New upstream version 1.0.29upstream/1.0.29

1 files changed, 2140 insertions, 0 deletions

diff --git a/backend/genesys/gl847.cpp b/backend/genesys/gl847.cpp
new file mode 100644
index 0000000..cb0b527
--- /dev/null
+++ b/backend/genesys/gl847.cpp
@@ -0,0 +1,2140 @@
+/* sane - Scanner Access Now Easy.
+
+   Copyright (C) 2010-2013 Stéphane Voltz <stef.dev@free.fr>
+
+
+   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 "gl847.h"
+#include "gl847_registers.h"
+#include "test_settings.h"
+
+#include <vector>
+
+namespace genesys {
+namespace gl847 {
+
+/**
+ * compute the step multiplier used
+ */
+static int
+gl847_get_step_multiplier (Genesys_Register_Set * regs)
+{
+    GenesysRegister *r = sanei_genesys_get_address(regs, 0x9d);
+    int value = 1;
+    if (r != nullptr)
+    {
+      value = (r->value & 0x0f)>>1;
+      value = 1 << value;
+    }
+  DBG (DBG_io, "%s: step multiplier is %d\n", __func__, value);
+  return value;
+}
+
+/** @brief sensor specific settings
+*/
+static void gl847_setup_sensor(Genesys_Device * dev, const Genesys_Sensor& sensor,
+                               Genesys_Register_Set* regs)
+{
+    DBG_HELPER(dbg);
+
+    for (const auto& reg : sensor.custom_regs) {
+        regs->set8(reg.address, reg.value);
+    }
+
+    regs->set16(REG_EXPR, sensor.exposure.red);
+    regs->set16(REG_EXPG, sensor.exposure.green);
+    regs->set16(REG_EXPB, sensor.exposure.blue);
+
+    dev->segment_order = sensor.segment_order;
+}
+
+
+/** @brief set all registers to default values .
+ * This function is called only once at the beginning and
+ * fills register startup values for registers reused across scans.
+ * Those that are rarely modified or not modified are written
+ * individually.
+ * @param dev device structure holding register set to initialize
+ */
+static void
+gl847_init_registers (Genesys_Device * dev)
+{
+    DBG_HELPER(dbg);
+  int lide700=0;
+  uint8_t val;
+
+  /* 700F class needs some different initial settings */
+    if (dev->model->model_id == ModelId::CANON_LIDE_700F) {
+       lide700 = 1;
+    }
+
+    dev->reg.clear();
+
+    dev->reg.init_reg(0x01, 0x82);
+    dev->reg.init_reg(0x02, 0x18);
+    dev->reg.init_reg(0x03, 0x50);
+    dev->reg.init_reg(0x04, 0x12);
+    dev->reg.init_reg(0x05, 0x80);
+    dev->reg.init_reg(0x06, 0x50); // FASTMODE + POWERBIT
+    dev->reg.init_reg(0x08, 0x10);
+    dev->reg.init_reg(0x09, 0x01);
+    dev->reg.init_reg(0x0a, 0x00);
+    dev->reg.init_reg(0x0b, 0x01);
+    dev->reg.init_reg(0x0c, 0x02);
+
+    // LED exposures
+    dev->reg.init_reg(0x10, 0x00);
+    dev->reg.init_reg(0x11, 0x00);
+    dev->reg.init_reg(0x12, 0x00);
+    dev->reg.init_reg(0x13, 0x00);
+    dev->reg.init_reg(0x14, 0x00);
+    dev->reg.init_reg(0x15, 0x00);
+
+    dev->reg.init_reg(0x16, 0x10); // SENSOR_DEF
+    dev->reg.init_reg(0x17, 0x08); // SENSOR_DEF
+    dev->reg.init_reg(0x18, 0x00); // SENSOR_DEF
+
+    // EXPDMY
+    dev->reg.init_reg(0x19, 0x50); // SENSOR_DEF
+
+    dev->reg.init_reg(0x1a, 0x34); // SENSOR_DEF
+    dev->reg.init_reg(0x1b, 0x00); // SENSOR_DEF
+    dev->reg.init_reg(0x1c, 0x02); // SENSOR_DEF
+    dev->reg.init_reg(0x1d, 0x04); // SENSOR_DEF
+    dev->reg.init_reg(0x1e, 0x10);
+    dev->reg.init_reg(0x1f, 0x04);
+    dev->reg.init_reg(0x20, 0x02);
+    dev->reg.init_reg(0x21, 0x10);
+    dev->reg.init_reg(0x22, 0x7f);
+    dev->reg.init_reg(0x23, 0x7f);
+    dev->reg.init_reg(0x24, 0x10);
+    dev->reg.init_reg(0x25, 0x00);
+    dev->reg.init_reg(0x26, 0x00);
+    dev->reg.init_reg(0x27, 0x00);
+    dev->reg.init_reg(0x2c, 0x09);
+    dev->reg.init_reg(0x2d, 0x60);
+    dev->reg.init_reg(0x2e, 0x80);
+    dev->reg.init_reg(0x2f, 0x80);
+    dev->reg.init_reg(0x30, 0x00);
+    dev->reg.init_reg(0x31, 0x10);
+    dev->reg.init_reg(0x32, 0x15);
+    dev->reg.init_reg(0x33, 0x0e);
+    dev->reg.init_reg(0x34, 0x40);
+    dev->reg.init_reg(0x35, 0x00);
+    dev->reg.init_reg(0x36, 0x2a);
+    dev->reg.init_reg(0x37, 0x30);
+    dev->reg.init_reg(0x38, 0x2a);
+    dev->reg.init_reg(0x39, 0xf8);
+    dev->reg.init_reg(0x3d, 0x00);
+    dev->reg.init_reg(0x3e, 0x00);
+    dev->reg.init_reg(0x3f, 0x00);
+    dev->reg.init_reg(0x52, 0x03); // SENSOR_DEF
+    dev->reg.init_reg(0x53, 0x07); // SENSOR_DEF
+    dev->reg.init_reg(0x54, 0x00); // SENSOR_DEF
+    dev->reg.init_reg(0x55, 0x00); // SENSOR_DEF
+    dev->reg.init_reg(0x56, 0x00); // SENSOR_DEF
+    dev->reg.init_reg(0x57, 0x00); // SENSOR_DEF
+    dev->reg.init_reg(0x58, 0x2a); // SENSOR_DEF
+    dev->reg.init_reg(0x59, 0xe1); // SENSOR_DEF
+    dev->reg.init_reg(0x5a, 0x55); // SENSOR_DEF
+    dev->reg.init_reg(0x5e, 0x41);
+    dev->reg.init_reg(0x5f, 0x40);
+    dev->reg.init_reg(0x60, 0x00);
+    dev->reg.init_reg(0x61, 0x21);
+    dev->reg.init_reg(0x62, 0x40);
+    dev->reg.init_reg(0x63, 0x00);
+    dev->reg.init_reg(0x64, 0x21);
+    dev->reg.init_reg(0x65, 0x40);
+    dev->reg.init_reg(0x67, 0x80);
+    dev->reg.init_reg(0x68, 0x80);
+    dev->reg.init_reg(0x69, 0x20);
+    dev->reg.init_reg(0x6a, 0x20);
+
+    // CK1MAP
+    dev->reg.init_reg(0x74, 0x00); // SENSOR_DEF
+    dev->reg.init_reg(0x75, 0x00); // SENSOR_DEF
+    dev->reg.init_reg(0x76, 0x3c); // SENSOR_DEF
+
+    // CK3MAP
+    dev->reg.init_reg(0x77, 0x00); // SENSOR_DEF
+    dev->reg.init_reg(0x78, 0x00); // SENSOR_DEF
+    dev->reg.init_reg(0x79, 0x9f); // SENSOR_DEF
+
+    // CK4MAP
+    dev->reg.init_reg(0x7a, 0x00); // SENSOR_DEF
+    dev->reg.init_reg(0x7b, 0x00); // SENSOR_DEF
+    dev->reg.init_reg(0x7c, 0x55); // SENSOR_DEF
+
+    dev->reg.init_reg(0x7d, 0x00);
+
+    // NOTE: autoconf is a non working option
+    dev->reg.init_reg(0x87, 0x02);
+    dev->reg.init_reg(0x9d, 0x06);
+    dev->reg.init_reg(0xa2, 0x0f);
+    dev->reg.init_reg(0xbd, 0x18);
+    dev->reg.init_reg(0xfe, 0x08);
+
+    // gamma[0] and gamma[256] values
+    dev->reg.init_reg(0xbe, 0x00);
+    dev->reg.init_reg(0xc5, 0x00);
+    dev->reg.init_reg(0xc6, 0x00);
+    dev->reg.init_reg(0xc7, 0x00);
+    dev->reg.init_reg(0xc8, 0x00);
+    dev->reg.init_reg(0xc9, 0x00);
+    dev->reg.init_reg(0xca, 0x00);
+
+  /* LiDE 700 fixups */
+    if (lide700) {
+        dev->reg.init_reg(0x5f, 0x04);
+        dev->reg.init_reg(0x7d, 0x80);
+
+      /* we write to these registers only once */
+      val=0;
+        dev->interface->write_register(REG_0x7E, val);
+        dev->interface->write_register(REG_0x9E, val);
+        dev->interface->write_register(REG_0x9F, val);
+        dev->interface->write_register(REG_0xAB, val);
+    }
+
+    const auto& sensor = sanei_genesys_find_sensor_any(dev);
+    sanei_genesys_set_dpihw(dev->reg, sensor, sensor.optical_res);
+
+  /* initalize calibration reg */
+  dev->calib_reg = dev->reg;
+}
+
+/**@brief send slope table for motor movement
+ * Send slope_table in machine byte order
+ * @param dev device to send slope table
+ * @param table_nr index of the slope table in ASIC memory
+ * Must be in the [0-4] range.
