Update upstream source from tag 'upstream/1.0.29'

Update to upstream version '1.0.29'
with Debian dir 2d358af604988ebe4348e38096245d66036fe5ed

1 files changed, 3436 insertions, 0 deletions

diff --git a/backend/genesys/gl646.cpp b/backend/genesys/gl646.cpp
new file mode 100644
index 0000000..04ee85e
--- /dev/null
+++ b/backend/genesys/gl646.cpp
@@ -0,0 +1,3436 @@
+/* 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) 2005-2009 Pierre Willenbrock <pierre@pirsoft.dnsalias.org>
+   Copyright (C) 2007 Luke <iceyfor@gmail.com>
+   Copyright (C) 2011 Alexey Osipov <simba@lerlan.ru> for HP2400 description
+                      and tuning
+
+   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 "gl646.h"
+#include "gl646_registers.h"
+#include "test_settings.h"
+
+#include <vector>
+
+namespace genesys {
+namespace gl646 {
+
+namespace {
+constexpr unsigned CALIBRATION_LINES = 10;
+} // namespace
+
+static void gl646_send_slope_table(Genesys_Device* dev, int table_nr,
+                                   const std::vector<uint16_t>& slope_table,
+                                   int steps);
+
+/**
+ * reads value from gpio endpoint
+ */
+static void gl646_gpio_read(IUsbDevice& usb_dev, uint8_t* value)
+{
+    DBG_HELPER(dbg);
+    usb_dev.control_msg(REQUEST_TYPE_IN, REQUEST_REGISTER, GPIO_READ, INDEX, 1, value);
+}
+
+/**
+ * writes the given value to gpio endpoint
+ */
+static void gl646_gpio_write(IUsbDevice& usb_dev, uint8_t value)
+{
+    DBG_HELPER_ARGS(dbg, "(0x%02x)", value);
+    usb_dev.control_msg(REQUEST_TYPE_OUT, REQUEST_REGISTER, GPIO_WRITE, INDEX, 1, &value);
+}
+
+/**
+ * writes the given value to gpio output enable endpoint
+ */
+static void gl646_gpio_output_enable(IUsbDevice& usb_dev, uint8_t value)
+{
+    DBG_HELPER_ARGS(dbg, "(0x%02x)", value);
+    usb_dev.control_msg(REQUEST_TYPE_OUT, REQUEST_REGISTER, GPIO_OUTPUT_ENABLE, INDEX, 1, &value);
+}
+
+/**
+ * stop scanner's motor
+ * @param dev scanner's device
+ */
+static void gl646_stop_motor(Genesys_Device* dev)
+{
+    DBG_HELPER(dbg);
+    dev->interface->write_register(0x0f, 0x00);
+}
+
+/**
+ * find the closest match in mode tables for the given resolution and scan mode.
+ * @param sensor id of the sensor
+ * @param required required resolution
+ * @param color true is color mode
+ * @return the closest resolution for the sensor and mode
+ */
+static unsigned get_closest_resolution(SensorId sensor_id, int required, unsigned channels)
+{
+    unsigned best_res = 0;
+    unsigned best_diff = 9600;
+
+    for (const auto& sensor : *s_sensors) {
+        if (sensor_id != sensor.sensor_id)
+            continue;
+
+        // exit on perfect match
+        if (sensor.resolutions.matches(required) && sensor.matches_channel_count(channels)) {
+            DBG(DBG_info, "%s: match found for %d\n", __func__, required);
+            return required;
+        }
+
+        // computes distance and keep mode if it is closer than previous
+        if (sensor.matches_channel_count(channels)) {
+            for (auto res : sensor.resolutions.resolutions()) {
+                unsigned curr_diff = std::abs(static_cast<int>(res) - static_cast<int>(required));
+                if (curr_diff < best_diff) {
+                    best_res = res;
+                    best_diff = curr_diff;
+                }
+            }
+        }
+    }
+
+    DBG(DBG_info, "%s: closest match for %d is %d\n", __func__, required, best_res);
+    return best_res;
+}
+
+/**
+ * Returns the cksel values used by the required scan mode.
+ * @param sensor id of the sensor
+ * @param required required resolution
+ * @param color true is color mode
+ * @return cksel value for mode
+ */
+static int get_cksel(SensorId sensor_id, int required, unsigned channels)
+{
+    for (const auto& sensor : *s_sensors) {
+        // exit on perfect match
+        if (sensor.sensor_id == sensor_id && sensor.resolutions.matches(required) &&
+            sensor.matches_channel_count(channels))
+        {
+            unsigned cksel = sensor.ccd_pixels_per_system_pixel();
+            DBG(DBG_io, "%s: match found for %d (cksel=%d)\n", __func__, required, cksel);
+            return cksel;
+        }
+    }
+  DBG(DBG_error, "%s: failed to find match for %d dpi\n", __func__, required);
+  /* fail safe fallback */
+  return 1;
+}
+
+void CommandSetGl646::init_regs_for_scan_session(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                                 Genesys_Register_Set* regs,
+                                                 const ScanSession& session) const
+{
+    DBG_HELPER(dbg);
+    session.assert_computed();
+
+    debug_dump(DBG_info, sensor);
+
+    uint32_t move = session.params.starty;
+
+  int i, nb;
+  Motor_Master *motor = nullptr;
+  uint32_t z1, z2;
+  int feedl;
+
+
+  /* for the given resolution, search for master
+   * motor mode setting */
+  i = 0;
+  nb = sizeof (motor_master) / sizeof (Motor_Master);
+  while (i < nb)
+    {
+      if (dev->model->motor_id == motor_master[i].motor_id
+          && motor_master[i].dpi == session.params.yres
+          && motor_master[i].channels == session.params.channels)
+	{
+	  motor = &motor_master[i];
+	}
+      i++;
+    }
+  if (motor == nullptr)
+    {
+        throw SaneException("unable to find settings for motor %d at %d dpi, color=%d",
+                            static_cast<unsigned>(dev->model->motor_id),
+                            session.params.yres, session.params.channels);
+    }
+
+  /* now we can search for the specific sensor settings */
+  i = 0;
+
+    // now apply values from settings to registers
+    regs->set16(REG_EXPR, sensor.exposure.red);
+    regs->set16(REG_EXPG, sensor.exposure.green);
+    regs->set16(REG_EXPB, sensor.exposure.blue);
+
+    for (const auto& reg : sensor.custom_regs) {
+        regs->set8(reg.address, reg.value);
+    }
+
+  /* now generate slope tables : we are not using generate_slope_table3 yet */
+    auto slope_table1 = create_slope_table(motor->slope1, motor->slope1.max_speed_w, StepType::FULL,
+                                           1, 4, get_slope_table_max_size(AsicType::GL646));
+    auto slope_table2 = create_slope_table(motor->slope2, motor->slope2.max_speed_w, StepType::FULL,
+                                           1, 4, get_slope_table_max_size(AsicType::GL646));
+
+  /* R01 */
+  /* now setup other registers for final scan (ie with shading enabled) */
+  /* watch dog + shading + scan enable */
+    regs->find_reg(0x01).value |= REG_0x01_DOGENB | REG_0x01_DVDSET | REG_0x01_SCAN;
+    if (dev->model->is_cis) {
+        regs->find_reg(0x01).value |= REG_0x01_CISSET;
+    } else {
+        regs->find_reg(0x01).value &= ~REG_0x01_CISSET;
+    }
+
+  /* if device has no calibration, don't enable shading correction */
+  if (dev->model->flags & GENESYS_FLAG_NO_CALIBRATION)
+    {
+        regs->find_reg(0x01).value &= ~REG_0x01_DVDSET;
+    }
+
+    regs->find_reg(0x01).value &= ~REG_0x01_FASTMOD;
+    if (motor->fastmod) {
+        regs->find_reg(0x01).value |= REG_0x01_FASTMOD;
+    }
+
+  /* R02 */
+  /* allow moving when buffer full by default */
+    if (!dev->model->is_sheetfed) {
+        dev->reg.find_reg(0x02).value &= ~REG_0x02_ACDCDIS;
+    } else {
+        dev->reg.find_reg(0x02).value |= REG_0x02_ACDCDIS;
+    }
+
+  /* setup motor power and direction */
+  sanei_genesys_set_motor_power(*regs, true);
+
+    if (has_flag(session.params.flags, ScanFlag::REVERSE)) {
+        regs->find_reg(0x02).value |= REG_0x02_MTRREV;
+    } else {
+        regs->find_reg(0x02).value &= ~REG_0x02_MTRREV;
+    }
+
+  /* fastfed enabled (2 motor slope tables) */
+    if (motor->fastfed) {
+        regs->find_reg(0x02).value |= REG_0x02_FASTFED;
+    } else {
+        regs->find_reg(0x02).value &= ~REG_0x02_FASTFED;
+    }
+
+  /* step type */
+    regs->find_reg(0x02).value &= ~REG_0x02_STEPSEL;
+  switch (motor->steptype)
+    {
+    case StepType::FULL:
+      break;
+    case StepType::HALF:
+      regs->find_reg(0x02).value |= 1;
+      break;
+    case StepType::QUARTER:
+      regs->find_reg(0x02).value |= 2;
+      break;
+    default:
+      regs->find_reg(0x02).value |= 3;
+      break;
+    }
+
+    if (dev->model->is_sheetfed) {
+        regs->find_reg(0x02).value &= ~REG_0x02_AGOHOME;
+    } else {
+        regs->find_reg(0x02).value |= REG_0x02_AGOHOME;
+    }
+
+  /* R03 */
+    regs->find_reg(0x03).value &= ~REG_0x03_AVEENB;
+    // regs->find_reg(0x03).value |= REG_0x03_AVEENB;
+    regs->find_reg(0x03).value &= ~REG_0x03_LAMPDOG;
+
+  /* select XPA */
+    regs->find_reg(0x03).value &= ~REG_0x03_XPASEL;
+    if ((session.params.flags & ScanFlag::USE_XPA) != ScanFlag::NONE) {
+        regs->find_reg(0x03).value |= REG_0x03_XPASEL;
+    }
+    regs->state.is_xpa_on = (session.params.flags & ScanFlag::USE_XPA) != ScanFlag::NONE;
+
+  /* R04 */
+  /* monochrome / color scan */
+    switch (session.params.depth) {
+    case 8:
+            regs->find_reg(0x04).value &= ~(REG_0x04_LINEART | REG_0x04_BITSET);
+            break;
+    case 16:
+            regs->find_reg(0x04).value &= ~REG_0x04_LINEART;
+            regs->find_reg(0x04).value |= REG_0x04_BITSET;
+            break;
+    }
+
+    sanei_genesys_set_dpihw(*regs, sensor, sensor.optical_res);
+
+  /* gamma enable for scans */
+    if (dev->model->flags & GENESYS_FLAG_14BIT_GAMMA) {
+        regs->find_reg(0x05).value |= REG_0x05_GMM14BIT;
+    }
+
+    regs->find_reg(0x05).value &= ~REG_0x05_GMMENB;
+
+  /* true CIS gray if needed */
+    if (dev->model->is_cis && session.params.channels == 1 && dev->settings.true_gray) {
+        regs->find_reg(0x05).value |= REG_0x05_LEDADD;
+    } else {
+        regs->find_reg(0x05).value &= ~REG_0x05_LEDADD;
+    }
+
+  /* HP2400 1200dpi mode tuning */
+
+    if (dev->model->sensor_id == SensorId::CCD_HP2400) {
+      /* reset count of dummy lines to zero */
+        regs->find_reg(0x1e).value &= ~REG_0x1E_LINESEL;
+        if (session.params.xres >= 1200) {
+          /* there must be one dummy line */
+            regs->find_reg(0x1e).value |= 1 & REG_0x1E_LINESEL;
+
+          /* GPO12 need to be set to zero */
+          regs->find_reg(0x66).value &= ~0x20;
+        }
+        else
+        {
+          /* set GPO12 back to one */
+          regs->find_reg(0x66).value |= 0x20;
+        }
+    }
+
+  /* motor steps used */
+    unsigned forward_steps = motor->fwdbwd;
+    unsigned backward_steps = motor->fwdbwd;
+
+    // the steps count must be different by at most 128, otherwise it's impossible to construct
+    // a proper backtracking curve. We're using slightly lower limit to allow at least a minimum
+    // distance between accelerations (forward_steps, backward_steps)
+    if (slope_table1.steps_count > slope_table2.steps_count + 100) {
+        slope_table2.steps_count += slope_table1.steps_count - 100;
+    }
+    if (slope_table2.steps_count > slope_table1.steps_count + 100) {
+        slope_table1.steps_count += slope_table2.steps_count - 100;
+    }
+
+    if (slope_table1.steps_count >= slope_table2.steps_count) {
+        backward_steps += (slope_table1.steps_count - slope_table2.steps_count) * 2;
+    } else {
+        forward_steps += (slope_table2.steps_count - slope_table1.steps_count) * 2;
+    }
+
+    if (forward_steps > 255) {
+        if (backward_steps < (forward_steps - 255)) {
+            throw SaneException("Can't set backtracking parameters without skipping image");
+        }
+        backward_steps -= forward_steps - 255;
+    }
+    if (backward_steps > 255) {
+        if (forward_steps < (backward_steps - 255)) {
+            throw SaneException("Can't set backtracking parameters without skipping image");
+        }
+        forward_steps -= backward_steps - 255;
+    }
+
+    regs->find_reg(0x21).value = slope_table1.steps_count;
+    regs->find_reg(0x24).value = slope_table2.steps_count;
+    regs->find_reg(0x22).value = forward_steps;
+    regs->find_reg(0x23).value = backward_steps;
+
+  /* CIS scanners read one line per color channel
+   * since gray mode use 'add' we also read 3 channels even not in
+   * color mode */
+    if (dev->model->is_cis) {
+        regs->set24(REG_LINCNT, session.output_line_count * 3);
+    } else {
+        regs->set24(REG_LINCNT, session.output_line_count);
+    }
+
+    regs->set16(REG_STRPIXEL, session.pixel_startx);
+    regs->set16(REG_ENDPIXEL, session.pixel_endx);
+
+    regs->set24(REG_MAXWD, session.output_line_bytes);
+
+    regs->set16(REG_DPISET, session.output_resolution * session.ccd_size_divisor *
+                            sensor.ccd_pixels_per_system_pixel());
+    regs->set16(REG_LPERIOD, sensor.exposure_lperiod);
+
+  /* move distance must be adjusted to take into account the extra lines
+   * read to reorder data */
+  feedl = move;
+
+    if (session.num_staggered_lines + session.max_color_shift_lines > 0 && feedl != 0) {
+        int feed_offset = ((session.max_color_shift_lines + session.num_staggered_lines) * dev->motor.optical_ydpi) /
+                motor->dpi;
+        if (feedl > feed_offset) {
+            feedl = feedl - feed_offset;
+        }
+    }
+
+  /* we assume all scans are done with 2 tables */
+  /*
+     feedl = feed_steps - fast_slope_steps*2 -
+     (slow_slope_steps >> scan_step_type); */
+  /* but head has moved due to shading calibration => dev->scanhead_position_primary */
+  if (feedl > 0)
+    {
+      DBG(DBG_info, "%s: initial move=%d\n", __func__, feedl);
+
+      /* TODO clean up this when I'll fully understand.
