0xb1,0x07,0xe0,0x07,0xe0,0x07,0xe0,0x07,0xe0,0x07,0xe0,0x07,0xe0,0x07,0xe0,0x07,0xe0,0xc7,0xf1,0xc7,0xf1,0xc7,0xf1,0xc7,0xf1,0xc7,0xf1,0xc7,0xf1,0xc7,0xf1,0xc7,0xf1,0xc0,0x51,0xc0,0x51,0xc0,0x51,0xc0,0x51,0xc0,0x51,0xc0,0x51,0xc0,0x51,0xc0,0x51,0xc7,0x71,0xc7,0x71,0xc7,0x71,0xc7,0x71,0xc7,0x71,0xc7,0x71,0xc7,0x71,0xc7,0x71,0x07,0x20,0x07,0x20,0x07,0x20,0x07,0x20,0x07,0x20,0x07,0x20,0x07,0x20,0x07,0x20};
+uint8_t t300[]     = {0x08,0x32,0x08,0x32,0x08,0x32,0x08,0x32,0x08,0x32,0x08,0x32,0x08,0x32,0x08,0x32,0x00,0x13,0x00,0x13,0x00,0x13,0x00,0x13,0x00,0x13,0x00,0x13,0x00,0x13,0x00,0x13,0x08,0xb2,0x08,0xb2,0x08,0xb2,0x08,0xb2,0x08,0xb2,0x08,0xb2,0x08,0xb2,0x08,0xb2,0x0c,0xa0,0x0c,0xa0,0x0c,0xa0,0x0c,0xa0,0x0c,0xa0,0x0c,0xa0,0x0c,0xa0,0x0c,0xa0,0x08,0xf2,0x08,0xf2,0x08,0xf2,0x08,0xf2,0x08,0xf2,0x08,0xf2,0x08,0xf2,0x08,0xf2,0x00,0xd3,0x00,0xd3,0x00,0xd3,0x00,0xd3,0x00,0xd3,0x00,0xd3,0x00,0xd3,0x00,0xd3,0x08,0x72,0x08,0x72,0x08,0x72,0x08,0x72,0x08,0x72,0x08,0x72,0x08,0x72,0x08,0x72,0x0c,0x60,0x0c,0x60,0x0c,0x60,0x0c,0x60,0x0c,0x60,0x0c,0x60,0x0c,0x60,0x0c,0x60};
+uint8_t t150[]     = {0x0c,0x33,0xcf,0x33,0xcf,0x33,0xcf,0x33,0xcf,0x33,0xcf,0x33,0xcf,0x33,0xcf,0x33,0x40,0x14,0x80,0x15,0x80,0x15,0x80,0x15,0x80,0x15,0x80,0x15,0x80,0x15,0x80,0x15,0x0c,0xb3,0xcf,0xb3,0xcf,0xb3,0xcf,0xb3,0xcf,0xb3,0xcf,0xb3,0xcf,0xb3,0xcf,0xb3,0x11,0xa0,0x16,0xa0,0x16,0xa0,0x16,0xa0,0x16,0xa0,0x16,0xa0,0x16,0xa0,0x16,0xa0,0x0c,0xf3,0xcf,0xf3,0xcf,0xf3,0xcf,0xf3,0xcf,0xf3,0xcf,0xf3,0xcf,0xf3,0xcf,0xf3,0x40,0xd4,0x80,0xd5,0x80,0xd5,0x80,0xd5,0x80,0xd5,0x80,0xd5,0x80,0xd5,0x80,0xd5,0x0c,0x73,0xcf,0x73,0xcf,0x73,0xcf,0x73,0xcf,0x73,0xcf,0x73,0xcf,0x73,0xcf,0x73,0x11,0x60,0x16,0x60,0x16,0x60,0x16,0x60,0x16,0x60,0x16,0x60,0x16,0x60,0x16,0x60};
+
+uint8_t *table;
+
+  DBGSTART;
+  if(dev->model->motor_type == MOTOR_CANONLIDE80)
+    {
+      switch(ydpi)
+        {
+          case 3600:
+          case 1200:
+            table=t1200;
+            break;
+          case 900:
+          case 300:
+            table=t300;
+            break;
+          case 450:
+          case 150:
+            table=t150;
+            break;
+          default:
+            table=tdefault;
+        }
+      RIE(sanei_genesys_write_register(dev, 0x66, 0x00));
+      RIE(sanei_genesys_write_register(dev, 0x5b, 0x0c));
+      RIE(sanei_genesys_write_register(dev, 0x5c, 0x00));
+      RIE(sanei_genesys_bulk_write_data(dev, 0x28, table, 128));
+      RIE(sanei_genesys_write_register(dev, 0x5b, 0x00));
+      RIE(sanei_genesys_write_register(dev, 0x5c, 0x00));
+    }
+  DBGCOMPLETED;
+  return SANE_STATUS_GOOD;
+}
+
+
+static SANE_Status
+gl841_init_motor_regs(Genesys_Device * dev,
+                      const Genesys_Sensor& sensor,
+		      Genesys_Register_Set * reg,
+		      unsigned int feed_steps,/*1/base_ydpi*/
+/*maybe float for half/quarter step resolution?*/
+		      unsigned int action,
+		      unsigned int flags)
+{
+    SANE_Status status = SANE_STATUS_GOOD;
+    unsigned int fast_exposure;
+    int scan_power_mode;
+    int use_fast_fed = 0;
+    uint16_t fast_slope_table[256];
+    unsigned int fast_slope_steps = 0;
+    unsigned int feedl;
+    GenesysRegister* r;
+/*number of scan lines to add in a scan_lines line*/
+
+    DBG(DBG_proc, "%s : feed_steps=%d, action=%d, flags=%x\n", __func__, feed_steps, action, flags);
+
+    memset(fast_slope_table,0xff,512);
+
+    gl841_send_slope_table (dev, 0, fast_slope_table, 256);
+    gl841_send_slope_table (dev, 1, fast_slope_table, 256);
+    gl841_send_slope_table (dev, 2, fast_slope_table, 256);
+    gl841_send_slope_table (dev, 3, fast_slope_table, 256);
+    gl841_send_slope_table (dev, 4, fast_slope_table, 256);
+
+    gl841_write_freq(dev, dev->motor.base_ydpi / 4);
+
+    fast_slope_steps = 256;
+    if (action == MOTOR_ACTION_FEED || action == MOTOR_ACTION_GO_HOME)
+      {
+        /* FEED and GO_HOME can use fastest slopes available */
+        fast_exposure = gl841_exposure_time(dev, sensor,
+                                            dev->motor.base_ydpi / 4,
+                                            0,
+                                            0,
+                                            0,
+                                            &scan_power_mode);
+        DBG(DBG_info, "%s : fast_exposure=%d pixels\n", __func__, fast_exposure);
+      }
+
+    if (action == MOTOR_ACTION_HOME_FREE) {
+/* HOME_FREE must be able to stop in one step, so do not try to get faster */
+	fast_exposure = dev->motor.slopes[0][0].maximum_start_speed;
+    }
+
+     sanei_genesys_create_slope_table3 (
+	dev,
+	fast_slope_table,
+        256,
+	fast_slope_steps,
+	0,
+	fast_exposure,
+	dev->motor.base_ydpi / 4,
+	&fast_slope_steps,
+	&fast_exposure, 0);
+
+    feedl = feed_steps - fast_slope_steps*2;
+    use_fast_fed = 1;
+
+/* all needed slopes available. we did even decide which mode to use.
+   what next?
+   - transfer slopes
+SCAN:
+flags \ use_fast_fed    ! 0         1
+------------------------\--------------------
+                      0 ! 0,1,2     0,1,2,3
+MOTOR_FLAG_AUTO_GO_HOME ! 0,1,2,4   0,1,2,3,4
+OFF:       none
+FEED:      3
+GO_HOME:   3
+HOME_FREE: 3
+   - setup registers
+     * slope specific registers (already done)
+     * DECSEL for HOME_FREE/GO_HOME/SCAN
+     * FEEDL
+     * MTRREV
+     * MTRPWR
+     * FASTFED
+     * STEPSEL
+     * MTRPWM
+     * FSTPSEL
+     * FASTPWM
+     * HOMENEG
+     * BWDSTEP
+     * FWDSTEP
+     * Z1
+     * Z2
+ */
+
+    r = sanei_genesys_get_address(reg, 0x3d);
+    r->value = (feedl >> 16) & 0xf;
+    r = sanei_genesys_get_address(reg, 0x3e);
+    r->value = (feedl >> 8) & 0xff;
+    r = sanei_genesys_get_address(reg, 0x3f);
+    r->value = feedl & 0xff;
+    r = sanei_genesys_get_address(reg, 0x5e);
+    r->value &= ~0xe0;
+
+    r = sanei_genesys_get_address(reg, 0x25);
+    r->value = 0;
+    r = sanei_genesys_get_address(reg, 0x26);
+    r->value = 0;
+    r = sanei_genesys_get_address(reg, 0x27);
+    r->value = 0;
+
+    r = sanei_genesys_get_address(reg, 0x02);
+    r->value &= ~0x01; /*LONGCURV OFF*/
+    r->value &= ~0x80; /*NOT_HOME OFF*/
+
+    r->value |= 0x10;
+
+    if (action == MOTOR_ACTION_GO_HOME)
+	r->value |= 0x06;
+    else
+	r->value &= ~0x06;
+
+    if (use_fast_fed)
+	r->value |= 0x08;
+    else
+	r->value &= ~0x08;
+
+    if (flags & MOTOR_FLAG_AUTO_GO_HOME)
+	r->value |= 0x20;
+    else
+	r->value &= ~0x20;
+
+    r->value &= ~0x40;
+
+    status = gl841_send_slope_table (dev, 3, fast_slope_table, 256);
+
+    if (status != SANE_STATUS_GOOD)
+	return status;
+
+    r = sanei_genesys_get_address(reg, 0x67);
+    r->value = 0x3f;
+
+    r = sanei_genesys_get_address(reg, 0x68);
+    r->value = 0x3f;
+
+    r = sanei_genesys_get_address(reg, REG_STEPNO);
+    r->value = 0;
+
+    r = sanei_genesys_get_address(reg, REG_FASTNO);
+    r->value = 0;
+
+    r = sanei_genesys_get_address(reg, 0x69);
+    r->value = 0;
+
+    r = sanei_genesys_get_address(reg, 0x6a);
+    r->value = (fast_slope_steps >> 1) + (fast_slope_steps & 1);
+
+    r = sanei_genesys_get_address(reg, 0x5f);
+    r->value = (fast_slope_steps >> 1) + (fast_slope_steps & 1);
+
+
+    DBGCOMPLETED;
+    return SANE_STATUS_GOOD;
+}
+
+static SANE_Status
+gl841_init_motor_regs_scan(Genesys_Device * dev, const Genesys_Sensor& sensor,
+		      Genesys_Register_Set * reg,
+		      unsigned int scan_exposure_time,/*pixel*/
+		      float scan_yres,/*dpi, motor resolution*/
+		      int scan_step_type,/*0: full, 1: half, 2: quarter*/
+		      unsigned int scan_lines,/*lines, scan resolution*/
+		      unsigned int scan_dummy,
+/*number of scan lines to add in a scan_lines line*/
+		      unsigned int feed_steps,/*1/base_ydpi*/
+/*maybe float for half/quarter step resolution?*/
+		      int scan_power_mode,
+		      unsigned int flags)
+{
+    SANE_Status status = SANE_STATUS_GOOD;
+    unsigned int fast_exposure;
+    int use_fast_fed = 0;
+    int dummy_power_mode;
+    unsigned int fast_time;
+    unsigned int slow_time;
+    uint16_t slow_slope_table[256];
+    uint16_t fast_slope_table[256];
+    uint16_t back_slope_table[256];
+    unsigned int slow_slope_time;
+    unsigned int fast_slope_time;
+    unsigned int slow_slope_steps = 0;
+    unsigned int fast_slope_steps = 0;
+    unsigned int back_slope_steps = 0;
+    unsigned int feedl;
+    GenesysRegister* r;
+    unsigned int min_restep = 0x20;
+    uint32_t z1, z2;
+
+    DBG(DBG_proc, "%s : scan_exposure_time=%d, scan_yres=%g, scan_step_type=%d, scan_lines=%d,"
+        " scan_dummy=%d, feed_steps=%d, scan_power_mode=%d, flags=%x\n", __func__,
+        scan_exposure_time,
+        scan_yres,
+        scan_step_type,
+        scan_lines,
+        scan_dummy,
+        feed_steps,
+        scan_power_mode,
+        flags);
+
+    fast_exposure = gl841_exposure_time(dev, sensor,
+                                        dev->motor.base_ydpi / 4,
+                                        0,
+                                        0,
+                                        0,
+                                        &dummy_power_mode);
+
+    DBG(DBG_info, "%s : fast_exposure=%d pixels\n", __func__, fast_exposure);
+
+    memset(slow_slope_table,0xff,512);
+
+    gl841_send_slope_table (dev, 0, slow_slope_table, 256);
+    gl841_send_slope_table (dev, 1, slow_slope_table, 256);
+    gl841_send_slope_table (dev, 2, slow_slope_table, 256);
+    gl841_send_slope_table (dev, 3, slow_slope_table, 256);
+    gl841_send_slope_table (dev, 4, slow_slope_table, 256);
+
+    /* motor frequency table */
+    gl841_write_freq(dev, scan_yres);
+
+/*
+  we calculate both tables for SCAN. the fast slope step count depends on
+  how many steps we need for slow acceleration and how much steps we are
+  allowed to use.
+ */
+    slow_slope_time = sanei_genesys_create_slope_table3 (
+	dev,
+	slow_slope_table, 256,
+	256,
+	scan_step_type,
+	scan_exposure_time,
+	scan_yres,
+	&slow_slope_steps,
+	NULL,
+	scan_power_mode);
+
+     sanei_genesys_create_slope_table3 (
+	dev,
+	back_slope_table, 256,
+	256,
+	scan_step_type,
+	0,
+	scan_yres,
+	&back_slope_steps,
+	NULL,
+	scan_power_mode);
+
+    if (feed_steps < (slow_slope_steps >> scan_step_type)) {
+	/*TODO: what should we do here?? go back to exposure calculation?*/
+	feed_steps = slow_slope_steps >> scan_step_type;
+    }
+
+    if (feed_steps > fast_slope_steps*2 -
+	    (slow_slope_steps >> scan_step_type))
+	fast_slope_steps = 256;
+    else
+/* we need to shorten fast_slope_steps here. */
+	fast_slope_steps = (feed_steps -
+			    (slow_slope_steps >> scan_step_type))/2;
+
+    DBG(DBG_info, "%s: Maximum allowed slope steps for fast slope: %d\n", __func__,
+        fast_slope_steps);
+
+    fast_slope_time = sanei_genesys_create_slope_table3 (
+	dev,
+	fast_slope_table, 256,
+	fast_slope_steps,
+	0,
+	fast_exposure,
+	dev->motor.base_ydpi / 4,
+	&fast_slope_steps,
+	&fast_exposure,
+	scan_power_mode);
+
+    /* fast fed special cases handling */
+    if (dev->model->gpo_type == GPO_XP300
+     || dev->model->gpo_type == GPO_DP685)
+      {
+	/* quirk: looks like at least this scanner is unable to use
+	   2-feed mode */
+	use_fast_fed = 0;
+      }
+    else if (feed_steps < fast_slope_steps*2 + (slow_slope_steps >> scan_step_type)) {
+	use_fast_fed = 0;
+	DBG(DBG_info, "%s: feed too short, slow move forced.\n", __func__);
+    } else {
+/* for deciding whether we should use fast mode we need to check how long we
+   need for (fast)accelerating, moving, decelerating, (TODO: stopping?)
+   (slow)accelerating again versus (slow)accelerating and moving. we need
+   fast and slow tables here.
+*/
+/*NOTE: scan_exposure_time is per scan_yres*/
+/*NOTE: fast_exposure is per base_ydpi/4*/
+/*we use full steps as base unit here*/
+	fast_time =
+	    fast_exposure / 4 *
+	    (feed_steps - fast_slope_steps*2 -
+	     (slow_slope_steps >> scan_step_type))
+	    + fast_slope_time*2 + slow_slope_time;
+	slow_time =
+	    (scan_exposure_time * scan_yres) / dev->motor.base_ydpi *
+	    (feed_steps - (slow_slope_steps >> scan_step_type))
+	    + slow_slope_time;
+
+	DBG(DBG_info, "%s: Time for slow move: %d\n", __func__, slow_time);
+	DBG(DBG_info, "%s: Time for fast move: %d\n", __func__, fast_time);
+
+	use_fast_fed = fast_time < slow_time;
+    }
+
+    if (use_fast_fed)
+	feedl = feed_steps - fast_slope_steps*2 -
+	    (slow_slope_steps >> scan_step_type);
+    else
+	if ((feed_steps << scan_step_type) < slow_slope_steps)
+	    feedl = 0;
+	else
+	    feedl = (feed_steps << scan_step_type) - slow_slope_steps;
+    DBG(DBG_info, "%s: Decided to use %s mode\n", __func__, use_fast_fed?"fast feed":"slow feed");
+
+/* all needed slopes available. we did even decide which mode to use.
+   what next?
+   - transfer slopes
+SCAN:
+flags \ use_fast_fed    ! 0         1
+------------------------\--------------------
+                      0 ! 0,1,2     0,1,2,3
+MOTOR_FLAG_AUTO_GO_HOME ! 0,1,2,4   0,1,2,3,4
+OFF:       none
+FEED:      3
+GO_HOME:   3
+HOME_FREE: 3
+   - setup registers
+     * slope specific registers (already done)
+     * DECSEL for HOME_FREE/GO_HOME/SCAN
+     * FEEDL
+     * MTRREV
+     * MTRPWR
+     * FASTFED
+     * STEPSEL
+     * MTRPWM
+     * FSTPSEL
+     * FASTPWM
+     * HOMENEG
+     * BWDSTEP
+     * FWDSTEP
+     * Z1
+     * Z2
+ */
+
+    r = sanei_genesys_get_address (reg, 0x3d);
+    r->value = (feedl >> 16) & 0xf;
+    r = sanei_genesys_get_address (reg, 0x3e);
+    r->value = (feedl >> 8) & 0xff;
+    r = sanei_genesys_get_address (reg, 0x3f);
+    r->value = feedl & 0xff;
+    r = sanei_genesys_get_address (reg, 0x5e);
+    r->value &= ~0xe0;
+
+    r = sanei_genesys_get_address (reg, 0x25);
+    r->value = (scan_lines >> 16) & 0xf;
+    r = sanei_genesys_get_address (reg, 0x26);
+    r->value = (scan_lines >> 8) & 0xff;
+    r = sanei_genesys_get_address (reg, 0x27);
+    r->value = scan_lines & 0xff;
+
+    r = sanei_genesys_get_address (reg, 0x02);
+    r->value &= ~0x01; /*LONGCURV OFF*/
+    r->value &= ~0x80; /*NOT_HOME OFF*/
+    r->value |= 0x10;
+
+    r->value &= ~0x06;
+
+    if (use_fast_fed)
+	r->value |= 0x08;
+    else
+	r->value &= ~0x08;
+
+    if (flags & MOTOR_FLAG_AUTO_GO_HOME)
+	r->value |= 0x20;
+    else
+	r->value &= ~0x20;
+
+    if (flags & MOTOR_FLAG_DISABLE_BUFFER_FULL_MOVE)
+	r->value |= 0x40;
+    else
+	r->value &= ~0x40;
+
+    status = gl841_send_slope_table (dev, 0, slow_slope_table, 256);
+
+    if (status != SANE_STATUS_GOOD)
+	return status;
+
+    status = gl841_send_slope_table (dev, 1, back_slope_table, 256);
+
+    if (status != SANE_STATUS_GOOD)
+	return status;
+
+    status = gl841_send_slope_table (dev, 2, slow_slope_table, 256);
+
+    if (status != SANE_STATUS_GOOD)
+	return status;
+
+    if (use_fast_fed) {
+	status = gl841_send_slope_table (dev, 3, fast_slope_table, 256);
+
+	if (status != SANE_STATUS_GOOD)
+	    return status;
+    }
+
+    if (flags & MOTOR_FLAG_AUTO_GO_HOME){
+	status = gl841_send_slope_table (dev, 4, fast_slope_table, 256);
+
+	if (status != SANE_STATUS_GOOD)
+	    return status;
+    }
+
+
+/* now reg 0x21 and 0x24 are available, we can calculate reg 0x22 and 0x23,
+   reg 0x60-0x62 and reg 0x63-0x65
+   rule:
+   2*STEPNO+FWDSTEP=2*FASTNO+BWDSTEP
+*/
+/* steps of table 0*/
+    if (min_restep < slow_slope_steps*2+2)
+	min_restep = slow_slope_steps*2+2;
+/* steps of table 1*/
+    if (min_restep < back_slope_steps*2+2)
+	min_restep = back_slope_steps*2+2;
+/* steps of table 0*/
+    r = sanei_genesys_get_address (reg, REG_FWDSTEP);
+    r->value = min_restep - slow_slope_steps*2;
+/* steps of table 1*/
+    r = sanei_genesys_get_address (reg, REG_BWDSTEP);
+    r->value = min_restep - back_slope_steps*2;
+
+/*
+  for z1/z2:
+  in dokumentation mentioned variables a-d:
+  a = time needed for acceleration, table 1
+  b = time needed for reg 0x1f... wouldn't that be reg0x1f*exposure_time?