+ * @param slope_table pointer to 16 bit values array of the slope table
+ * @param steps number of elements in the slope table
+ */
+static void gl847_send_slope_table(Genesys_Device* dev, int table_nr,
+                                   const std::vector<uint16_t>& slope_table,
+                                   int steps)
+{
+    DBG_HELPER_ARGS(dbg, "table_nr = %d, steps = %d", table_nr, steps);
+  int i;
+  char msg[10000];
+
+  /* sanity check */
+  if(table_nr<0 || table_nr>4)
+    {
+        throw SaneException("invalid table number %d", table_nr);
+    }
+
+  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)
+    {
+        std::sprintf(msg, "write slope %d (%d)=", table_nr, steps);
+      for (i = 0; i < steps; i++)
+	{
+            std::sprintf(msg + std::strlen(msg), "%d", slope_table[i]);
+	}
+      DBG (DBG_io, "%s: %s\n", __func__, msg);
+    }
+
+    if (dev->interface->is_mock()) {
+        dev->interface->record_slope_table(table_nr, slope_table);
+    }
+    // slope table addresses are fixed
+    dev->interface->write_ahb(0x10000000 + 0x4000 * table_nr, steps * 2, table.data());
+}
+
+/**
+ * Set register values of Analog Device type frontend
+ * */
+static void gl847_set_ad_fe(Genesys_Device* dev, uint8_t set)
+{
+    DBG_HELPER(dbg);
+  int i;
+
+    // wait for FE to be ready
+    auto status = scanner_read_status(*dev);
+    while (status.is_front_end_busy) {
+        dev->interface->sleep_ms(10);
+        status = scanner_read_status(*dev);
+    };
+
+  if (set == AFE_INIT)
+    {
+        DBG(DBG_proc, "%s(): setting DAC %u\n", __func__,
+            static_cast<unsigned>(dev->model->adc_id));
+
+      dev->frontend = dev->frontend_initial;
+    }
+
+    // reset DAC
+    dev->interface->write_fe_register(0x00, 0x80);
+
+    // write them to analog frontend
+    dev->interface->write_fe_register(0x00, dev->frontend.regs.get_value(0x00));
+
+    dev->interface->write_fe_register(0x01, dev->frontend.regs.get_value(0x01));
+
+    for (i = 0; i < 3; i++) {
+        dev->interface->write_fe_register(0x02 + i, dev->frontend.get_gain(i));
+    }
+    for (i = 0; i < 3; i++) {
+        dev->interface->write_fe_register(0x05 + i, dev->frontend.get_offset(i));
+    }
+}
+
+// Set values of analog frontend
+void CommandSetGl847::set_fe(Genesys_Device* dev, const Genesys_Sensor& sensor, uint8_t set) const
+{
+    DBG_HELPER_ARGS(dbg, "%s", set == AFE_INIT ? "init" :
+                               set == AFE_SET ? "set" :
+                               set == AFE_POWER_SAVE ? "powersave" : "huh?");
+
+    (void) sensor;
+
+    uint8_t val = dev->interface->read_register(REG_0x04);
+    uint8_t frontend_type = val & REG_0x04_FESET;
+
+    // route to AD devices
+    if (frontend_type == 0x02) {
+        gl847_set_ad_fe(dev, set);
+        return;
+    }
+
+    throw SaneException("unsupported frontend type %d", frontend_type);
+}
+
+
+// @brief set up motor related register for scan
+static void gl847_init_motor_regs_scan(Genesys_Device* dev,
+                                       const Genesys_Sensor& sensor,
+                                       Genesys_Register_Set* reg,
+                                       const Motor_Profile& motor_profile,
+                                       unsigned int scan_exposure_time,
+                                       unsigned scan_yres,
+                                       unsigned int scan_lines,
+                                       unsigned int scan_dummy,
+                                       unsigned int feed_steps,
+                                       MotorFlag flags)
+{
+    DBG_HELPER_ARGS(dbg, "scan_exposure_time=%d, can_yres=%d, step_type=%d, scan_lines=%d, "
+                         "scan_dummy=%d, feed_steps=%d, flags=%x",
+                    scan_exposure_time, scan_yres, static_cast<unsigned>(motor_profile.step_type),
+                    scan_lines, scan_dummy, feed_steps, static_cast<unsigned>(flags));
+  int use_fast_fed;
+  unsigned int fast_dpi;
+  unsigned int feedl, dist;
+  GenesysRegister *r;
+  uint32_t z1, z2;
+  unsigned int min_restep = 0x20;
+    uint8_t val;
+  unsigned int ccdlmt,tgtime;
+
+    unsigned step_multiplier = gl847_get_step_multiplier (reg);
+
+  use_fast_fed=0;
+  /* no fast fed since feed works well */
+    if (dev->settings.yres==4444 && feed_steps > 100 && (!has_flag(flags, MotorFlag::FEED)))
+    {
+      use_fast_fed=1;
+    }
+  DBG(DBG_io, "%s: use_fast_fed=%d\n", __func__, use_fast_fed);
+
+    reg->set24(REG_LINCNT, scan_lines);
+  DBG(DBG_io, "%s: lincnt=%d\n", __func__, scan_lines);
+
+  /* compute register 02 value */
+    r = sanei_genesys_get_address(reg, REG_0x02);
+  r->value = 0x00;
+  sanei_genesys_set_motor_power(*reg, true);
+
+    if (use_fast_fed) {
+        r->value |= REG_0x02_FASTFED;
+    } else {
+        r->value &= ~REG_0x02_FASTFED;
+    }
+
+    if (has_flag(flags, MotorFlag::AUTO_GO_HOME)) {
+        r->value |= REG_0x02_AGOHOME | REG_0x02_NOTHOME;
+    }
+
+  if (has_flag(flags, MotorFlag::DISABLE_BUFFER_FULL_MOVE)
+      ||(scan_yres>=sensor.optical_res))
+    {
+        r->value |= REG_0x02_ACDCDIS;
+    }
+
+    if (has_flag(flags, MotorFlag::REVERSE)) {
+        r->value |= REG_0x02_MTRREV;
+    } else {
+        r->value &= ~REG_0x02_MTRREV;
+    }
+
+  /* scan and backtracking slope table */
+    auto scan_table = sanei_genesys_slope_table(dev->model->asic_type, scan_yres,
+                                                scan_exposure_time, dev->motor.base_ydpi,
+                                                step_multiplier, motor_profile);
+    gl847_send_slope_table(dev, SCAN_TABLE, scan_table.table, scan_table.steps_count);
+    gl847_send_slope_table(dev, BACKTRACK_TABLE, scan_table.table, scan_table.steps_count);
+
+  /* fast table */
+  fast_dpi=sanei_genesys_get_lowest_ydpi(dev);
+    StepType fast_step_type = motor_profile.step_type;
+    if (static_cast<unsigned>(motor_profile.step_type) >= static_cast<unsigned>(StepType::QUARTER)) {
+        fast_step_type = StepType::QUARTER;
+    }
+
+    Motor_Profile fast_motor_profile = motor_profile;
+    fast_motor_profile.step_type = fast_step_type;
+
+    auto fast_table = sanei_genesys_slope_table(dev->model->asic_type, fast_dpi,
+                                                scan_exposure_time, dev->motor.base_ydpi,
+                                                step_multiplier, fast_motor_profile);
+
+    gl847_send_slope_table(dev, STOP_TABLE, fast_table.table, fast_table.steps_count);
+    gl847_send_slope_table(dev, FAST_TABLE, fast_table.table, fast_table.steps_count);
+    gl847_send_slope_table(dev, HOME_TABLE, fast_table.table, fast_table.steps_count);
+
+  /* correct move distance by acceleration and deceleration amounts */
+  feedl=feed_steps;
+  if (use_fast_fed)
+    {
+        feedl <<= static_cast<unsigned>(fast_step_type);
+        dist = (scan_table.steps_count + 2 * fast_table.steps_count);
+        /* TODO read and decode REG_0xAB */
+        r = sanei_genesys_get_address (reg, 0x5e);
+        dist += (r->value & 31);
+        /* FEDCNT */
+        r = sanei_genesys_get_address (reg, REG_FEDCNT);
+        dist += r->value;
+    }
+  else
+    {
+        feedl <<= static_cast<unsigned>(motor_profile.step_type);
+        dist = scan_table.steps_count;
+        if (has_flag(flags, MotorFlag::FEED)) {
+            dist *= 2;
+        }
+    }
+  DBG(DBG_io2, "%s: acceleration distance=%d\n", __func__, dist);
+
+  /* check for overflow */
+    if (dist < feedl) {
+        feedl -= dist;
+    } else {
+        feedl = 0;
+    }
+
+    reg->set24(REG_FEEDL, feedl);
+  DBG(DBG_io ,"%s: feedl=%d\n", __func__, feedl);
+
+    r = sanei_genesys_get_address(reg, REG_0x0C);
+    ccdlmt = (r->value & REG_0x0C_CCDLMT) + 1;
+
+    r = sanei_genesys_get_address(reg, REG_0x1C);
+    tgtime = 1<<(r->value & REG_0x1C_TGTIME);
+
+    // hi res motor speed GPIO
+    uint8_t effective = dev->interface->read_register(REG_0x6C);