+       * for now, special casing each motor */
+        switch (dev->model->motor_id) {
+            case MotorId::MD_5345:
+                    switch (motor->dpi) {
+	    case 200:
+	      feedl -= 70;
+	      break;
+	    case 300:
+	      feedl -= 70;
+	      break;
+	    case 400:
+	      feedl += 130;
+	      break;
+	    case 600:
+	      feedl += 160;
+	      break;
+	    case 1200:
+	      feedl += 160;
+	      break;
+	    case 2400:
+	      feedl += 180;
+	      break;
+	    default:
+	      break;
+	    }
+	  break;
+            case MotorId::HP2300:
+                    switch (motor->dpi) {
+	    case 75:
+	      feedl -= 180;
+	      break;
+	    case 150:
+	      feedl += 0;
+	      break;
+	    case 300:
+	      feedl += 30;
+	      break;
+	    case 600:
+	      feedl += 35;
+	      break;
+	    case 1200:
+	      feedl += 45;
+	      break;
+	    default:
+	      break;
+	    }
+	  break;
+            case MotorId::HP2400:
+                    switch (motor->dpi) {
+	    case 150:
+	      feedl += 150;
+	      break;
+	    case 300:
+	      feedl += 220;
+	      break;
+	    case 600:
+	      feedl += 260;
+	      break;
+	    case 1200:
+	      feedl += 280; /* 300 */
+	      break;
+	    case 50:
+	      feedl += 0;
+	      break;
+	    case 100:
+	      feedl += 100;
+	      break;
+	    default:
+	      break;
+	    }
+	  break;
+
+	  /* theorical value */
+        default: {
+            unsigned step_shift = static_cast<unsigned>(motor->steptype);
+
+	  if (motor->fastfed)
+        {
+                feedl = feedl - 2 * slope_table2.steps_count -
+                        (slope_table1.steps_count >> step_shift);
+	    }
+	  else
+	    {
+                feedl = feedl - (slope_table1.steps_count >> step_shift);
+	    }
+	  break;
+        }
+	}
+      /* security */
+      if (feedl < 0)
+	feedl = 0;
+    }
+
+  DBG(DBG_info, "%s: final move=%d\n", __func__, feedl);
+    regs->set24(REG_FEEDL, feedl);
+
+  regs->find_reg(0x65).value = motor->mtrpwm;
+
+    sanei_genesys_calculate_zmod(regs->find_reg(0x02).value & REG_0x02_FASTFED,
+                                 sensor.exposure_lperiod,
+                                 slope_table1.table,
+                                 slope_table1.steps_count,
+                                  move, motor->fwdbwd, &z1, &z2);
+
+  /* no z1/z2 for sheetfed scanners */
+    if (dev->model->is_sheetfed) {
+      z1 = 0;
+      z2 = 0;
+    }
+    regs->set16(REG_Z1MOD, z1);
+    regs->set16(REG_Z2MOD, z2);
+    regs->find_reg(0x6b).value = slope_table2.steps_count;
+  regs->find_reg(0x6c).value =
+    (regs->find_reg(0x6c).value & REG_0x6C_TGTIME) | ((z1 >> 13) & 0x38) | ((z2 >> 16)
+								   & 0x07);
+
+    write_control(dev, sensor, session.output_resolution);
+
+    // setup analog frontend
+    gl646_set_fe(dev, sensor, AFE_SET, session.output_resolution);
+
+    dev->read_buffer.clear();
+    dev->read_buffer.alloc(session.buffer_size_read);
+
+    build_image_pipeline(dev, session);
+
+    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;
+
+    /* select color filter based on settings */
+    regs->find_reg(0x04).value &= ~REG_0x04_FILTER;
+    if (session.params.channels == 1) {
+        switch (session.params.color_filter) {
+            case ColorFilter::RED:
+                regs->find_reg(0x04).value |= 0x04;
+                break;
+            case ColorFilter::GREEN:
+                regs->find_reg(0x04).value |= 0x08;
+                break;
+            case ColorFilter::BLUE:
+                regs->find_reg(0x04).value |= 0x0c;
+                break;
+            default:
+                break;
+        }
+    }
+
+    gl646_send_slope_table(dev, 0, slope_table1.table, regs->get8(0x21));
+    gl646_send_slope_table(dev, 1, slope_table2.table, regs->get8(0x6b));
+}
+
+
+/** copy sensor specific settings */
+/* *dev  : device infos
+   *regs : regiters to be set
+   extended : do extended set up
+   ccd_size_divisor: set up for half ccd resolution
+   all registers 08-0B, 10-1D, 52-5E are set up. They shouldn't
+   appear anywhere else but in register init
+*/
+static void
+gl646_setup_sensor (Genesys_Device * dev, const Genesys_Sensor& sensor, Genesys_Register_Set * regs)
+{
+    (void) dev;
+    DBG(DBG_proc, "%s: start\n", __func__);
+
+    for (const auto& reg_setting : sensor.custom_base_regs) {
+        regs->set8(reg_setting.address, reg_setting.value);
+    }
+    // FIXME: all other drivers don't set exposure here
+    regs_set_exposure(AsicType::GL646, *regs, sensor.exposure);
+
+    DBG(DBG_proc, "%s: end\n", __func__);
+}
+
+/**
+ * Set all registers to default values after init
+ * @param dev scannerr's device to set
+ */
+static void
+gl646_init_regs (Genesys_Device * dev)
+{
+  int addr;
+
+  DBG(DBG_proc, "%s\n", __func__);
+
+    dev->reg.clear();
+
+    for (addr = 1; addr <= 0x0b; addr++)
+        dev->reg.init_reg(addr, 0);
+    for (addr = 0x10; addr <= 0x29; addr++)
+        dev->reg.init_reg(addr, 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 <= 0x5e; addr++)
+        dev->reg.init_reg(addr, 0);
+    for (addr = 0x60; addr <= 0x6d; addr++)
+        dev->reg.init_reg(addr, 0);
+
+  dev->reg.find_reg(0x01).value = 0x20 /*0x22 */ ;	/* enable shading, CCD, color, 1M */
+  dev->reg.find_reg(0x02).value = 0x30 /*0x38 */ ;	/* auto home, one-table-move, full step */
+    if (dev->model->motor_id == MotorId::MD_5345) {
+        dev->reg.find_reg(0x02).value |= 0x01; // half-step
+    }
+    switch (dev->model->motor_id) {
+        case MotorId::MD_5345:
+      dev->reg.find_reg(0x02).value |= 0x01;	/* half-step */
+      break;
+        case MotorId::XP200:
+      /* for this sheetfed scanner, no AGOHOME, nor backtracking */
+      dev->reg.find_reg(0x02).value = 0x50;
+      break;
+        default:
+      break;
+    }
+  dev->reg.find_reg(0x03).value = 0x1f /*0x17 */ ;	/* lamp on */
+  dev->reg.find_reg(0x04).value = 0x13 /*0x03 */ ;	/* 8 bits data, 16 bits A/D, color, Wolfson fe *//* todo: according to spec, 0x0 is reserved? */
+  switch (dev->model->adc_id)
+    {
+    case AdcId::AD_XP200:
+      dev->reg.find_reg(0x04).value = 0x12;
+      break;
+    default:
+      /* Wolfson frontend */
+      dev->reg.find_reg(0x04).value = 0x13;
+      break;
+    }
+
+  const auto& sensor = sanei_genesys_find_sensor_any(dev);
+
+  dev->reg.find_reg(0x05).value = 0x00;	/* 12 bits gamma, disable gamma, 24 clocks/pixel */
+    sanei_genesys_set_dpihw(dev->reg, sensor, sensor.optical_res);
+
+    if (dev->model->flags & GENESYS_FLAG_14BIT_GAMMA) {
+        dev->reg.find_reg(0x05).value |= REG_0x05_GMM14BIT;
+    }
+    if (dev->model->adc_id == AdcId::AD_XP200) {
+        dev->reg.find_reg(0x05).value |= 0x01;	/* 12 clocks/pixel */
+    }
+
+    if (dev->model->sensor_id == SensorId::CCD_HP2300) {
+        dev->reg.find_reg(0x06).value = 0x00; // PWRBIT off, shading gain=4, normal AFE image capture
+    } else {
+        dev->reg.find_reg(0x06).value = 0x18; // PWRBIT on, shading gain=8, normal AFE image capture
+    }
+
+
+  gl646_setup_sensor(dev, sensor, &dev->reg);
+
+  dev->reg.find_reg(0x1e).value = 0xf0;	/* watch-dog time */
+
+  switch (dev->model->sensor_id)
+    {
+    case SensorId::CCD_HP2300:
+      dev->reg.find_reg(0x1e).value = 0xf0;
+      dev->reg.find_reg(0x1f).value = 0x10;
+      dev->reg.find_reg(0x20).value = 0x20;
+      break;
+    case SensorId::CCD_HP2400:
+      dev->reg.find_reg(0x1e).value = 0x80;
+      dev->reg.find_reg(0x1f).value = 0x10;
+      dev->reg.find_reg(0x20).value = 0x20;
+      break;
+    case SensorId::CCD_HP3670:
+      dev->reg.find_reg(0x19).value = 0x2a;
+      dev->reg.find_reg(0x1e).value = 0x80;
+      dev->reg.find_reg(0x1f).value = 0x10;
+      dev->reg.find_reg(0x20).value = 0x20;
+      break;
+    case SensorId::CIS_XP200:
+      dev->reg.find_reg(0x1e).value = 0x10;
+      dev->reg.find_reg(0x1f).value = 0x01;
+      dev->reg.find_reg(0x20).value = 0x50;
+      break;
+    default:
+      dev->reg.find_reg(0x1f).value = 0x01;
+      dev->reg.find_reg(0x20).value = 0x50;
+      break;
+    }
+
+  dev->reg.find_reg(0x21).value = 0x08 /*0x20 */ ;	/* table one steps number for forward slope curve of the acc/dec */
+  dev->reg.find_reg(0x22).value = 0x10 /*0x08 */ ;	/* steps number of the forward steps for start/stop */
+  dev->reg.find_reg(0x23).value = 0x10 /*0x08 */ ;	/* steps number of the backward steps for start/stop */
+  dev->reg.find_reg(0x24).value = 0x08 /*0x20 */ ;	/* table one steps number backward slope curve of the acc/dec */
+  dev->reg.find_reg(0x25).value = 0x00;	/* scan line numbers (7000) */
+  dev->reg.find_reg(0x26).value = 0x00 /*0x1b */ ;
+  dev->reg.find_reg(0x27).value = 0xd4 /*0x58 */ ;
+  dev->reg.find_reg(0x28).value = 0x01;	/* PWM duty for lamp control */
+  dev->reg.find_reg(0x29).value = 0xff;
+
+  dev->reg.find_reg(0x2c).value = 0x02;	/* set resolution (600 DPI) */
+  dev->reg.find_reg(0x2d).value = 0x58;
+  dev->reg.find_reg(0x2e).value = 0x78;	/* set black&white threshold high level */
+  dev->reg.find_reg(0x2f).value = 0x7f;	/* set black&white threshold low level */
+
+  dev->reg.find_reg(0x30).value = 0x00;	/* begin pixel position (16) */
+  dev->reg.find_reg(0x31).value = sensor.dummy_pixel /*0x10 */ ;	/* TGW + 2*TG_SHLD + x  */
+  dev->reg.find_reg(0x32).value = 0x2a /*0x15 */ ;	/* end pixel position (5390) */
+  dev->reg.find_reg(0x33).value = 0xf8 /*0x0e */ ;	/* TGW + 2*TG_SHLD + y   */
+  dev->reg.find_reg(0x34).value = sensor.dummy_pixel;
+  dev->reg.find_reg(0x35).value = 0x01 /*0x00 */ ;	/* set maximum word size per line, for buffer full control (10800) */
+  dev->reg.find_reg(0x36).value = 0x00 /*0x2a */ ;
+  dev->reg.find_reg(0x37).value = 0x00 /*0x30 */ ;