+  c = time needed for acceleration, table 1
+  d = time needed for reg 0x22... wouldn't that be reg0x22*exposure_time?
+  z1 = (c+d-1) % exposure_time
+  z2 = (a+b-1) % exposure_time
+*/
+/* i don't see any effect of this. i can only guess that this will enhance
+   sub-pixel accuracy
+   z1 = (slope_0_time-1) % exposure_time;
+   z2 = (slope_0_time-1) % exposure_time;
+*/
+    z1 = z2 = 0;
+
+    DBG(DBG_info, "%s: z1 = %d\n", __func__, z1);
+    DBG(DBG_info, "%s: z2 = %d\n", __func__, z2);
+    r = sanei_genesys_get_address (reg, 0x60);
+    r->value = ((z1 >> 16) & 0xff);
+    r = sanei_genesys_get_address (reg, 0x61);
+    r->value = ((z1 >> 8) & 0xff);
+    r = sanei_genesys_get_address (reg, 0x62);
+    r->value = (z1 & 0xff);
+    r = sanei_genesys_get_address (reg, 0x63);
+    r->value = ((z2 >> 16) & 0xff);
+    r = sanei_genesys_get_address (reg, 0x64);
+    r->value = ((z2 >> 8) & 0xff);
+    r = sanei_genesys_get_address (reg, 0x65);
+    r->value = (z2 & 0xff);
+
+    r = sanei_genesys_get_address (reg, REG1E);
+    r->value &= REG1E_WDTIME;
+    r->value |= scan_dummy;
+
+    r = sanei_genesys_get_address (reg, 0x67);
+    r->value = 0x3f | (scan_step_type << 6);
+
+    r = sanei_genesys_get_address (reg, 0x68);
+    r->value = 0x3f;
+
+    r = sanei_genesys_get_address (reg, REG_STEPNO);
+    r->value = (slow_slope_steps >> 1) + (slow_slope_steps & 1);
+
+    r = sanei_genesys_get_address (reg, REG_FASTNO);
+    r->value = (back_slope_steps >> 1) + (back_slope_steps & 1);
+
+    r = sanei_genesys_get_address (reg, 0x69);
+    r->value = (slow_slope_steps >> 1) + (slow_slope_steps & 1);
+
+    r = sanei_genesys_get_address (reg, 0x6a);
+    r->value = (fast_slope_steps >> 1) + (fast_slope_steps & 1);
+
+    r = sanei_genesys_get_address (reg, 0x5f);
+    r->value = (fast_slope_steps >> 1) + (fast_slope_steps & 1);
+
+
+    DBGCOMPLETED;
+    return SANE_STATUS_GOOD;
+}
+
+static int
+gl841_get_dpihw(Genesys_Device * dev)
+{
+  GenesysRegister* r;
+  r = sanei_genesys_get_address(&dev->reg, 0x05);
+  if ((r->value & REG05_DPIHW) == REG05_DPIHW_600)
+    return 600;
+  if ((r->value & REG05_DPIHW) == REG05_DPIHW_1200)
+    return 1200;
+  if ((r->value & REG05_DPIHW) == REG05_DPIHW_2400)
+    return 2400;
+  return 0;
+}
+
+static SANE_Status
+gl841_init_optical_regs_off(Genesys_Register_Set * reg)
+{
+    GenesysRegister* r;
+
+    DBGSTART;
+
+    r = sanei_genesys_get_address(reg, 0x01);
+    r->value &= ~REG01_SCAN;
+
+    DBGCOMPLETED;
+    return SANE_STATUS_GOOD;
+}
+
+static SANE_Status
+gl841_init_optical_regs_scan(Genesys_Device * dev,
+                             const Genesys_Sensor& sensor,
+			     Genesys_Register_Set * reg,
+			     unsigned int exposure_time,
+			     unsigned int used_res,
+			     unsigned int start,
+			     unsigned int pixels,
+			     int channels,
+			     int depth,
+			     SANE_Bool half_ccd,
+                             ColorFilter color_filter,
+			     int flags
+    )
+{
+    unsigned int words_per_line;
+    unsigned int end;
+    unsigned int dpiset;
+    GenesysRegister* r;
+    SANE_Status status = SANE_STATUS_GOOD;
+    uint16_t expavg, expr, expb, expg;
+
+    DBG(DBG_proc, "%s :  exposure_time=%d, used_res=%d, start=%d, pixels=%d, channels=%d, depth=%d, "
+        "half_ccd=%d, flags=%x\n", __func__,
+        exposure_time,
+        used_res,
+        start,
+        pixels,
+        channels,
+        depth,
+        half_ccd,
+        flags);
+
+    end = start + pixels;
+
+    status = gl841_set_fe(dev, sensor, AFE_SET);
+    if (status != SANE_STATUS_GOOD)
+    {
+        DBG(DBG_error, "%s: failed to set frontend: %s\n", __func__, sane_strstatus(status));
+	return status;
+    }
+
+    /* adjust used_res for chosen dpihw */
+    used_res = used_res * gl841_get_dpihw(dev) / sensor.optical_res;
+
+/*
+  with half_ccd the optical resolution of the ccd is halved. We don't apply this
+  to dpihw, so we need to double dpiset.
+
+  For the scanner only the ratio of dpiset and dpihw is of relevance to scale
+  down properly.
+*/
+    if (half_ccd)
+	dpiset = used_res * 2;
+    else
+	dpiset = used_res;
+
+    /* gpio part.*/
+    if (dev->model->gpo_type == GPO_CANONLIDE35)
+      {
+	r = sanei_genesys_get_address (reg, REG6C);
+	if (half_ccd)
+	  r->value &= ~0x80;
+	else
+	  r->value |= 0x80;
+      }
+    if (dev->model->gpo_type == GPO_CANONLIDE80)
+      {
+	r = sanei_genesys_get_address (reg, REG6C);
+	if (half_ccd)
+          {
+	    r->value &= ~0x40;
+	    r->value |= 0x20;
+          }
+	else
+          {
+	    r->value &= ~0x20;
+	    r->value |= 0x40;
+          }
+      }
+
+    /* enable shading */
+    r = sanei_genesys_get_address (reg, 0x01);
+    r->value |= REG01_SCAN;
+    if ((flags & OPTICAL_FLAG_DISABLE_SHADING) ||
+	(dev->model->flags & GENESYS_FLAG_NO_CALIBRATION))
+	r->value &= ~REG01_DVDSET;
+    else
+	r->value |= REG01_DVDSET;
+
+    /* average looks better than deletion, and we are already set up to
+       use  one of the average enabled resolutions
+    */
+    r = sanei_genesys_get_address (reg, 0x03);
+    r->value |= REG03_AVEENB;
+    sanei_genesys_set_lamp_power(dev, sensor, *reg, !(flags & OPTICAL_FLAG_DISABLE_LAMP));
+
+    /* BW threshold */
+    r = sanei_genesys_get_address (reg, 0x2e);
+    r->value = dev->settings.threshold;
+    r = sanei_genesys_get_address (reg, 0x2f);
+    r->value = dev->settings.threshold;
+
+
+    /* monochrome / color scan */
+    r = sanei_genesys_get_address (reg, 0x04);
+    switch (depth) {
+	case 1:
+	    r->value &= ~REG04_BITSET;
+	    r->value |= REG04_LINEART;
+	    break;
+	case 8:
+	    r->value &= ~(REG04_LINEART | REG04_BITSET);
+	    break;
+	case 16:
+	    r->value &= ~REG04_LINEART;
+	    r->value |= REG04_BITSET;
+	    break;
+    }
+
+    /* AFEMOD should depend on FESET, and we should set these
+     * bits separately */
+    r->value &= ~(REG04_FILTER | REG04_AFEMOD);
+    if (flags & OPTICAL_FLAG_ENABLE_LEDADD)
+      {
+	r->value |= 0x10;	/* no filter */
+      }
+    else if (channels == 1)
+      {
+	switch (color_filter)
+	  {
+            case ColorFilter::RED:
+                r->value |= 0x14;
+                break;
+            case ColorFilter::GREEN:
+                r->value |= 0x18;
+                break;
+            case ColorFilter::BLUE:
+                r->value |= 0x1c;
+                break;
+            default:
+                r->value |= 0x10;
+                break;
+	  }
+      }
+    else
+      {
+        if (dev->model->ccd_type == CCD_PLUSTEK_3600)
+          {
+            r->value |= 0x22;	/* slow color pixel by pixel */
+          }
+	else
+          {
+	    r->value |= 0x10;	/* color pixel by pixel */
+          }
+      }
+
+    /* CIS scanners can do true gray by setting LEDADD */
+    r = sanei_genesys_get_address (reg, 0x87);
+    r->value &= ~REG87_LEDADD;
+    if (flags & OPTICAL_FLAG_ENABLE_LEDADD)
+      {
+        r->value |= REG87_LEDADD;
+	sanei_genesys_get_double (reg, REG_EXPR, &expr);
+	sanei_genesys_get_double (reg, REG_EXPG, &expg);
+	sanei_genesys_get_double (reg, REG_EXPB, &expb);
+
+	/* use minimal exposure for best image quality */
+	expavg = expg;
+	if (expr < expg)
+	  expavg = expr;
+	if (expb < expavg)
+	  expavg = expb;
+
+        sanei_genesys_set_double(&dev->reg, REG_EXPR, expavg);
+        sanei_genesys_set_double(&dev->reg, REG_EXPG, expavg);
+        sanei_genesys_set_double(&dev->reg, REG_EXPB, expavg);
+      }
+
+    /* enable gamma tables */
+    r = sanei_genesys_get_address (reg, 0x05);
+    if (flags & OPTICAL_FLAG_DISABLE_GAMMA)
+	r->value &= ~REG05_GMMENB;
+    else
+	r->value |= REG05_GMMENB;
+
+    /* sensor parameters */
+    sanei_gl841_setup_sensor(dev, sensor, &dev->reg, 1, half_ccd);
+
+    r = sanei_genesys_get_address (reg, 0x29);
+    r->value = 255; /*<<<"magic" number, only suitable for cis*/
+
+    sanei_genesys_set_double(reg, REG_DPISET, dpiset);
+    sanei_genesys_set_double(reg, REG_STRPIXEL, start);
+    sanei_genesys_set_double(reg, REG_ENDPIXEL, end);
+    DBG(DBG_io2, "%s: STRPIXEL=%d, ENDPIXEL=%d\n", __func__, start, end);
+
+    /* words(16bit) before gamma, conversion to 8 bit or lineart*/
+    words_per_line = (pixels * dpiset) / gl841_get_dpihw(dev);
+
+    words_per_line *= channels;
+
+    if (depth == 1)
+	words_per_line = (words_per_line >> 3) + ((words_per_line & 7)?1:0);
+    else
+	words_per_line *= depth / 8;
+
+    dev->wpl = words_per_line;
+    dev->bpl = words_per_line;
+
+    r = sanei_genesys_get_address (reg, 0x35);
+    r->value = LOBYTE (HIWORD (words_per_line));
+    r = sanei_genesys_get_address (reg, 0x36);
+    r->value = HIBYTE (LOWORD (words_per_line));
+    r = sanei_genesys_get_address (reg, 0x37);
+    r->value = LOBYTE (LOWORD (words_per_line));
+
+    sanei_genesys_set_double(reg, REG_LPERIOD, exposure_time);
+
+    r = sanei_genesys_get_address (reg, 0x34);
+    r->value = sensor.dummy_pixel;
+
+    DBGCOMPLETED;
+    return SANE_STATUS_GOOD;
+}
+
+static int
+gl841_get_led_exposure(Genesys_Device * dev, const Genesys_Sensor& sensor)
+{
+    int d,r,g,b,m;
+    if (!dev->model->is_cis)
+	return 0;
+    d = dev->reg.find_reg(0x19).value;
+
+    r = sensor.exposure.red;
+    g = sensor.exposure.green;
+    b = sensor.exposure.blue;
+
+    m = r;
+    if (m < g)
+	m = g;
+    if (m < b)
+	m = b;
+
+    return m + d;
+}
+
+/** @brief compute exposure time
+ * Compute exposure time for the device and the given scan resolution,
+ * also compute scan_power_mode
+ */
+static int
+gl841_exposure_time(Genesys_Device *dev, const Genesys_Sensor& sensor,
+                    float slope_dpi,
+                    int scan_step_type,
+                    int start,
+                    int used_pixels,
+                    int *scan_power_mode)
+{
+int exposure_time = 0;
+int exposure_time2 = 0;
+int led_exposure;
+
+  *scan_power_mode=0;
+  led_exposure=gl841_get_led_exposure(dev, sensor);
+  exposure_time = sanei_genesys_exposure_time2(
+      dev,
+      slope_dpi,
+      scan_step_type,
+      start+used_pixels,/*+tgtime? currently done in sanei_genesys_exposure_time2 with tgtime = 32 pixel*/
+      led_exposure,
+      *scan_power_mode);
+
+  while(*scan_power_mode + 1 < dev->motor.power_mode_count) {
+      exposure_time2 = sanei_genesys_exposure_time2(
+	  dev,
+	  slope_dpi,
+	  scan_step_type,
+	  start+used_pixels,/*+tgtime? currently done in sanei_genesys_exposure_time2 with tgtime = 32 pixel*/
+	  led_exposure,
+	  *scan_power_mode + 1);
+      if (exposure_time < exposure_time2)
+	  break;
+      exposure_time = exposure_time2;
+      (*scan_power_mode)++;
+  }
+
+  return exposure_time;
+}
+
+/**@brief compute scan_step_type
+ * Try to do at least 4 steps per line. if that is impossible we will have to
+ * live with that.
+ * @param dev device
+ * @param yres motor resolution
+ */
+static int
+gl841_scan_step_type(Genesys_Device *dev, int yres)
+{
+int scan_step_type=0;
+
+  /* TODO : check if there is a bug around the use of max_step_type   */
+  /* should be <=1, need to chek all devices entry in genesys_devices */
+  if (yres*4 < dev->motor.base_ydpi || dev->motor.max_step_type <= 0)
+    {
+      scan_step_type = 0;
+    }
+  else if (yres*4 < dev->motor.base_ydpi*2 || dev->motor.max_step_type <= 1)
+    {
+      scan_step_type = 1;
+    }
+  else
+    {
+      scan_step_type = 2;
+    }
+
+  /* this motor behaves differently */
+  if (dev->model->motor_type==MOTOR_CANONLIDE80)
+    {
+      /* driven by 'frequency' tables ? */
+      scan_step_type = 0;
+    }
+
+  return scan_step_type;
+}
+
+/* set up registers for an actual scan
+ *
+ * this function sets up the scanner to scan in normal or single line mode
+ */
+static
+SANE_Status
+gl841_init_scan_regs(Genesys_Device * dev, const Genesys_Sensor& sensor, Genesys_Register_Set * reg,
+                     SetupParams& params)
+{
+    params.assert_valid();
+
+  int used_res;
+  int start, used_pixels;
+  int bytes_per_line;
+  int move;
+  unsigned int lincnt;
+  int exposure_time;
+  int scan_power_mode;
+  int i;
+  int stagger;
+  int avg;
+
+  int slope_dpi = 0;
+  int dummy = 0;
+  int scan_step_type = 1;
+  int max_shift;
+  size_t requested_buffer_size, read_buffer_size;
+
+  SANE_Bool half_ccd;		/* false: full CCD res is used, true, half max CCD res is used */
+  int optical_res;
+  SANE_Status status = SANE_STATUS_GOOD;
+  unsigned int oflags;          /**> optical flags */
+
+    DBG(DBG_info, "%s ", __func__);
+    debug_dump(DBG_info, params);
+
+/*
+results:
+
+for scanner:
+half_ccd
+start
+end
+dpiset
+exposure_time
+dummy
+z1
+z2
+
+for ordered_read:
+  dev->words_per_line
+  dev->read_factor
+  dev->requested_buffer_size
+  dev->read_buffer_size
+  dev->read_pos
+  dev->read_bytes_in_buffer
+  dev->read_bytes_left
+  dev->max_shift
+  dev->stagger
+
+independent of our calculated values:
+  dev->total_bytes_read
+  dev->bytes_to_read
+ */
+
+/* half_ccd */
+  /* we have 2 domains for ccd: xres below or above half ccd max dpi */
+  if (sensor.get_ccd_size_divisor_for_dpi(params.xres) > 1) {
+      half_ccd = SANE_TRUE;
+  } else {
+      half_ccd = SANE_FALSE;
+  }
+
+/* optical_res */
+
+  optical_res = sensor.optical_res;
+  if (half_ccd)
+      optical_res /= 2;
+
+/* stagger */
+
+  if ((!half_ccd) && (dev->model->flags & GENESYS_FLAG_STAGGERED_LINE))
+    stagger = (4 * params.yres) / dev->motor.base_ydpi;
+  else
+    stagger = 0;
+  DBG(DBG_info, "%s : stagger=%d lines\n", __func__, stagger);
+
+/* used_res */
+  i = optical_res / params.xres;
+
+/* gl841 supports 1/1 1/2 1/3 1/4 1/5 1/6 1/8 1/10 1/12 1/15 averaging */
+
+  if (i < 2 || (params.flags & SCAN_FLAG_USE_OPTICAL_RES)) /* optical_res >= xres > optical_res/2 */
+      used_res = optical_res;
+  else if (i < 3)  /* optical_res/2 >= xres > optical_res/3 */
+      used_res = optical_res/2;
+  else if (i < 4)  /* optical_res/3 >= xres > optical_res/4 */
+      used_res = optical_res/3;
+  else if (i < 5)  /* optical_res/4 >= xres > optical_res/5 */
+      used_res = optical_res/4;
+  else if (i < 6)  /* optical_res/5 >= xres > optical_res/6 */
+      used_res = optical_res/5;
+  else if (i < 8)  /* optical_res/6 >= xres > optical_res/8 */
+      used_res = optical_res/6;
+  else if (i < 10)  /* optical_res/8 >= xres > optical_res/10 */
+      used_res = optical_res/8;
+  else if (i < 12)  /* optical_res/10 >= xres > optical_res/12 */
+      used_res = optical_res/10;
+  else if (i < 15)  /* optical_res/12 >= xres > optical_res/15 */
+      used_res = optical_res/12;
+  else
+      used_res = optical_res/15;
+
+  /* compute scan parameters values */
+  /* pixels are allways given at half or full CCD optical resolution */
+  /* use detected left margin  and fixed value */
+  /* start */
+  /* add x coordinates */
+  start = ((sensor.CCD_start_xoffset + params.startx) * used_res) / sensor.optical_res;
+
+  /* needs to be aligned for used_res */
+  start = (start * optical_res) / used_res;
+
+  start += sensor.dummy_pixel + 1;
+
+  if (stagger > 0)
+    start |= 1;
+
+  /* in case of SHDAREA, we need to align start
+   * on pixel average factor, startx is different of
+   * 0 only when calling for function to setup for
+   * scan, where shading data needs to be align */
+  if((dev->reg.find_reg(0x01).value & REG01_SHDAREA) != 0)
+    {
+      avg=optical_res/used_res;
+      start=(start/avg)*avg;
+    }
+
+  /* compute correct pixels number */
+  /* pixels */
+  used_pixels = (params.pixels * optical_res) / params.xres;
+
+  /* round up pixels number if needed */
+  if (used_pixels * params.xres < params.pixels * optical_res)
+      used_pixels++;
+
+/* dummy */
+  /* dummy lines: may not be usefull, for instance 250 dpi works with 0 or 1
+     dummy line. Maybe the dummy line adds correctness since the motor runs
+     slower (higher dpi)
+  */
+/* for cis this creates better aligned color lines:
+dummy \ scanned lines
+   0: R           G           B           R ...