+
+    // if quarter step, bipolar Vref2
+
+    if (motor_profile.step_type == StepType::QUARTER) {
+        val = effective & ~REG_0x6C_GPIO13;
+    } else if (static_cast<unsigned>(motor_profile.step_type) > static_cast<unsigned>(StepType::QUARTER)) {
+        val = effective | REG_0x6C_GPIO13;
+    } else {
+        val = effective;
+    }
+    dev->interface->write_register(REG_0x6C, val);
+
+    // effective scan
+    effective = dev->interface->read_register(REG_0x6C);
+    val = effective | REG_0x6C_GPIO10;
+    dev->interface->write_register(REG_0x6C, val);
+
+    min_restep = scan_table.steps_count / (2 * step_multiplier) - 1;
+    if (min_restep < 1) {
+        min_restep = 1;
+    }
+    r = sanei_genesys_get_address(reg, REG_FWDSTEP);
+  r->value = min_restep;
+    r = sanei_genesys_get_address(reg, REG_BWDSTEP);
+  r->value = min_restep;
+
+    sanei_genesys_calculate_zmod(use_fast_fed,
+			         scan_exposure_time*ccdlmt*tgtime,
+                                 scan_table.table,
+                                 scan_table.steps_count,
+				 feedl,
+                                 min_restep * step_multiplier,
+                                 &z1,
+                                 &z2);
+
+  DBG(DBG_info, "%s: z1 = %d\n", __func__, z1);
+    reg->set24(REG_0x60, z1 | (static_cast<unsigned>(motor_profile.step_type) << (16+REG_0x60S_STEPSEL)));
+
+  DBG(DBG_info, "%s: z2 = %d\n", __func__, z2);
+    reg->set24(REG_0x63, z2 | (static_cast<unsigned>(motor_profile.step_type) << (16+REG_0x63S_FSTPSEL)));
+
+  r = sanei_genesys_get_address (reg, 0x1e);
+  r->value &= 0xf0;		/* 0 dummy lines */
+  r->value |= scan_dummy;	/* dummy lines */
+
+    r = sanei_genesys_get_address(reg, REG_0x67);
+    r->value = REG_0x67_MTRPWM;
+
+    r = sanei_genesys_get_address(reg, REG_0x68);
+    r->value = REG_0x68_FASTPWM;
+
+    reg->set8(REG_STEPNO, scan_table.steps_count / step_multiplier);
+    reg->set8(REG_FASTNO, scan_table.steps_count / step_multiplier);
+    reg->set8(REG_FSHDEC, scan_table.steps_count / step_multiplier);
+    reg->set8(REG_FMOVNO, fast_table.steps_count / step_multiplier);
+    reg->set8(REG_FMOVDEC, fast_table.steps_count / step_multiplier);
+}
+
+
+/** @brief set up registers related to sensor
+ * Set up the following registers
+   0x01
+   0x03
+   0x10-0x015     R/G/B exposures
+   0x19           EXPDMY
+   0x2e           BWHI
+   0x2f           BWLO
+   0x04
+   0x87
+   0x05
+   0x2c,0x2d      DPISET
+   0x30,0x31      STRPIXEL
+   0x32,0x33      ENDPIXEL
+   0x35,0x36,0x37 MAXWD [25:2] (>>2)
+   0x38,0x39      LPERIOD
+   0x34           DUMMY
+ */
+static void gl847_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                         Genesys_Register_Set* reg, unsigned int exposure_time,
+                                         const ScanSession& session)
+{
+    DBG_HELPER_ARGS(dbg, "exposure_time=%d", exposure_time);
+    unsigned dpihw;
+  GenesysRegister *r;
+
+    // resolution is divided according to ccd_pixels_per_system_pixel()
+    unsigned ccd_pixels_per_system_pixel = sensor.ccd_pixels_per_system_pixel();
+    DBG(DBG_io2, "%s: ccd_pixels_per_system_pixel=%d\n", __func__, ccd_pixels_per_system_pixel);
+
+    // to manage high resolution device while keeping good low resolution scanning speed, we make
+    // hardware dpi vary
+    dpihw = sensor.get_register_hwdpi(session.params.xres * ccd_pixels_per_system_pixel);
+  DBG(DBG_io2, "%s: dpihw=%d\n", __func__, dpihw);
+
+    gl847_setup_sensor(dev, sensor, reg);
+
+    dev->cmd_set->set_fe(dev, sensor, AFE_SET);
+
+  /* enable shading */
+    regs_set_optical_off(dev->model->asic_type, *reg);
+    r = sanei_genesys_get_address(reg, REG_0x01);
+    r->value |= REG_0x01_SHDAREA;
+
+    if (has_flag(session.params.flags, ScanFlag::DISABLE_SHADING) ||
+        (dev->model->flags & GENESYS_FLAG_NO_CALIBRATION))
+    {
+        r->value &= ~REG_0x01_DVDSET;
+    }
+  else
+    {
+        r->value |= REG_0x01_DVDSET;
+    }
+
+  r = sanei_genesys_get_address (reg, REG_0x03);
+  r->value &= ~REG_0x03_AVEENB;
+
+    sanei_genesys_set_lamp_power(dev, sensor, *reg,
+                                 !has_flag(session.params.flags, ScanFlag::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, REG_0x04);
+    switch (session.params.depth) {
+    case 8:
+            r->value &= ~(REG_0x04_LINEART | REG_0x04_BITSET);
+      break;
+    case 16:
+            r->value &= ~REG_0x04_LINEART;
+            r->value |= REG_0x04_BITSET;
+      break;
+    }
+
+    r->value &= ~(REG_0x04_FILTER | REG_0x04_AFEMOD);
+  if (session.params.channels == 1)
+    {
+      switch (session.params.color_filter)
+	{
+
+           case ColorFilter::RED:
+               r->value |= 0x14;
+               break;
+           case ColorFilter::BLUE:
+               r->value |= 0x1c;
+               break;
+           case ColorFilter::GREEN:
+               r->value |= 0x18;
+               break;
+           default:
+               break; // should not happen
+	}
+    } else {
+        r->value |= 0x10; // mono
+    }
+
+    sanei_genesys_set_dpihw(*reg, sensor, dpihw);
+
+    if (should_enable_gamma(session, sensor)) {
+        reg->find_reg(REG_0x05).value |= REG_0x05_GMMENB;
+    } else {
+        reg->find_reg(REG_0x05).value &= ~REG_0x05_GMMENB;
+    }
+
+  /* CIS scanners can do true gray by setting LEDADD */
+  /* we set up LEDADD only when asked */
+    if (dev->model->is_cis) {
+        r = sanei_genesys_get_address (reg, 0x87);
+        r->value &= ~REG_0x87_LEDADD;
+        if (session.enable_ledadd) {
+            r->value |= REG_0x87_LEDADD;
+        }
+      /* RGB weighting
+        r = sanei_genesys_get_address (reg, 0x01);
+        r->value &= ~REG_0x01_TRUEGRAY;
+        if (session.enable_ledadd) {
+            r->value |= REG_0x01_TRUEGRAY;
+        }
+        */
+    }
+
+    unsigned dpiset = session.params.xres * ccd_pixels_per_system_pixel;
+    reg->set16(REG_DPISET, dpiset);
+    DBG (DBG_io2, "%s: dpiset used=%d\n", __func__, dpiset);
+
+    reg->set16(REG_STRPIXEL, session.pixel_startx);
+    reg->set16(REG_ENDPIXEL, session.pixel_endx);
+
+    build_image_pipeline(dev, session);
+
+  /* MAXWD is expressed in 4 words unit */
+    // BUG: we shouldn't multiply by channels here
+    reg->set24(REG_MAXWD, (session.output_line_bytes_raw * session.params.channels >> 2));
+
+    reg->set16(REG_LPERIOD, exposure_time);
+  DBG(DBG_io2, "%s: exposure_time used=%d\n", __func__, exposure_time);
+
+  r = sanei_genesys_get_address (reg, 0x34);
+  r->value = sensor.dummy_pixel;
+}
+
+void CommandSetGl847::init_regs_for_scan_session(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                                 Genesys_Register_Set* reg,
+                                                 const ScanSession& session) const
+{
+    DBG_HELPER(dbg);
+    session.assert_computed();
+
+  int move;
+  int exposure_time;
+
+  int slope_dpi = 0;
+  int dummy = 0;
+
+    dummy = 3 - session.params.channels;
+
+/* 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 = session.params.yres * session.params.channels;
+    } else {
+        slope_dpi = session.params.yres;
+    }
+
+  slope_dpi = slope_dpi * (1 + dummy);
+
+    exposure_time = sensor.exposure_lperiod;
+    const auto& motor_profile = sanei_genesys_get_motor_profile(*gl847_motor_profiles,
+                                                                dev->model->motor_id,
+                                                                exposure_time);
+
+  DBG(DBG_info, "%s : exposure_time=%d pixels\n", __func__, exposure_time);
+    DBG(DBG_info, "%s : scan_step_type=%d\n", __func__,
+        static_cast<unsigned>(motor_profile.step_type));
+
+  /* we enable true gray for cis scanners only, and just when doing
+   * scan since color calibration is OK for this mode
+   */
+    gl847_init_optical_regs_scan(dev, sensor, reg, exposure_time, session);
+
+    move = session.params.starty;