+  dev->reg.find_reg(0x38).value = 0x2a; // line period (exposure time = 11000 pixels) */
+  dev->reg.find_reg(0x39).value = 0xf8;
+  dev->reg.find_reg(0x3d).value = 0x00;	/* set feed steps number of motor move */
+  dev->reg.find_reg(0x3e).value = 0x00;
+  dev->reg.find_reg(0x3f).value = 0x01 /*0x00 */ ;
+
+  dev->reg.find_reg(0x60).value = 0x00;	/* Z1MOD, 60h:61h:(6D b5:b3), remainder for start/stop */
+  dev->reg.find_reg(0x61).value = 0x00;	/* (21h+22h)/LPeriod */
+  dev->reg.find_reg(0x62).value = 0x00;	/* Z2MODE, 62h:63h:(6D b2:b0), remainder for start scan */
+  dev->reg.find_reg(0x63).value = 0x00;	/* (3Dh+3Eh+3Fh)/LPeriod for one-table mode,(21h+1Fh)/LPeriod */
+  dev->reg.find_reg(0x64).value = 0x00;	/* motor PWM frequency */
+  dev->reg.find_reg(0x65).value = 0x00;	/* PWM duty cycle for table one motor phase (63 = max) */
+    if (dev->model->motor_id == MotorId::MD_5345) {
+        // PWM duty cycle for table one motor phase (63 = max)
+        dev->reg.find_reg(0x65).value = 0x02;
+    }
+
+    for (const auto& reg : dev->gpo.regs) {
+        dev->reg.set8(reg.address, reg.value);
+    }
+
+    switch (dev->model->motor_id) {
+        case MotorId::HP2300:
+        case MotorId::HP2400:
+      dev->reg.find_reg(0x6a).value = 0x7f;	/* table two steps number for acc/dec */
+      dev->reg.find_reg(0x6b).value = 0x78;	/* table two steps number for acc/dec */
+      dev->reg.find_reg(0x6d).value = 0x7f;
+      break;
+        case MotorId::MD_5345:
+      dev->reg.find_reg(0x6a).value = 0x42;	/* table two fast moving step type, PWM duty for table two */
+      dev->reg.find_reg(0x6b).value = 0xff;	/* table two steps number for acc/dec */
+      dev->reg.find_reg(0x6d).value = 0x41;	/* select deceleration steps whenever go home (0), accel/decel stop time (31 * LPeriod) */
+      break;
+        case MotorId::XP200:
+      dev->reg.find_reg(0x6a).value = 0x7f;	/* table two fast moving step type, PWM duty for table two */
+      dev->reg.find_reg(0x6b).value = 0x08;	/* table two steps number for acc/dec */
+      dev->reg.find_reg(0x6d).value = 0x01;	/* select deceleration steps whenever go home (0), accel/decel stop time (31 * LPeriod) */
+      break;
+        case MotorId::HP3670:
+      dev->reg.find_reg(0x6a).value = 0x41;	/* table two steps number for acc/dec */
+      dev->reg.find_reg(0x6b).value = 0xc8;	/* table two steps number for acc/dec */
+      dev->reg.find_reg(0x6d).value = 0x7f;
+      break;
+        default:
+      dev->reg.find_reg(0x6a).value = 0x40;	/* table two fast moving step type, PWM duty for table two */
+      dev->reg.find_reg(0x6b).value = 0xff;	/* table two steps number for acc/dec */
+      dev->reg.find_reg(0x6d).value = 0x01;	/* select deceleration steps whenever go home (0), accel/decel stop time (31 * LPeriod) */
+      break;
+    }
+  dev->reg.find_reg(0x6c).value = 0x00;	/* peroid times for LPeriod, expR,expG,expB, Z1MODE, Z2MODE (one period time) */
+}
+
+
+// Send slope table for motor movement slope_table in machine byte order
+static void gl646_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)=%d .. %d", table_nr, steps, slope_table[0],
+                    slope_table[steps - 1]);
+  int dpihw;
+  int start_address;
+
+  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 = 0x1f800;
+    else {
+        throw SaneException("Unexpected dpihw");
+    }
+
+  std::vector<uint8_t> table(steps * 2);
+  for (int i = 0; i < steps; i++)
+    {
+      table[i * 2] = slope_table[i] & 0xff;
+      table[i * 2 + 1] = slope_table[i] >> 8;
+    }
+
+    if (dev->interface->is_mock()) {
+        dev->interface->record_slope_table(table_nr, slope_table);
+    }
+    dev->interface->write_buffer(0x3c, start_address + table_nr * 0x100, table.data(), steps * 2);
+}
+
+// Set values of Analog Device type frontend
+static void gl646_set_ad_fe(Genesys_Device* dev, uint8_t set)
+{
+    DBG_HELPER(dbg);
+  int i;
+
+  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;
+
+        // 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));
+    }
+  if (set == AFE_SET)
+    {
+        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));
+        }
+    }
+  /*
+     if (set == AFE_POWER_SAVE)
+     {
+        dev->interface->write_fe_register(0x00, dev->frontend.reg[0] | 0x04);
+     } */
+}
+
+/** set up analog frontend
+ * set up analog frontend
+ * @param dev device to set up
+ * @param set action from AFE_SET, AFE_INIT and AFE_POWERSAVE
+ * @param dpi resolution of the scan since it affects settings
+ */
+static void gl646_wm_hp3670(Genesys_Device* dev, const Genesys_Sensor& sensor, uint8_t set,
+                            unsigned dpi)
+{
+    DBG_HELPER(dbg);
+  int i;
+
+  switch (set)
+    {
+    case AFE_INIT:
+        dev->interface->write_fe_register(0x04, 0x80);
+        dev->interface->sleep_ms(200);
+    dev->interface->write_register(0x50, 0x00);
+      dev->frontend = dev->frontend_initial;
+        dev->interface->write_fe_register(0x01, dev->frontend.regs.get_value(0x01));
+        dev->interface->write_fe_register(0x02, dev->frontend.regs.get_value(0x02));
+        gl646_gpio_output_enable(dev->interface->get_usb_device(), 0x07);
+      break;
+    case AFE_POWER_SAVE:
+        dev->interface->write_fe_register(0x01, 0x06);
+        dev->interface->write_fe_register(0x06, 0x0f);
+            return;
+      break;
+    default:			/* AFE_SET */
+      /* mode setup */
+      i = dev->frontend.regs.get_value(0x03);
+      if (dpi > sensor.optical_res / 2)
+	{
+      /* fe_reg_0x03 must be 0x12 for 1200 dpi in WOLFSON_HP3670.
+       * WOLFSON_HP2400 in 1200 dpi mode works well with
+	   * fe_reg_0x03 set to 0x32 or 0x12 but not to 0x02 */
+	  i = 0x12;
+	}
+        dev->interface->write_fe_register(0x03, i);
+      /* offset and sign (or msb/lsb ?) */
+        for (i = 0; i < 3; i++) {
+            dev->interface->write_fe_register(0x20 + i, dev->frontend.get_offset(i));
+            dev->interface->write_fe_register(0x24 + i, dev->frontend.regs.get_value(0x24 + i));
+        }
+
+        // gain
+        for (i = 0; i < 3; i++) {
+            dev->interface->write_fe_register(0x28 + i, dev->frontend.get_gain(i));
+        }
+    }
+}
+
+/** Set values of analog frontend
+ * @param dev device to set
+ * @param set action to execute
+ * @param dpi dpi to setup the AFE
+ */
+static void gl646_set_fe(Genesys_Device* dev, const Genesys_Sensor& sensor, uint8_t set, int dpi)
+{
+    DBG_HELPER_ARGS(dbg, "%s,%d", set == AFE_INIT ? "init" :
+                                  set == AFE_SET ? "set" :
+                                  set == AFE_POWER_SAVE ? "powersave" : "huh?", dpi);
+  int i;
+  uint8_t val;
+
+  /* Analog Device type frontend */
+    uint8_t frontend_type = dev->reg.find_reg(0x04).value & REG_0x04_FESET;
+    if (frontend_type == 0x02) {
+        gl646_set_ad_fe(dev, set);
+        return;
+    }
+
+  /* Wolfson type frontend */
+    if (frontend_type != 0x03) {
+        throw SaneException("unsupported frontend type %d", frontend_type);
+    }
+
+  /* per frontend function to keep code clean */
+  switch (dev->model->adc_id)
+    {
+    case AdcId::WOLFSON_HP3670:
+    case AdcId::WOLFSON_HP2400:
+            gl646_wm_hp3670(dev, sensor, set, dpi);
+            return;
+    default:
+      DBG(DBG_proc, "%s(): using old method\n", __func__);
+      break;
+    }
+
+  /* initialize analog frontend */
+  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 only done on init
+        dev->interface->write_fe_register(0x04, 0x80);
+
+      /* enable GPIO for some models */
+        if (dev->model->sensor_id == SensorId::CCD_HP2300) {
+	  val = 0x07;
+            gl646_gpio_output_enable(dev->interface->get_usb_device(), val);
+	}
+        return;
+    }
+
+    // set fontend to power saving mode
+    if (set == AFE_POWER_SAVE) {
+        dev->interface->write_fe_register(0x01, 0x02);
+        return;
+    }
+
+  /* here starts AFE_SET */
+  /* TODO :  base this test on cfg reg3 or a CCD family flag to be created */
+  /* if (dev->model->ccd_type != SensorId::CCD_HP2300
+     && dev->model->ccd_type != SensorId::CCD_HP3670
+     && dev->model->ccd_type != SensorId::CCD_HP2400) */
+  {
+        dev->interface->write_fe_register(0x00, dev->frontend.regs.get_value(0x00));
+        dev->interface->write_fe_register(0x02, dev->frontend.regs.get_value(0x02));
+  }
+
+    // start with reg3
+    dev->interface->write_fe_register(0x03, dev->frontend.regs.get_value(0x03));
+
+  switch (dev->model->sensor_id)
+    {
+    default:
+            for (i = 0; i < 3; i++) {
+                dev->interface->write_fe_register(0x24 + i, dev->frontend.regs.get_value(0x24 + i));
+                dev->interface->write_fe_register(0x28 + i, dev->frontend.get_gain(i));
+                dev->interface->write_fe_register(0x20 + i, dev->frontend.get_offset(i));
+            }
+      break;
+      /* just can't have it to work ....
+         case SensorId::CCD_HP2300:
+         case SensorId::CCD_HP2400:
+         case SensorId::CCD_HP3670:
+
+        dev->interface->write_fe_register(0x23, dev->frontend.get_offset(1));
+        dev->interface->write_fe_register(0x28, dev->frontend.get_gain(1));
+         break; */
+    }
+
+    // end with reg1
+    dev->interface->write_fe_register(0x01, dev->frontend.regs.get_value(0x01));
+}
+
+/** Set values of analog frontend
+ * this this the public interface, the gl646 as to use one more
+ * parameter to work effectively, hence the redirection
+ * @param dev device to set
+ * @param set action to execute
+ */
+void CommandSetGl646::set_fe(Genesys_Device* dev, const Genesys_Sensor& sensor, uint8_t set) const
+{
+    gl646_set_fe(dev, sensor, set, dev->settings.yres);
+}
+
+/**
+ * enters or leaves power saving mode
+ * limited to AFE for now.