+   1: R        G        B        -        R ...
+   2: R      G      B       -      -      R ...
+   3: R     G     B     -     -     -     R ...
+   4: R    G    B     -   -     -    -    R ...
+   5: R    G   B    -   -   -    -   -    R ...
+   6: R   G   B   -   -   -   -   -   -   R ...
+   7: R   G  B   -  -   -   -  -   -  -   R ...
+   8: R  G  B   -  -  -   -  -  -   -  -  R ...
+   9: R  G  B  -  -  -  -  -  -  -  -  -  R ...
+  10: R  G B  -  -  -  - -  -  -  -  - -  R ...
+  11: R  G B  - -  - -  -  - -  - -  - -  R ...
+  12: R G  B - -  - -  - -  - -  - - -  - R ...
+  13: R G B  - - - -  - - -  - - - -  - - R ...
+  14: R G B - - -  - - - - - -  - - - - - R ...
+  15: R G B - - - - - - - - - - - - - - - R ...
+ -- pierre
+ */
+  dummy = 0;
+
+/* slope_dpi */
+/* cis color scan is effectively a gray scan with 3 gray lines per color
+   line and a FILTER of 0 */
+  if (dev->model->is_cis)
+      slope_dpi = params.yres* params.channels;
+  else
+      slope_dpi = params.yres;
+
+  slope_dpi = slope_dpi * (1 + dummy);
+
+  scan_step_type = gl841_scan_step_type(dev, params.yres);
+  exposure_time = gl841_exposure_time(dev, sensor,
+                    slope_dpi,
+                    scan_step_type,
+                    start,
+                    used_pixels,
+                    &scan_power_mode);
+  DBG(DBG_info, "%s : exposure_time=%d pixels\n", __func__, exposure_time);
+
+  /*** optical parameters ***/
+  /* in case of dynamic lineart, we use an internal 8 bit gray scan
+   * to generate 1 lineart data */
+  if(params.flags & SCAN_FLAG_DYNAMIC_LINEART)
+    {
+      params.depth=8;
+    }
+
+  oflags=0;
+  if (params.flags & SCAN_FLAG_DISABLE_SHADING)
+    {
+      oflags |= OPTICAL_FLAG_DISABLE_SHADING;
+    }
+  if ((params.flags & SCAN_FLAG_DISABLE_GAMMA) || (params.depth==16))
+    {
+      oflags |= OPTICAL_FLAG_DISABLE_GAMMA;
+    }
+  if (params.flags & SCAN_FLAG_DISABLE_LAMP)
+    {
+      oflags |= OPTICAL_FLAG_DISABLE_LAMP;
+    }
+  if (params.flags & SCAN_FLAG_ENABLE_LEDADD)
+    {
+      oflags |= OPTICAL_FLAG_ENABLE_LEDADD;
+    }
+
+  status = gl841_init_optical_regs_scan(dev, sensor,
+					reg,
+					exposure_time,
+					used_res,
+					start,
+					used_pixels,
+                                         params.channels,
+                                        params.depth,
+					half_ccd,
+                                        params.color_filter,
+                                        oflags);
+  if (status != SANE_STATUS_GOOD)
+    {
+      return status;
+    }
+
+/*** motor parameters ***/
+
+  /* scanned area must be enlarged by max color shift needed */
+  max_shift=sanei_genesys_compute_max_shift(dev, params.channels,params.yres,params.flags);
+
+  /* lincnt */
+  lincnt = params.lines + max_shift + stagger;
+
+  /* add tl_y to base movement */
+  move = params.starty;
+  DBG(DBG_info, "%s: move=%d steps\n", __func__, move);
+
+  /* subtract current head position */
+  move -= dev->scanhead_position_in_steps;
+  DBG(DBG_info, "%s: move=%d steps\n", __func__, move);
+
+  if (move < 0)
+      move = 0;
+
+  /* round it */
+/* the move is not affected by dummy -- pierre */
+/*  move = ((move + dummy) / (dummy + 1)) * (dummy + 1);
+    DBG(DBG_info, "%s: move=%d steps\n", __func__, move);*/
+
+  if (params.flags & SCAN_FLAG_SINGLE_LINE)
+      status = gl841_init_motor_regs_off(reg, dev->model->is_cis?lincnt* params.channels:lincnt);
+  else
+      status = gl841_init_motor_regs_scan(dev, sensor,
+					  reg,
+					  exposure_time,
+					  slope_dpi,
+					  scan_step_type,
+                                          dev->model->is_cis?lincnt* params.channels:lincnt,
+					  dummy,
+					  move,
+					  scan_power_mode,
+                                          (params.flags & SCAN_FLAG_DISABLE_BUFFER_FULL_MOVE)?
+					  MOTOR_FLAG_DISABLE_BUFFER_FULL_MOVE:0
+	  );
+
+  if (status != SANE_STATUS_GOOD)
+      return status;
+
+
+  /*** prepares data reordering ***/
+
+/* words_per_line */
+  bytes_per_line = (used_pixels * used_res) / optical_res;
+  bytes_per_line = (bytes_per_line *  params.channels * params.depth) / 8;
+
+  requested_buffer_size = 8 * bytes_per_line;
+  /* we must use a round number of bytes_per_line */
+  if (requested_buffer_size > sanei_genesys_get_bulk_max_size(dev))
+    requested_buffer_size =
+      (sanei_genesys_get_bulk_max_size(dev) / bytes_per_line) * bytes_per_line;
+
+  read_buffer_size =
+    2 * requested_buffer_size +
+    ((max_shift + stagger) * used_pixels *  params.channels * params.depth) / 8;
+
+    dev->read_buffer.clear();
+    dev->read_buffer.alloc(read_buffer_size);
+
+    dev->lines_buffer.clear();
+    dev->lines_buffer.alloc(read_buffer_size);
+
+    dev->shrink_buffer.clear();
+    dev->shrink_buffer.alloc(requested_buffer_size);
+
+    dev->out_buffer.clear();
+    dev->out_buffer.alloc((8 * dev->settings.pixels *  params.channels * params.depth) / 8);
+
+  dev->read_bytes_left = bytes_per_line * lincnt;
+
+  DBG(DBG_info, "%s: physical bytes to read = %lu\n", __func__, (u_long) dev->read_bytes_left);
+  dev->read_active = SANE_TRUE;
+
+  dev->current_setup.params = params;
+  dev->current_setup.pixels = (used_pixels * used_res)/optical_res;
+  dev->current_setup.lines = lincnt;
+  dev->current_setup.depth = params.depth;
+  dev->current_setup.channels =  params.channels;
+  dev->current_setup.exposure_time = exposure_time;
+  dev->current_setup.xres = used_res;
+  dev->current_setup.yres = params.yres;
+  dev->current_setup.ccd_size_divisor = half_ccd ? 2 : 1;
+  dev->current_setup.stagger = stagger;
+  dev->current_setup.max_shift = max_shift + stagger;
+
+/* TODO: should this be done elsewhere? */
+  /* scan bytes to send to the frontend */
+  /* theory :
+     target_size =
+     (dev->settings.pixels * dev->settings.lines * channels * depth) / 8;
+     but it suffers from integer overflow so we do the following:
+
+     1 bit color images store color data byte-wise, eg byte 0 contains
+     8 bits of red data, byte 1 contains 8 bits of green, byte 2 contains
+     8 bits of blue.
+     This does not fix the overflow, though.
+     644mp*16 = 10gp, leading to an overflow
+   -- pierre
+   */
+
+  dev->total_bytes_read = 0;
+  if (params.depth == 1)
+      dev->total_bytes_to_read =
+	  ((dev->settings.pixels * dev->settings.lines) / 8 +
+	   (((dev->settings.pixels * dev->settings.lines)%8)?1:0)
+              ) *  params.channels;
+  else
+      dev->total_bytes_to_read =
+          dev->settings.pixels * dev->settings.lines *  params.channels * (params.depth / 8);
+
+  DBG(DBG_info, "%s: total bytes to send = %lu\n", __func__, (u_long) dev->total_bytes_to_read);
+/* END TODO */
+
+  DBG(DBG_proc, "%s: completed\n", __func__);
+  return SANE_STATUS_GOOD;
+}
+
+static void gl841_calculate_current_setup(Genesys_Device * dev, const Genesys_Sensor& sensor)
+{
+  int channels;
+  int depth;
+  int start;
+
+  int used_res;
+  int used_pixels;
+  unsigned int lincnt;
+  int exposure_time;
+  int scan_power_mode;
+  int i;
+  int stagger;
+
+  int slope_dpi = 0;
+  int dummy = 0;
+  int scan_step_type = 1;
+  int max_shift;
+
+  SANE_Bool half_ccd;		/* false: full CCD res is used, true, half max CCD res is used */
+  int optical_res;
+
+    DBG(DBG_info, "%s ", __func__);
+    debug_dump(DBG_info, dev->settings);
+
+/* channels */
+  if (dev->settings.scan_mode == ScanColorMode::COLOR_SINGLE_PASS)
+    channels = 3;
+  else
+    channels = 1;
+
+/* depth */
+  depth = dev->settings.depth;
+  if (dev->settings.scan_mode == ScanColorMode::LINEART)
+      depth = 1;
+
+/* start */
+  start = SANE_UNFIX (dev->model->x_offset);
+
+  start += dev->settings.tl_x;
+
+  start = (start * sensor.optical_res) / MM_PER_INCH;
+
+    SetupParams params;
+    params.xres = dev->settings.xres;
+    params.yres = dev->settings.yres;
+    params.startx = start;
+    params.starty = 0; // not used
+    params.pixels = dev->settings.pixels;
+    params.lines = dev->settings.lines;
+    params.depth = depth;
+    params.channels = channels;
+    params.scan_method = dev->settings.scan_method;
+    params.scan_mode = dev->settings.scan_mode;
+    params.color_filter = dev->settings.color_filter;
+    params.flags = 0;
+
+    DBG(DBG_info, "%s ", __func__);
+    debug_dump(DBG_info, params);
+
+/* half_ccd */
+  /* we have 2 domains for ccd: xres below or above half ccd max dpi */
+  if (sensor.get_ccd_size_divisor_for_dpi(params.xres) > 1) {
+      half_ccd = SANE_TRUE;
+  } else {
+      half_ccd = SANE_FALSE;
+  }
+
+/* optical_res */
+
+  optical_res = sensor.optical_res;
+  if (half_ccd)
+      optical_res /= 2;
+
+/* stagger */
+
+  if ((!half_ccd) && (dev->model->flags & GENESYS_FLAG_STAGGERED_LINE))
+    stagger = (4 * params.yres) / dev->motor.base_ydpi;
+  else
+    stagger = 0;
+  DBG(DBG_info, "%s: stagger=%d lines\n", __func__, stagger);
+
+/* used_res */
+  i = optical_res / params.xres;
+
+/* gl841 supports 1/1 1/2 1/3 1/4 1/5 1/6 1/8 1/10 1/12 1/15 averaging */
+
+  if (i < 2) /* optical_res >= xres > optical_res/2 */
+      used_res = optical_res;
+  else if (i < 3)  /* optical_res/2 >= xres > optical_res/3 */
+      used_res = optical_res/2;
+  else if (i < 4)  /* optical_res/3 >= xres > optical_res/4 */
+      used_res = optical_res/3;
+  else if (i < 5)  /* optical_res/4 >= xres > optical_res/5 */
+      used_res = optical_res/4;
+  else if (i < 6)  /* optical_res/5 >= xres > optical_res/6 */
+      used_res = optical_res/5;
+  else if (i < 8)  /* optical_res/6 >= xres > optical_res/8 */
+      used_res = optical_res/6;
+  else if (i < 10)  /* optical_res/8 >= xres > optical_res/10 */
+      used_res = optical_res/8;
+  else if (i < 12)  /* optical_res/10 >= xres > optical_res/12 */
+      used_res = optical_res/10;
+  else if (i < 15)  /* optical_res/12 >= xres > optical_res/15 */
+      used_res = optical_res/12;
+  else
+      used_res = optical_res/15;
+
+  /* compute scan parameters values */
+  /* pixels are allways given at half or full CCD optical resolution */
+  /* use detected left margin  and fixed value */
+    start = ((sensor.CCD_start_xoffset + params.startx) * used_res) / sensor.optical_res;
+
+/* needs to be aligned for used_res */
+  start = (start * optical_res) / used_res;
+
+  start += sensor.dummy_pixel + 1;
+
+  if (stagger > 0) {
+    start |= 1;
+  }
+
+    used_pixels = (params.pixels * optical_res) / params.xres;
+
+    // round up pixels number if needed
+    if (used_pixels * params.xres < params.pixels * optical_res) {
+        used_pixels++;
+    }
+
+  /* dummy lines: may not be usefull, for instance 250 dpi works with 0 or 1
+     dummy line. Maybe the dummy line adds correctness since the motor runs
+     slower (higher dpi)
+  */
+/* for cis this creates better aligned color lines:
+dummy \ scanned lines
+   0: R           G           B           R ...
+   1: R        G        B        -        R ...
+   2: R      G      B       -      -      R ...
+   3: R     G     B     -     -     -     R ...
+   4: R    G    B     -   -     -    -    R ...
+   5: R    G   B    -   -   -    -   -    R ...
+   6: R   G   B   -   -   -   -   -   -   R ...
+   7: R   G  B   -  -   -   -  -   -  -   R ...
+   8: R  G  B   -  -  -   -  -  -   -  -  R ...
+   9: R  G  B  -  -  -  -  -  -  -  -  -  R ...
+  10: R  G B  -  -  -  - -  -  -  -  - -  R ...
+  11: R  G B  - -  - -  -  - -  - -  - -  R ...
+  12: R G  B - -  - -  - -  - -  - - -  - R ...
+  13: R G B  - - - -  - - -  - - - -  - - R ...
+  14: R G B - - -  - - - - - -  - - - - - R ...
+  15: R G B - - - - - - - - - - - - - - - R ...