+    DBG(DBG_info, "%s: move=%d steps\n", __func__, move);
+
+    MotorFlag mflags = MotorFlag::NONE;
+    if (has_flag(session.params.flags, ScanFlag::DISABLE_BUFFER_FULL_MOVE)) {
+        mflags |= MotorFlag::DISABLE_BUFFER_FULL_MOVE;
+    }
+    if (has_flag(session.params.flags, ScanFlag::FEEDING)) {
+        mflags |= MotorFlag::FEED;
+  }
+    if (has_flag(session.params.flags, ScanFlag::REVERSE)) {
+        mflags |= MotorFlag::REVERSE;
+    }
+
+    gl847_init_motor_regs_scan(dev, sensor, reg, motor_profile, exposure_time, slope_dpi,
+                               dev->model->is_cis ? session.output_line_count * session.params.channels
+                                                  : session.output_line_count,
+                               dummy, move, mflags);
+
+    dev->read_buffer.clear();
+    dev->read_buffer.alloc(session.buffer_size_read);
+
+    dev->read_active = true;
+
+    dev->session = session;
+
+    dev->total_bytes_read = 0;
+    dev->total_bytes_to_read = session.output_line_bytes_requested * session.params.lines;
+
+    DBG(DBG_info, "%s: total bytes to send = %zu\n", __func__, dev->total_bytes_to_read);
+}
+
+ScanSession CommandSetGl847::calculate_scan_session(const Genesys_Device* dev,
+                                                    const Genesys_Sensor& sensor,
+                                                    const Genesys_Settings& settings) const
+{
+  int start;
+
+    DBG(DBG_info, "%s ", __func__);
+    debug_dump(DBG_info, settings);
+
+  /* start */
+    start = static_cast<int>(dev->model->x_offset);
+    start = static_cast<int>(start + settings.tl_x);
+    start = static_cast<int>((start * sensor.optical_res) / MM_PER_INCH);
+
+    ScanSession session;
+    session.params.xres = settings.xres;
+    session.params.yres = settings.yres;
+    session.params.startx = start; // not used
+    session.params.starty = 0; // not used
+    session.params.pixels = settings.pixels;
+    session.params.requested_pixels = settings.requested_pixels;
+    session.params.lines = settings.lines;
+    session.params.depth = settings.depth;
+    session.params.channels = settings.get_channels();
+    session.params.scan_method = settings.scan_method;
+    session.params.scan_mode = settings.scan_mode;
+    session.params.color_filter = settings.color_filter;
+    session.params.flags = ScanFlag::NONE;
+
+    compute_session(dev, session, sensor);
+
+    return session;
+}
+
+// for fast power saving methods only, like disabling certain amplifiers
+void CommandSetGl847::save_power(Genesys_Device* dev, bool enable) const
+{
+    DBG_HELPER_ARGS(dbg, "enable = %d", enable);
+    (void) dev;
+}
+
+void CommandSetGl847::set_powersaving(Genesys_Device* dev, int delay /* in minutes */) const
+{
+    (void) dev;
+    DBG_HELPER_ARGS(dbg, "delay = %d", delay);
+}
+
+// Send the low-level scan command
+void CommandSetGl847::begin_scan(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                 Genesys_Register_Set* reg, bool start_motor) const
+{
+    DBG_HELPER(dbg);
+    (void) sensor;
+  uint8_t val;
+  GenesysRegister *r;
+
+    // clear GPIO 10
+    if (dev->model->gpio_id != GpioId::CANON_LIDE_700F) {
+        val = dev->interface->read_register(REG_0x6C);
+        val &= ~REG_0x6C_GPIO10;
+        dev->interface->write_register(REG_0x6C, val);
+    }
+
+    val = REG_0x0D_CLRLNCNT;
+    dev->interface->write_register(REG_0x0D, val);
+    val = REG_0x0D_CLRMCNT;
+    dev->interface->write_register(REG_0x0D, val);
+
+    val = dev->interface->read_register(REG_0x01);
+    val |= REG_0x01_SCAN;
+    dev->interface->write_register(REG_0x01, val);
+    r = sanei_genesys_get_address (reg, REG_0x01);
+  r->value = val;
+
+    scanner_start_action(*dev, start_motor);
+
+    dev->advance_head_pos_by_session(ScanHeadId::PRIMARY);
+}
+
+
+// Send the stop scan command
+void CommandSetGl847::end_scan(Genesys_Device* dev, Genesys_Register_Set* reg,
+                               bool check_stop) const
+{
+    (void) reg;
+    DBG_HELPER_ARGS(dbg, "check_stop = %d", check_stop);
+
+    if (!dev->model->is_sheetfed) {
+        scanner_stop_action(*dev);
+    }
+}
+
+/** Park head
+ * Moves the slider to the home (top) position slowly
+ * @param dev device to park
+ * @param wait_until_home true to make the function waiting for head
+ * to be home before returning, if fals returne immediately
+*/
+void CommandSetGl847::move_back_home(Genesys_Device* dev, bool wait_until_home) const
+{
+    scanner_move_back_home(*dev, wait_until_home);
+}
+
+// Automatically set top-left edge of the scan area by scanning a 200x200 pixels area at 600 dpi
+// from very top of scanner
+void CommandSetGl847::search_start_position(Genesys_Device* dev) const
+{
+    DBG_HELPER(dbg);
+  int size;
+  Genesys_Register_Set local_reg;
+
+  int pixels = 600;
+  int dpi = 300;
+
+  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.
+    const auto& sensor = sanei_genesys_find_sensor(dev, dpi, 1, dev->model->default_method);
+
+    ScanSession session;
+    session.params.xres = dpi;
+    session.params.yres = dpi;
+    session.params.startx =  0;
+    session.params.starty =  0; /*we should give a small offset here~60 steps */
+    session.params.pixels = 600;
+    session.params.lines = dev->model->search_lines;
+    session.params.depth = 8;
+    session.params.channels =  1;
+    session.params.scan_method = dev->settings.scan_method;
+    session.params.scan_mode = ScanColorMode::GRAY;
+    session.params.color_filter = ColorFilter::GREEN;
+    session.params.flags = ScanFlag::DISABLE_SHADING |
+                           ScanFlag::DISABLE_GAMMA |
+                           ScanFlag::IGNORE_LINE_DISTANCE;
+    compute_session(dev, session, sensor);
+
+    init_regs_for_scan_session(dev, sensor, &local_reg, session);
+
+    // send to scanner
+    dev->interface->write_registers(local_reg);
+
+  size = pixels * dev->model->search_lines;
+
+  std::vector<uint8_t> data(size);
+
+    begin_scan(dev, sensor, &local_reg, true);
+
+    if (is_testing_mode()) {
+        dev->interface->test_checkpoint("search_start_position");
+        end_scan(dev, &local_reg, true);
+        dev->reg = local_reg;
+        return;
+    }
+
+    wait_until_buffer_non_empty(dev);
+
+    // now we're on target, we can read data
+    sanei_genesys_read_data_from_scanner(dev, data.data(), size);
+
+    if (DBG_LEVEL >= DBG_data) {
+        sanei_genesys_write_pnm_file("gl847_search_position.pnm", data.data(), 8, 1, pixels,
+                                     dev->model->search_lines);
+    }
+
+    end_scan(dev, &local_reg, true);
+
+  /* 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
+    for (auto& sensor_update :
+            sanei_genesys_find_sensors_all_for_write(dev, dev->model->default_method))
+    {
+        sanei_genesys_search_reference_point(dev, sensor_update, data.data(), 0, dpi, pixels,
+                                             dev->model->search_lines);
+    }
+}
+
+// sets up register for coarse gain calibration
+// todo: check it for scanners using it
+void CommandSetGl847::init_regs_for_coarse_calibration(Genesys_Device* dev,
+                                                       const Genesys_Sensor& sensor,
+                                                       Genesys_Register_Set& regs) const
+{
+    DBG_HELPER(dbg);
+
+    ScanSession session;
+    session.params.xres = dev->settings.xres;
+    session.params.yres = dev->settings.yres;
+    session.params.startx = 0;
+    session.params.starty = 0;
+    session.params.pixels = sensor.optical_res / sensor.ccd_pixels_per_system_pixel();
+    session.params.lines = 20;
+    session.params.depth = 16;
+    session.params.channels = dev->settings.get_channels();
+    session.params.scan_method = dev->settings.scan_method;
+    session.params.scan_mode = dev->settings.scan_mode;
+    session.params.color_filter = dev->settings.color_filter;