+ * @param dev scanner's device
+ * @param enable true to enable power saving, false to leave it
+ */
+void CommandSetGl646::save_power(Genesys_Device* dev, bool enable) const
+{
+    DBG_HELPER_ARGS(dbg, "enable = %d", enable);
+
+  const auto& sensor = sanei_genesys_find_sensor_any(dev);
+
+  if (enable)
+    {
+        // gl646_set_fe(dev, sensor, AFE_POWER_SAVE);
+    }
+  else
+    {
+      gl646_set_fe(dev, sensor, AFE_INIT, 0);
+    }
+}
+
+void CommandSetGl646::set_powersaving(Genesys_Device* dev, int delay /* in minutes */) const
+{
+    DBG_HELPER_ARGS(dbg, "delay = %d", delay);
+  Genesys_Register_Set local_reg(Genesys_Register_Set::SEQUENTIAL);
+  int rate, exposure_time, tgtime, time;
+
+  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) & ~REG_0x05_BASESEL);   // 24 clocks/pixel
+  local_reg.init_reg(0x38, 0x00); // line period low
+  local_reg.init_reg(0x39, 0x00); //line period high
+  local_reg.init_reg(0x6c, 0x00); // period times for LPeriod, expR,expG,expB, Z1MODE, Z2MODE
+
+  if (!delay)
+    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.get8(0x03) & 0xf0) | 0x09;	/* enable lampdog and set lamptime = 1 */
+  else
+    local_reg.find_reg(0x03).value = (local_reg.get8(0x03) & 0xf0) | 0x0f;	/* enable lampdog and set lamptime = 7 */
+
+  time = delay * 1000 * 60;	/* -> msec */
+    exposure_time = static_cast<std::uint32_t>((time * 32000.0 /
+                (24.0 * 64.0 * (local_reg.get8(0x03) & REG_0x03_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(0x6c).value |= tgtime << 6;
+  exposure_time /= rate;
+
+  if (exposure_time > 65535)
+    exposure_time = 65535;
+
+  local_reg.find_reg(0x38).value = exposure_time / 256;
+  local_reg.find_reg(0x39).value = exposure_time & 255;
+
+    dev->interface->write_registers(local_reg);
+}
+
+
+/**
+ * loads document into scanner
+ * currently only used by XP200
+ * bit2 (0x04) of gpio is paper event (document in/out) on XP200
+ * HOMESNR is set if no document in front of sensor, the sequence of events is
+ * paper event -> document is in the sheet feeder
+ * HOMESNR becomes 0 -> document reach sensor
+ * HOMESNR becomes 1 ->document left sensor
+ * paper event -> document is out
+ */
+void CommandSetGl646::load_document(Genesys_Device* dev) const
+{
+    DBG_HELPER(dbg);
+
+  // FIXME: sequential not really needed in this case
+  Genesys_Register_Set regs(Genesys_Register_Set::SEQUENTIAL);
+    unsigned count;
+
+  /* no need to load document is flatbed scanner */
+    if (!dev->model->is_sheetfed) {
+      DBG(DBG_proc, "%s: nothing to load\n", __func__);
+      DBG(DBG_proc, "%s: end\n", __func__);
+      return;
+    }
+
+    auto status = scanner_read_status(*dev);
+
+    // home sensor is set if a document is inserted
+    if (status.is_at_home) {
+      /* if no document, waits for a paper event to start loading */
+      /* with a 60 seconde minutes timeout                        */
+      count = 0;
+        std::uint8_t val = 0;
+        do {
+            gl646_gpio_read(dev->interface->get_usb_device(), &val);
+
+	  DBG(DBG_info, "%s: GPIO=0x%02x\n", __func__, val);
+	  if ((val & 0x04) != 0x04)
+	    {
+              DBG(DBG_warn, "%s: no paper detected\n", __func__);
+	    }
+            dev->interface->sleep_ms(200);
+            count++;
+        }
+      while (((val & 0x04) != 0x04) && (count < 300));	/* 1 min time out */
+      if (count == 300)
+	{
+        throw SaneException(SANE_STATUS_NO_DOCS, "timeout waiting for document");
+    }
+    }
+
+  /* set up to fast move before scan then move until document is detected */
+  regs.init_reg(0x01, 0x90);
+
+  /* AGOME, 2 slopes motor moving */
+  regs.init_reg(0x02, 0x79);
+
+  /* motor feeding steps to 0 */
+  regs.init_reg(0x3d, 0);
+  regs.init_reg(0x3e, 0);
+  regs.init_reg(0x3f, 0);
+
+  /* 50 fast moving steps */
+  regs.init_reg(0x6b, 50);
+
+  /* set GPO */
+  regs.init_reg(0x66, 0x30);
+
+  /* stesp NO */
+  regs.init_reg(0x21, 4);
+  regs.init_reg(0x22, 1);
+  regs.init_reg(0x23, 1);
+  regs.init_reg(0x24, 4);
+
+  /* generate slope table 2 */
+    auto slope_table = create_slope_table(MotorSlope::create_from_steps(6000, 2400, 50), 2400,
+                                          StepType::FULL, 1, 4,
+                                          get_slope_table_max_size(AsicType::GL646));
+    // document loading:
+    // send regs
+    // start motor
+    // wait e1 status to become e0
+    gl646_send_slope_table(dev, 1, slope_table.table, slope_table.steps_count);
+
+    dev->interface->write_registers(regs);
+
+    scanner_start_action(*dev, true);
+
+  count = 0;
+  do
+    {
+        status = scanner_read_status(*dev);
+        dev->interface->sleep_ms(200);
+      count++;
+    } while (status.is_motor_enabled && (count < 300));
+
+  if (count == 300)
+    {
+      throw SaneException(SANE_STATUS_JAMMED, "can't load document");
+    }
+
+  /* when loading OK, document is here */
+    dev->document = true;
+
+  /* set up to idle */
+  regs.set8(0x02, 0x71);
+  regs.set8(0x3f, 1);
+  regs.set8(0x6b, 8);
+    dev->interface->write_registers(regs);
+}
+
+/**
+ * detects end of document and adjust current scan
+ * to take it into account
+ * used by sheetfed scanners
+ */
+void CommandSetGl646::detect_document_end(Genesys_Device* dev) const
+{
+    DBG_HELPER(dbg);
+    std::uint8_t gpio;
+    unsigned int bytes_left;
+
+    // test for document presence
+    scanner_read_print_status(*dev);
+
+    gl646_gpio_read(dev->interface->get_usb_device(), &gpio);
+  DBG(DBG_info, "%s: GPIO=0x%02x\n", __func__, gpio);
+
+  /* detect document event. There one event when the document go in,
+   * then another when it leaves */
+    if (dev->document && (gpio & 0x04) && (dev->total_bytes_read > 0)) {
+      DBG(DBG_info, "%s: no more document\n", __func__);
+        dev->document = false;
+
+      /* adjust number of bytes to read:
+       * total_bytes_to_read is the number of byte to send to frontend
+       * total_bytes_read is the number of bytes sent to frontend
+       * read_bytes_left is the number of bytes to read from the scanner
+       */
+      DBG(DBG_io, "%s: total_bytes_to_read=%zu\n", __func__, dev->total_bytes_to_read);
+      DBG(DBG_io, "%s: total_bytes_read   =%zu\n", __func__, dev->total_bytes_read);
+
+        // amount of data available from scanner is what to scan
+        sanei_genesys_read_valid_words(dev, &bytes_left);
+
+        unsigned lines_in_buffer = bytes_left / dev->session.output_line_bytes_raw;
+
+        // we add the number of lines needed to read the last part of the document in
+        unsigned lines_offset = static_cast<unsigned>(
+                (dev->model->y_offset * dev->session.params.yres) / MM_PER_INCH);
+
+        unsigned remaining_lines = lines_in_buffer + lines_offset;
+
+        bytes_left = remaining_lines * dev->session.output_line_bytes_raw;
+
+        if (bytes_left < dev->get_pipeline_source().remaining_bytes()) {
+            dev->get_pipeline_source().set_remaining_bytes(bytes_left);
+            dev->total_bytes_to_read = dev->total_bytes_read + bytes_left;
+        }
+      DBG(DBG_io, "%s: total_bytes_to_read=%zu\n", __func__, dev->total_bytes_to_read);
+      DBG(DBG_io, "%s: total_bytes_read   =%zu\n", __func__, dev->total_bytes_read);
+    }
+}
+
+/**
+ * eject document from the feeder
+ * currently only used by XP200
+ * TODO we currently rely on AGOHOME not being set for sheetfed scanners,
+ * maybe check this flag in eject to let the document being eject automaticaly
+ */
+void CommandSetGl646::eject_document(Genesys_Device* dev) const
+{
+    DBG_HELPER(dbg);
+
+  // FIXME: SEQUENTIAL not really needed in this case
+  Genesys_Register_Set regs((Genesys_Register_Set::SEQUENTIAL));
+    unsigned count;
+    std::uint8_t gpio;
+
+  /* at the end there will be noe more document */
+    dev->document = false;
+
+    // first check for document event
+    gl646_gpio_read(dev->interface->get_usb_device(), &gpio);
+
+  DBG(DBG_info, "%s: GPIO=0x%02x\n", __func__, gpio);
+
+    // test status : paper event + HOMESNR -> no more doc ?
+    auto status = scanner_read_status(*dev);
+
+    // home sensor is set when document is inserted
+    if (status.is_at_home) {
+        dev->document = false;
+      DBG(DBG_info, "%s: no more document to eject\n", __func__);
+      DBG(DBG_proc, "%s: end\n", __func__);
+      return;
+    }
+
+    // there is a document inserted, eject it
+    dev->interface->write_register(0x01, 0xb0);
+
+  /* wait for motor to stop */
+    do {
+        dev->interface->sleep_ms(200);
+        status = scanner_read_status(*dev);
+    }
+    while (status.is_motor_enabled);
+
+  /* set up to fast move before scan then move until document is detected */
+  regs.init_reg(0x01, 0xb0);
+
+  /* AGOME, 2 slopes motor moving , eject 'backward' */
+  regs.init_reg(0x02, 0x5d);
+
+  /* motor feeding steps to 119880 */
+  regs.init_reg(0x3d, 1);
+  regs.init_reg(0x3e, 0xd4);
+  regs.init_reg(0x3f, 0x48);
+
+  /* 60 fast moving steps */
+  regs.init_reg(0x6b, 60);
+
+  /* set GPO */
+  regs.init_reg(0x66, 0x30);
+
+  /* stesp NO */
+  regs.init_reg(0x21, 4);
+  regs.init_reg(0x22, 1);
+  regs.init_reg(0x23, 1);
+  regs.init_reg(0x24, 4);
+
+  /* generate slope table 2 */
+    auto slope_table = create_slope_table(MotorSlope::create_from_steps(10000, 1600, 60), 1600,
+                                          StepType::FULL, 1, 4,
+                                          get_slope_table_max_size(AsicType::GL646));
+    // document eject:
+    // send regs
+    // start motor
+    // wait c1 status to become c8 : HOMESNR and ~MOTFLAG
+    gl646_send_slope_table(dev, 1, slope_table.table, slope_table.steps_count);
+
+    dev->interface->write_registers(regs);
+
+    scanner_start_action(*dev, true);
+
+  /* loop until paper sensor tells paper is out, and till motor is running */
+  /* use a 30 timeout */
+  count = 0;
+    do {
+        status = scanner_read_status(*dev);
+
+        dev->interface->sleep_ms(200);
+      count++;
+    } while (!status.is_at_home && (count < 150));
+
+    // read GPIO on exit
+    gl646_gpio_read(dev->interface->get_usb_device(), &gpio);
+
+  DBG(DBG_info, "%s: GPIO=0x%02x\n", __func__, gpio);
+}
+
+// Send the low-level scan command
+void CommandSetGl646::begin_scan(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                 Genesys_Register_Set* reg, bool start_motor) const
+{
+    DBG_HELPER(dbg);
+    (void) sensor;
+  // FIXME: SEQUENTIAL not really needed in this case
+  Genesys_Register_Set local_reg(Genesys_Register_Set::SEQUENTIAL);
+
+    local_reg.init_reg(0x03, reg->get8(0x03));
+    local_reg.init_reg(0x01, reg->get8(0x01) | REG_0x01_SCAN);
+
+    if (start_motor) {
+        local_reg.init_reg(0x0f, 0x01);
+    } else {
+        local_reg.init_reg(0x0f, 0x00); // do not start motor yet
+    }
+
+    dev->interface->write_registers(local_reg);
+
+    dev->advance_head_pos_by_session(ScanHeadId::PRIMARY);
+}
+
+
+// Send the stop scan command
+static void end_scan_impl(Genesys_Device* dev, Genesys_Register_Set* reg, bool check_stop,
+                          bool eject)
+{
+    DBG_HELPER_ARGS(dbg, "check_stop = %d, eject = %d", check_stop, eject);
+
+    scanner_stop_action_no_move(*dev, *reg);
+
+    unsigned wait_limit_seconds = 30;
+
+  /* for sheetfed scanners, we may have to eject document */
+    if (dev->model->is_sheetfed) {
+        if (eject && dev->document) {
+            dev->cmd_set->eject_document(dev);
+        }
+        wait_limit_seconds = 3;
+    }
+
+    if (is_testing_mode()) {
+        return;
+    }
+
+    dev->interface->sleep_ms(100);
+
+    if (check_stop) {
+        for (unsigned i = 0; i < wait_limit_seconds * 10; i++) {
+            if (scanner_is_motor_stopped(*dev)) {
+                return;
+            }
+
+            dev->interface->sleep_ms(100);
+        }
+        throw SaneException(SANE_STATUS_IO_ERROR, "could not stop motor");
+    }
+}
+
+// Send the stop scan command
+void CommandSetGl646::end_scan(Genesys_Device* dev, Genesys_Register_Set* reg,
+                               bool check_stop) const
+{
+    end_scan_impl(dev, reg, check_stop, false);
+}
+
+/**
+ * parks head
+ * @param dev scanner's device
+ * @param wait_until_home true if the function waits until head parked
+ */
+void CommandSetGl646::move_back_home(Genesys_Device* dev, bool wait_until_home) const
+{
+    DBG_HELPER_ARGS(dbg, "wait_until_home = %d\n", wait_until_home);
+  int i;
+  int loop = 0;
+
+    auto status = scanner_read_status(*dev);
+
+    if (status.is_at_home) {
+      DBG(DBG_info, "%s: end since already at home\n", __func__);
+        dev->set_head_pos_zero(ScanHeadId::PRIMARY);
+        return;
+    }
+
+  /* stop motor if needed */
+    if (status.is_motor_enabled) {
+        gl646_stop_motor(dev);
+        dev->interface->sleep_ms(200);
+    }
+
+  /* when scanhead is moving then wait until scanhead stops or timeout */
+  DBG(DBG_info, "%s: ensuring that motor is off\n", __func__);
+    for (i = 400; i > 0; i--) {
+        // do not wait longer than 40 seconds, count down to get i = 0 when busy
+
+        status = scanner_read_status(*dev);
+
+        if (!status.is_motor_enabled && status.is_at_home) {
+            DBG(DBG_info, "%s: already at home and not moving\n", __func__);
+            dev->set_head_pos_zero(ScanHeadId::PRIMARY);
+            return;
+        }
+        if (!status.is_motor_enabled) {
+            break;
+        }
+
+        dev->interface->sleep_ms(100);
+    }
+
+  if (!i)			/* the loop counted down to 0, scanner still is busy */
+    {
+        dev->set_head_pos_unknown();
+        throw SaneException(SANE_STATUS_DEVICE_BUSY, "motor is still on: device busy");
+    }
+
+    // setup for a backward scan of 65535 steps, with no actual data reading
+    auto resolution = sanei_genesys_get_lowest_dpi(dev);
+
+    const auto& sensor = sanei_genesys_find_sensor(dev, resolution, 3,
+                                                   dev->model->default_method);
+
+    ScanSession session;
+    session.params.xres = resolution;
+    session.params.yres = resolution;
+    session.params.startx = 0;