+ -- pierre
+ */
+  dummy = 0;
+
+/* cis color scan is effectively a gray scan with 3 gray lines per color
+   line and a FILTER of 0 */
+    if (dev->model->is_cis) {
+        slope_dpi = params.yres * params.channels;
+    } else {
+        slope_dpi = params.yres;
+    }
+
+  slope_dpi = slope_dpi * (1 + dummy);
+
+  scan_step_type = gl841_scan_step_type(dev, params.yres);
+  exposure_time = gl841_exposure_time(dev, sensor,
+                    slope_dpi,
+                    scan_step_type,
+                    start,
+                    used_pixels,
+                    &scan_power_mode);
+  DBG(DBG_info, "%s : exposure_time=%d pixels\n", __func__, exposure_time);
+
+  /* scanned area must be enlarged by max color shift needed */
+    max_shift = sanei_genesys_compute_max_shift(dev, params.channels, params.yres, 0);
+
+    lincnt = params.lines + max_shift + stagger;
+
+  dev->current_setup.params = params;
+  dev->current_setup.pixels = (used_pixels * used_res)/optical_res;
+  dev->current_setup.lines = lincnt;
+  dev->current_setup.depth = params.depth;
+  dev->current_setup.channels = params.channels;
+  dev->current_setup.exposure_time = exposure_time;
+  dev->current_setup.xres = used_res;
+  dev->current_setup.yres = params.yres;
+  dev->current_setup.ccd_size_divisor = half_ccd ? 2 : 1;
+  dev->current_setup.stagger = stagger;
+  dev->current_setup.max_shift = max_shift + stagger;
+
+  DBGCOMPLETED;
+}
+
+/*for fast power saving methods only, like disabling certain amplifiers*/
+static SANE_Status gl841_save_power(Genesys_Device * dev, SANE_Bool enable)
+{
+    uint8_t val;
+
+    const auto& sensor = sanei_genesys_find_sensor_any(dev);
+
+    DBG(DBG_proc, "%s: enable = %d\n", __func__, enable);
+
+    if (enable)
+    {
+	if (dev->model->gpo_type == GPO_CANONLIDE35)
+	{
+/* expect GPIO17 to be enabled, and GPIO9 to be disabled,
+   while GPIO8 is disabled*/
+/* final state: GPIO8 disabled, GPIO9 enabled, GPIO17 disabled,
+   GPIO18 disabled*/
+
+	    sanei_genesys_read_register(dev, REG6D, &val);
+	    sanei_genesys_write_register(dev, REG6D, val | 0x80);
+
+            sanei_genesys_sleep_ms(1);
+
+	    /*enable GPIO9*/
+	    sanei_genesys_read_register(dev, REG6C, &val);
+	    sanei_genesys_write_register(dev, REG6C, val | 0x01);
+
+	    /*disable GPO17*/
+	    sanei_genesys_read_register(dev, REG6B, &val);
+	    sanei_genesys_write_register(dev, REG6B, val & ~REG6B_GPO17);
+
+	    /*disable GPO18*/
+	    sanei_genesys_read_register(dev, REG6B, &val);
+	    sanei_genesys_write_register(dev, REG6B, val & ~REG6B_GPO18);
+
+            sanei_genesys_sleep_ms(1);
+
+	    sanei_genesys_read_register(dev, REG6D, &val);
+	    sanei_genesys_write_register(dev, REG6D, val & ~0x80);
+
+	}
+	if (dev->model->gpo_type == GPO_DP685)
+	  {
+	    sanei_genesys_read_register(dev, REG6B, &val);
+	    sanei_genesys_write_register(dev, REG6B, val & ~REG6B_GPO17);
+            dev->reg.find_reg(0x6b).value &= ~REG6B_GPO17;
+            dev->calib_reg.find_reg(0x6b).value &= ~REG6B_GPO17;
+	  }
+
+        gl841_set_fe(dev, sensor, AFE_POWER_SAVE);
+
+    }
+    else
+    {
+	if (dev->model->gpo_type == GPO_CANONLIDE35)
+	{
+/* expect GPIO17 to be enabled, and GPIO9 to be disabled,
+   while GPIO8 is disabled*/
+/* final state: GPIO8 enabled, GPIO9 disabled, GPIO17 enabled,
+   GPIO18 enabled*/
+
+	    sanei_genesys_read_register(dev, REG6D, &val);
+	    sanei_genesys_write_register(dev, REG6D, val | 0x80);
+
+            sanei_genesys_sleep_ms(10);
+
+	    /*disable GPIO9*/
+	    sanei_genesys_read_register(dev, REG6C, &val);
+	    sanei_genesys_write_register(dev, REG6C, val & ~0x01);
+
+	    /*enable GPIO10*/
+	    sanei_genesys_read_register(dev, REG6C, &val);
+	    sanei_genesys_write_register(dev, REG6C, val | 0x02);
+
+	    /*enable GPO17*/
+	    sanei_genesys_read_register(dev, REG6B, &val);
+	    sanei_genesys_write_register(dev, REG6B, val | REG6B_GPO17);
+            dev->reg.find_reg(0x6b).value |= REG6B_GPO17;
+            dev->calib_reg.find_reg(0x6b).value |= REG6B_GPO17;
+
+	    /*enable GPO18*/
+	    sanei_genesys_read_register(dev, REG6B, &val);
+	    sanei_genesys_write_register(dev, REG6B, val | REG6B_GPO18);
+            dev->reg.find_reg(0x6b).value |= REG6B_GPO18;
+            dev->calib_reg.find_reg(0x6b).value |= REG6B_GPO18;
+
+	}
+	if (dev->model->gpo_type == GPO_DP665
+            || dev->model->gpo_type == GPO_DP685)
+	  {
+	    sanei_genesys_read_register(dev, REG6B, &val);
+	    sanei_genesys_write_register(dev, REG6B, val | REG6B_GPO17);
+            dev->reg.find_reg(0x6b).value |= REG6B_GPO17;
+            dev->calib_reg.find_reg(0x6b).value |= REG6B_GPO17;
+	  }
+
+    }
+
+    return SANE_STATUS_GOOD;
+}
+
+static SANE_Status
+gl841_set_powersaving (Genesys_Device * dev,
+			     int delay /* in minutes */ )
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+  // FIXME: SEQUENTIAL not really needed in this case
+  Genesys_Register_Set local_reg(Genesys_Register_Set::SEQUENTIAL);
+  int rate, exposure_time, tgtime, time;
+
+  DBG(DBG_proc, "%s (delay = %d)\n", __func__, delay);
+
+    local_reg.init_reg(0x01, dev->reg.get8(0x01));	/* disable fastmode */
+    local_reg.init_reg(0x03, dev->reg.get8(0x03));	/* Lamp power control */
+    local_reg.init_reg(0x05, dev->reg.get8(0x05)); /*& ~REG05_BASESEL*/;	/* 24 clocks/pixel */
+    local_reg.init_reg(0x18, 0x00); // Set CCD type
+    local_reg.init_reg(0x38, 0x00);
+    local_reg.init_reg(0x39, 0x00);
+
+    // period times for LPeriod, expR,expG,expB, Z1MODE, Z2MODE
+    local_reg.init_reg(0x1c, dev->reg.get8(0x05) & ~REG1C_TGTIME);
+
+    if (!delay) {
+        local_reg.find_reg(0x03).value = local_reg.find_reg(0x03).value & 0xf0;	/* disable lampdog and set lamptime = 0 */
+    } else if (delay < 20) {
+        local_reg.find_reg(0x03).value = (local_reg.find_reg(0x03).value & 0xf0) | 0x09;	/* enable lampdog and set lamptime = 1 */
+    } else {
+        local_reg.find_reg(0x03).value = (local_reg.find_reg(0x03).value & 0xf0) | 0x0f;	/* enable lampdog and set lamptime = 7 */
+    }
+
+  time = delay * 1000 * 60;	/* -> msec */
+  exposure_time =
+    (uint32_t) (time * 32000.0 /
+                 (24.0 * 64.0 * (local_reg.find_reg(0x03).value & REG03_LAMPTIM) *
+		  1024.0) + 0.5);
+  /* 32000 = system clock, 24 = clocks per pixel */
+  rate = (exposure_time + 65536) / 65536;
+  if (rate > 4)
+    {
+      rate = 8;
+      tgtime = 3;
+    }
+  else if (rate > 2)
+    {
+      rate = 4;
+      tgtime = 2;
+    }
+  else if (rate > 1)
+    {
+      rate = 2;
+      tgtime = 1;
+    }
+  else
+    {
+      rate = 1;
+      tgtime = 0;
+    }
+
+  local_reg.find_reg(0x1c).value |= tgtime;
+  exposure_time /= rate;
+
+  if (exposure_time > 65535)
+    exposure_time = 65535;
+
+  local_reg.set8(0x38, exposure_time >> 8);
+  local_reg.set8(0x39, exposure_time & 255);	/* lowbyte */
+
+  status = sanei_genesys_bulk_write_register(dev, local_reg);
+  if (status != SANE_STATUS_GOOD)
+    DBG(DBG_error, "%s: failed to bulk write registers: %s\n", __func__, sane_strstatus(status));
+
+  DBG(DBG_proc, "%s: completed\n", __func__);
+  return status;
+}
+
+static SANE_Status
+gl841_start_action (Genesys_Device * dev)
+{
+  return sanei_genesys_write_register (dev, 0x0f, 0x01);
+}
+
+static SANE_Status
+gl841_stop_action (Genesys_Device * dev)
+{
+  Genesys_Register_Set local_reg;
+  SANE_Status status = SANE_STATUS_GOOD;
+  uint8_t val40, val;
+  unsigned int loop;
+
+  DBG(DBG_proc, "%s\n", __func__);
+
+  status = sanei_genesys_get_status (dev, &val);
+  if (DBG_LEVEL >= DBG_io)
+    {
+      sanei_genesys_print_status (val);
+    }
+
+  status = sanei_genesys_read_register(dev, 0x40, &val40);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to read home sensor: %s\n", __func__, sane_strstatus(status));
+      DBGCOMPLETED;
+      return status;
+    }
+
+  /* only stop action if needed */
+  if (!(val40 & REG40_DATAENB) && !(val40 & REG40_MOTMFLG))
+    {
+      DBG(DBG_info, "%s: already stopped\n", __func__);
+      DBGCOMPLETED;
+      return SANE_STATUS_GOOD;
+    }
+
+  local_reg = dev->reg;
+
+  gl841_init_optical_regs_off(&local_reg);
+
+  gl841_init_motor_regs_off(&local_reg,0);
+  status = sanei_genesys_bulk_write_register(dev, local_reg);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to bulk write registers: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  /* looks like writing the right registers to zero is enough to get the chip
+     out of scan mode into command mode, actually triggering(writing to
+     register 0x0f) seems to be unnecessary */
+
+  loop = 10;
+  while (loop > 0)
+    {
+      status = sanei_genesys_read_register(dev, 0x40, &val40);
+      if (DBG_LEVEL >= DBG_io)
+	{
+	  sanei_genesys_print_status (val);
+        }
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: failed to read home sensor: %s\n", __func__, sane_strstatus(status));
+	  DBGCOMPLETED;
+	  return status;
+	}
+
+      /* if scanner is in command mode, we are done */
+      if (!(val40 & REG40_DATAENB) && !(val40 & REG40_MOTMFLG))
+	{
+	  DBGCOMPLETED;
+	  return SANE_STATUS_GOOD;
+	}
+
+      sanei_genesys_sleep_ms(100);
+      loop--;
+    }
+
+  DBGCOMPLETED;
+  return SANE_STATUS_IO_ERROR;
+}
+
+static SANE_Status
+gl841_get_paper_sensor(Genesys_Device * dev, SANE_Bool * paper_loaded)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+  uint8_t val;
+
+  status = sanei_genesys_read_register(dev, REG6D, &val);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to read gpio: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+  *paper_loaded = (val & 0x1) == 0;
+  return SANE_STATUS_GOOD;
+}
+
+static SANE_Status
+gl841_eject_document (Genesys_Device * dev)
+{
+  Genesys_Register_Set local_reg;
+  SANE_Status status = SANE_STATUS_GOOD;
+  uint8_t val;
+  SANE_Bool paper_loaded;
+  unsigned int init_steps;
+  float feed_mm;
+  int loop;
+
+  DBG(DBG_proc, "%s\n", __func__);
+
+  if (dev->model->is_sheetfed == SANE_FALSE)
+    {
+      DBG(DBG_proc, "%s: there is no \"eject sheet\"-concept for non sheet fed\n", __func__);
+      DBG(DBG_proc, "%s: finished\n", __func__);
+      return SANE_STATUS_GOOD;
+    }
+
+
+  local_reg.clear();
+  val = 0;
+
+  status = sanei_genesys_get_status (dev, &val);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to read status register: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  status = gl841_stop_action (dev);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to stop motor: %s\n", __func__, sane_strstatus(status));
+      return SANE_STATUS_IO_ERROR;
+    }
+
+  local_reg = dev->reg;
+
+  gl841_init_optical_regs_off(&local_reg);
+
+  const auto& sensor = sanei_genesys_find_sensor_any(dev);
+  gl841_init_motor_regs(dev, sensor, &local_reg,
+			65536,MOTOR_ACTION_FEED,0);
+
+  status = sanei_genesys_bulk_write_register(dev, local_reg);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to bulk write registers: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+    try {
+        status = gl841_start_action (dev);
+    } catch (...) {
+        DBG(DBG_error, "%s: failed to start motor: %s\n", __func__, sane_strstatus(status));
+        try {
+            gl841_stop_action(dev);
+        } catch (...) {}
+        try {
+            // restore original registers
+            sanei_genesys_bulk_write_register(dev, dev->reg);
+        } catch (...) {}
+        throw;
+    }
+
+    if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to start motor: %s\n", __func__, sane_strstatus(status));
+      gl841_stop_action (dev);
+      /* send original registers */
+      sanei_genesys_bulk_write_register(dev, dev->reg);
+      return status;
+    }
+
+  RIE(gl841_get_paper_sensor(dev, &paper_loaded));
+  if (paper_loaded)
+    {
+      DBG(DBG_info, "%s: paper still loaded\n", __func__);
+      /* force document TRUE, because it is definitely present */
+      dev->document = SANE_TRUE;
+      dev->scanhead_position_in_steps = 0;
+
+      loop = 300;
+      while (loop > 0)		/* do not wait longer then 30 seconds */
+	{
+
+	  RIE(gl841_get_paper_sensor(dev, &paper_loaded));
+
+	  if (!paper_loaded)
+	    {
+	      DBG(DBG_info, "%s: reached home position\n", __func__);
+	      DBG(DBG_proc, "%s: finished\n", __func__);
+	      break;
+	    }
+          sanei_genesys_sleep_ms(100);
+	  --loop;
+	}
+
+      if (loop == 0)
+	{
+	  /* when we come here then the scanner needed too much time for this, so we better stop the motor */
+	  gl841_stop_action (dev);
+	  DBG(DBG_error, "%s: timeout while waiting for scanhead to go home\n", __func__);
+	  return SANE_STATUS_IO_ERROR;
+	}
+    }
+
+  feed_mm = SANE_UNFIX(dev->model->eject_feed);
+  if (dev->document)
+    {
+      feed_mm += SANE_UNFIX(dev->model->post_scan);
+    }
+
+  status = sanei_genesys_read_feed_steps(dev, &init_steps);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to read feed steps: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  /* now feed for extra <number> steps */
+  loop = 0;
+  while (loop < 300)		/* do not wait longer then 30 seconds */
+    {
+      unsigned int steps;
+
+      status = sanei_genesys_read_feed_steps(dev, &steps);
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: failed to read feed steps: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+
+      DBG(DBG_info, "%s: init_steps: %d, steps: %d\n", __func__, init_steps, steps);
+
+      if (steps > init_steps + (feed_mm * dev->motor.base_ydpi) / MM_PER_INCH)
+	{
+	  break;
+	}
+
+      sanei_genesys_sleep_ms(100);
+      ++loop;
+    }
+
+  status = gl841_stop_action(dev);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to stop motor: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  dev->document = SANE_FALSE;
+
+  DBG(DBG_proc, "%s: finished\n", __func__);
+  return SANE_STATUS_GOOD;
+}
+
+
+static SANE_Status
+gl841_load_document (Genesys_Device * dev)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+  SANE_Bool paper_loaded;
+  int loop = 300;
+  DBG(DBG_proc, "%s\n", __func__);
+  while (loop > 0)		/* do not wait longer then 30 seconds */
+    {
+
+      RIE(gl841_get_paper_sensor(dev, &paper_loaded));
+
+      if (paper_loaded)
+	{
+	  DBG(DBG_info, "%s: document inserted\n", __func__);
+
+	  /* when loading OK, document is here */
+	  dev->document = SANE_TRUE;
+
+          // give user some time to place document correctly
+          sanei_genesys_sleep_ms(1000);
+	  break;
+	}
+      sanei_genesys_sleep_ms(100);
+      --loop;
+    }
+
+  if (loop == 0)
+    {
+      /* when we come here then the user needed to much time for this */
+      DBG(DBG_error, "%s: timeout while waiting for document\n", __func__);
+      return SANE_STATUS_IO_ERROR;
+    }
+
+  DBG(DBG_proc, "%s: finished\n", __func__);
+  return SANE_STATUS_GOOD;
+}
+
+/**
+ * detects end of document and adjust current scan
+ * to take it into account
+ * used by sheetfed scanners
+ */
+static SANE_Status
+gl841_detect_document_end (Genesys_Device * dev)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+  SANE_Bool paper_loaded;
+  unsigned int scancnt = 0, lincnt, postcnt;
+  uint8_t val;
+  size_t total_bytes_to_read;
+
+  DBG(DBG_proc, "%s: begin\n", __func__);
+
+  RIE (gl841_get_paper_sensor (dev, &paper_loaded));
+
+  /* sheetfed scanner uses home sensor as paper present */
+  if ((dev->document == SANE_TRUE) && !paper_loaded)
+    {
+      DBG(DBG_info, "%s: no more document\n", __func__);
+      dev->document = SANE_FALSE;
+
+      /* we can't rely on total_bytes_to_read since the frontend
+       * might have been slow to read data, so we re-evaluate the
+       * amount of data to scan form the hardware settings
+       */
+        try {
+            status = sanei_genesys_read_scancnt(dev, &scancnt);
+        } catch (...) {
+            dev->total_bytes_to_read = dev->total_bytes_read;
+            dev->read_bytes_left = 0;
+            throw;
+        }
+
+        if(status!=SANE_STATUS_GOOD)
+        {
+          dev->total_bytes_to_read = dev->total_bytes_read;
+          dev->read_bytes_left = 0;
+          DBG(DBG_proc, "%s: finished\n", __func__);
+          return SANE_STATUS_GOOD;
+        }
+      if (dev->settings.scan_mode == ScanColorMode::COLOR_SINGLE_PASS && dev->model->is_cis)
+        {
+          scancnt/=3;
+        }
+      DBG(DBG_io, "%s: scancnt=%u lines\n", __func__, scancnt);
+
+      RIE(sanei_genesys_read_register(dev, 0x25, &val));
+      lincnt=65536*val;
+      RIE(sanei_genesys_read_register(dev, 0x26, &val));
+      lincnt+=256*val;
+      RIE(sanei_genesys_read_register(dev, 0x27, &val));
+      lincnt+=val;
+      DBG(DBG_io, "%s: lincnt=%u lines\n", __func__, lincnt);
+      postcnt=(SANE_UNFIX(dev->model->post_scan)/MM_PER_INCH)*dev->settings.yres;
+      DBG(DBG_io, "%s: postcnt=%u lines\n", __func__, postcnt);
+
+      /* the current scancnt is also the final one, so we use it to
+       * compute total bytes to read. We also add the line count to eject document */
+      total_bytes_to_read=(scancnt+postcnt)*dev->wpl;
+
+      DBG(DBG_io, "%s: old total_bytes_to_read=%u\n", __func__,
+          (unsigned int)dev->total_bytes_to_read);
+      DBG(DBG_io, "%s: new total_bytes_to_read=%u\n", __func__, (unsigned int)total_bytes_to_read);
+
+      /* assign new end value */
+      if(dev->total_bytes_to_read>total_bytes_to_read)
+        {
+          DBG(DBG_io, "%s: scan shorten\n", __func__);
+          dev->total_bytes_to_read=total_bytes_to_read;
+        }
+    }
+
+  DBG(DBG_proc, "%s: finished\n", __func__);
+  return SANE_STATUS_GOOD;
+}
+
+/* Send the low-level scan command */
+/* todo : is this that useful ? */
+static SANE_Status
+gl841_begin_scan (Genesys_Device * dev, const Genesys_Sensor& sensor, Genesys_Register_Set * reg,
+			SANE_Bool start_motor)
+{
+    (void) sensor;
+  SANE_Status status = SANE_STATUS_GOOD;
+  // FIXME: SEQUENTIAL not really needed in this case
+  Genesys_Register_Set local_reg(Genesys_Register_Set::SEQUENTIAL);
+  uint8_t val;
+
+  DBG(DBG_proc, "%s\n", __func__);
+
+  if (dev->model->gpo_type == GPO_CANONLIDE80)
+    {
+      RIE (sanei_genesys_read_register (dev, REG6B, &val));
+      val = REG6B_GPO18;
+      RIE (sanei_genesys_write_register (dev, REG6B, val));
+    }
+
+    if (dev->model->ccd_type != CCD_PLUSTEK_3600) {
+        local_reg.init_reg(0x03, sanei_genesys_read_reg_from_set(reg, 0x03) | REG03_LAMPPWR);
+    } else {
+        // TODO PLUSTEK_3600: why ??