+    session.params.flags = ScanFlag::DISABLE_SHADING |
+                           ScanFlag::DISABLE_GAMMA |
+                           ScanFlag::SINGLE_LINE |
+                           ScanFlag::IGNORE_LINE_DISTANCE;
+    compute_session(dev, session, sensor);
+
+    init_regs_for_scan_session(dev, sensor, &regs, session);
+
+  DBG(DBG_info, "%s: optical sensor res: %d dpi, actual res: %d\n", __func__,
+      sensor.optical_res / sensor.ccd_pixels_per_system_pixel(), dev->settings.xres);
+
+    dev->interface->write_registers(regs);
+}
+
+// init registers for shading calibration
+void CommandSetGl847::init_regs_for_shading(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                            Genesys_Register_Set& regs) const
+{
+    DBG_HELPER(dbg);
+
+  dev->calib_channels = 3;
+
+  /* initial calibration reg values */
+  regs = dev->reg;
+
+    dev->calib_resolution = sensor.get_register_hwdpi(dev->settings.xres);
+
+    const auto& calib_sensor = sanei_genesys_find_sensor(dev, dev->calib_resolution,
+                                                         dev->calib_channels,
+                                                         dev->settings.scan_method);
+
+  dev->calib_total_bytes_to_read = 0;
+  dev->calib_lines = dev->model->shading_lines;
+    if (dev->calib_resolution == 4800) {
+        dev->calib_lines *= 2;
+    }
+    dev->calib_pixels = (calib_sensor.sensor_pixels * dev->calib_resolution) /
+                        calib_sensor.optical_res;
+
+    DBG(DBG_io, "%s: calib_lines  = %zu\n", __func__, dev->calib_lines);
+    DBG(DBG_io, "%s: calib_pixels = %zu\n", __func__, dev->calib_pixels);
+
+    ScanSession session;
+    session.params.xres = dev->calib_resolution;
+    session.params.yres = dev->motor.base_ydpi;
+    session.params.startx = 0;
+    session.params.starty = 20;
+    session.params.pixels = dev->calib_pixels;
+    session.params.lines = dev->calib_lines;
+    session.params.depth = 16;
+    session.params.channels = dev->calib_channels;
+    session.params.scan_method = dev->settings.scan_method;
+    session.params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    session.params.color_filter = dev->settings.color_filter;
+    session.params.flags = ScanFlag::DISABLE_SHADING |
+                           ScanFlag::DISABLE_GAMMA |
+                           ScanFlag::DISABLE_BUFFER_FULL_MOVE |
+                           ScanFlag::IGNORE_LINE_DISTANCE;
+    compute_session(dev, session, calib_sensor);
+
+    init_regs_for_scan_session(dev, calib_sensor, &regs, session);
+
+    dev->interface->write_registers(regs);
+
+  /* we use GENESYS_FLAG_SHADING_REPARK */
+    dev->set_head_pos_zero(ScanHeadId::PRIMARY);
+}
+
+/** @brief set up registers for the actual scan
+ */
+void CommandSetGl847::init_regs_for_scan(Genesys_Device* dev, const Genesys_Sensor& sensor) const
+{
+    DBG_HELPER(dbg);
+  float move;
+  int move_dpi;
+  float start;
+
+    debug_dump(DBG_info, dev->settings);
+
+  /* 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:
+     float y_offset;
+     float y_size;
+     float 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 = static_cast<float>(dev->model->y_offset);
+    move = static_cast<float>(move + dev->settings.tl_y);
+    move = static_cast<float>((move * move_dpi) / MM_PER_INCH);
+    move -= dev->head_pos(ScanHeadId::PRIMARY);
+  DBG(DBG_info, "%s: move=%f steps\n", __func__, move);
+
+  /* fast move to scan area */
+  /* we don't move fast the whole distance since it would involve
+   * computing acceleration/deceleration distance for scan
+   * resolution. So leave a remainder for it so scan makes the final
+   * move tuning */
+    if (dev->settings.get_channels() * dev->settings.yres >= 600 && move > 700) {
+        scanner_move(*dev, dev->model->default_method, static_cast<unsigned>(move - 500),
+                     Direction::FORWARD);
+      move=500;
+    }
+
+  DBG(DBG_info, "%s: move=%f steps\n", __func__, move);
+  DBG(DBG_info, "%s: move=%f steps\n", __func__, move);
+
+  /* start */
+    start = static_cast<float>(dev->model->x_offset);
+    start = static_cast<float>(start + dev->settings.tl_x);
+    start = static_cast<float>((start * sensor.optical_res) / MM_PER_INCH);
+
+    ScanSession session;
+    session.params.xres = dev->settings.xres;
+    session.params.yres = dev->settings.yres;
+    session.params.startx = static_cast<unsigned>(start);
+    session.params.starty = static_cast<unsigned>(move);
+    session.params.pixels = dev->settings.pixels;
+    session.params.requested_pixels = dev->settings.requested_pixels;
+    session.params.lines = dev->settings.lines;
+    session.params.depth = dev->settings.depth;
+    session.params.channels = dev->settings.get_channels();
+    session.params.scan_method = dev->settings.scan_method;
+    session.params.scan_mode = dev->settings.scan_mode;
+    session.params.color_filter = dev->settings.color_filter;
+    // backtracking isn't handled well, so don't enable it
+    session.params.flags = ScanFlag::DISABLE_BUFFER_FULL_MOVE;
+    compute_session(dev, session, sensor);
+
+    init_regs_for_scan_session(dev, sensor, &dev->reg, session);
+}
+
+
+/**
+ * Send shading calibration data. The buffer is considered to always hold values
+ * for all the channels.
+ */
+void CommandSetGl847::send_shading_data(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                        uint8_t* data, int size) const
+{
+    DBG_HELPER_ARGS(dbg, "writing %d bytes of shading data", size);
+  uint32_t addr, length, i, x, factor, pixels;
+    uint32_t dpiset, dpihw;
+  uint8_t val,*ptr,*src;
+
+  /* shading data is plit in 3 (up to 5 with IR) areas
+     write(0x10014000,0x00000dd8)
+     URB 23429  bulk_out len  3544  wrote 0x33 0x10 0x....
+     write(0x1003e000,0x00000dd8)
+     write(0x10068000,0x00000dd8)
+   */
+    length = static_cast<std::uint32_t>(size / 3);
+    std::uint32_t strpixel = dev->session.pixel_startx;
+    std::uint32_t endpixel = dev->session.pixel_endx;
+
+  /* compute deletion factor */
+    dpiset = dev->reg.get16(REG_DPISET);
+    dpihw = sensor.get_register_hwdpi(dpiset);
+  factor=dpihw/dpiset;
+  DBG(DBG_io2, "%s: factor=%d\n", __func__, factor);
+
+  pixels=endpixel-strpixel;
+
+  /* since we're using SHDAREA, substract startx coordinate from shading */
+    strpixel -= (sensor.ccd_start_xoffset * 600) / sensor.optical_res;
+
+  /* turn pixel value into bytes 2x16 bits words */
+  strpixel*=2*2;
+  pixels*=2*2;
+
+    dev->interface->record_key_value("shading_offset", std::to_string(strpixel));
+    dev->interface->record_key_value("shading_pixels", std::to_string(pixels));
+    dev->interface->record_key_value("shading_length", std::to_string(length));
+    dev->interface->record_key_value("shading_factor", std::to_string(factor));
+
+  std::vector<uint8_t> buffer(pixels, 0);
+
+  DBG(DBG_io2, "%s: using chunks of %d (0x%04x) bytes\n", __func__, pixels, pixels);
+
+  /* base addr of data has been written in reg D0-D4 in 4K word, so AHB address
+   * is 8192*reg value */
+
+  /* write actual color channel data */
+  for(i=0;i<3;i++)
+    {
+      /* build up actual shading data by copying the part from the full width one
+       * to the one corresponding to SHDAREA */
+      ptr = buffer.data();
+
+      /* iterate on both sensor segment */
+      for(x=0;x<pixels;x+=4*factor)
+        {
+          /* coefficient source */
+          src=(data+strpixel+i*length)+x;
+
+          /* coefficient copy */
+          ptr[0]=src[0];
+          ptr[1]=src[1];
+          ptr[2]=src[2];
+          ptr[3]=src[3];
+
+          /* next shading coefficient */
+          ptr+=4;
+        }
+
+        val = dev->interface->read_register(0xd0+i);
+        addr = val * 8192 + 0x10000000;
+        dev->interface->write_ahb(addr, pixels, buffer.data());
+    }
+}
+
+/** @brief calibrates led exposure
+ * Calibrate exposure by scanning a white area until the used exposure gives
+ * data white enough.