+    session.params.starty = 65535;
+    session.params.pixels = 600;
+    session.params.requested_pixels = 600;
+    session.params.lines = 1;
+    session.params.depth = 8;
+    session.params.channels = 3;
+    session.params.scan_method = dev->model->default_method;
+    session.params.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    session.params.color_filter = ColorFilter::RED;
+    session.params.flags = ScanFlag::USE_XCORRECTION |
+                            ScanFlag::REVERSE;
+    if (dev->model->default_method == ScanMethod::TRANSPARENCY) {
+        session.params.flags |= ScanFlag::USE_XPA;
+    }
+    compute_session(dev, session, sensor);
+
+    init_regs_for_scan_session(dev, sensor, &dev->reg, session);
+
+  /* backward , no actual data scanned TODO more setup flags to avoid this register manipulations ? */
+    regs_set_optical_off(dev->model->asic_type, dev->reg);
+
+    // sets frontend
+    gl646_set_fe(dev, sensor, AFE_SET, resolution);
+
+  /* write scan registers */
+    try {
+        dev->interface->write_registers(dev->reg);
+    } catch (...) {
+        DBG(DBG_error, "%s: failed to bulk write registers\n", __func__);
+    }
+
+  /* registers are restored to an iddl state, give up if no head to park */
+    if (dev->model->is_sheetfed) {
+      DBG(DBG_proc, "%s: end \n", __func__);
+      return;
+    }
+
+    // starts scan
+    {
+        // this is effectively the same as dev->cmd_set->begin_scan(dev, sensor, &dev->reg, true);
+        // except that we don't modify the head position calculations
+
+        // FIXME: SEQUENTIAL not really needed in this case
+        Genesys_Register_Set scan_local_reg(Genesys_Register_Set::SEQUENTIAL);
+
+        scan_local_reg.init_reg(0x03, dev->reg.get8(0x03));
+        scan_local_reg.init_reg(0x01, dev->reg.get8(0x01) | REG_0x01_SCAN);
+        scan_local_reg.init_reg(0x0f, 0x01);
+
+        dev->interface->write_registers(scan_local_reg);
+    }
+
+    if (is_testing_mode()) {
+        dev->interface->test_checkpoint("move_back_home");
+        dev->set_head_pos_zero(ScanHeadId::PRIMARY);
+        return;
+    }
+
+  /* loop until head parked */
+  if (wait_until_home)
+    {
+      while (loop < 300)		/* do not wait longer then 30 seconds */
+	{
+            auto status = scanner_read_status(*dev);
+
+            if (status.is_at_home) {
+	      DBG(DBG_info, "%s: reached home position\n", __func__);
+	      DBG(DBG_proc, "%s: end\n", __func__);
+                dev->interface->sleep_ms(500);
+                dev->set_head_pos_zero(ScanHeadId::PRIMARY);
+                return;
+            }
+            dev->interface->sleep_ms(100);
+            ++loop;
+        }
+
+        // when we come here then the scanner needed too much time for this, so we better
+        // stop the motor
+        catch_all_exceptions(__func__, [&](){ gl646_stop_motor (dev); });
+        catch_all_exceptions(__func__, [&](){ end_scan_impl(dev, &dev->reg, true, false); });
+        dev->set_head_pos_unknown();
+        throw SaneException(SANE_STATUS_IO_ERROR, "timeout while waiting for scanhead to go home");
+    }
+
+
+  DBG(DBG_info, "%s: scanhead is still moving\n", __func__);
+}
+
+/**
+ * Automatically set top-left edge of the scan area by scanning an
+ * area at 300 dpi from very top of scanner
+ * @param dev  device stucture describing the scanner
+ */
+void CommandSetGl646::search_start_position(Genesys_Device* dev) const
+{
+    DBG_HELPER(dbg);
+  Genesys_Settings settings;
+  unsigned int resolution, x, y;
+
+  /* we scan at 300 dpi */
+  resolution = get_closest_resolution(dev->model->sensor_id, 300, 1);
+
+    // 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, resolution, 1,
+                                                   dev->model->default_method);
+
+  /* fill settings for a gray level scan */
+  settings.scan_method = dev->model->default_method;
+  settings.scan_mode = ScanColorMode::GRAY;
+  settings.xres = resolution;
+  settings.yres = resolution;
+  settings.tl_x = 0;
+  settings.tl_y = 0;
+  settings.pixels = 600;
+    settings.requested_pixels = settings.pixels;
+  settings.lines = dev->model->search_lines;
+  settings.depth = 8;
+  settings.color_filter = ColorFilter::RED;
+
+  settings.disable_interpolation = 0;
+  settings.threshold = 0;
+
+    // scan the desired area
+    std::vector<uint8_t> data;
+    simple_scan(dev, sensor, settings, true, true, false, data, "search_start_position");
+
+    // handle stagger case : reorder gray data and thus loose some lines
+    auto staggered_lines = dev->session.num_staggered_lines;
+    if (staggered_lines > 0) {
+        DBG(DBG_proc, "%s: 'un-staggering'\n", __func__);
+        for (y = 0; y < settings.lines - staggered_lines; y++) {
+            /* one point out of 2 is 'unaligned' */
+            for (x = 0; x < settings.pixels; x += 2)
+        {
+                data[y * settings.pixels + x] = data[(y + staggered_lines) * settings.pixels + x];
+        }
+          }
+        /* correct line number */
+        settings.lines -= staggered_lines;
+    }
+
+    if (DBG_LEVEL >= DBG_data)
+      {
+        sanei_genesys_write_pnm_file("gl646_search_position.pnm", data.data(), settings.depth, 1,
+                                     settings.pixels, settings.lines);
+      }
+
+    // now search reference points on the data
+    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,
+                                             resolution, settings.pixels, settings.lines);
+    }
+}
+
+/**
+ * internally overriden during effective calibration
+ * sets up register for coarse gain calibration
+ */
+void CommandSetGl646::init_regs_for_coarse_calibration(Genesys_Device* dev,
+                                                       const Genesys_Sensor& sensor,
+                                                       Genesys_Register_Set& regs) const
+{
+    DBG_HELPER(dbg);
+    (void) dev;
+    (void) sensor;
+    (void) regs;
+}
+
+
+/**
+ * init registers for shading calibration
+ * we assume that scanner's head is on an area suiting shading calibration.
+ * We scan a full scan width area by the shading line number for the device
+ * at either at full sensor's resolution or half depending upon ccd_size_divisor
+ * @param dev scanner's device
+ */
+void CommandSetGl646::init_regs_for_shading(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                            Genesys_Register_Set& regs) const
+{
+    DBG_HELPER(dbg);
+    (void) regs;
+  Genesys_Settings settings;
+  int cksel = 1;
+
+  /* fill settings for scan : always a color scan */
+  int channels = 3;
+
+    const auto& calib_sensor = sanei_genesys_find_sensor(dev, dev->settings.xres, channels,
+                                                         dev->settings.scan_method);
+
+    unsigned ccd_size_divisor = calib_sensor.get_ccd_size_divisor_for_dpi(dev->settings.xres);
+
+  settings.scan_method = dev->settings.scan_method;
+  settings.scan_mode = dev->settings.scan_mode;
+    if (!dev->model->is_cis) {
+      // FIXME: always a color scan, but why don't we set scan_mode to COLOR_SINGLE_PASS always?
+      settings.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    }
+  settings.xres = sensor.optical_res / ccd_size_divisor;
+  cksel = get_cksel(dev->model->sensor_id, dev->settings.xres, channels);
+  settings.xres = settings.xres / cksel;
+  settings.yres = settings.xres;
+  settings.tl_x = 0;
+  settings.tl_y = 0;
+    settings.pixels = (calib_sensor.sensor_pixels * settings.xres) / calib_sensor.optical_res;
+    settings.requested_pixels = settings.pixels;
+  dev->calib_lines = dev->model->shading_lines;
+  settings.lines = dev->calib_lines * (3 - ccd_size_divisor);
+  settings.depth = 16;
+  settings.color_filter = dev->settings.color_filter;
+
+  settings.disable_interpolation = dev->settings.disable_interpolation;
+  settings.threshold = dev->settings.threshold;
+
+    // we don't want top offset, but we need right margin to be the same than the one for the final
+    // scan
+    setup_for_scan(dev, calib_sensor, &dev->reg, settings, true, false, false, false);
+
+  /* used when sending shading calibration data */
+  dev->calib_pixels = settings.pixels;
+    dev->calib_channels = dev->session.params.channels;
+    if (!dev->model->is_cis) {
+      dev->calib_channels = 3;
+    }
+
+  /* no shading */
+    dev->reg.find_reg(0x01).value &= ~REG_0x01_DVDSET;
+    dev->reg.find_reg(0x02).value |= REG_0x02_ACDCDIS;	/* ease backtracking */
+    dev->reg.find_reg(0x02).value &= ~(REG_0x02_FASTFED | REG_0x02_AGOHOME);
+    dev->reg.find_reg(0x05).value &= ~REG_0x05_GMMENB;
+  sanei_genesys_set_motor_power(dev->reg, false);
+
+  /* TODO another flag to setup regs ? */
+  /* enforce needed LINCNT, getting rid of extra lines for color reordering */
+    if (!dev->model->is_cis) {
+        dev->reg.set24(REG_LINCNT, dev->calib_lines);
+    } else {
+        dev->reg.set24(REG_LINCNT, dev->calib_lines * 3);
+    }
+
+  /* copy reg to calib_reg */
+  dev->calib_reg = dev->reg;
+
+  DBG(DBG_info, "%s:\n\tdev->settings.xres=%d\n\tdev->settings.yres=%d\n", __func__,
+      dev->settings.xres, dev->settings.yres);
+}
+
+bool CommandSetGl646::needs_home_before_init_regs_for_scan(Genesys_Device* dev) const
+{
+    return dev->is_head_pos_known(ScanHeadId::PRIMARY) &&
+            dev->head_pos(ScanHeadId::PRIMARY) &&
+            dev->settings.scan_method == ScanMethod::FLATBED;
+}
+
+/**
+ * set up registers for the actual scan. The scan's parameters are given
+ * through the device settings. It allocates the scan buffers.
+ */
+void CommandSetGl646::init_regs_for_scan(Genesys_Device* dev, const Genesys_Sensor& sensor) const
+{
+    DBG_HELPER(dbg);
+
+    debug_dump(DBG_info, dev->settings);
+
+    ScanSession session = calculate_scan_session(dev, sensor, dev->settings);
+
+    init_regs_for_scan_session(dev, sensor, &dev->reg, session);
+
+  /* gamma is only enabled at final scan time */
+    if (dev->settings.depth < 16) {
+        dev->reg.find_reg(0x05).value |= REG_0x05_GMMENB;
+    }
+}
+
+/**
+ * set up registers for the actual scan. The scan's parameters are given
+ * through the device settings. It allocates the scan buffers.
+ * @param dev scanner's device
+ * @param regs     registers to set up
+ * @param settings settings of scan
+ * @param split true if move to scan area is split from scan, false is
+ *              scan first moves to area
+ * @param xcorrection take x geometry correction into account (fixed and detected offsets)
+ * @param ycorrection take y geometry correction into account
+ */
+static void setup_for_scan(Genesys_Device* dev,
+                           const Genesys_Sensor& sensor,
+                           Genesys_Register_Set*regs,
+                           Genesys_Settings settings,
+                           bool split,
+                           bool xcorrection,
+                           bool ycorrection,
+                           bool reverse)
+{
+    DBG_HELPER(dbg);
+
+    debug_dump(DBG_info, dev->settings);
+
+    // compute distance to move
+    float move = 0;
+    // XXX STEF XXX MD5345 -> optical_ydpi, other base_ydpi => half/full step ? */
+    if (!split) {
+        if (!dev->model->is_sheetfed) {
+            if (ycorrection) {
+                move = static_cast<float>(dev->model->y_offset);
+            }
+
+            // add tl_y to base movement
+        }
+        move += static_cast<float>(settings.tl_y);
+
+        if (move < 0) {
+            DBG(DBG_error, "%s: overriding negative move value %f\n", __func__, move);
+            move = 0;
+        }
+    }
+    move = static_cast<float>((move * dev->motor.optical_ydpi) / MM_PER_INCH);
+    DBG(DBG_info, "%s: move=%f steps\n", __func__, move);
+
+    float start = static_cast<float>(settings.tl_x);
+    if (xcorrection) {
+        if (settings.scan_method == ScanMethod::FLATBED) {
+            start += static_cast<float>(dev->model->x_offset);
+        } else {
+            start += static_cast<float>(dev->model->x_offset_ta);
+        }
+    }
+    start = static_cast<float>((start * sensor.optical_res) / MM_PER_INCH);
+
+    ScanSession session;
+    session.params.xres = settings.xres;
+    session.params.yres = settings.yres;
+    session.params.startx = static_cast<unsigned>(start);
+    session.params.starty = static_cast<unsigned>(move);
+    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 = dev->settings.scan_method;
+    session.params.scan_mode = settings.scan_mode;
+    session.params.color_filter = settings.color_filter;
+    session.params.flags = ScanFlag::NONE;
+    if (settings.scan_method == ScanMethod::TRANSPARENCY) {
+        session.params.flags |= ScanFlag::USE_XPA;
+    }
+    if (xcorrection) {
+        session.params.flags |= ScanFlag::USE_XCORRECTION;
+    }
+    if (reverse) {
+        session.params.flags |= ScanFlag::REVERSE;
+    }
+    compute_session(dev, session, sensor);
+
+    dev->cmd_set->init_regs_for_scan_session(dev, sensor, regs, session);
+}
+
+/**
+ * this function send gamma table to ASIC
+ */
+void CommandSetGl646::send_gamma_table(Genesys_Device* dev, const Genesys_Sensor& sensor) const
+{
+    DBG_HELPER(dbg);
+  int size;
+  int address;
+  int bits;
+
+  /* gamma table size */
+  if (dev->model->flags & GENESYS_FLAG_14BIT_GAMMA)
+    {
+      size = 16384;
+      bits = 14;
+    }
+  else
+    {
+      size = 4096;
+      bits = 12;
+    }
+
+  /* allocate temporary gamma tables: 16 bits words, 3 channels */
+  std::vector<uint8_t> gamma(size * 2 * 3);
+
+    sanei_genesys_generate_gamma_buffer(dev, sensor, bits, size-1, size, gamma.data());
+
+  /* table address */
+  switch (dev->reg.find_reg(0x05).value >> 6)
+    {
+    case 0:			/* 600 dpi */
+      address = 0x09000;
+      break;
+    case 1:			/* 1200 dpi */
+      address = 0x11000;
+      break;
+    case 2:			/* 2400 dpi */
+      address = 0x20000;
+      break;
+    default:
+            throw SaneException("invalid dpi");
+    }
+
+    dev->interface->write_buffer(0x3c, address, gamma.data(), size * 2 * 3);
+}
+
+/** @brief this function does the led calibration.