+        local_reg.init_reg(0x03, sanei_genesys_read_reg_from_set(reg, 0x03));
+    }
+
+    local_reg.init_reg(0x01, sanei_genesys_read_reg_from_set(reg, 0x01) | REG01_SCAN);	/* set scan bit */
+    local_reg.init_reg(0x0d, 0x01);
+
+    if (start_motor) {
+        local_reg.init_reg(0x0f, 0x01);
+    } else {
+        // do not start motor yet
+        local_reg.init_reg(0x0f, 0x00);
+    }
+
+  status = sanei_genesys_bulk_write_register(dev, local_reg);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to bulk write registers: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  DBG(DBG_proc, "%s: completed\n", __func__);
+
+  return status;
+}
+
+
+/* Send the stop scan command */
+static SANE_Status
+gl841_end_scan (Genesys_Device * dev, Genesys_Register_Set __sane_unused__ * reg,
+		      SANE_Bool check_stop)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+
+  DBG(DBG_proc, "%s (check_stop = %d)\n", __func__, check_stop);
+
+  if (dev->model->is_sheetfed == SANE_TRUE)
+    {
+      status = SANE_STATUS_GOOD;
+    }
+  else				/* flat bed scanners */
+    {
+      status = gl841_stop_action (dev);
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: failed to stop: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+    }
+
+  DBG(DBG_proc, "%s: completed\n", __func__);
+
+  return status;
+}
+
+/* Moves the slider to steps */
+static SANE_Status
+gl841_feed (Genesys_Device * dev, int steps)
+{
+  Genesys_Register_Set local_reg;
+  SANE_Status status = SANE_STATUS_GOOD;
+  uint8_t val;
+  int loop;
+
+  DBG(DBG_proc, "%s (steps = %d)\n", __func__, steps);
+
+  status = gl841_stop_action (dev);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to stop action: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  // FIXME: we should pick sensor according to the resolution scanner is currently operating on
+  const auto& sensor = sanei_genesys_find_sensor_any(dev);
+
+  local_reg = dev->reg;
+
+  gl841_init_optical_regs_off(&local_reg);
+
+  gl841_init_motor_regs(dev, sensor, &local_reg, steps,MOTOR_ACTION_FEED,0);
+
+  status = sanei_genesys_bulk_write_register(dev, local_reg);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to bulk write registers: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+    try {
+        status = gl841_start_action (dev);
+    } catch (...) {
+        DBG(DBG_error, "%s: failed to start motor: %s\n", __func__, sane_strstatus(status));
+        try {
+            gl841_stop_action (dev);
+        } catch (...) {}
+        try {
+            // send original registers
+            sanei_genesys_bulk_write_register(dev, dev->reg);
+        } catch (...) {}
+        throw;
+    }
+
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to start motor: %s\n", __func__, sane_strstatus(status));
+      gl841_stop_action (dev);
+      /* send original registers */
+      sanei_genesys_bulk_write_register(dev, dev->reg);
+      return status;
+    }
+
+  loop = 0;
+  while (loop < 300)		/* do not wait longer then 30 seconds */
+  {
+      status = sanei_genesys_get_status (dev, &val);
+      if (status != SANE_STATUS_GOOD)
+      {
+          DBG(DBG_error, "%s: failed to read home sensor: %s\n", __func__, sane_strstatus(status));
+	  return status;
+      }
+
+      if (!(val & REG41_MOTORENB))	/* motor enabled */
+      {
+          DBG(DBG_proc, "%s: finished\n", __func__);
+	  dev->scanhead_position_in_steps += steps;
+	  return SANE_STATUS_GOOD;
+      }
+      sanei_genesys_sleep_ms(100);
+      ++loop;
+  }
+
+  /* when we come here then the scanner needed too much time for this, so we better stop the motor */
+  gl841_stop_action (dev);
+
+  DBG(DBG_error, "%s: timeout while waiting for scanhead to go home\n", __func__);
+  return SANE_STATUS_IO_ERROR;
+}
+
+/* Moves the slider to the home (top) position slowly */
+static SANE_Status
+gl841_slow_back_home (Genesys_Device * dev, SANE_Bool wait_until_home)
+{
+  Genesys_Register_Set local_reg;
+  SANE_Status status = SANE_STATUS_GOOD;
+  GenesysRegister *r;
+  uint8_t val;
+  int loop = 0;
+
+  DBG(DBG_proc, "%s (wait_until_home = %d)\n", __func__, wait_until_home);
+
+  if (dev->model->is_sheetfed == SANE_TRUE)
+    {
+      DBG(DBG_proc, "%s: there is no \"home\"-concept for sheet fed\n", __func__);
+      DBG(DBG_proc, "%s: finished\n", __func__);
+      return SANE_STATUS_GOOD;
+    }
+
+  /* reset gpio pin */
+  if (dev->model->gpo_type == GPO_CANONLIDE35)
+    {
+      RIE (sanei_genesys_read_register (dev, REG6C, &val));
+      val = dev->gpo.value[0];
+      RIE (sanei_genesys_write_register (dev, REG6C, val));
+    }
+  if (dev->model->gpo_type == GPO_CANONLIDE80)
+    {
+      RIE (sanei_genesys_read_register (dev, REG6B, &val));
+      val = REG6B_GPO18 | REG6B_GPO17;
+      RIE (sanei_genesys_write_register (dev, REG6B, val));
+    }
+  gl841_save_power(dev, SANE_FALSE);
+
+  /* first read gives HOME_SENSOR true */
+  status = sanei_genesys_get_status (dev, &val);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to read home sensor: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+  if (DBG_LEVEL >= DBG_io)
+    {
+      sanei_genesys_print_status (val);
+    }
+  sanei_genesys_sleep_ms(100);
+
+  /* second is reliable */
+  status = sanei_genesys_get_status (dev, &val);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to read home sensor: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+  if (DBG_LEVEL >= DBG_io)
+    {
+      sanei_genesys_print_status (val);
+    }
+
+  dev->scanhead_position_in_steps = 0;
+
+  if (val & REG41_HOMESNR)	/* is sensor at home? */
+    {
+      DBG(DBG_info, "%s: already at home, completed\n", __func__);
+      dev->scanhead_position_in_steps = 0;
+      return SANE_STATUS_GOOD;
+    }
+
+  /* end previous scan if any */
+  r = sanei_genesys_get_address(&dev->reg, REG01);
+  r->value &= ~REG01_SCAN;
+  status = sanei_genesys_write_register (dev, REG01, r->value);
+
+  /* if motor is on, stop current action */
+  if (val & REG41_MOTORENB)
+    {
+      status = gl841_stop_action (dev);
+      if (status != SANE_STATUS_GOOD)
+        {
+          DBG(DBG_error, "%s: failed to stop motor: %s\n", __func__, sane_strstatus(status));
+          return SANE_STATUS_IO_ERROR;
+        }
+    }
+
+  local_reg = dev->reg;
+
+  const auto& sensor = sanei_genesys_find_sensor_any(dev);
+
+  gl841_init_motor_regs(dev, sensor, &local_reg, 65536,MOTOR_ACTION_GO_HOME,0);
+
+  /* set up for reverse and no scan */
+  r = sanei_genesys_get_address(&local_reg, REG02);
+  r->value |= REG02_MTRREV;
+  r = sanei_genesys_get_address(&local_reg, REG01);
+  r->value &= ~REG01_SCAN;
+
+  RIE (sanei_genesys_bulk_write_register(dev, local_reg));
+
+    try {
+        status = gl841_start_action (dev);
+    } catch (...) {
+        DBG(DBG_error, "%s: failed to start motor: %s\n", __func__, sane_strstatus(status));
+        try {
+            gl841_stop_action(dev);
+        } catch (...) {}
+        try {
+            sanei_genesys_bulk_write_register(dev, dev->reg);
+        } catch (...) {}
+        throw;
+    }
+
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to start motor: %s\n", __func__, sane_strstatus(status));
+      gl841_stop_action (dev);
+      /* send original registers */
+      sanei_genesys_bulk_write_register(dev, dev->reg);
+      return status;
+    }
+
+  if (wait_until_home)
+    {
+      while (loop < 300)		/* do not wait longer then 30 seconds */
+	{
+	  status = sanei_genesys_get_status (dev, &val);
+	  if (status != SANE_STATUS_GOOD)
+	    {
+	      DBG(DBG_error, "%s: failed to read home sensor: %s\n", __func__,
+		  sane_strstatus(status));
+	      return status;
+	    }
+
+	  if (val & REG41_HOMESNR)	/* home sensor */
+	    {
+	      DBG(DBG_info, "%s: reached home position\n", __func__);
+	      DBG(DBG_proc, "%s: finished\n", __func__);
+	      return SANE_STATUS_GOOD;
+	    }
+          sanei_genesys_sleep_ms(100);
+	  ++loop;
+	}
+
+      /* when we come here then the scanner needed too much time for this, so we better stop the motor */
+      gl841_stop_action (dev);
+      DBG(DBG_error, "%s: timeout while waiting for scanhead to go home\n", __func__);
+      return SANE_STATUS_IO_ERROR;
+    }
+
+  DBG(DBG_info, "%s: scanhead is still moving\n", __func__);
+  DBG(DBG_proc, "%s: finished\n", __func__);
+  return SANE_STATUS_GOOD;
+}
+
+/* Automatically set top-left edge of the scan area by scanning a 200x200 pixels
+   area at 600 dpi from very top of scanner */
+static SANE_Status
+gl841_search_start_position (Genesys_Device * dev)
+{
+  int size;
+  SANE_Status status = SANE_STATUS_GOOD;
+  Genesys_Register_Set local_reg;
+  int steps;
+
+  int pixels = 600;
+  int dpi = 300;
+
+  DBGSTART;
+
+  local_reg = dev->reg;
+
+  /* sets for a 200 lines * 600 pixels */
+  /* normal scan with no shading */
+
+  // FIXME: the current approach of doing search only for one resolution does not work on scanners
+  // whith employ different sensors with potentially different settings.
+  auto& sensor = sanei_genesys_find_sensor_for_write(dev, dpi);
+
+    SetupParams params;
+    params.xres = dpi;
+    params.yres = dpi;
+    params.startx = 0;
+    params.starty = 0; /*we should give a small offset here~60 steps*/
+    params.pixels = 600;
+    params.lines = dev->model->search_lines;
+    params.depth = 8;
+    params.channels = 1;
+    params.scan_method = dev->settings.scan_method;
+    params.scan_mode = ScanColorMode::GRAY;
+    params.color_filter = ColorFilter::GREEN;
+    params.flags = SCAN_FLAG_DISABLE_SHADING |
+                   SCAN_FLAG_DISABLE_GAMMA |
+                   SCAN_FLAG_IGNORE_LINE_DISTANCE |
+                   SCAN_FLAG_DISABLE_BUFFER_FULL_MOVE;
+
+    status = gl841_init_scan_regs(dev, sensor, &local_reg, params);
+
+  if(status!=SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to init scan registers: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  /* send to scanner */
+  status = sanei_genesys_bulk_write_register(dev, local_reg);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to bulk write registers: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  size = pixels * dev->model->search_lines;
+
+  std::vector<uint8_t> data(size);
+
+  status = gl841_begin_scan(dev, sensor, &local_reg, SANE_TRUE);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to begin scan: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  /* waits for valid data */
+  do
+    sanei_genesys_test_buffer_empty (dev, &steps);
+  while (steps);
+
+  /* now we're on target, we can read data */
+  status = sanei_genesys_read_data_from_scanner(dev, data.data(), size);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to read data: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  if (DBG_LEVEL >= DBG_data)
+    sanei_genesys_write_pnm_file("gl841_search_position.pnm", data.data(), 8, 1, pixels,
+                                 dev->model->search_lines);
+
+  status = gl841_end_scan(dev, &local_reg, SANE_TRUE);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to end scan: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  /* update regs to copy ASIC internal state */
+  dev->reg = local_reg;
+
+/*TODO: find out where sanei_genesys_search_reference_point
+  stores information, and use that correctly*/
+  status =
+    sanei_genesys_search_reference_point (dev, sensor, data.data(), 0, dpi, pixels,
+					  dev->model->search_lines);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to set search reference point: %s\n", __func__,
+          sane_strstatus(status));
+      return status;
+    }
+
+  return SANE_STATUS_GOOD;
+}
+
+/*
+ * sets up register for coarse gain calibration
+ * todo: check it for scanners using it */
+static SANE_Status
+gl841_init_regs_for_coarse_calibration(Genesys_Device * dev, const Genesys_Sensor& sensor,
+                                       Genesys_Register_Set& regs)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+  uint8_t channels;
+  uint8_t cksel;
+
+  DBGSTART;
+
+  cksel = (regs.find_reg(0x18).value & REG18_CKSEL) + 1;	/* clock speed = 1..4 clocks */
+
+  /* set line size */
+  if (dev->settings.scan_mode == ScanColorMode::COLOR_SINGLE_PASS)
+    channels = 3;
+  else {
+    channels = 1;
+  }
+
+    SetupParams params;
+    params.xres = dev->settings.xres;
+    params.yres = dev->settings.yres;
+    params.startx = 0;
+    params.starty = 0;
+    params.pixels = sensor.optical_res / cksel; /* XXX STEF XXX !!! */
+    params.lines = 20;
+    params.depth = 16;
+    params.channels = channels;
+    params.scan_method = dev->settings.scan_method;
+    params.scan_mode = dev->settings.scan_mode;
+    params.color_filter = dev->settings.color_filter;
+    params.flags = SCAN_FLAG_DISABLE_SHADING |
+                   SCAN_FLAG_DISABLE_GAMMA |
+                   SCAN_FLAG_SINGLE_LINE |
+                   SCAN_FLAG_IGNORE_LINE_DISTANCE;
+
+    status = gl841_init_scan_regs(dev, sensor, &regs, params);
+
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to setup scan: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  DBG(DBG_info, "%s: optical sensor res: %d dpi, actual res: %d\n", __func__,
+      sensor.optical_res / cksel, dev->settings.xres);
+
+  status = sanei_genesys_bulk_write_register(dev, regs);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to bulk write registers: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+
+/*  if (DBG_LEVEL >= DBG_info)
+    sanei_gl841_print_registers (regs);*/
+
+  DBGCOMPLETED;
+  return SANE_STATUS_GOOD;
+}
+
+
+/* init registers for shading calibration */
+static SANE_Status
+gl841_init_regs_for_shading(Genesys_Device * dev, const Genesys_Sensor& sensor,
+                            Genesys_Register_Set& regs)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+  SANE_Int ydpi;
+  float starty=0;
+
+  DBGSTART;
+  DBG(DBG_proc, "%s: lines = %d\n", __func__, (int)(dev->calib_lines));
+
+  /* initial calibration reg values */
+  regs = dev->reg;
+
+  ydpi = dev->motor.base_ydpi;
+  if (dev->model->motor_type == MOTOR_PLUSTEK_3600)  /* TODO PLUSTEK_3600: 1200dpi not yet working, produces dark bar */
+    {
+      ydpi = 600;
+    }
+  if (dev->model->motor_type == MOTOR_CANONLIDE80)
+    {
+      ydpi = gl841_get_dpihw(dev);
+      /* get over extra dark area for this model.
+	 It looks like different devices have dark areas of different width
+	 due to manufacturing variability. The initial value of starty was 140,
+	 but it moves the sensor almost past the dark area completely in places
+	 on certain devices.
+
+	 On a particular device the black area starts at roughly position
+	 160 to 230 depending on location (the dark area is not completely
+	 parallel to the frame).
+      */
+      starty = 70;
+    }
+
+  dev->calib_channels = 3;
+  dev->calib_lines = dev->model->shading_lines;
+
+    SetupParams params;
+    params.xres = dev->settings.xres;
+    params.yres = ydpi;
+    params.startx = 0;
+    params.starty = starty;
+    params.pixels = (sensor.sensor_pixels * dev->settings.xres) / sensor.optical_res;
+    params.lines = dev->calib_lines;
+    params.depth = 16;
+    params.channels = dev->calib_channels;
+    params.scan_method = dev->settings.scan_method;
+    params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    params.color_filter = dev->settings.color_filter;
+    params.flags = SCAN_FLAG_DISABLE_SHADING |
+                   SCAN_FLAG_DISABLE_GAMMA |
+                   SCAN_FLAG_USE_OPTICAL_RES |
+                   /*SCAN_FLAG_DISABLE_BUFFER_FULL_MOVE |*/
+                   SCAN_FLAG_IGNORE_LINE_DISTANCE;
+
+    status = gl841_init_scan_regs(dev, sensor, &regs, params);
+
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to setup scan: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  dev->calib_pixels = dev->current_setup.pixels;
+  dev->scanhead_position_in_steps += dev->calib_lines + starty;
+
+  status = sanei_genesys_bulk_write_register(dev, regs);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to bulk write registers: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  DBGCOMPLETED;
+  return SANE_STATUS_GOOD;
+}
+
+/* set up registers for the actual scan
+ */
+static SANE_Status
+gl841_init_regs_for_scan (Genesys_Device * dev, const Genesys_Sensor& sensor)
+{
+  int channels;
+  int flags;
+  int depth;
+  float move;
+  int move_dpi;
+  float start;
+
+  SANE_Status status = SANE_STATUS_GOOD;
+
+    DBG(DBG_info, "%s ", __func__);
+    debug_dump(DBG_info, dev->settings);
+
+/* channels */
+  if (dev->settings.scan_mode == ScanColorMode::COLOR_SINGLE_PASS)
+    channels = 3;
+  else
+    channels = 1;
+
+/* depth */
+  depth = dev->settings.depth;
+  if (dev->settings.scan_mode == ScanColorMode::LINEART)
+      depth = 1;
+
+
+  /* steps to move to reach scanning area:
+     - first we move to physical start of scanning
+     either by a fixed steps amount from the black strip
+     or by a fixed amount from parking position,
+     minus the steps done during shading calibration
+     - then we move by the needed offset whitin physical
+     scanning area
+
+     assumption: steps are expressed at maximum motor resolution
+
+     we need:
+     SANE_Fixed y_offset;
+     SANE_Fixed y_size;
+     SANE_Fixed y_offset_calib;
+     mm_to_steps()=motor dpi / 2.54 / 10=motor dpi / MM_PER_INCH */
+
+  /* if scanner uses GENESYS_FLAG_SEARCH_START y_offset is
+     relative from origin, else, it is from parking position */
+
+  move_dpi = dev->motor.base_ydpi;
+
+  move = 0;
+  if (dev->model->flags & GENESYS_FLAG_SEARCH_START)
+    {
+      move += SANE_UNFIX (dev->model->y_offset_calib);
+    }
+
+  DBG(DBG_info, "%s move=%f steps\n", __func__, move);
+
+  move += SANE_UNFIX (dev->model->y_offset);
+  DBG(DBG_info, "%s: move=%f steps\n", __func__, move);
+
+  move += dev->settings.tl_y;
+  DBG(DBG_info, "%s: move=%f steps\n", __func__, move);
+
+  move = (move * move_dpi) / MM_PER_INCH;
+
+/* start */
+  start = SANE_UNFIX (dev->model->x_offset);
+
+  start += dev->settings.tl_x;
+
+  start = (start * sensor.optical_res) / MM_PER_INCH;
+
+  flags=0;
+
+  /* we enable true gray for cis scanners only, and just when doing
+   * scan since color calibration is OK for this mode
+   */
+  flags = 0;
+
+  /* true gray (led add for cis scanners) */
+  if(dev->model->is_cis && dev->settings.true_gray
+    && dev->settings.scan_mode != ScanColorMode::COLOR_SINGLE_PASS
+    && dev->model->ccd_type != CIS_CANONLIDE80)
+    {
+      // on Lide 80 the LEDADD bit results in only red LED array being lit
+      DBG(DBG_io, "%s: activating LEDADD\n", __func__);
+      flags |= SCAN_FLAG_ENABLE_LEDADD;
+    }
+
+  /* enable emulated lineart from gray data */
+  if(dev->settings.scan_mode == ScanColorMode::LINEART
+     && dev->settings.dynamic_lineart)
+    {
+      flags |= SCAN_FLAG_DYNAMIC_LINEART;
+    }
+
+    SetupParams params;
+    params.xres = dev->settings.xres;
+    params.yres = dev->settings.yres;
+    params.startx = start;
+    params.starty = move;
+    params.pixels = dev->settings.pixels;
+    params.lines = dev->settings.lines;
+    params.depth = depth;
+    params.channels = channels;
+    params.scan_method = dev->settings.scan_method;
+    params.scan_mode = dev->settings.scan_mode;
+    params.color_filter = dev->settings.color_filter;
+    params.flags = flags;
+
+    status = gl841_init_scan_regs(dev, sensor, &dev->reg, params);
+
+  if (status != SANE_STATUS_GOOD)
+      return status;
+
+
+  DBG(DBG_proc, "%s: completed\n", __func__);
+  return SANE_STATUS_GOOD;
+}
+
+/*
+ * this function sends generic gamma table (ie linear ones)
+ * or the Sensor specific one if provided
+ */
+static SANE_Status
+gl841_send_gamma_table(Genesys_Device * dev, const Genesys_Sensor& sensor)
+{
+  int size;
+  SANE_Status status = SANE_STATUS_GOOD;
+
+  DBGSTART;
+
+  size = 256;
+
+  /* allocate temporary gamma tables: 16 bits words, 3 channels */
+  std::vector<uint8_t> gamma(size * 2 * 3);
+
+  RIE(sanei_genesys_generate_gamma_buffer(dev, sensor, 16, 65535, size, gamma.data()));
+
+  /* send address */
+  status = gl841_set_buffer_address_gamma (dev, 0x00000);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to set buffer address: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  /* send data */
+  status = sanei_genesys_bulk_write_data(dev, 0x28, gamma.data(), size * 2 * 3);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to send gamma table: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  DBGCOMPLETED;
+  return SANE_STATUS_GOOD;
+}
+
+
+/* this function does the led calibration by scanning one line of the calibration
+   area below scanner's top on white strip.