+ * @param dev device to calibrate
+ */
+SensorExposure CommandSetGl847::led_calibration(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                                Genesys_Register_Set& regs) const
+{
+    DBG_HELPER(dbg);
+  int num_pixels;
+  int total_size;
+  int used_res;
+  int i, j;
+  int val;
+    int channels;
+  int avg[3], top[3], bottom[3];
+  int turn;
+  uint16_t exp[3];
+  float move;
+
+    move = static_cast<float>(dev->model->y_offset_calib_white);
+    move = static_cast<float>((move * (dev->motor.base_ydpi / 4)) / MM_PER_INCH);
+    if (move > 20) {
+        scanner_move(*dev, dev->model->default_method, static_cast<unsigned>(move),
+                     Direction::FORWARD);
+    }
+  DBG(DBG_io, "%s: move=%f steps\n", __func__, move);
+
+  /* offset calibration is always done in color mode */
+  channels = 3;
+    used_res = sensor.get_register_hwdpi(dev->settings.xres);
+    const auto& calib_sensor = sanei_genesys_find_sensor(dev, used_res, channels,
+                                                         dev->settings.scan_method);
+    num_pixels = (calib_sensor.sensor_pixels * used_res) / calib_sensor.optical_res;
+
+  /* initial calibration reg values */
+  regs = dev->reg;
+
+    ScanSession session;
+    session.params.xres = used_res;
+    session.params.yres = used_res;
+    session.params.startx = 0;
+    session.params.starty = 0;
+    session.params.pixels = num_pixels;
+    session.params.lines = 1;
+    session.params.depth = 16;
+    session.params.channels = channels;
+    session.params.scan_method = dev->settings.scan_method;
+    session.params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    session.params.color_filter = dev->settings.color_filter;
+    session.params.flags = ScanFlag::DISABLE_SHADING |
+                           ScanFlag::DISABLE_GAMMA |
+                           ScanFlag::SINGLE_LINE |
+                           ScanFlag::IGNORE_LINE_DISTANCE;
+    compute_session(dev, session, calib_sensor);
+
+    init_regs_for_scan_session(dev, calib_sensor, &regs, session);
+
+    total_size = num_pixels * channels * (session.params.depth/8) * 1;
+  std::vector<uint8_t> line(total_size);
+
+    // initial loop values and boundaries
+    exp[0] = calib_sensor.exposure.red;
+    exp[1] = calib_sensor.exposure.green;
+    exp[2] = calib_sensor.exposure.blue;
+
+    bottom[0] = 28000;
+    bottom[1] = 28000;
+    bottom[2] = 28000;
+
+    top[0] = 32000;
+    top[1] = 32000;
+    top[2] = 32000;
+
+  turn = 0;
+
+  /* no move during led calibration */
+    bool acceptable = false;
+  sanei_genesys_set_motor_power(regs, false);
+  do
+    {
+        // set up exposure
+        regs.set16(REG_EXPR,exp[0]);
+        regs.set16(REG_EXPG,exp[1]);
+        regs.set16(REG_EXPB,exp[2]);
+
+        // write registers and scan data
+        dev->interface->write_registers(regs);
+
+      DBG(DBG_info, "%s: starting line reading\n", __func__);
+        begin_scan(dev, calib_sensor, &regs, true);
+
+        if (is_testing_mode()) {
+            dev->interface->test_checkpoint("led_calibration");
+            scanner_stop_action(*dev);
+            move_back_home(dev, true);
+            return calib_sensor.exposure;
+        }
+
+        sanei_genesys_read_data_from_scanner(dev, line.data(), total_size);
+
+        // stop scanning
+        scanner_stop_action(*dev);
+
+      if (DBG_LEVEL >= DBG_data)
+	{
+          char fn[30];
+            std::snprintf(fn, 30, "gl847_led_%02d.pnm", turn);
+            sanei_genesys_write_pnm_file(fn, line.data(), session.params.depth,
+                                         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]);
+
+      /* check if exposure gives average within the boundaries */
+        acceptable = true;
+      for(i=0;i<3;i++)
+        {
+            if (avg[i] < bottom[i] || avg[i] > top[i]) {
+                auto target = (bottom[i] + top[i]) / 2;
+                exp[i] = (exp[i] * target) / avg[i];
+                acceptable = false;
+            }
+        }
+
+      turn++;
+    }
+  while (!acceptable && turn < 100);
+
+  DBG(DBG_info, "%s: acceptable exposure: %d,%d,%d\n", __func__, exp[0], exp[1], exp[2]);
+
+    // set these values as final ones for scan
+    dev->reg.set16(REG_EXPR, exp[0]);
+    dev->reg.set16(REG_EXPG, exp[1]);
+    dev->reg.set16(REG_EXPB, exp[2]);
+
+    // go back home
+    if (move>20) {
+        move_back_home(dev, true);
+    }
+
+    return { exp[0], exp[1], exp[2] };
+}
+
+/**
+ * set up GPIO/GPOE for idle state
+ */
+static void gl847_init_gpio(Genesys_Device* dev)
+{
+    DBG_HELPER(dbg);
+  int idx=0;
+
+  /* search GPIO profile */
+    while(gpios[idx].gpio_id != GpioId::UNKNOWN && dev->model->gpio_id != gpios[idx].gpio_id) {
+      idx++;
+    }
+    if (gpios[idx].gpio_id == GpioId::UNKNOWN) {
+        throw SaneException("failed to find GPIO profile for sensor_id=%d",
+                            static_cast<unsigned>(dev->model->sensor_id));
+    }
+
+    dev->interface->write_register(REG_0xA7, gpios[idx].ra7);
+    dev->interface->write_register(REG_0xA6, gpios[idx].ra6);
+
+    dev->interface->write_register(REG_0x6E, gpios[idx].r6e);
+    dev->interface->write_register(REG_0x6C, 0x00);
+
+    dev->interface->write_register(REG_0x6B, gpios[idx].r6b);
+    dev->interface->write_register(REG_0x6C, gpios[idx].r6c);
+    dev->interface->write_register(REG_0x6D, gpios[idx].r6d);
+    dev->interface->write_register(REG_0x6E, gpios[idx].r6e);
+    dev->interface->write_register(REG_0x6F, gpios[idx].r6f);
+
+    dev->interface->write_register(REG_0xA8, gpios[idx].ra8);
+    dev->interface->write_register(REG_0xA9, gpios[idx].ra9);
+}
+
+/**
+ * set memory layout by filling values in dedicated registers
+ */
+static void gl847_init_memory_layout(Genesys_Device* dev)
+{
+    DBG_HELPER(dbg);
+  int idx = 0;
+  uint8_t val;
+
+  /* point to per model memory layout */
+  idx = 0;
+    if (dev->model->model_id == ModelId::CANON_LIDE_100) {
+      idx = 0;
+    }
+    if (dev->model->model_id == ModelId::CANON_LIDE_200) {
+      idx = 1;
+    }
+    if (dev->model->model_id == ModelId::CANON_5600F) {
+      idx = 2;
+    }
+    if (dev->model->model_id == ModelId::CANON_LIDE_700F) {
+      idx = 3;
+    }
+
+  /* CLKSET nd DRAMSEL */
+  val = layouts[idx].dramsel;
+    dev->interface->write_register(REG_0x0B, val);
+  dev->reg.find_reg(0x0b).value = val;
+
+  /* prevent further writings by bulk write register */
+  dev->reg.remove_reg(0x0b);
+
+  /* setup base address for shading data. */
+  /* values must be multiplied by 8192=0x4000 to give address on AHB */
+  /* R-Channel shading bank0 address setting for CIS */
+    dev->interface->write_register(0xd0, layouts[idx].rd0);
+  /* G-Channel shading bank0 address setting for CIS */
+    dev->interface->write_register(0xd1, layouts[idx].rd1);
+  /* B-Channel shading bank0 address setting for CIS */
+    dev->interface->write_register(0xd2, layouts[idx].rd2);
+
+  /* setup base address for scanned data. */
+  /* values must be multiplied by 1024*2=0x0800 to give address on AHB */
+  /* R-Channel ODD image buffer 0x0124->0x92000 */
+  /* size for each buffer is 0x16d*1k word */
+    dev->interface->write_register(0xe0, layouts[idx].re0);
+    dev->interface->write_register(0xe1, layouts[idx].re1);
+  /* R-Channel ODD image buffer end-address 0x0291->0x148800 => size=0xB6800*/
+    dev->interface->write_register(0xe2, layouts[idx].re2);
+    dev->interface->write_register(0xe3, layouts[idx].re3);
+
+  /* R-Channel EVEN image buffer 0x0292 */
+    dev->interface->write_register(0xe4, layouts[idx].re4);
+    dev->interface->write_register(0xe5, layouts[idx].re5);
+  /* R-Channel EVEN image buffer end-address 0x03ff*/
+    dev->interface->write_register(0xe6, layouts[idx].re6);
+    dev->interface->write_register(0xe7, layouts[idx].re7);
+
+  /* same for green, since CIS, same addresses */
+    dev->interface->write_register(0xe8, layouts[idx].re0);
+    dev->interface->write_register(0xe9, layouts[idx].re1);
+    dev->interface->write_register(0xea, layouts[idx].re2);
+    dev->interface->write_register(0xeb, layouts[idx].re3);
+    dev->interface->write_register(0xec, layouts[idx].re4);
+    dev->interface->write_register(0xed, layouts[idx].re5);
+    dev->interface->write_register(0xee, layouts[idx].re6);
+    dev->interface->write_register(0xef, layouts[idx].re7);
+
+/* same for blue, since CIS, same addresses */
+    dev->interface->write_register(0xf0, layouts[idx].re0);
+    dev->interface->write_register(0xf1, layouts[idx].re1);
+    dev->interface->write_register(0xf2, layouts[idx].re2);
+    dev->interface->write_register(0xf3, layouts[idx].re3);
+    dev->interface->write_register(0xf4, layouts[idx].re4);
+    dev->interface->write_register(0xf5, layouts[idx].re5);
+    dev->interface->write_register(0xf6, layouts[idx].re6);
+    dev->interface->write_register(0xf7, layouts[idx].re7);
+}
+
+/* *
+ * initialize ASIC from power on condition
+ */
+void CommandSetGl847::asic_boot(Genesys_Device* dev, bool cold) const
+{
+    DBG_HELPER(dbg);
+
+    // reset ASIC if cold boot
+    if (cold) {
+        dev->interface->write_register(0x0e, 0x01);
+        dev->interface->write_register(0x0e, 0x00);
+    }
+
+    // test CHKVER
+    uint8_t val = dev->interface->read_register(REG_0x40);
+    if (val & REG_0x40_CHKVER) {
+        val = dev->interface->read_register(0x00);
+        DBG(DBG_info, "%s: reported version for genesys chip is 0x%02x\n", __func__, val);
+    }
+
+  /* Set default values for registers */
+  gl847_init_registers (dev);
+
+    // Write initial registers
+    dev->interface->write_registers(dev->reg);
+
+  /* Enable DRAM by setting a rising edge on bit 3 of reg 0x0b */
+    val = dev->reg.find_reg(0x0b).value & REG_0x0B_DRAMSEL;
+    val = (val | REG_0x0B_ENBDRAM);
+    dev->interface->write_register(REG_0x0B, val);
+    dev->reg.find_reg(0x0b).value = val;
+
+  /* CIS_LINE */
+    dev->reg.init_reg(0x08, REG_0x08_CIS_LINE);
+    dev->interface->write_register(0x08, dev->reg.find_reg(0x08).value);
+
+    // set up end access
+    dev->interface->write_0x8c(0x10, 0x0b);
+    dev->interface->write_0x8c(0x13, 0x0e);
+
+    // setup gpio
+    gl847_init_gpio(dev);
+
+    // setup internal memory layout
+    gl847_init_memory_layout (dev);
+
+    dev->reg.init_reg(0xf8, 0x01);
+    dev->interface->write_register(0xf8, dev->reg.find_reg(0xf8).value);
+}
+
+/**
+ * initialize backend and ASIC : registers, motor tables, and gamma tables
+ * then ensure scanner's head is at home
+ */
+void CommandSetGl847::init(Genesys_Device* dev) const
+{
+  DBG_INIT ();
+    DBG_HELPER(dbg);
+
+    sanei_genesys_asic_init(dev, 0);
+}
+
+void CommandSetGl847::update_hardware_sensors(Genesys_Scanner* s) const
+{
+    DBG_HELPER(dbg);
+  /* do what is needed to get a new set of events, but try to not lose
+     any of them.