+ * this function does the led calibration by scanning one line of the calibration
+ * area below scanner's top on white strip. The scope of this function is
+ * currently limited to the XP200
+ */
+SensorExposure CommandSetGl646::led_calibration(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                                Genesys_Register_Set& regs) const
+{
+    DBG_HELPER(dbg);
+    (void) regs;
+  int total_size;
+  unsigned int i, j;
+  int val;
+  int avg[3], avga, avge;
+  int turn;
+  uint16_t expr, expg, expb;
+  Genesys_Settings settings;
+  SANE_Int resolution;
+
+    unsigned channels = dev->settings.get_channels();
+
+  /* get led calibration resolution */
+  if (dev->settings.scan_mode == ScanColorMode::COLOR_SINGLE_PASS)
+    {
+      settings.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+    }
+  else
+    {
+      settings.scan_mode = ScanColorMode::GRAY;
+    }
+  resolution = get_closest_resolution(dev->model->sensor_id, sensor.optical_res, channels);
+
+  /* offset calibration is always done in color mode */
+    settings.scan_method = dev->model->default_method;
+  settings.xres = resolution;
+  settings.yres = resolution;
+  settings.tl_x = 0;
+  settings.tl_y = 0;
+    settings.pixels = (sensor.sensor_pixels * resolution) / sensor.optical_res;
+    settings.requested_pixels = settings.pixels;
+  settings.lines = 1;
+  settings.depth = 16;
+  settings.color_filter = ColorFilter::RED;
+
+  settings.disable_interpolation = 0;
+  settings.threshold = 0;
+
+  /* colors * bytes_per_color * scan lines */
+  total_size = settings.pixels * channels * 2 * 1;
+
+  std::vector<uint8_t> line(total_size);
+
+/*
+   we try to get equal bright leds here:
+
+   loop:
+     average per color
+     adjust exposure times
+ */
+  expr = sensor.exposure.red;
+  expg = sensor.exposure.green;
+  expb = sensor.exposure.blue;
+
+  turn = 0;
+
+    auto calib_sensor = sensor;
+
+    bool acceptable = false;
+    do {
+        calib_sensor.exposure.red = expr;
+        calib_sensor.exposure.green = expg;
+        calib_sensor.exposure.blue = expb;
+
+      DBG(DBG_info, "%s: starting first line reading\n", __func__);
+
+        simple_scan(dev, calib_sensor, settings, false, true, false, line, "led_calibration");
+
+        if (is_testing_mode()) {
+            return calib_sensor.exposure;
+        }
+
+      if (DBG_LEVEL >= DBG_data)
+	{
+          char fn[30];
+            std::snprintf(fn, 30, "gl646_led_%02d.pnm", turn);
+          sanei_genesys_write_pnm_file(fn, line.data(), 16, channels, settings.pixels, 1);
+	}
+
+        acceptable = true;
+
+      for (j = 0; j < channels; j++)
+	{
+	  avg[j] = 0;
+	  for (i = 0; i < settings.pixels; i++)
+	    {
+	      if (dev->model->is_cis)
+		val =
+		  line[i * 2 + j * 2 * settings.pixels + 1] * 256 +
+		  line[i * 2 + j * 2 * settings.pixels];
+	      else
+		val =
+		  line[i * 2 * channels + 2 * j + 1] * 256 +
+		  line[i * 2 * channels + 2 * j];
+	      avg[j] += val;
+	    }
+
+	  avg[j] /= settings.pixels;
+	}
+
+      DBG(DBG_info, "%s: average: %d,%d,%d\n", __func__, avg[0], avg[1], avg[2]);
+
+        acceptable = true;
+
+      if (!acceptable)
+	{
+	  avga = (avg[0] + avg[1] + avg[2]) / 3;
+	  expr = (expr * avga) / avg[0];
+	  expg = (expg * avga) / avg[1];
+	  expb = (expb * avga) / avg[2];
+
+	  /* keep exposure time in a working window */
+	  avge = (expr + expg + expb) / 3;
+	  if (avge > 0x2000)
+	    {
+	      expr = (expr * 0x2000) / avge;
+	      expg = (expg * 0x2000) / avge;
+	      expb = (expb * 0x2000) / avge;
+	    }
+	  if (avge < 0x400)
+	    {
+	      expr = (expr * 0x400) / avge;
+	      expg = (expg * 0x400) / avge;
+	      expb = (expb * 0x400) / avge;
+	    }
+	}
+
+      turn++;
+
+    }
+  while (!acceptable && turn < 100);
+
+  DBG(DBG_info,"%s: acceptable exposure: 0x%04x,0x%04x,0x%04x\n", __func__, expr, expg, expb);
+    // BUG: we don't store the result of the last iteration to the sensor
+    return calib_sensor.exposure;
+}
+
+/**
+ * average dark pixels of a 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;
+}
+
+
+/** @brief calibration for AD frontend devices
+ * we do simple scan until all black_pixels are higher than 0,
+ * raising offset at each turn.
+ */
+static void ad_fe_offset_calibration(Genesys_Device* dev, const Genesys_Sensor& sensor)
+{
+    DBG_HELPER(dbg);
+    (void) sensor;
+
+  unsigned int channels;
+  int pass = 0;
+  SANE_Int resolution;
+  Genesys_Settings settings;
+  unsigned int x, y, adr, min;
+  unsigned int bottom, black_pixels;
+
+  channels = 3;
+  resolution = get_closest_resolution(dev->model->sensor_id, sensor.optical_res, channels);
+    const auto& calib_sensor = sanei_genesys_find_sensor(dev, resolution, 3, ScanMethod::FLATBED);
+    black_pixels = (calib_sensor.black_pixels * resolution) / calib_sensor.optical_res;
+  DBG(DBG_io2, "%s: black_pixels=%d\n", __func__, black_pixels);
+
+    settings.scan_method = dev->model->default_method;
+  settings.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+  settings.xres = resolution;
+  settings.yres = resolution;
+  settings.tl_x = 0;
+  settings.tl_y = 0;
+    settings.pixels = (calib_sensor.sensor_pixels * resolution) / calib_sensor.optical_res;
+    settings.requested_pixels = settings.pixels;
+  settings.lines = CALIBRATION_LINES;
+  settings.depth = 8;
+  settings.color_filter = ColorFilter::RED;
+
+  settings.disable_interpolation = 0;
+  settings.threshold = 0;
+
+  /* scan first line of data with no gain */
+  dev->frontend.set_gain(0, 0);
+  dev->frontend.set_gain(1, 0);
+  dev->frontend.set_gain(2, 0);
+
+  std::vector<uint8_t> line;
+
+  /* scan with no move */
+  bottom = 1;
+  do
+    {
+      pass++;
+      dev->frontend.set_offset(0, bottom);
+      dev->frontend.set_offset(1, bottom);
+      dev->frontend.set_offset(2, bottom);
+        simple_scan(dev, calib_sensor, settings, false, true, false, line,
+                    "ad_fe_offset_calibration");
+
+        if (is_testing_mode()) {
+            return;
+        }
+
+      if (DBG_LEVEL >= DBG_data)
+	{
+          char title[30];
+          std::snprintf(title, 30, "gl646_offset%03d.pnm", static_cast<int>(bottom));
+          sanei_genesys_write_pnm_file (title, line.data(), 8, channels,
+					settings.pixels, settings.lines);
+	}
+
+      min = 0;
+      for (y = 0; y < settings.lines; y++)
+	{
+	  for (x = 0; x < black_pixels; x++)
+	    {
+	      adr = (x + y * settings.pixels) * channels;
+	      if (line[adr] > min)
+		min = line[adr];
+	      if (line[adr + 1] > min)
+		min = line[adr + 1];
+	      if (line[adr + 2] > min)
+		min = line[adr + 2];
+	    }
+	}
+
+      DBG(DBG_io2, "%s: pass=%d, min=%d\n", __func__, pass, min);
+      bottom++;
+    }
+  while (pass < 128 && min == 0);
+  if (pass == 128)
+    {
+        throw SaneException(SANE_STATUS_INVAL, "failed to find correct offset");
+    }
+
+  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));
+}
+
+/**
+ * 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.
+ * genesys_search_start() must have been called so that the offsets and margins
+ * are already known.
+ * @param dev scanner's device
+*/
+void CommandSetGl646::offset_calibration(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                         Genesys_Register_Set& regs) const
+{
+    DBG_HELPER(dbg);
+    (void) regs;
+
+  unsigned int channels;
+  int pass = 0, avg;
+  Genesys_Settings settings;
+  int topavg, bottomavg;
+  int top, bottom, black_pixels;
+
+    if (dev->model->adc_id == AdcId::AD_XP200) {
+        ad_fe_offset_calibration(dev, sensor);
+        return;
+    }
+
+  DBG(DBG_proc, "%s: start\n", __func__); // TODO
+
+  /* setup for a RGB scan, one full sensor's width line */
+  /* resolution is the one from the final scan          */
+    channels = 3;
+    int resolution = get_closest_resolution(dev->model->sensor_id, dev->settings.xres, channels);
+
+    const auto& calib_sensor = sanei_genesys_find_sensor(dev, resolution, 3, ScanMethod::FLATBED);
+    black_pixels = (calib_sensor.black_pixels * resolution) / calib_sensor.optical_res;
+
+  DBG(DBG_io2, "%s: black_pixels=%d\n", __func__, black_pixels);
+
+    settings.scan_method = dev->model->default_method;
+  settings.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+  settings.xres = resolution;
+  settings.yres = resolution;
+  settings.tl_x = 0;
+  settings.tl_y = 0;
+    settings.pixels = (calib_sensor.sensor_pixels * resolution) / calib_sensor.optical_res;
+    settings.requested_pixels = settings.pixels;
+  settings.lines = CALIBRATION_LINES;
+  settings.depth = 8;
+  settings.color_filter = ColorFilter::RED;
+
+  settings.disable_interpolation = 0;
+  settings.threshold = 0;
+
+  /* scan first line of data with no gain, but with offset from
+   * last calibration */
+  dev->frontend.set_gain(0, 0);
+  dev->frontend.set_gain(1, 0);
+  dev->frontend.set_gain(2, 0);
+
+  /* scan with no move */
+  bottom = 90;
+  dev->frontend.set_offset(0, bottom);
+  dev->frontend.set_offset(1, bottom);
+  dev->frontend.set_offset(2, bottom);
+
+  std::vector<uint8_t> first_line, second_line;
+
+    simple_scan(dev, calib_sensor, settings, false, true, false, first_line,
+                "offset_first_line");
+
+  if (DBG_LEVEL >= DBG_data)
+    {
+      char title[30];
+        std::snprintf(title, 30, "gl646_offset%03d.pnm", bottom);
+      sanei_genesys_write_pnm_file(title, first_line.data(), 8, channels,
+                                   settings.pixels, settings.lines);
+    }
+  bottomavg = dark_average(first_line.data(), settings.pixels, settings.lines, channels,
+                           black_pixels);
+  DBG(DBG_io2, "%s: bottom avg=%d\n", __func__, bottomavg);
+
+  /* now top value */
+  top = 231;
+  dev->frontend.set_offset(0, top);
+  dev->frontend.set_offset(1, top);
+  dev->frontend.set_offset(2, top);
+    simple_scan(dev, calib_sensor, settings, false, true, false, second_line,
+                "offset_second_line");
+
+  if (DBG_LEVEL >= DBG_data)
+    {
+      char title[30];
+        std::snprintf(title, 30, "gl646_offset%03d.pnm", top);
+      sanei_genesys_write_pnm_file (title, second_line.data(), 8, channels,
+				    settings.pixels, settings.lines);
+    }
+  topavg = dark_average(second_line.data(), settings.pixels, settings.lines, channels,
+                        black_pixels);
+  DBG(DBG_io2, "%s: top avg=%d\n", __func__, topavg);
+
+    if (is_testing_mode()) {
+        return;
+    }
+
+  /* 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
+        simple_scan(dev, calib_sensor, settings, false, true, false, second_line,
+                    "offset_calibration_i");
+
+      if (DBG_LEVEL >= DBG_data)
+	{
+          char title[30];
+            std::snprintf(title, 30, "gl646_offset%03d.pnm", dev->frontend.get_offset(1));
+          sanei_genesys_write_pnm_file (title, second_line.data(), 8, channels,
+					settings.pixels, settings.lines);
+	}
+
+      avg =
+        dark_average (second_line.data(), settings.pixels, settings.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));
+}
+
+/** @brief gain calibration for Analog Device frontends
+ * Alternative coarse gain calibration
+ */
+static void ad_fe_coarse_gain_calibration(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                          Genesys_Register_Set& regs, int dpi)
+{
+    DBG_HELPER(dbg);
+    (void) sensor;
+    (void) regs;
+
+  unsigned int i, channels, val;
+  unsigned int size, count, resolution, pass;
+  float average;
+  Genesys_Settings settings;
+  char title[32];
+
+  /* setup for a RGB scan, one full sensor's width line */
+  /* resolution is the one from the final scan          */
+  channels = 3;
+  resolution = get_closest_resolution(dev->model->sensor_id, dpi, channels);
+
+    const auto& calib_sensor = sanei_genesys_find_sensor(dev, resolution, 3, ScanMethod::FLATBED);
+
+  settings.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+
+    settings.scan_method = dev->model->default_method;
+  settings.xres = resolution;
+  settings.yres = resolution;
+  settings.tl_x = 0;
+  settings.tl_y = 0;
+    settings.pixels = (calib_sensor.sensor_pixels * resolution) / calib_sensor.optical_res;
+    settings.requested_pixels = settings.pixels;
+  settings.lines = CALIBRATION_LINES;
+  settings.depth = 8;
+  settings.color_filter = ColorFilter::RED;
+
+  settings.disable_interpolation = 0;
+  settings.threshold = 0;
+
+  size = channels * settings.pixels * settings.lines;
+
+  /* start gain value */
+  dev->frontend.set_gain(0, 1);
+  dev->frontend.set_gain(1, 1);
+  dev->frontend.set_gain(2, 1);
+
+  average = 0;
+  pass = 0;
+
+  std::vector<uint8_t> line;
+
+    // loop until each channel raises to acceptable level
+    while ((average < calib_sensor.gain_white_ref) && (pass < 30)) {
+        // scan with no move
+        simple_scan(dev, calib_sensor, settings, false, true, false, line,
+                    "ad_fe_coarse_gain_calibration");
+
+      /* log scanning data */
+      if (DBG_LEVEL >= DBG_data)
+	{
+            std::sprintf(title, "gl646_alternative_gain%02d.pnm", pass);
+          sanei_genesys_write_pnm_file(title, line.data(), 8, channels, settings.pixels,
+                                       settings.lines);
+	}
+      pass++;
+
+      /* computes white average */
+      average = 0;
+      count = 0;
+      for (i = 0; i < size; i++)
+	{
+	  val = line[i];
+	  average += val;
+	  count++;
+	}
+      average = average / count;
+
+        uint8_t gain0 = dev->frontend.get_gain(0);
+        // adjusts gain for the channel
+        if (average < calib_sensor.gain_white_ref) {
+            gain0 += 1;
+        }
+
+        dev->frontend.set_gain(0, gain0);
+        dev->frontend.set_gain(1, gain0);
+        dev->frontend.set_gain(2, gain0);
+
+      DBG(DBG_proc, "%s: average = %.2f, gain = %d\n", __func__, average, gain0);
+    }
+
+  DBG(DBG_info, "%s: gains=(%d,%d,%d)\n", __func__,
+      dev->frontend.get_gain(0),
+      dev->frontend.get_gain(1),
+      dev->frontend.get_gain(2));
+}
+
+/**
+ * Alternative coarse gain calibration
+ * this on uses the settings from offset_calibration. First scan moves so
+ * we can go to calibration area for XPA.