+
+-needs working coarse/gain
+*/
+static SANE_Status
+gl841_led_calibration (Genesys_Device * dev, Genesys_Sensor& sensor, Genesys_Register_Set& regs)
+{
+  int num_pixels;
+  int total_size;
+  int i, j;
+  SANE_Status status = SANE_STATUS_GOOD;
+  int val;
+  int channels;
+  int avg[3], avga, avge;
+  int turn;
+  uint16_t exp[3], target;
+  int move;
+
+  SANE_Bool acceptable = SANE_FALSE;
+
+  /* these 2 boundaries should be per sensor */
+  uint16_t min_exposure=500;
+  uint16_t max_exposure;
+
+  DBGSTART;
+
+  /* feed to white strip if needed */
+  if (dev->model->y_offset_calib>0)
+    {
+      move = SANE_UNFIX (dev->model->y_offset_calib);
+      move = (move * (dev->motor.base_ydpi)) / MM_PER_INCH;
+      DBG(DBG_io, "%s: move=%d lines\n", __func__, move);
+      status = gl841_feed(dev, move);
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: failed to feed: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+    }
+
+  /* offset calibration is always done in color mode */
+  channels = 3;
+
+    SetupParams params;
+    params.xres = dev->settings.xres;
+    params.yres = dev->settings.yres;
+    params.startx = 0;
+    params.starty = 0;
+    params.pixels = (sensor.sensor_pixels*dev->settings.xres) / sensor.optical_res;
+    params.lines = 1;
+    params.depth = 16;
+    params.channels = channels;
+    params.scan_method = dev->settings.scan_method;
+    params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    params.color_filter = dev->settings.color_filter;
+    params.flags = SCAN_FLAG_DISABLE_SHADING |
+                   SCAN_FLAG_DISABLE_GAMMA |
+                   SCAN_FLAG_SINGLE_LINE |
+                   SCAN_FLAG_IGNORE_LINE_DISTANCE |
+                   SCAN_FLAG_USE_OPTICAL_RES;
+
+    status = gl841_init_scan_regs(dev, sensor, &regs, params);
+
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to setup scan: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  RIE(sanei_genesys_bulk_write_register(dev, regs));
+
+  num_pixels = dev->current_setup.pixels;
+
+  total_size = num_pixels * channels * 2 * 1;	/* colors * bytes_per_color * scan lines */
+
+  std::vector<uint8_t> line(total_size);
+
+/*
+   we try to get equal bright leds here:
+
+   loop:
+     average per color
+     adjust exposure times
+ */
+
+  exp[0] = sensor.exposure.red;
+  exp[1] = sensor.exposure.green;
+  exp[2] = sensor.exposure.blue;
+
+  turn = 0;
+  /* max exposure is set to ~2 time initial average
+   * exposure, or 2 time last calibration exposure */
+  max_exposure=((exp[0]+exp[1]+exp[2])/3)*2;
+  target=sensor.gain_white_ref*256;
+
+  do {
+        sensor.exposure.red = exp[0];
+        sensor.exposure.green = exp[1];
+        sensor.exposure.blue = exp[2];
+
+        sanei_genesys_set_exposure(regs, sensor.exposure);
+        RIE(sanei_genesys_write_register(dev, 0x10, (sensor.exposure.red >> 8) & 0xff));
+        RIE(sanei_genesys_write_register(dev, 0x11, sensor.exposure.red & 0xff));
+        RIE(sanei_genesys_write_register(dev, 0x12, (sensor.exposure.green >> 8) & 0xff));
+        RIE(sanei_genesys_write_register(dev, 0x13, sensor.exposure.green & 0xff));
+        RIE(sanei_genesys_write_register(dev, 0x14, (sensor.exposure.blue >> 8) & 0xff));
+        RIE(sanei_genesys_write_register(dev, 0x15, sensor.exposure.blue & 0xff));
+
+      RIE(sanei_genesys_bulk_write_register(dev, regs));
+
+      DBG(DBG_info, "%s: starting line reading\n", __func__);
+      RIE(gl841_begin_scan(dev, sensor, &regs, SANE_TRUE));
+      RIE(sanei_genesys_read_data_from_scanner(dev, line.data(), total_size));
+
+      if (DBG_LEVEL >= DBG_data) {
+          char fn[30];
+          snprintf(fn, 30, "gl841_led_%d.pnm", turn);
+          sanei_genesys_write_pnm_file(fn, line.data(), 16, channels, num_pixels, 1);
+      }
+
+     /* compute average */
+      for (j = 0; j < channels; j++)
+      {
+	  avg[j] = 0;
+	  for (i = 0; i < num_pixels; i++)
+	  {
+	      if (dev->model->is_cis)
+		  val =
+		      line[i * 2 + j * 2 * num_pixels + 1] * 256 +
+		      line[i * 2 + j * 2 * num_pixels];
+	      else
+		  val =
+		      line[i * 2 * channels + 2 * j + 1] * 256 +
+		      line[i * 2 * channels + 2 * j];
+	      avg[j] += val;
+	  }
+
+	  avg[j] /= num_pixels;
+      }
+
+      DBG(DBG_info,"%s: average: %d,%d,%d\n", __func__, avg[0], avg[1], avg[2]);
+
+      acceptable = SANE_TRUE;
+
+     /* exposure is acceptable if each color is in the %5 range
+      * of other color channels */
+      if (avg[0] < avg[1] * 0.95 || avg[1] < avg[0] * 0.95 ||
+	  avg[0] < avg[2] * 0.95 || avg[2] < avg[0] * 0.95 ||
+	  avg[1] < avg[2] * 0.95 || avg[2] < avg[1] * 0.95)
+        {
+	  acceptable = SANE_FALSE;
+        }
+
+      /* led exposure is not acceptable if white level is too low
+       * ~80 hardcoded value for white level */
+      if(avg[0]<20000 || avg[1]<20000 || avg[2]<20000)
+        {
+	  acceptable = SANE_FALSE;
+        }
+
+      /* for scanners using target value */
+      if(target>0)
+        {
+          acceptable = SANE_TRUE;
+          for(i=0;i<3;i++)
+            {
+              /* we accept +- 2% delta from target */
+              if(abs(avg[i]-target)>target/50)
+                {
+                  exp[i]=(exp[i]*target)/avg[i];
+                  acceptable = SANE_FALSE;
+                }
+            }
+        }
+      else
+        {
+          if (!acceptable)
+            {
+              avga = (avg[0]+avg[1]+avg[2])/3;
+              exp[0] = (exp[0] * avga) / avg[0];
+              exp[1] = (exp[1] * avga) / avg[1];
+              exp[2] = (exp[2] * avga) / avg[2];
+              /*
+                keep the resulting exposures below this value.
+                too long exposure drives the ccd into saturation.
+                we may fix this by relying on the fact that
+                we get a striped scan without shading, by means of
+                statistical calculation
+              */
+              avge = (exp[0] + exp[1] + exp[2]) / 3;
+
+              if (avge > max_exposure) {
+                  exp[0] = (exp[0] * max_exposure) / avge;
+                  exp[1] = (exp[1] * max_exposure) / avge;
+                  exp[2] = (exp[2] * max_exposure) / avge;
+              }
+              if (avge < min_exposure) {
+                  exp[0] = (exp[0] * min_exposure) / avge;
+                  exp[1] = (exp[1] * min_exposure) / avge;
+                  exp[2] = (exp[2] * min_exposure) / avge;
+              }
+
+            }
+        }
+
+      RIE (gl841_stop_action (dev));
+
+      turn++;
+
+  } while (!acceptable && turn < 100);
+
+  DBG(DBG_info,"%s: acceptable exposure: %d,%d,%d\n", __func__, exp[0], exp[1], exp[2]);
+
+  gl841_slow_back_home(dev, SANE_TRUE);
+
+  DBGCOMPLETED;
+  return status;
+}
+
+/** @brief calibration for AD frontend devices
+ * offset calibration assumes that the scanning head is on a black area
+ * For LiDE80 analog frontend
+ * 0x0003 : is gain and belongs to [0..63]
+ * 0x0006 : is offset
+ * We scan a line with no gain until average offset reaches the target
+ */
+static SANE_Status
+ad_fe_offset_calibration (Genesys_Device * dev, const Genesys_Sensor& sensor,
+                          Genesys_Register_Set& regs)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+  int num_pixels;
+  int total_size;
+  int i;
+  int average;
+  int turn;
+  int top;
+  int bottom;
+  int target;
+
+  DBGSTART;
+
+  /* don't impact 3600 behavior since we can't test it */
+  if (dev->model->ccd_type == CCD_PLUSTEK_3600)
+    {
+      DBGCOMPLETED;
+      return status;
+    }
+
+    SetupParams params;
+    params.xres = dev->settings.xres;
+    params.yres = dev->settings.yres;
+    params.startx = 0;
+    params.starty = 0;
+    params.pixels = (sensor.sensor_pixels*dev->settings.xres) / sensor.optical_res;
+    params.lines = 1;
+    params.depth = 8;
+    params.channels = 3;
+    params.scan_method = dev->settings.scan_method;
+    params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    params.color_filter = dev->settings.color_filter;
+    params.flags = SCAN_FLAG_DISABLE_SHADING |
+                   SCAN_FLAG_DISABLE_GAMMA |
+                   SCAN_FLAG_SINGLE_LINE |
+                   SCAN_FLAG_IGNORE_LINE_DISTANCE |
+                   SCAN_FLAG_USE_OPTICAL_RES;
+
+    status = gl841_init_scan_regs(dev, sensor, &regs, params);
+
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to setup scan: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  num_pixels = dev->current_setup.pixels;
+  total_size = num_pixels * 3 * 2 * 1;
+
+  std::vector<uint8_t> line(total_size);
+
+  dev->frontend.set_gain(0, 0);
+  dev->frontend.set_gain(1, 0);
+  dev->frontend.set_gain(2, 0);
+
+  /* loop on scan until target offset is reached */
+  turn=0;
+  target=24;
+  bottom=0;
+  top=255;
+  do {
+      /* set up offset mid range */
+      dev->frontend.set_offset(0, (top + bottom) / 2);
+      dev->frontend.set_offset(1, (top + bottom) / 2);
+      dev->frontend.set_offset(2, (top + bottom) / 2);
+
+      /* scan line */
+      DBG(DBG_info, "%s: starting line reading\n", __func__);
+      sanei_genesys_bulk_write_register(dev, regs);
+      gl841_set_fe(dev, sensor, AFE_SET);
+      gl841_begin_scan(dev, sensor, &regs, SANE_TRUE);
+      sanei_genesys_read_data_from_scanner(dev, line.data(), total_size);
+      gl841_stop_action (dev);
+      if (DBG_LEVEL >= DBG_data) {
+          char fn[30];
+          snprintf(fn, 30, "gl841_offset_%02d.pnm", turn);
+          sanei_genesys_write_pnm_file(fn, line.data(), 8, 3, num_pixels, 1);
+      }
+
+      /* search for minimal value */
+      average=0;
+      for(i=0;i<total_size;i++)
+        {
+          average+=line[i];
+        }
+      average/=total_size;
+      DBG(DBG_data, "%s: average=%d\n", __func__, average);
+
+      /* if min value is above target, the current value becomes the new top
+       * else it is the new bottom */
+      if(average>target)
+        {
+          top=(top+bottom)/2;
+        }
+      else
+        {
+          bottom=(top+bottom)/2;
+        }
+      turn++;
+  } while ((top-bottom)>1 && turn < 100);
+
+  // FIXME: don't overwrite the calibrated values
+  dev->frontend.set_offset(0, 0);
+  dev->frontend.set_offset(1, 0);
+  dev->frontend.set_offset(2, 0);
+  DBG(DBG_info, "%s: offset=(%d,%d,%d)\n", __func__,
+      dev->frontend.get_offset(0),
+      dev->frontend.get_offset(1),
+      dev->frontend.get_offset(2));
+  DBGCOMPLETED;
+  return status;
+}
+
+/* this function does the offset calibration by scanning one line of the calibration
+   area below scanner's top. There is a black margin and the remaining is white.
+   sanei_genesys_search_start() must have been called so that the offsets and margins
+   are allready known.
+
+this function expects the slider to be where?
+*/
+static SANE_Status
+gl841_offset_calibration(Genesys_Device * dev, const Genesys_Sensor& sensor,
+                         Genesys_Register_Set& regs)
+{
+  int num_pixels;
+  int total_size;
+  int i, j;
+  SANE_Status status = SANE_STATUS_GOOD;
+  int val;
+  int channels;
+  int off[3],offh[3],offl[3],off1[3],off2[3];
+  int min1[3],min2[3];
+  int cmin[3],cmax[3];
+  int turn;
+  SANE_Bool acceptable = SANE_FALSE;
+  int mintgt = 0x400;
+
+  DBG(DBG_proc, "%s\n", __func__);
+
+  /* Analog Device fronted have a different calibration */
+  if ((dev->reg.find_reg(0x04).value & REG04_FESET) == 0x02)
+    {
+      return ad_fe_offset_calibration(dev, sensor, regs);
+    }
+
+  /* offset calibration is always done in color mode */
+  channels = 3;
+
+    SetupParams params;
+    params.xres = dev->settings.xres;
+    params.yres = dev->settings.yres;
+    params.startx = 0;
+    params.starty = 0;
+    params.pixels = (sensor.sensor_pixels*dev->settings.xres) / sensor.optical_res;
+    params.lines = 1;
+    params.depth = 16;
+    params.channels = channels;
+    params.scan_method = dev->settings.scan_method;
+    params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    params.color_filter = dev->settings.color_filter;
+    params.flags = SCAN_FLAG_DISABLE_SHADING |
+                   SCAN_FLAG_DISABLE_GAMMA |
+                   SCAN_FLAG_SINGLE_LINE |
+                   SCAN_FLAG_IGNORE_LINE_DISTANCE |
+                   SCAN_FLAG_USE_OPTICAL_RES |
+                   SCAN_FLAG_DISABLE_LAMP;
+
+    status = gl841_init_scan_regs(dev, sensor, &regs, params);
+
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to setup scan: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  num_pixels = dev->current_setup.pixels;
+
+  total_size = num_pixels * channels * 2 * 1;	/* colors * bytes_per_color * scan lines */
+
+  std::vector<uint8_t> first_line(total_size);
+  std::vector<uint8_t> second_line(total_size);
+
+  /* scan first line of data with no offset nor gain */
+/*WM8199: gain=0.73; offset=-260mV*/
+/*okay. the sensor black level is now at -260mV. we only get 0 from AFE...*/
+/* we should probably do real calibration here:
+ * -detect acceptable offset with binary search
+ * -calculate offset from this last version
+ *
+ * acceptable offset means
+ *   - few completely black pixels(<10%?)
+ *   - few completely white pixels(<10%?)
+ *
+ * final offset should map the minimum not completely black
+ * pixel to 0(16 bits)
+ *
+ * this does account for dummy pixels at the end of ccd
+ * this assumes slider is at black strip(which is not quite as black as "no
+ * signal").