+   */
+  uint8_t val;
+  uint8_t scan, file, email, copy;
+    switch(s->dev->model->gpio_id) {
+    case GpioId::CANON_LIDE_700F:
+        scan=0x04;
+        file=0x02;
+        email=0x01;
+        copy=0x08;
+        break;
+    default:
+        scan=0x01;
+        file=0x02;
+        email=0x04;
+        copy=0x08;
+    }
+    val = s->dev->interface->read_register(REG_0x6D);
+
+    s->buttons[BUTTON_SCAN_SW].write((val & scan) == 0);
+    s->buttons[BUTTON_FILE_SW].write((val & file) == 0);
+    s->buttons[BUTTON_EMAIL_SW].write((val & email) == 0);
+    s->buttons[BUTTON_COPY_SW].write((val & copy) == 0);
+}
+
+void CommandSetGl847::update_home_sensor_gpio(Genesys_Device& dev) const
+{
+    DBG_HELPER(dbg);
+
+    if (dev.model->gpio_id == GpioId::CANON_LIDE_700F) {
+        std::uint8_t val = dev.interface->read_register(REG_0x6C);
+        val &= ~REG_0x6C_GPIO10;
+        dev.interface->write_register(REG_0x6C, val);
+    } else {
+        std::uint8_t val = dev.interface->read_register(REG_0x6C);
+        val |= REG_0x6C_GPIO10;
+        dev.interface->write_register(REG_0x6C, val);
+    }
+}
+
+/** @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 true if searching forward, false if searching backward
+ * @param black true if searching for a black strip, false for a white strip
+ */
+void CommandSetGl847::search_strip(Genesys_Device* dev, const Genesys_Sensor& sensor, bool forward,
+                                   bool black) const
+{
+    DBG_HELPER_ARGS(dbg, "%s %s", black ? "black" : "white", forward ? "forward" : "reverse");
+  unsigned int pixels, lines, channels;
+  Genesys_Register_Set local_reg;
+  size_t size;
+  unsigned int pass, count, found, x, y;
+  char title[80];
+
+    set_fe(dev, sensor, AFE_SET);
+    scanner_stop_action(*dev);
+
+    // set up for a gray scan at lowest dpi
+    const auto& resolution_settings = dev->model->get_resolution_settings(dev->settings.scan_method);
+    unsigned dpi = resolution_settings.get_min_resolution_x();
+  channels = 1;
+  /* 10 MM */
+  /* lines = (10 * dpi) / MM_PER_INCH; */
+  /* shading calibation is done with dev->motor.base_ydpi */
+  lines = (dev->model->shading_lines * dpi) / dev->motor.base_ydpi;
+  pixels = (sensor.sensor_pixels * dpi) / sensor.optical_res;
+    dev->set_head_pos_zero(ScanHeadId::PRIMARY);
+
+  local_reg = dev->reg;
+
+    ScanSession session;
+    session.params.xres = dpi;
+    session.params.yres = dpi;
+    session.params.startx = 0;
+    session.params.starty = 0;
+    session.params.pixels = pixels;
+    session.params.lines = lines;
+    session.params.depth = 8;
+    session.params.channels = channels;
+    session.params.scan_method = dev->settings.scan_method;
+    session.params.scan_mode = ScanColorMode::GRAY;
+    session.params.color_filter = ColorFilter::RED;
+    session.params.flags = ScanFlag::DISABLE_SHADING |
+                           ScanFlag::DISABLE_GAMMA;
+    if (!forward) {
+        session.params.flags |= ScanFlag::REVERSE;
+    }
+    compute_session(dev, session, sensor);
+
+    size = pixels * channels * lines * (session.params.depth / 8);
+    std::vector<uint8_t> data(size);
+
+    init_regs_for_scan_session(dev, sensor, &local_reg, session);
+
+    dev->interface->write_registers(local_reg);
+
+    begin_scan(dev, sensor, &local_reg, true);
+
+    if (is_testing_mode()) {
+        dev->interface->test_checkpoint("search_strip");
+        scanner_stop_action(*dev);
+        return;
+    }
+
+    wait_until_buffer_non_empty(dev);
+
+    // now we're on target, we can read data
+    sanei_genesys_read_data_from_scanner(dev, data.data(), size);
+
+    scanner_stop_action(*dev);
+
+  pass = 0;
+  if (DBG_LEVEL >= DBG_data)
+    {
+        std::sprintf(title, "gl847_search_strip_%s_%s%02d.pnm",
+                     black ? "black" : "white", forward ? "fwd" : "bwd", pass);
+        sanei_genesys_write_pnm_file(title, data.data(), session.params.depth,
+                                     channels, pixels, lines);
+    }
+
+  /* loop until strip is found or maximum pass number done */
+  found = 0;
+  while (pass < 20 && !found)
+    {
+        dev->interface->write_registers(local_reg);
+
+        // now start scan
+        begin_scan(dev, sensor, &local_reg, true);
+
+        wait_until_buffer_non_empty(dev);
+
+        // now we're on target, we can read data
+        sanei_genesys_read_data_from_scanner(dev, data.data(), size);
+
+    scanner_stop_action(*dev);
+
+      if (DBG_LEVEL >= DBG_data)
+	{
+            std::sprintf(title, "gl847_search_strip_%s_%s%02d.pnm",
+                         black ? "black" : "white",
+                         forward ? "fwd" : "bwd", static_cast<int>(pass));
+            sanei_genesys_write_pnm_file(title, data.data(), session.params.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] > 90)
+		    {
+		      count++;
+		    }
+		  /* when searching for white, detect black pixels */
+		  if (!black && data[y * pixels + x] < 60)
+		    {
+		      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] > 90)
+		    {
+		      count++;
+		    }
+		  /* when searching for white, detect black pixels */
+		  if (!black && data[y * pixels + x] < 60)
+		    {
+		      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)
+    {
+      DBG(DBG_info, "%s: %s strip found\n", __func__, black ? "black" : "white");
+    }
+  else
+    {
+        throw SaneException(SANE_STATUS_UNSUPPORTED, "%s strip not found", black ? "black" : "white");
+    }
+}
+
+/**
+ * average dark pixels of a 8 bits scan
+ */
+static int
+dark_average (uint8_t * data, unsigned int pixels, unsigned int lines,
+	      unsigned int channels, unsigned int black)
+{
+  unsigned int i, j, k, average, count;
+  unsigned int avg[3];
+  uint8_t val;
+
+  /* computes average value on black margin */
+  for (k = 0; k < channels; k++)
+    {
+      avg[k] = 0;
+      count = 0;
+      for (i = 0; i < lines; i++)
+	{
+	  for (j = 0; j < black; j++)
+	    {
+	      val = data[i * channels * pixels + j + k];
+	      avg[k] += val;
+	      count++;
+	    }
+	}
+      if (count)
+	avg[k] /= count;
+      DBG(DBG_info, "%s: avg[%d] = %d\n", __func__, k, avg[k]);
+    }
+  average = 0;
+  for (i = 0; i < channels; i++)
+    average += avg[i];
+  average /= channels;
+  DBG(DBG_info, "%s: average = %d\n", __func__, average);
+  return average;
+}
+
+void CommandSetGl847::offset_calibration(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                         Genesys_Register_Set& regs) const
+{
+    DBG_HELPER(dbg);
+    unsigned channels;
+  int pass = 0, avg, total_size;
+    int topavg, bottomavg, lines;
+  int top, bottom, black_pixels, pixels;
+
+    // no gain nor offset for AKM AFE
+    uint8_t reg04 = dev->interface->read_register(REG_0x04);
+    if ((reg04 & REG_0x04_FESET) == 0x02) {
+      return;
+    }
+
+  /* offset calibration is always done in color mode */
+  channels = 3;
+  dev->calib_pixels = sensor.sensor_pixels;
+  lines=1;
+    pixels= (sensor.sensor_pixels * sensor.optical_res) / sensor.optical_res;
+    black_pixels = (sensor.black_pixels * sensor.optical_res) / sensor.optical_res;
+  DBG(DBG_io2, "%s: black_pixels=%d\n", __func__, black_pixels);
+
+    ScanSession session;
+    session.params.xres = sensor.optical_res;
+    session.params.yres = sensor.optical_res;
+    session.params.startx = 0;
+    session.params.starty = 0;
+    session.params.pixels = pixels;
+    session.params.lines = lines;
+    session.params.depth = 8;
+    session.params.channels = channels;
+    session.params.scan_method = dev->settings.scan_method;
+    session.params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    session.params.color_filter = dev->settings.color_filter;
+    session.params.flags = ScanFlag::DISABLE_SHADING |
+                           ScanFlag::DISABLE_GAMMA |
+                           ScanFlag::SINGLE_LINE |
+                           ScanFlag::IGNORE_LINE_DISTANCE;
+    compute_session(dev, session, sensor);
+
+    init_regs_for_scan_session(dev, sensor, &regs, session);
+
+  sanei_genesys_set_motor_power(regs, false);
+
+  /* allocate memory for scans */