+ * @param dev device for scan
+ * @param dpi resolutnio to calibrate at
+ */
+void CommandSetGl646::coarse_gain_calibration(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                              Genesys_Register_Set& regs, int dpi) const
+{
+    DBG_HELPER(dbg);
+    (void) dpi;
+
+  unsigned int i, j, k, channels, val, maximum, idx;
+  unsigned int count, resolution, pass;
+  float average[3];
+  Genesys_Settings settings;
+  char title[32];
+
+    if (dev->model->sensor_id == SensorId::CIS_XP200) {
+      return ad_fe_coarse_gain_calibration(dev, sensor, regs, sensor.optical_res);
+    }
+
+  /* setup for a RGB scan, one full sensor's width line */
+  /* resolution is the one from the final scan          */
+  channels = 3;
+
+  /* we are searching a sensor resolution */
+    resolution = get_closest_resolution(dev->model->sensor_id, dev->settings.xres, channels);
+
+    const auto& calib_sensor = sanei_genesys_find_sensor(dev, resolution, channels,
+                                                         ScanMethod::FLATBED);
+
+  settings.scan_method = dev->settings.scan_method;
+  settings.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+  settings.xres = resolution;
+  settings.yres = resolution;
+  settings.tl_y = 0;
+  if (settings.scan_method == ScanMethod::FLATBED)
+    {
+      settings.tl_x = 0;
+        settings.pixels = (calib_sensor.sensor_pixels * resolution) / calib_sensor.optical_res;
+    }
+  else
+    {
+        settings.tl_x = dev->model->x_offset_ta;
+        settings.pixels = static_cast<unsigned>((dev->model->x_size_ta * resolution) / MM_PER_INCH);
+    }
+    settings.requested_pixels = settings.pixels;
+  settings.lines = CALIBRATION_LINES;
+  settings.depth = 8;
+  settings.color_filter = ColorFilter::RED;
+
+  settings.disable_interpolation = 0;
+  settings.threshold = 0;
+
+  /* start gain value */
+  dev->frontend.set_gain(0, 1);
+  dev->frontend.set_gain(1, 1);
+  dev->frontend.set_gain(2, 1);
+
+  if (channels > 1)
+    {
+      average[0] = 0;
+      average[1] = 0;
+      average[2] = 0;
+      idx = 0;
+    }
+  else
+    {
+      average[0] = 255;
+      average[1] = 255;
+      average[2] = 255;
+        switch (dev->settings.color_filter) {
+            case ColorFilter::RED: idx = 0; break;
+            case ColorFilter::GREEN: idx = 1; break;
+            case ColorFilter::BLUE: idx = 2; break;
+            default: idx = 0; break; // should not happen
+        }
+      average[idx] = 0;
+    }
+  pass = 0;
+
+  std::vector<uint8_t> line;
+
+  /* loop until each channel raises to acceptable level */
+    while (((average[0] < calib_sensor.gain_white_ref) ||
+            (average[1] < calib_sensor.gain_white_ref) ||
+            (average[2] < calib_sensor.gain_white_ref)) && (pass < 30))
+    {
+        // scan with no move
+        simple_scan(dev, calib_sensor, settings, false, true, false, line,
+                    "coarse_gain_calibration");
+
+      /* log scanning data */
+      if (DBG_LEVEL >= DBG_data)
+	{
+          std::sprintf(title, "gl646_gain%02d.pnm", pass);
+          sanei_genesys_write_pnm_file(title, line.data(), 8, channels, settings.pixels,
+                                       settings.lines);
+	}
+      pass++;
+
+      /* 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 (k = idx; k < idx + channels; k++)
+	{
+	  /* we find the maximum white value, so we can deduce a threshold
+	     to average white values */
+	  maximum = 0;
+	  for (i = 0; i < settings.lines; i++)
+	    {
+	      for (j = 0; j < settings.pixels; j++)
+		{
+		  val = line[i * channels * settings.pixels + j + k];
+		  if (val > maximum)
+		    maximum = val;
+		}
+	    }
+
+	  /* threshold */
+            maximum = static_cast<int>(maximum * 0.9);
+
+	  /* computes white average */
+	  average[k] = 0;
+	  count = 0;
+	  for (i = 0; i < settings.lines; i++)
+	    {
+	      for (j = 0; j < settings.pixels; j++)
+		{
+		  /* averaging only white points allow us not to care about dark margins */
+		  val = line[i * channels * settings.pixels + j + k];
+		  if (val > maximum)
+		    {
+		      average[k] += val;
+		      count++;
+		    }
+		}
+	    }
+	  average[k] = average[k] / count;
+
+	  /* adjusts gain for the channel */
+          if (average[k] < calib_sensor.gain_white_ref)
+            dev->frontend.set_gain(k, dev->frontend.get_gain(k) + 1);
+
+	  DBG(DBG_proc, "%s: channel %d, average = %.2f, gain = %d\n", __func__, k, average[k],
+              dev->frontend.get_gain(k));
+	}
+    }
+
+    if (channels < 3) {
+        dev->frontend.set_gain(1, dev->frontend.get_gain(0));
+        dev->frontend.set_gain(2, dev->frontend.get_gain(0));
+    }
+
+  DBG(DBG_info, "%s: gains=(%d,%d,%d)\n", __func__,
+      dev->frontend.get_gain(0),
+      dev->frontend.get_gain(1),
+      dev->frontend.get_gain(2));
+}
+
+/**
+ * sets up the scanner's register for warming up. We scan 2 lines without moving.
+ *
+ */
+void CommandSetGl646::init_regs_for_warmup(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                           Genesys_Register_Set* local_reg, int* channels,
+                                           int* total_size) const
+{
+    DBG_HELPER(dbg);
+    (void) sensor;
+
+  Genesys_Settings settings;
+  int resolution, lines;
+
+  dev->frontend = dev->frontend_initial;
+
+  resolution = get_closest_resolution(dev->model->sensor_id, 300, 1);
+
+    const auto& local_sensor = sanei_genesys_find_sensor(dev, resolution, 1,
+                                                         dev->settings.scan_method);
+
+  /* set up for a half width 2 lines gray scan without moving */
+    settings.scan_method = dev->model->default_method;
+  settings.scan_mode = ScanColorMode::GRAY;
+  settings.xres = resolution;
+  settings.yres = resolution;
+  settings.tl_x = 0;
+  settings.tl_y = 0;
+    settings.pixels = (local_sensor.sensor_pixels * resolution) / local_sensor.optical_res;
+    settings.requested_pixels = settings.pixels;
+  settings.lines = 2;
+  settings.depth = 8;
+  settings.color_filter = ColorFilter::RED;
+
+  settings.disable_interpolation = 0;
+  settings.threshold = 0;
+
+    // setup for scan
+    setup_for_scan(dev, local_sensor, &dev->reg, settings, true, false, false, false);
+
+  /* we are not going to move, so clear these bits */
+    dev->reg.find_reg(0x02).value &= ~(REG_0x02_FASTFED | REG_0x02_AGOHOME);
+
+  /* don't enable any correction for this scan */
+    dev->reg.find_reg(0x01).value &= ~REG_0x01_DVDSET;
+
+  /* copy to local_reg */
+  *local_reg = dev->reg;
+
+  /* turn off motor during this scan */
+  sanei_genesys_set_motor_power(*local_reg, false);
+
+  /* returned value to higher level warmup function */
+  *channels = 1;
+    lines = local_reg->get24(REG_LINCNT) + 1;
+  *total_size = lines * settings.pixels;
+
+    // now registers are ok, write them to scanner
+    gl646_set_fe(dev, local_sensor, AFE_SET, settings.xres);
+    dev->interface->write_registers(*local_reg);
+}
+
+
+/*
+ * 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 void gl646_repark_head(Genesys_Device* dev)
+{
+    DBG_HELPER(dbg);
+  Genesys_Settings settings;
+  unsigned int expected, steps;
+
+    settings.scan_method = dev->model->default_method;
+  settings.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+  settings.xres = get_closest_resolution(dev->model->sensor_id, 75, 1);
+  settings.yres = settings.xres;
+  settings.tl_x = 0;
+  settings.tl_y = 5;
+  settings.pixels = 600;
+    settings.requested_pixels = settings.pixels;
+  settings.lines = 4;
+  settings.depth = 8;
+  settings.color_filter = ColorFilter::RED;
+
+  settings.disable_interpolation = 0;
+  settings.threshold = 0;
+
+    const auto& sensor = sanei_genesys_find_sensor(dev, settings.xres, 3,
+                                                   dev->model->default_method);
+
+    setup_for_scan(dev, sensor, &dev->reg, settings, false, false, false, false);
+
+  /* TODO seems wrong ... no effective scan */
+    regs_set_optical_off(dev->model->asic_type, dev->reg);
+
+    dev->interface->write_registers(dev->reg);
+
+    // start scan
+    dev->cmd_set->begin_scan(dev, sensor, &dev->reg, true);
+
+    expected = dev->reg.get24(REG_FEEDL);
+  do
+    {
+        dev->interface->sleep_ms(100);
+        sanei_genesys_read_feed_steps (dev, &steps);
+    }
+  while (steps < expected);
+
+    // toggle motor flag, put an huge step number and redo move backward
+    dev->cmd_set->move_back_home(dev, 1);
+}
+
+/* *
+ * initialize ASIC : registers, motor tables, and gamma tables
+ * then ensure scanner's head is at home
+ * @param dev device description of the scanner to initailize
+ */
+void CommandSetGl646::init(Genesys_Device* dev) const
+{
+    DBG_INIT();
+    DBG_HELPER(dbg);
+
+    uint8_t val = 0;
+  uint32_t addr = 0xdead;
+  size_t len;
+
+    // to detect real power up condition, we write to REG_0x41 with pwrbit set, then read it back.
+    // When scanner is cold (just replugged) PWRBIT will be set in the returned value
+    auto status = scanner_read_status(*dev);
+    if (status.is_replugged) {
+      DBG(DBG_info, "%s: device is cold\n", __func__);
+    } else {
+      DBG(DBG_info, "%s: device is hot\n", __func__);
+    }
+
+  const auto& sensor = sanei_genesys_find_sensor_any(dev);
+
+  /* if scanning session hasn't been initialized, set it up */
+  if (!dev->already_initialized)
+    {
+      dev->dark_average_data.clear();
+      dev->white_average_data.clear();
+
+      dev->settings.color_filter = ColorFilter::GREEN;
+
+      /* Set default values for registers */
+      gl646_init_regs (dev);
+
+        // Init shading data
+        sanei_genesys_init_shading_data(dev, sensor, sensor.sensor_pixels);
+
+      /* initial calibration reg values */
+      dev->calib_reg = dev->reg;
+    }
+
+    // execute physical unit init only if cold
+    if (status.is_replugged)
+    {
+      DBG(DBG_info, "%s: device is cold\n", __func__);
+
+        val = 0x04;
+        dev->interface->get_usb_device().control_msg(REQUEST_TYPE_OUT, REQUEST_REGISTER,
+                                                     VALUE_INIT, INDEX, 1, &val);
+
+        // ASIC reset
+        dev->interface->write_register(0x0e, 0x00);
+        dev->interface->sleep_ms(100);
+
+        // Write initial registers
+        dev->interface->write_registers(dev->reg);
+
+        // send gamma tables if needed
+        dev->cmd_set->send_gamma_table(dev, sensor);
+
+        // Set powersaving(default = 15 minutes)
+        dev->cmd_set->set_powersaving(dev, 15);
+    }
+
+    // Set analog frontend
+    gl646_set_fe(dev, sensor, AFE_INIT, 0);
+
+  /* GPO enabling for XP200 */
+    if (dev->model->sensor_id == SensorId::CIS_XP200) {
+        dev->interface->write_register(0x68, dev->gpo.regs.get_value(0x68));
+        dev->interface->write_register(0x69, dev->gpo.regs.get_value(0x69));
+
+        // enable GPIO
+        gl646_gpio_output_enable(dev->interface->get_usb_device(), 6);
+
+        // writes 0 to GPIO
+        gl646_gpio_write(dev->interface->get_usb_device(), 0);
+
+        // clear GPIO enable
+        gl646_gpio_output_enable(dev->interface->get_usb_device(), 0);
+
+        dev->interface->write_register(0x66, 0x10);
+        dev->interface->write_register(0x66, 0x00);
+        dev->interface->write_register(0x66, 0x10);
+    }
+
+  /* MD6471/G2410 and XP200 read/write data from an undocumented memory area which
+   * is after the second slope table */
+    if (dev->model->gpio_id != GpioId::HP3670 &&
+        dev->model->gpio_id != GpioId::HP2400)
+    {
+      switch (sensor.optical_res)
+	{
+	case 600:
+	  addr = 0x08200;
+	  break;
+	case 1200:
+	  addr = 0x10200;
+	  break;
+	case 2400:
+	  addr = 0x1fa00;
+	  break;
+	}
+    sanei_genesys_set_buffer_address(dev, addr);
+
+      sanei_usb_set_timeout (2 * 1000);
+      len = 6;
+        // for some reason, read fails here for MD6471, HP2300 and XP200 one time out of
+        // 2 scanimage launches
+        try {
+            dev->interface->bulk_read_data(0x45, dev->control, len);
+        } catch (...) {
+            dev->interface->bulk_read_data(0x45, dev->control, len);
+        }
+        DBG(DBG_info, "%s: control read=0x%02x 0x%02x 0x%02x 0x%02x 0x%02x 0x%02x\n", __func__,
+            dev->control[0], dev->control[1], dev->control[2], dev->control[3], dev->control[4],
+            dev->control[5]);
+      sanei_usb_set_timeout (30 * 1000);
+    }
+  else
+    /* HP2400 and HP3670 case */
+    {
+      dev->control[0] = 0x00;
+      dev->control[1] = 0x00;
+      dev->control[2] = 0x01;
+      dev->control[3] = 0x00;
+      dev->control[4] = 0x00;
+      dev->control[5] = 0x00;
+    }
+
+  /* ensure head is correctly parked, and check lock */
+    if (!dev->model->is_sheetfed) {
+      if (dev->model->flags & GENESYS_FLAG_REPARK)
+	{
+            // FIXME: if repark fails, we should print an error message that the scanner is locked and
+            // the user should unlock the lock. We should also rethrow with SANE_STATUS_JAMMED
+            gl646_repark_head(dev);
+	}
+      else
+    {
+            move_back_home(dev, true);
+	}
+    }
+
+  /* here session and device are initialized */
+    dev->already_initialized = true;
+}
+
+void CommandSetGl646::move_to_ta(Genesys_Device* dev) const
+{
+    DBG_HELPER(dbg);
+
+    simple_move(dev, static_cast<int>(dev->model->y_offset_sensor_to_ta));
+}
+
+
+/**
+ * Does a simple scan: ie no line reordering and avanced data buffering and
+ * shading correction. Memory for data is allocated in this function
+ * and must be freed by caller.