+ *
+ */
+  dev->frontend.set_gain(0, 0);
+  dev->frontend.set_gain(1, 0);
+  dev->frontend.set_gain(2, 0);
+  offh[0] = 0xff;
+  offh[1] = 0xff;
+  offh[2] = 0xff;
+  offl[0] = 0x00;
+  offl[1] = 0x00;
+  offl[2] = 0x00;
+  turn = 0;
+
+  do {
+
+      RIE(sanei_genesys_bulk_write_register(dev, regs));
+
+      for (j=0; j < channels; j++) {
+	  off[j] = (offh[j]+offl[j])/2;
+          dev->frontend.set_offset(j, off[j]);
+      }
+
+      status = gl841_set_fe(dev, sensor, AFE_SET);
+
+      if (status != SANE_STATUS_GOOD)
+      {
+          DBG(DBG_error, "%s: failed to setup frontend: %s\n", __func__, sane_strstatus(status));
+	  return status;
+      }
+
+      DBG(DBG_info, "%s: starting first line reading\n", __func__);
+      RIE(gl841_begin_scan(dev, sensor, &regs, SANE_TRUE));
+
+      RIE(sanei_genesys_read_data_from_scanner (dev, first_line.data(), total_size));
+
+      if (DBG_LEVEL >= DBG_data) {
+          char fn[30];
+          snprintf(fn, 30, "gl841_offset1_%02d.pnm", turn);
+          sanei_genesys_write_pnm_file(fn, first_line.data(), 16, channels, num_pixels, 1);
+      }
+
+      acceptable = SANE_TRUE;
+
+      for (j = 0; j < channels; j++)
+      {
+	  cmin[j] = 0;
+	  cmax[j] = 0;
+
+	  for (i = 0; i < num_pixels; i++)
+	  {
+	      if (dev->model->is_cis)
+		  val =
+		      first_line[i * 2 + j * 2 * num_pixels + 1] * 256 +
+		      first_line[i * 2 + j * 2 * num_pixels];
+	      else
+		  val =
+		      first_line[i * 2 * channels + 2 * j + 1] * 256 +
+		      first_line[i * 2 * channels + 2 * j];
+	      if (val < 10)
+		  cmin[j]++;
+	      if (val > 65525)
+		  cmax[j]++;
+	  }
+
+          /* TODO the DP685 has a black strip in the middle of the sensor
+           * should be handled in a more elegant way , could be a bug */
+          if (dev->model->ccd_type == CCD_DP685)
+              cmin[j] -= 20;
+
+	  if (cmin[j] > num_pixels/100) {
+	      acceptable = SANE_FALSE;
+	      if (dev->model->is_cis)
+		  offl[0] = off[0];
+	      else
+		  offl[j] = off[j];
+	  }
+	  if (cmax[j] > num_pixels/100) {
+	      acceptable = SANE_FALSE;
+	      if (dev->model->is_cis)
+		  offh[0] = off[0];
+	      else
+		  offh[j] = off[j];
+	  }
+      }
+
+      DBG(DBG_info,"%s: black/white pixels: %d/%d,%d/%d,%d/%d\n", __func__, cmin[0], cmax[0],
+          cmin[1], cmax[1], cmin[2], cmax[2]);
+
+      if (dev->model->is_cis) {
+	  offh[2] = offh[1] = offh[0];
+	  offl[2] = offl[1] = offl[0];
+      }
+
+      RIE(gl841_stop_action(dev));
+
+      turn++;
+  } while (!acceptable && turn < 100);
+
+  DBG(DBG_info,"%s: acceptable offsets: %d,%d,%d\n", __func__, off[0], off[1], off[2]);
+
+
+  for (j = 0; j < channels; j++)
+  {
+      off1[j] = off[j];
+
+      min1[j] = 65536;
+
+      for (i = 0; i < num_pixels; i++)
+      {
+	  if (dev->model->is_cis)
+	      val =
+		  first_line[i * 2 + j * 2 * num_pixels + 1] * 256 +
+		  first_line[i * 2 + j * 2 * num_pixels];
+	  else
+	      val =
+		  first_line[i * 2 * channels + 2 * j + 1] * 256 +
+		  first_line[i * 2 * channels + 2 * j];
+	  if (min1[j] > val && val >= 10)
+	      min1[j] = val;
+      }
+  }
+
+
+  offl[0] = off[0];
+  offl[1] = off[0];
+  offl[2] = off[0];
+  turn = 0;
+
+  do {
+
+      for (j=0; j < channels; j++) {
+	  off[j] = (offh[j]+offl[j])/2;
+          dev->frontend.set_offset(j, off[j]);
+      }
+
+      status = gl841_set_fe(dev, sensor, AFE_SET);
+
+      if (status != SANE_STATUS_GOOD)
+      {
+        DBG(DBG_error, "%s: failed to setup frontend: %s\n", __func__, sane_strstatus(status));
+	  return status;
+      }
+
+      DBG(DBG_info, "%s: starting second line reading\n", __func__);
+      RIE(sanei_genesys_bulk_write_register(dev, regs));
+      RIE(gl841_begin_scan(dev, sensor, &regs, SANE_TRUE));
+      RIE(sanei_genesys_read_data_from_scanner (dev, second_line.data(), total_size));
+
+      if (DBG_LEVEL >= DBG_data) {
+          char fn[30];
+          snprintf(fn, 30, "gl841_offset2_%02d.pnm", turn);
+          sanei_genesys_write_pnm_file(fn, second_line.data(), 16, channels, num_pixels, 1);
+      }
+
+      acceptable = SANE_TRUE;
+
+      for (j = 0; j < channels; j++)
+      {
+	  cmin[j] = 0;
+	  cmax[j] = 0;
+
+	  for (i = 0; i < num_pixels; i++)
+	  {
+	      if (dev->model->is_cis)
+		  val =
+		      second_line[i * 2 + j * 2 * num_pixels + 1] * 256 +
+		      second_line[i * 2 + j * 2 * num_pixels];
+	      else
+		  val =
+		      second_line[i * 2 * channels + 2 * j + 1] * 256 +
+		      second_line[i * 2 * channels + 2 * j];
+	      if (val < 10)
+		  cmin[j]++;
+	      if (val > 65525)
+		  cmax[j]++;
+	  }
+
+	  if (cmin[j] > num_pixels/100) {
+	      acceptable = SANE_FALSE;
+	      if (dev->model->is_cis)
+		  offl[0] = off[0];
+	      else
+		  offl[j] = off[j];
+	  }
+	  if (cmax[j] > num_pixels/100) {
+	      acceptable = SANE_FALSE;
+	      if (dev->model->is_cis)
+		  offh[0] = off[0];
+	      else
+		  offh[j] = off[j];
+	  }
+      }
+
+      DBG(DBG_info, "%s: black/white pixels: %d/%d,%d/%d,%d/%d\n", __func__, cmin[0], cmax[0],
+          cmin[1], cmax[1], cmin[2], cmax[2]);
+
+      if (dev->model->is_cis) {
+	  offh[2] = offh[1] = offh[0];
+	  offl[2] = offl[1] = offl[0];
+      }
+
+      RIE(gl841_stop_action (dev));
+
+      turn++;
+
+  } while (!acceptable && turn < 100);
+
+  DBG(DBG_info, "%s: acceptable offsets: %d,%d,%d\n", __func__, off[0], off[1], off[2]);
+
+
+  for (j = 0; j < channels; j++)
+  {
+      off2[j] = off[j];
+
+      min2[j] = 65536;
+
+      for (i = 0; i < num_pixels; i++)
+      {
+	  if (dev->model->is_cis)
+	      val =
+		  second_line[i * 2 + j * 2 * num_pixels + 1] * 256 +
+		  second_line[i * 2 + j * 2 * num_pixels];
+	  else
+	      val =
+		  second_line[i * 2 * channels + 2 * j + 1] * 256 +
+		  second_line[i * 2 * channels + 2 * j];
+	  if (min2[j] > val && val != 0)
+	      min2[j] = val;
+      }
+  }
+
+  DBG(DBG_info, "%s: first set: %d/%d,%d/%d,%d/%d\n", __func__, off1[0], min1[0], off1[1], min1[1],
+      off1[2], min1[2]);
+
+  DBG(DBG_info, "%s: second set: %d/%d,%d/%d,%d/%d\n", __func__, off2[0], min2[0], off2[1], min2[1],
+      off2[2], min2[2]);
+
+/*
+  calculate offset for each channel
+  based on minimal pixel value min1 at offset off1 and minimal pixel value min2
+  at offset off2
+
+  to get min at off, values are linearly interpolated:
+  min=real+off*fact
+  min1=real+off1*fact
+  min2=real+off2*fact
+
+  fact=(min1-min2)/(off1-off2)
+  real=min1-off1*(min1-min2)/(off1-off2)
+
+  off=(min-min1+off1*(min1-min2)/(off1-off2))/((min1-min2)/(off1-off2))
+
+  off=(min*(off1-off2)+min1*off2-off1*min2)/(min1-min2)
+
+ */
+  for (j = 0; j < channels; j++)
+  {
+      if (min2[j]-min1[j] == 0) {
+/*TODO: try to avoid this*/
+	  DBG(DBG_warn, "%s: difference too small\n", __func__);
+	  if (mintgt * (off1[j] - off2[j]) + min1[j] * off2[j] - min2[j] * off1[j] >= 0)
+	      off[j] = 0x0000;
+	  else
+	      off[j] = 0xffff;
+      } else
+	  off[j] = (mintgt * (off1[j] - off2[j]) + min1[j] * off2[j] - min2[j] * off1[j])/(min1[j]-min2[j]);
+      if (off[j] > 255)
+	  off[j] = 255;
+      if (off[j] < 0)
+	  off[j] = 0;
+      dev->frontend.set_offset(j, off[j]);
+  }
+
+  DBG(DBG_info, "%s: final offsets: %d,%d,%d\n", __func__, off[0], off[1], off[2]);
+
+  if (dev->model->is_cis) {
+      if (off[0] < off[1])
+	  off[0] = off[1];
+      if (off[0] < off[2])
+	  off[0] = off[2];
+      dev->frontend.set_offset(0, off[0]);
+      dev->frontend.set_offset(1, off[0]);
+      dev->frontend.set_offset(2, off[0]);
+  }
+
+  if (channels == 1)
+    {
+      dev->frontend.set_offset(1, dev->frontend.get_offset(0));
+      dev->frontend.set_offset(2, dev->frontend.get_offset(0));
+    }
+
+  DBG(DBG_proc, "%s: completed\n", __func__);
+  return status;
+}
+
+
+/* alternative coarse gain calibration
+   this on uses the settings from offset_calibration and
+   uses only one scanline
+ */
+/*
+  with offset and coarse calibration we only want to get our input range into
+  a reasonable shape. the fine calibration of the upper and lower bounds will
+  be done with shading.
+ */
+static SANE_Status
+gl841_coarse_gain_calibration(Genesys_Device * dev, const Genesys_Sensor& sensor,
+                              Genesys_Register_Set& regs, int dpi)
+{
+  int num_pixels;
+  int total_size;
+  int i, j, channels;
+  SANE_Status status = SANE_STATUS_GOOD;
+  int max[3];
+  float gain[3];
+  int val;
+  int lines=1;
+  int move;
+
+  DBG(DBG_proc, "%s: dpi=%d\n", __func__, dpi);
+
+  /* feed to white strip if needed */
+  if (dev->model->y_offset_calib>0)
+    {
+      move = SANE_UNFIX (dev->model->y_offset_calib);
+      move = (move * (dev->motor.base_ydpi)) / MM_PER_INCH;
+      DBG(DBG_io, "%s: move=%d lines\n", __func__, move);
+      status = gl841_feed(dev, move);
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: failed to feed: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+    }
+
+  /* coarse gain calibration is allways done in color mode */
+  channels = 3;
+
+    SetupParams params;
+    params.xres = dev->settings.xres;
+    params.yres = dev->settings.yres;
+    params.startx = 0;
+    params.starty = 0;
+    params.pixels = (sensor.sensor_pixels*dev->settings.xres) / sensor.optical_res;
+    params.lines = lines;
+    params.depth = 16;
+    params.channels = channels;
+    params.scan_method = dev->settings.scan_method;
+    params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    params.color_filter = dev->settings.color_filter;
+    params.flags = SCAN_FLAG_DISABLE_SHADING |
+                   SCAN_FLAG_DISABLE_GAMMA |
+                   SCAN_FLAG_SINGLE_LINE |
+                   SCAN_FLAG_IGNORE_LINE_DISTANCE |
+                   SCAN_FLAG_USE_OPTICAL_RES;
+
+    status = gl841_init_scan_regs(dev, sensor, &regs, params);
+
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to setup scan: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  RIE(sanei_genesys_bulk_write_register(dev, regs));
+
+  num_pixels = dev->current_setup.pixels;
+
+  total_size = num_pixels * channels * 2 * lines;	/* colors * bytes_per_color * scan lines */
+
+  std::vector<uint8_t> line(total_size);
+
+  RIE(gl841_begin_scan(dev, sensor, &regs, SANE_TRUE));
+  RIE(sanei_genesys_read_data_from_scanner(dev, line.data(), total_size));
+
+  if (DBG_LEVEL >= DBG_data)
+    sanei_genesys_write_pnm_file("gl841_gain.pnm", line.data(), 16, channels, num_pixels, lines);
+
+  /* average high level for each channel and compute gain
+     to reach the target code
+     we only use the central half of the CCD data         */
+  for (j = 0; j < channels; j++)
+    {
+      max[j] = 0;
+      for (i = 0; i < num_pixels; i++)
+	{
+	  if (dev->model->is_cis)
+	      val =
+		  line[i * 2 + j * 2 * num_pixels + 1] * 256 +
+		  line[i * 2 + j * 2 * num_pixels];
+	  else
+	      val =
+		  line[i * 2 * channels + 2 * j + 1] * 256 +
+		  line[i * 2 * channels + 2 * j];
+
+	  if (val > max[j])
+	    max[j] = val;
+	}
+
+      gain[j] = 65535.0/max[j];
+
+      uint8_t out_gain = 0;
+
+      if (dev->model->dac_type == DAC_CANONLIDE35 ||
+	  dev->model->dac_type == DAC_WOLFSON_XP300 ||
+	  dev->model->dac_type == DAC_WOLFSON_DSM600)
+        {
+	  gain[j] *= 0.69;/*seems we don't get the real maximum. empirically derived*/
+	  if (283 - 208/gain[j] > 255)
+              out_gain = 255;
+	  else if (283 - 208/gain[j] < 0)
+              out_gain = 0;
+	  else
+              out_gain = 283 - 208/gain[j];
+        }
+      else if (dev->model->dac_type == DAC_CANONLIDE80)
+        {
+              out_gain = gain[j]*12;
+        }
+      dev->frontend.set_gain(j, out_gain);
+
+      DBG(DBG_proc, "%s: channel %d, max=%d, gain = %f, setting:%d\n", __func__, j, max[j], gain[j],
+          out_gain);
+    }
+
+  for (j = 0; j < channels; j++)
+    {
+      if(gain[j] > 10)
+        {
+	  DBG (DBG_error0, "**********************************************\n");
+	  DBG (DBG_error0, "**********************************************\n");
+	  DBG (DBG_error0, "****                                      ****\n");
+	  DBG (DBG_error0, "****  Extremely low Brightness detected.  ****\n");
+	  DBG (DBG_error0, "****  Check the scanning head is          ****\n");
+	  DBG (DBG_error0, "****  unlocked and moving.                ****\n");
+	  DBG (DBG_error0, "****                                      ****\n");
+	  DBG (DBG_error0, "**********************************************\n");
+	  DBG (DBG_error0, "**********************************************\n");
+          return SANE_STATUS_JAMMED;
+        }
+
+    }
+
+    if (dev->model->is_cis) {
+        uint8_t gain0 = dev->frontend.get_gain(0);
+        if (gain0 > dev->frontend.get_gain(1)) {
+            gain0 = dev->frontend.get_gain(1);
+        }
+        if (gain0 > dev->frontend.get_gain(2)) {
+            gain0 = dev->frontend.get_gain(2);
+        }
+        dev->frontend.set_gain(0, gain0);
+        dev->frontend.set_gain(1, gain0);
+        dev->frontend.set_gain(2, gain0);
+    }
+
+    if (channels == 1) {
+        dev->frontend.set_gain(0, dev->frontend.get_gain(1));
+        dev->frontend.set_gain(2, dev->frontend.get_gain(1));
+    }
+
+  DBG(DBG_info, "%s: gain=(%d,%d,%d)\n", __func__,
+      dev->frontend.get_gain(0),
+      dev->frontend.get_gain(1),
+      dev->frontend.get_gain(2));
+
+  RIE (gl841_stop_action (dev));
+
+  gl841_slow_back_home(dev, SANE_TRUE);
+
+  DBGCOMPLETED;
+  return status;
+}
+
+/*
+ * wait for lamp warmup by scanning the same line until difference
+ * between 2 scans is below a threshold
+ */
+static SANE_Status
+gl841_init_regs_for_warmup (Genesys_Device * dev,
+                            const Genesys_Sensor& sensor,
+				       Genesys_Register_Set * local_reg,
+				       int *channels, int *total_size)
+{
+  int num_pixels = (int) (4 * 300);
+  SANE_Status status = SANE_STATUS_GOOD;
+
+  DBG(DBG_proc, "%s\n", __func__);
+
+  *local_reg = dev->reg;
+
+/* okay.. these should be defaults stored somewhere */
+  dev->frontend.set_gain(0, 0);
+  dev->frontend.set_gain(1, 0);
+  dev->frontend.set_gain(2, 0);
+  dev->frontend.set_offset(0, 0x80);
+  dev->frontend.set_offset(1, 0x80);
+  dev->frontend.set_offset(2, 0x80);
+
+    SetupParams params;
+    params.xres = sensor.optical_res;
+    params.yres = dev->settings.yres;
+    params.startx = sensor.dummy_pixel;
+    params.starty = 0;
+    params.pixels = num_pixels;
+    params.lines = 1;
+    params.depth = 16;
+    params.channels = *channels;
+    params.scan_method = dev->settings.scan_method;
+      if (*channels == 3) {
+          params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+      } else {
+          params.scan_mode = ScanColorMode::GRAY;
+      }
+    params.color_filter = dev->settings.color_filter;
+    params.flags = SCAN_FLAG_DISABLE_SHADING |
+                   SCAN_FLAG_DISABLE_GAMMA |
+                   SCAN_FLAG_SINGLE_LINE |
+                   SCAN_FLAG_IGNORE_LINE_DISTANCE |
+                   SCAN_FLAG_USE_OPTICAL_RES;
+
+    status = gl841_init_scan_regs(dev, sensor, local_reg, params);
+
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to setup scan: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  num_pixels = dev->current_setup.pixels;
+
+  *total_size = num_pixels * 3 * 2 * 1;	/* colors * bytes_per_color * scan lines */
+
+  RIE(sanei_genesys_bulk_write_register(dev, *local_reg));
+
+  return status;
+}
+
+
+/*
+ * this function moves head without scanning, forward, then backward
+ * so that the head goes to park position.
+ * as a by-product, also check for lock
+ */
+static SANE_Status
+sanei_gl841_repark_head (Genesys_Device * dev)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+
+  DBG(DBG_proc, "%s\n", __func__);
+
+  status = gl841_feed(dev,232);
+
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to feed: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  /* toggle motor flag, put an huge step number and redo move backward */
+  status = gl841_slow_back_home (dev, SANE_TRUE);
+  DBG(DBG_proc, "%s: completed\n", __func__);
+  return status;
+}
+
+static bool
+gl841_is_compatible_calibration (Genesys_Device * dev, const Genesys_Sensor& sensor,
+				 Genesys_Calibration_Cache *cache,
+				 int for_overwrite)
+{
+#ifdef HAVE_SYS_TIME_H
+  struct timeval time;
+#endif
+
+  DBGSTART;
+
+  /* calibration cache not working yet for this model */
+  if (dev->model->ccd_type == CCD_PLUSTEK_3600)
+    {
+      return false;
+    }
+
+    gl841_calculate_current_setup (dev, sensor);
+
+  DBG(DBG_proc, "%s: checking\n", __func__);
+
+  if (dev->current_setup.ccd_size_divisor != cache->used_setup.ccd_size_divisor)
+    return false;
+
+  /* a cache entry expires after 30 minutes for non sheetfed scanners */
+  /* this is not taken into account when overwriting cache entries    */
+#ifdef HAVE_SYS_TIME_H
+  if(for_overwrite == SANE_FALSE)
+    {
+      gettimeofday (&time, NULL);
+      if ((time.tv_sec - cache->last_calibration > 30 * 60)
+          && (dev->model->is_sheetfed == SANE_FALSE))
+        {
+          DBG(DBG_proc, "%s: expired entry, non compatible cache\n", __func__);
+          return false;
+        }
+    }
+#endif
+
+  DBGCOMPLETED;
+  return true;
+}
+
+/*
+ * initialize ASIC : registers, motor tables, and gamma tables
+ * then ensure scanner's head is at home
+ */
+static SANE_Status
+gl841_init (Genesys_Device * dev)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+  uint8_t val;
+  size_t size;
+
+  DBG_INIT ();
+  DBGSTART;
+
+  dev->scanhead_position_in_steps = 0;
+
+  /* Check if the device has already been initialized and powered up */
+  if (dev->already_initialized)
+    {
+      RIE (sanei_genesys_get_status (dev, &val));
+      if (val & REG41_PWRBIT)
+	{
+	  DBG(DBG_info, "%s: already initialized\n", __func__);
+          DBGCOMPLETED;
+	  return SANE_STATUS_GOOD;
+	}
+    }
+
+  dev->dark_average_data.clear();
+  dev->white_average_data.clear();
+
+  dev->settings.color_filter = ColorFilter::RED;
+
+  /* ASIC reset */
+  RIE (sanei_genesys_write_register (dev, 0x0e, 0x01));
+  RIE (sanei_genesys_write_register (dev, 0x0e, 0x00));
+
+  /* Set default values for registers */
+  gl841_init_registers (dev);
+
+  /* Write initial registers */
+  RIE(sanei_genesys_bulk_write_register(dev, dev->reg));
+
+  /* Test ASIC and RAM */
+  if (!(dev->model->flags & GENESYS_FLAG_LAZY_INIT))
+    {
+      RIE (sanei_gl841_asic_test (dev));
+    }
+
+  const auto& sensor = sanei_genesys_find_sensor_any(dev);
+
+  /* Set analog frontend */
+  RIE (gl841_set_fe(dev, sensor, AFE_INIT));
+
+  /* Move home */
+  RIE (gl841_slow_back_home (dev, SANE_TRUE));
+
+  /* Init shading data */
+  RIE (sanei_genesys_init_shading_data(dev, sensor, sensor.sensor_pixels));
+
+  /* ensure head is correctly parked, and check lock */
+  if (dev->model->flags & GENESYS_FLAG_REPARK)
+    {
+      status = sanei_gl841_repark_head (dev);
+      if (status != SANE_STATUS_GOOD)
+	{
+	  if (status == SANE_STATUS_INVAL)
+	    DBG(DBG_error0, "Your scanner is locked. Please move the lock switch to the unlocked "
+		"position\n");
+	  else
+	    DBG(DBG_error, "%s: sanei_gl841_repark_head failed: %s\n", __func__,
+		sane_strstatus(status));
+	  return status;
+	}
+    }
+
+  /* send gamma tables */
+  status = gl841_send_gamma_table(dev, sensor);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to send initial gamma tables: %s\n", __func__,
+          sane_strstatus(status));
+      return status;
+    }
+
+  /* initial calibration reg values */
+  Genesys_Register_Set& regs = dev->calib_reg;
+  regs = dev->reg;
+
+    SetupParams params;
+    params.xres = 300;
+    params.yres = 300;
+    params.startx = 0;
+    params.starty = 0;
+    params.pixels = (16 * 300) / sensor.optical_res;
+    params.lines = 1;
+    params.depth = 16;
+    params.channels = 3;
+    params.scan_method = dev->settings.scan_method;
+    params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    params.color_filter = ColorFilter::RED;
+    params.flags = SCAN_FLAG_DISABLE_SHADING |
+                   SCAN_FLAG_DISABLE_GAMMA |
+                   SCAN_FLAG_SINGLE_LINE |
+                   SCAN_FLAG_IGNORE_LINE_DISTANCE |
+                   SCAN_FLAG_USE_OPTICAL_RES;
+
+    status = gl841_init_scan_regs(dev, sensor, &regs, params);
+
+  RIE(sanei_genesys_bulk_write_register(dev, regs));
+
+  size = dev->current_setup.pixels * 3 * 2 * 1;	/* colors * bytes_per_color * scan lines */
+
+  std::vector<uint8_t> line(size);
+
+  DBG(DBG_info, "%s: starting dummy data reading\n", __func__);
+  RIE(gl841_begin_scan(dev, sensor, &regs, SANE_TRUE));
+
+  sanei_usb_set_timeout(1000);/* 1 second*/
+
+/*ignore errors. next read will succeed*/
+  sanei_genesys_read_data_from_scanner(dev, line.data(), size);
+
+  sanei_usb_set_timeout(30 * 1000);/* 30 seconds*/
+
+  RIE (gl841_end_scan(dev, &regs, SANE_TRUE));
+
+  regs = dev->reg;
+
+  /* Set powersaving (default = 15 minutes) */
+  RIE (gl841_set_powersaving (dev, 15));
+  dev->already_initialized = SANE_TRUE;
+
+  DBGCOMPLETED;
+  return SANE_STATUS_GOOD;
+}
+
+static SANE_Status
+gl841_update_hardware_sensors (Genesys_Scanner * s)
+{
+  /* do what is needed to get a new set of events, but try to not lose
+     any of them.