+  total_size = pixels * channels * lines * (session.params.depth / 8);	/* colors * bytes_per_color * scan lines */
+
+  std::vector<uint8_t> first_line(total_size);
+  std::vector<uint8_t> second_line(total_size);
+
+  /* init gain */
+  dev->frontend.set_gain(0, 0);
+  dev->frontend.set_gain(1, 0);
+  dev->frontend.set_gain(2, 0);
+
+  /* scan with no move */
+  bottom = 10;
+  dev->frontend.set_offset(0, bottom);
+  dev->frontend.set_offset(1, bottom);
+  dev->frontend.set_offset(2, bottom);
+
+    set_fe(dev, sensor, AFE_SET);
+    dev->interface->write_registers(regs);
+  DBG(DBG_info, "%s: starting first line reading\n", __func__);
+    begin_scan(dev, sensor, &regs, true);
+
+    if (is_testing_mode()) {
+        dev->interface->test_checkpoint("offset_calibration");
+        return;
+    }
+
+    sanei_genesys_read_data_from_scanner(dev, first_line.data(), total_size);
+  if (DBG_LEVEL >= DBG_data)
+   {
+      char fn[30];
+        std::snprintf(fn, 30, "gl847_offset%03d.pnm", bottom);
+        sanei_genesys_write_pnm_file(fn, first_line.data(), session.params.depth,
+                                     channels, pixels, lines);
+   }
+
+  bottomavg = dark_average (first_line.data(), pixels, lines, channels, black_pixels);
+  DBG(DBG_io2, "%s: bottom avg=%d\n", __func__, bottomavg);
+
+  /* now top value */
+  top = 255;
+  dev->frontend.set_offset(0, top);
+  dev->frontend.set_offset(1, top);
+  dev->frontend.set_offset(2, top);
+    set_fe(dev, sensor, AFE_SET);
+    dev->interface->write_registers(regs);
+  DBG(DBG_info, "%s: starting second line reading\n", __func__);
+    begin_scan(dev, sensor, &regs, true);
+    sanei_genesys_read_data_from_scanner(dev, second_line.data(), total_size);
+
+  topavg = dark_average(second_line.data(), pixels, lines, channels, black_pixels);
+  DBG(DBG_io2, "%s: top avg=%d\n", __func__, topavg);
+
+  /* loop until acceptable level */
+  while ((pass < 32) && (top - bottom > 1))
+    {
+      pass++;
+
+      /* settings for new scan */
+      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 with no move
+        set_fe(dev, sensor, AFE_SET);
+        dev->interface->write_registers(regs);
+      DBG(DBG_info, "%s: starting second line reading\n", __func__);
+        begin_scan(dev, sensor, &regs, true);
+        sanei_genesys_read_data_from_scanner(dev, second_line.data(), total_size);
+
+      if (DBG_LEVEL >= DBG_data)
+	{
+          char fn[30];
+          std::snprintf(fn, 30, "gl847_offset%03d.pnm", dev->frontend.get_offset(1));
+          sanei_genesys_write_pnm_file(fn, second_line.data(), session.params.depth,
+                                       channels, pixels, lines);
+	}
+
+      avg = dark_average(second_line.data(), pixels, lines, channels, black_pixels);
+      DBG(DBG_info, "%s: avg=%d offset=%d\n", __func__, avg, dev->frontend.get_offset(1));
+
+      /* compute new boundaries */
+      if (topavg == avg)
+	{
+	  topavg = avg;
+          top = dev->frontend.get_offset(1);
+	}
+      else
+	{
+	  bottomavg = avg;
+          bottom = dev->frontend.get_offset(1);
+	}
+    }
+  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));
+}
+
+void CommandSetGl847::coarse_gain_calibration(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                              Genesys_Register_Set& regs, int dpi) const
+{
+    DBG_HELPER_ARGS(dbg, "dpi = %d", dpi);
+  int pixels;
+  int total_size;
+  int i, j, channels;
+  int max[3];
+  float gain[3],coeff;
+  int val, code, lines;
+
+    // no gain nor offset for AKM AFE
+    uint8_t reg04 = dev->interface->read_register(REG_0x04);
+    if ((reg04 & REG_0x04_FESET) == 0x02) {
+      return;
+    }
+
+  /* coarse gain calibration is always done in color mode */
+  channels = 3;
+
+  /* follow CKSEL */
+  if(dev->settings.xres<sensor.optical_res)
+    {
+        coeff = 0.9f;
+    }
+  else
+    {
+      coeff=1.0;
+    }
+  lines=10;
+    pixels = (sensor.sensor_pixels * sensor.optical_res) / sensor.optical_res;
+
+    ScanSession session;
+    session.params.xres = sensor.optical_res;
+    session.params.yres = sensor.optical_res;
+    session.params.startx = 0;
+    session.params.starty = 0;
+    session.params.pixels = pixels;
+    session.params.lines = lines;
+    session.params.depth = 8;
+    session.params.channels = channels;
+    session.params.scan_method = dev->settings.scan_method;
+    session.params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    session.params.color_filter = dev->settings.color_filter;
+    session.params.flags = ScanFlag::DISABLE_SHADING |
+                           ScanFlag::DISABLE_GAMMA |
+                           ScanFlag::SINGLE_LINE |
+                           ScanFlag::IGNORE_LINE_DISTANCE;
+    compute_session(dev, session, sensor);
+
+    try {
+        init_regs_for_scan_session(dev, sensor, &regs, session);
+    } catch (...) {
+        catch_all_exceptions(__func__, [&](){ sanei_genesys_set_motor_power(regs, false); });
+        throw;
+    }
+
+    sanei_genesys_set_motor_power(regs, false);
+
+    dev->interface->write_registers(regs);
+
+    total_size = pixels * channels * (16 / session.params.depth) * lines;
+
+  std::vector<uint8_t> line(total_size);
+
+    set_fe(dev, sensor, AFE_SET);
+    begin_scan(dev, sensor, &regs, true);
+
+    if (is_testing_mode()) {
+        dev->interface->test_checkpoint("coarse_gain_calibration");
+        scanner_stop_action(*dev);
+        move_back_home(dev, true);
+        return;
+    }
+
+    sanei_genesys_read_data_from_scanner(dev, line.data(), total_size);
+
+    if (DBG_LEVEL >= DBG_data) {
+        sanei_genesys_write_pnm_file("gl847_gain.pnm", line.data(), session.params.depth,
+                                     channels, pixels, lines);
+    }
+
+  /* average value on each channel */
+  for (j = 0; j < channels; j++)
+    {
+      max[j] = 0;
+      for (i = pixels/4; i < (pixels*3/4); i++)
+	{
+            if (dev->model->is_cis) {
+                val = line[i + j * pixels];
+            } else {
+                val = line[i * channels + j];
+            }
+
+	    max[j] += val;
+	}
+      max[j] = max[j] / (pixels/2);
+
+      gain[j] = (static_cast<float>(sensor.gain_white_ref) * coeff) / max[j];
+
+      /* turn logical gain value into gain code, checking for overflow */
+        code = static_cast<int>(283 - 208 / gain[j]);
+      if (code > 255)
+	code = 255;
+      else if (code < 0)
+	code = 0;
+      dev->frontend.set_gain(j, code);
+
+      DBG(DBG_proc, "%s: channel %d, max=%d, gain = %f, setting:%d\n", __func__, j, max[j], gain[j],
+          dev->frontend.get_gain(j));
+    }
+
+    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));
+    }
+
+    scanner_stop_action(*dev);
+
+    move_back_home(dev, true);
+}
+
+bool CommandSetGl847::needs_home_before_init_regs_for_scan(Genesys_Device* dev) const
+{
+    (void) dev;
+    return false;
+}
+
+void CommandSetGl847::init_regs_for_warmup(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                           Genesys_Register_Set* regs, int* channels,
+                                           int* total_size) const
+{
+    (void) dev;
+    (void) sensor;
+    (void) regs;
+    (void) channels;
+    (void) total_size;
+    throw SaneException("not implemented");
+}
+
+void CommandSetGl847::send_gamma_table(Genesys_Device* dev, const Genesys_Sensor& sensor) const
+{
+    sanei_genesys_send_gamma_table(dev, sensor);
+}
+
+void CommandSetGl847::wait_for_motor_stop(Genesys_Device* dev) const
+{
+    (void) dev;
+}
+
+void CommandSetGl847::load_document(Genesys_Device* dev) const
+{
+    (void) dev;
+    throw SaneException("not implemented");
+}
+
+void CommandSetGl847::detect_document_end(Genesys_Device* dev) const
+{
+    (void) dev;
+    throw SaneException("not implemented");
+}
+
+void CommandSetGl847::eject_document(Genesys_Device* dev) const
+{
+    (void) dev;
+    throw SaneException("not implemented");
+}
+
+void CommandSetGl847::move_to_ta(Genesys_Device* dev) const
+{
+    (void) dev;
+    throw SaneException("not implemented");
+}
+
+std::unique_ptr<CommandSet> create_gl847_cmd_set()
+{
+    return std::unique_ptr<CommandSet>(new CommandSetGl847{});
+}
+
+} // namespace gl847
+} // namespace genesys