+   */
+  SANE_Status status = SANE_STATUS_GOOD;
+  uint8_t val;
+
+  if (s->dev->model->gpo_type == GPO_CANONLIDE35
+   || s->dev->model->gpo_type == GPO_CANONLIDE80)
+    {
+        RIE(sanei_genesys_read_register(s->dev, REG6D, &val));
+        s->buttons[BUTTON_SCAN_SW].write((val & 0x01) == 0);
+        s->buttons[BUTTON_FILE_SW].write((val & 0x02) == 0);
+        s->buttons[BUTTON_EMAIL_SW].write((val & 0x04) == 0);
+        s->buttons[BUTTON_COPY_SW].write((val & 0x08) == 0);
+    }
+
+  if (s->dev->model->gpo_type == GPO_XP300 ||
+      s->dev->model->gpo_type == GPO_DP665 ||
+      s->dev->model->gpo_type == GPO_DP685)
+    {
+        RIE(sanei_genesys_read_register(s->dev, REG6D, &val));
+
+        s->buttons[BUTTON_PAGE_LOADED_SW].write((val & 0x01) == 0);
+        s->buttons[BUTTON_SCAN_SW].write((val & 0x02) == 0);
+    }
+
+  return status;
+}
+
+/** @brief search for a full width black or white strip.
+ * This function searches for a black or white stripe across the scanning area.
+ * When searching backward, the searched area must completely be of the desired
+ * color since this area will be used for calibration which scans forward.
+ * @param dev scanner device
+ * @param forward SANE_TRUE if searching forward, SANE_FALSE if searching backward
+ * @param black SANE_TRUE if searching for a black strip, SANE_FALSE for a white strip
+ * @return SANE_STATUS_GOOD if a matching strip is found, SANE_STATUS_UNSUPPORTED if not
+ */
+static SANE_Status
+gl841_search_strip(Genesys_Device * dev, const Genesys_Sensor& sensor,
+                   SANE_Bool forward, SANE_Bool black)
+{
+  unsigned int pixels, lines, channels;
+  SANE_Status status = SANE_STATUS_GOOD;
+  Genesys_Register_Set local_reg;
+  size_t size;
+  int steps, depth, dpi;
+  unsigned int pass, count, found, x, y, length;
+  char title[80];
+  GenesysRegister *r;
+  uint8_t white_level=90;  /**< default white level to detect white dots */
+  uint8_t black_level=60;  /**< default black level to detect black dots */
+
+  DBG(DBG_proc, "%s %s %s\n", __func__, black ? "black" : "white", forward ? "forward" : "reverse");
+
+  /* use maximum gain when doing forward white strip detection
+   * since we don't have calibrated the sensor yet */
+  if(!black && forward)
+    {
+      dev->frontend.set_gain(0, 0xff);
+      dev->frontend.set_gain(1, 0xff);
+      dev->frontend.set_gain(2, 0xff);
+    }
+
+  gl841_set_fe(dev, sensor, AFE_SET);
+  status = gl841_stop_action (dev);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to stop: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  /* set up for a gray scan at lowest dpi */
+  dpi = 9600;
+  for (x = 0; x < MAX_RESOLUTIONS; x++)
+    {
+      if (dev->model->xdpi_values[x] > 0 && dev->model->xdpi_values[x] < dpi)
+	dpi = dev->model->xdpi_values[x];
+    }
+  channels = 1;
+
+  /* shading calibation is done with dev->motor.base_ydpi */
+  /* lines = (dev->model->shading_lines * dpi) / dev->motor.base_ydpi; */
+  lines = (10*dpi)/MM_PER_INCH;
+
+  depth = 8;
+  pixels = (sensor.sensor_pixels * dpi) / sensor.optical_res;
+  size = pixels * channels * lines * (depth / 8);
+  std::vector<uint8_t> data(size);
+
+  /* 20 cm max length for calibration sheet */
+  length = ((200 * dpi) / MM_PER_INCH)/lines;
+
+  dev->scanhead_position_in_steps = 0;
+
+  local_reg = dev->reg;
+
+    SetupParams params;
+    params.xres = dpi;
+    params.yres = dpi;
+    params.startx = 0;
+    params.starty = 0;
+    params.pixels = pixels;
+    params.lines = lines;
+    params.depth = depth;
+    params.channels = channels;
+    params.scan_method = dev->settings.scan_method;
+    params.scan_mode = ScanColorMode::GRAY;
+    params.color_filter = ColorFilter::RED;
+    params.flags = SCAN_FLAG_DISABLE_SHADING | SCAN_FLAG_DISABLE_GAMMA;
+
+    status = gl841_init_scan_regs(dev, sensor, &local_reg, params);
+
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to setup for scan: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  /* set up for reverse or forward */
+  r = sanei_genesys_get_address(&local_reg, 0x02);
+  if (forward)
+    r->value &= ~4;
+  else
+    r->value |= 4;
+
+
+  status = sanei_genesys_bulk_write_register(dev, local_reg);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to bulk write registers: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  status = gl841_begin_scan(dev, sensor, &local_reg, SANE_TRUE);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to begin scan: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  /* waits for valid data */
+  do
+    sanei_genesys_test_buffer_empty (dev, &steps);
+  while (steps);
+
+  /* now we're on target, we can read data */
+  status = sanei_genesys_read_data_from_scanner(dev, data.data(), size);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: failed to read data: %s\n", __func__, sane_strstatus(status));
+      return status;
+    }
+
+  status = gl841_stop_action (dev);
+  if (status != SANE_STATUS_GOOD)
+    {
+      DBG(DBG_error, "%s: gl841_stop_action failed\n", __func__);
+      return status;
+    }
+
+  pass = 0;
+  if (DBG_LEVEL >= DBG_data)
+    {
+      sprintf(title, "gl841_search_strip_%s_%s%02u.pnm", black ? "black" : "white",
+              forward ? "fwd" : "bwd", pass);
+      sanei_genesys_write_pnm_file(title, data.data(), depth, channels, pixels, lines);
+    }
+
+  /* loop until strip is found or maximum pass number done */
+  found = 0;
+  while (pass < length && !found)
+    {
+      status = sanei_genesys_bulk_write_register(dev, local_reg);
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: failed to bulk write registers: %s\n", __func__,
+	      sane_strstatus(status));
+	  return status;
+	}
+
+      /* now start scan */
+      status = gl841_begin_scan(dev, sensor, &local_reg, SANE_TRUE);
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error,"%s: failed to begin scan: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+
+      /* waits for valid data */
+      do
+	sanei_genesys_test_buffer_empty (dev, &steps);
+      while (steps);
+
+      /* now we're on target, we can read data */
+      status = sanei_genesys_read_data_from_scanner (dev, data.data(), size);
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "g%s: failed to read data: %s\n", __func__, sane_strstatus(status));
+	  return status;
+	}
+
+      status = gl841_stop_action (dev);
+      if (status != SANE_STATUS_GOOD)
+	{
+	  DBG(DBG_error, "%s: gl841_stop_action failed\n", __func__);
+	  return status;
+	}
+
+      if (DBG_LEVEL >= DBG_data)
+	{
+          sprintf(title, "gl841_search_strip_%s_%s%02u.pnm",
+                  black ? "black" : "white", forward ? "fwd" : "bwd", pass);
+          sanei_genesys_write_pnm_file(title, data.data(), depth, channels, pixels, lines);
+	}
+
+      /* search data to find black strip */
+      /* when searching forward, we only need one line of the searched color since we
+       * will scan forward. But when doing backward search, we need all the area of the
+       * same color */
+      if (forward)
+	{
+	  for (y = 0; y < lines && !found; y++)
+	    {
+	      count = 0;
+	      /* count of white/black pixels depending on the color searched */
+	      for (x = 0; x < pixels; x++)
+		{
+		  /* when searching for black, detect white pixels */
+		  if (black && data[y * pixels + x] > white_level)
+		    {
+		      count++;
+		    }
+		  /* when searching for white, detect black pixels */
+		  if (!black && data[y * pixels + x] < black_level)
+		    {
+		      count++;
+		    }
+		}
+
+	      /* at end of line, if count >= 3%, line is not fully of the desired color
+	       * so we must go to next line of the buffer */
+	      /* count*100/pixels < 3 */
+	      if ((count * 100) / pixels < 3)
+		{
+		  found = 1;
+		  DBG(DBG_data, "%s: strip found forward during pass %d at line %d\n", __func__,
+		      pass, y);
+		}
+	      else
+		{
+		  DBG(DBG_data, "%s: pixels=%d, count=%d (%d%%)\n", __func__, pixels, count,
+		      (100 * count) / pixels);
+		}
+	    }
+	}
+      else			/* since calibration scans are done forward, we need the whole area
+				   to be of the required color when searching backward */
+	{
+	  count = 0;
+	  for (y = 0; y < lines; y++)
+	    {
+	      /* count of white/black pixels depending on the color searched */
+	      for (x = 0; x < pixels; x++)
+		{
+		  /* when searching for black, detect white pixels */
+		  if (black && data[y * pixels + x] > white_level)
+		    {
+		      count++;
+		    }
+		  /* when searching for white, detect black pixels */
+		  if (!black && data[y * pixels + x] < black_level)
+		    {
+		      count++;
+		    }
+		}
+	    }
+
+	  /* at end of area, if count >= 3%, area is not fully of the desired color
+	   * so we must go to next buffer */
+	  if ((count * 100) / (pixels * lines) < 3)
+	    {
+	      found = 1;
+	      DBG(DBG_data, "%s: strip found backward during pass %d \n", __func__, pass);
+	    }
+	  else
+	    {
+	      DBG(DBG_data, "%s: pixels=%d, count=%d (%d%%)\n", __func__, pixels, count,
+		  (100 * count) / pixels);
+	    }
+	}
+      pass++;
+    }
+
+  if (found)
+    {
+      status = SANE_STATUS_GOOD;
+      DBG(DBG_info, "%s: %s strip found\n", __func__, black ? "black" : "white");
+    }
+  else
+    {
+      status = SANE_STATUS_UNSUPPORTED;
+      DBG(DBG_info, "%s: %s strip not found\n", __func__, black ? "black" : "white");
+    }
+
+  DBG(DBG_proc, "%s: completed\n", __func__);
+  return status;
+}
+
+/**
+ * Send shading calibration data. The buffer is considered to always hold values
+ * for all the channels.
+ */
+static
+SANE_Status
+gl841_send_shading_data (Genesys_Device * dev, const Genesys_Sensor& sensor,
+                         uint8_t * data, int size)
+{
+  SANE_Status status = SANE_STATUS_GOOD;
+  uint32_t length, x, factor, pixels, i;
+  uint32_t lines, channels;
+  uint16_t dpiset, dpihw, strpixel ,endpixel, beginpixel;
+  uint8_t *ptr,*src;
+
+  DBGSTART;
+  DBG(DBG_io2, "%s: writing %d bytes of shading data\n", __func__, size);
+
+  /* old method if no SHDAREA */
+  if((dev->reg.find_reg(0x01).value & REG01_SHDAREA) == 0)
+    {
+      /* start address */
+      status = sanei_genesys_set_buffer_address (dev, 0x0000);
+      if (status != SANE_STATUS_GOOD)
+        {
+          DBG(DBG_error, "%s: failed to set buffer address: %s\n", __func__,
+              sane_strstatus(status));
+          return status;
+        }
+
+      /* shading data whole line */
+      status = dev->model->cmd_set->bulk_write_data (dev, 0x3c, data, size);
+      if (status != SANE_STATUS_GOOD)
+        {
+          DBG(DBG_error, "%s: failed to send shading table: %s\n", __func__,
+              sane_strstatus(status));
+          return status;
+        }
+      DBGCOMPLETED;
+      return status;
+    }
+
+  /* data is whole line, we extract only the part for the scanned area */
+  length = (uint32_t) (size / 3);
+  sanei_genesys_get_double(&dev->reg,REG_STRPIXEL,&strpixel);
+  sanei_genesys_get_double(&dev->reg,REG_ENDPIXEL,&endpixel);
+  DBG(DBG_io2, "%s: STRPIXEL=%d, ENDPIXEL=%d, PIXELS=%d\n", __func__, strpixel, endpixel,
+      endpixel-strpixel);
+
+  /* compute deletion/average factor */
+  sanei_genesys_get_double(&dev->reg,REG_DPISET,&dpiset);
+  dpihw = gl841_get_dpihw(dev);
+  unsigned ccd_size_divisor = dev->current_setup.ccd_size_divisor;
+  factor=dpihw/dpiset;
+  DBG(DBG_io2, "%s: dpihw=%d, dpiset=%d, ccd_size_divisor=%d, factor=%d\n", __func__, dpihw, dpiset,
+      ccd_size_divisor, factor);
+
+  /* binary data logging */
+  if(DBG_LEVEL>=DBG_data)
+    {
+      dev->binary=fopen("binary.pnm","wb");
+      sanei_genesys_get_triple(&dev->reg, REG_LINCNT, &lines);
+      channels=dev->current_setup.channels;
+      if(dev->binary!=NULL)
+        {
+          fprintf(dev->binary,"P5\n%d %d\n%d\n",(endpixel-strpixel)/factor*channels,lines/channels,255);
+        }
+    }
+
+  /* turn pixel value into bytes 2x16 bits words */
+  strpixel*=2*2; /* 2 words of 2 bytes */
+  endpixel*=2*2;
+  pixels=endpixel-strpixel;
+
+  /* shading pixel begin is start pixel minus start pixel during shading
+   * calibration. Currently only cases handled are full and half ccd resolution.
+   */
+  beginpixel = sensor.CCD_start_xoffset / ccd_size_divisor;
+  beginpixel += sensor.dummy_pixel + 1;
+  DBG(DBG_io2, "%s: ORIGIN PIXEL=%d\n", __func__, beginpixel);
+  beginpixel = (strpixel-beginpixel*2*2)/factor;
+  DBG(DBG_io2, "%s: BEGIN PIXEL=%d\n", __func__, beginpixel/4);
+
+  DBG(DBG_io2, "%s: using chunks of %d bytes (%d shading data pixels)\n", __func__, length,
+      length/4);
+  std::vector<uint8_t> buffer(pixels, 0);
+
+  /* write actual shading data contigously
+   * channel by channel, starting at addr 0x0000
+   * */
+  for(i=0;i<3;i++)
+    {
+      /* copy data to work buffer and process it */
+          /* coefficent destination */
+      ptr=buffer.data();
+
+      /* iterate on both sensor segment, data has been averaged,
+       * so is in the right order and we only have to copy it */
+      for(x=0;x<pixels;x+=4)
+        {
+          /* coefficient source */
+          src=data+x+beginpixel+i*length;
+          ptr[0]=src[0];
+          ptr[1]=src[1];
+          ptr[2]=src[2];
+          ptr[3]=src[3];
+
+          /* next shading coefficient */
+          ptr+=4;
+        }
+
+      /* 0x5400 alignment for LIDE80 internal memory */
+      RIE(sanei_genesys_set_buffer_address(dev, 0x5400*i));
+      RIE(dev->model->cmd_set->bulk_write_data(dev, 0x3c, buffer.data(), pixels));
+    }
+
+  DBGCOMPLETED;
+
+  return status;
+}
+
+
+/** the gl841 command set */
+static Genesys_Command_Set gl841_cmd_set = {
+  "gl841-generic",		/* the name of this set */
+
+  [](Genesys_Device* dev) -> bool { (void) dev; return true; },
+
+  gl841_init,
+  gl841_init_regs_for_warmup,
+  gl841_init_regs_for_coarse_calibration,
+  gl841_init_regs_for_shading,
+  gl841_init_regs_for_scan,
+
+  gl841_get_filter_bit,
+  gl841_get_lineart_bit,
+  gl841_get_bitset_bit,
+  gl841_get_gain4_bit,
+  gl841_get_fast_feed_bit,
+  gl841_test_buffer_empty_bit,
+  gl841_test_motor_flag_bit,
+
+  gl841_set_fe,
+  gl841_set_powersaving,
+  gl841_save_power,
+
+  gl841_begin_scan,
+  gl841_end_scan,
+
+  gl841_send_gamma_table,
+
+  gl841_search_start_position,
+
+  gl841_offset_calibration,
+  gl841_coarse_gain_calibration,
+  gl841_led_calibration,
+
+  NULL,
+  gl841_slow_back_home,
+  NULL,
+
+  sanei_genesys_bulk_write_register,
+  sanei_genesys_bulk_write_data,
+  sanei_genesys_bulk_read_data,
+
+  gl841_update_hardware_sensors,
+
+  gl841_load_document,
+  gl841_detect_document_end,
+  gl841_eject_document,
+  gl841_search_strip,
+
+  gl841_is_compatible_calibration,
+  NULL,
+  gl841_send_shading_data,
+  gl841_calculate_current_setup,
+  NULL
+};
+
+SANE_Status
+sanei_gl841_init_cmd_set (Genesys_Device * dev)
+{
+  dev->model->cmd_set = &gl841_cmd_set;
+  return SANE_STATUS_GOOD;
+}