+ * @param dev device of the scanner
+ * @param settings parameters of the scan
+ * @param move true if moving during scan
+ * @param forward true if moving forward during scan
+ * @param shading true to enable shading correction
+ * @param data pointer for the data
+ */
+static void simple_scan(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                        Genesys_Settings settings, bool move, bool forward,
+                        bool shading, std::vector<uint8_t>& data,
+                        const char* scan_identifier)
+{
+    DBG_HELPER_ARGS(dbg, "move=%d, forward=%d, shading=%d", move, forward, shading);
+  unsigned int size, lines, x, y, bpp;
+    bool split;
+
+  /* round up to multiple of 3 in case of CIS scanner */
+    if (dev->model->is_cis) {
+      settings.lines = ((settings.lines + 2) / 3) * 3;
+    }
+
+  /* setup for move then scan */
+    split = !(move && settings.tl_y > 0);
+    setup_for_scan(dev, sensor, &dev->reg, settings, split, false, false, !forward);
+
+  /* allocate memory fo scan : LINCNT may have been adjusted for CCD reordering */
+    if (dev->model->is_cis) {
+        lines = dev->reg.get24(REG_LINCNT) / 3;
+    } else {
+        lines = dev->reg.get24(REG_LINCNT) + 1;
+    }
+  size = lines * settings.pixels;
+    if (settings.depth == 16) {
+        bpp = 2;
+    } else {
+        bpp = 1;
+    }
+    size *= bpp * settings.get_channels();
+  data.clear();
+  data.resize(size);
+
+  DBG(DBG_io, "%s: allocated %d bytes of memory for %d lines\n", __func__, size, lines);
+
+  /* put back real line number in settings */
+  settings.lines = lines;
+
+    // initialize frontend
+    gl646_set_fe(dev, sensor, AFE_SET, settings.xres);
+
+  /* no shading correction and not watch dog for simple scan */
+    dev->reg.find_reg(0x01).value &= ~(REG_0x01_DVDSET | REG_0x01_DOGENB);
+    if (shading) {
+      dev->reg.find_reg(0x01).value |= REG_0x01_DVDSET;
+    }
+
+  /* enable gamma table for the scan */
+    dev->reg.find_reg(0x05).value |= REG_0x05_GMMENB;
+
+  /* one table movement for simple scan */
+    dev->reg.find_reg(0x02).value &= ~REG_0x02_FASTFED;
+
+    if (!move) {
+      sanei_genesys_set_motor_power(dev->reg, false);
+
+      /* no automatic go home if no movement */
+        dev->reg.find_reg(0x02).value &= ~REG_0x02_AGOHOME;
+    }
+
+  /* no automatic go home when using XPA */
+  if (settings.scan_method == ScanMethod::TRANSPARENCY) {
+        dev->reg.find_reg(0x02).value &= ~REG_0x02_AGOHOME;
+    }
+
+    // write scan registers
+    dev->interface->write_registers(dev->reg);
+
+    // starts scan
+    dev->cmd_set->begin_scan(dev, sensor, &dev->reg, move);
+
+    if (is_testing_mode()) {
+        dev->interface->test_checkpoint(scan_identifier);
+        return;
+    }
+
+    wait_until_buffer_non_empty(dev, true);
+
+    // now we're on target, we can read data
+    sanei_genesys_read_data_from_scanner(dev, data.data(), size);
+
+  /* in case of CIS scanner, we must reorder data */
+    if (dev->model->is_cis && settings.scan_mode == ScanColorMode::COLOR_SINGLE_PASS) {
+      /* alloc one line sized working buffer */
+      std::vector<uint8_t> buffer(settings.pixels * 3 * bpp);
+
+      /* reorder one line of data and put it back to buffer */
+      if (bpp == 1)
+	{
+	  for (y = 0; y < lines; y++)
+	    {
+	      /* reorder line */
+	      for (x = 0; x < settings.pixels; x++)
+		{
+                  buffer[x * 3] = data[y * settings.pixels * 3 + x];
+                  buffer[x * 3 + 1] = data[y * settings.pixels * 3 + settings.pixels + x];
+                  buffer[x * 3 + 2] = data[y * settings.pixels * 3 + 2 * settings.pixels + x];
+		}
+	      /* copy line back */
+              memcpy (data.data() + settings.pixels * 3 * y, buffer.data(),
+		      settings.pixels * 3);
+	    }
+	}
+      else
+	{
+	  for (y = 0; y < lines; y++)
+	    {
+	      /* reorder line */
+	      for (x = 0; x < settings.pixels; x++)
+		{
+                  buffer[x * 6] = data[y * settings.pixels * 6 + x * 2];
+                  buffer[x * 6 + 1] = data[y * settings.pixels * 6 + x * 2 + 1];
+                  buffer[x * 6 + 2] = data[y * settings.pixels * 6 + 2 * settings.pixels + x * 2];
+                  buffer[x * 6 + 3] = data[y * settings.pixels * 6 + 2 * settings.pixels + x * 2 + 1];
+                  buffer[x * 6 + 4] = data[y * settings.pixels * 6 + 4 * settings.pixels + x * 2];
+                  buffer[x * 6 + 5] = data[y * settings.pixels * 6 + 4 * settings.pixels + x * 2 + 1];
+		}
+	      /* copy line back */
+              memcpy (data.data() + settings.pixels * 6 * y, buffer.data(),
+		      settings.pixels * 6);
+	    }
+	}
+    }
+
+    // end scan , waiting the motor to stop if needed (if moving), but without ejecting doc
+    end_scan_impl(dev, &dev->reg, true, false);
+}
+
+/**
+ * Does a simple move of the given distance by doing a scan at lowest resolution
+ * shading correction. Memory for data is allocated in this function
+ * and must be freed by caller.
+ * @param dev device of the scanner
+ * @param distance distance to move in MM
+ */
+static void simple_move(Genesys_Device* dev, SANE_Int distance)
+{
+    DBG_HELPER_ARGS(dbg, "%d mm", distance);
+  Genesys_Settings settings;
+
+    unsigned resolution = sanei_genesys_get_lowest_dpi(dev);
+
+  const auto& sensor = sanei_genesys_find_sensor(dev, resolution, 3, dev->model->default_method);
+
+  /* TODO give a no AGOHOME flag */
+    settings.scan_method = dev->model->default_method;
+  settings.scan_mode = ScanColorMode::COLOR_SINGLE_PASS;
+  settings.xres = resolution;
+  settings.yres = resolution;
+  settings.tl_y = 0;
+  settings.tl_x = 0;
+  settings.pixels = (sensor.sensor_pixels * settings.xres) / sensor.optical_res;
+    settings.requested_pixels = settings.pixels;
+    settings.lines = static_cast<unsigned>((distance * settings.xres) / MM_PER_INCH);
+  settings.depth = 8;
+  settings.color_filter = ColorFilter::RED;
+
+  settings.disable_interpolation = 0;
+  settings.threshold = 0;
+
+  std::vector<uint8_t> data;
+    simple_scan(dev, sensor, settings, true, true, false, data, "simple_move");
+}
+
+/**
+ * update the status of the required sensor in the scanner session
+ * the button fileds are used to make events 'sticky'
+ */
+void CommandSetGl646::update_hardware_sensors(Genesys_Scanner* session) const
+{
+    DBG_HELPER(dbg);
+  Genesys_Device *dev = session->dev;
+  uint8_t value;
+
+    // do what is needed to get a new set of events, but try to not loose any of them.
+    gl646_gpio_read(dev->interface->get_usb_device(), &value);
+    DBG(DBG_io, "%s: GPIO=0x%02x\n", __func__, value);
+
+    // scan button
+    if (dev->model->buttons & GENESYS_HAS_SCAN_SW) {
+        switch (dev->model->gpio_id) {
+        case GpioId::XP200:
+            session->buttons[BUTTON_SCAN_SW].write((value & 0x02) != 0);
+            break;
+        case GpioId::MD_5345:
+            session->buttons[BUTTON_SCAN_SW].write(value == 0x16);
+            break;
+        case GpioId::HP2300:
+            session->buttons[BUTTON_SCAN_SW].write(value == 0x6c);
+            break;
+        case GpioId::HP3670:
+        case GpioId::HP2400:
+            session->buttons[BUTTON_SCAN_SW].write((value & 0x20) == 0);
+            break;
+        default:
+                throw SaneException(SANE_STATUS_UNSUPPORTED, "unknown gpo type");
+	}
+    }
+
+    // email button
+    if (dev->model->buttons & GENESYS_HAS_EMAIL_SW) {
+        switch (dev->model->gpio_id) {
+        case GpioId::MD_5345:
+            session->buttons[BUTTON_EMAIL_SW].write(value == 0x12);
+            break;
+        case GpioId::HP3670:
+        case GpioId::HP2400:
+            session->buttons[BUTTON_EMAIL_SW].write((value & 0x08) == 0);
+            break;
+        default:
+                throw SaneException(SANE_STATUS_UNSUPPORTED, "unknown gpo type");
+    }
+    }
+
+    // copy button
+    if (dev->model->buttons & GENESYS_HAS_COPY_SW) {
+        switch (dev->model->gpio_id) {
+        case GpioId::MD_5345:
+            session->buttons[BUTTON_COPY_SW].write(value == 0x11);
+            break;
+        case GpioId::HP2300:
+            session->buttons[BUTTON_COPY_SW].write(value == 0x5c);
+            break;
+        case GpioId::HP3670:
+        case GpioId::HP2400:
+            session->buttons[BUTTON_COPY_SW].write((value & 0x10) == 0);
+            break;
+        default:
+                throw SaneException(SANE_STATUS_UNSUPPORTED, "unknown gpo type");
+    }
+    }
+
+    // power button
+    if (dev->model->buttons & GENESYS_HAS_POWER_SW) {
+        switch (dev->model->gpio_id) {
+        case GpioId::MD_5345:
+            session->buttons[BUTTON_POWER_SW].write(value == 0x14);
+            break;
+        default:
+                throw SaneException(SANE_STATUS_UNSUPPORTED, "unknown gpo type");
+    }
+    }
+
+    // ocr button
+    if (dev->model->buttons & GENESYS_HAS_OCR_SW) {
+        switch (dev->model->gpio_id) {
+    case GpioId::MD_5345:
+            session->buttons[BUTTON_OCR_SW].write(value == 0x13);
+            break;
+	default:
+                throw SaneException(SANE_STATUS_UNSUPPORTED, "unknown gpo type");
+    }
+    }
+
+    // document detection
+    if (dev->model->buttons & GENESYS_HAS_PAGE_LOADED_SW) {
+        switch (dev->model->gpio_id) {
+        case GpioId::XP200:
+            session->buttons[BUTTON_PAGE_LOADED_SW].write((value & 0x04) != 0);
+            break;
+        default:
+                throw SaneException(SANE_STATUS_UNSUPPORTED, "unknown gpo type");
+    }
+    }
+
+  /* XPA detection */
+  if (dev->model->flags & GENESYS_FLAG_XPA)
+    {
+        switch (dev->model->gpio_id) {
+            case GpioId::HP3670:
+            case GpioId::HP2400:
+	  /* test if XPA is plugged-in */
+	  if ((value & 0x40) == 0)
+	    {
+	      DBG(DBG_io, "%s: enabling XPA\n", __func__);
+	      session->opt[OPT_SOURCE].cap &= ~SANE_CAP_INACTIVE;
+	    }
+	  else
+	    {
+	      DBG(DBG_io, "%s: disabling XPA\n", __func__);
+	      session->opt[OPT_SOURCE].cap |= SANE_CAP_INACTIVE;
+	    }
+      break;
+            default:
+                throw SaneException(SANE_STATUS_UNSUPPORTED, "unknown gpo type");
+    }
+    }
+}
+
+
+static void write_control(Genesys_Device* dev, const Genesys_Sensor& sensor, int resolution)
+{
+    DBG_HELPER(dbg);
+  uint8_t control[4];
+  uint32_t addr = 0xdead;
+
+  /* 2300 does not write to 'control' */
+    if (dev->model->motor_id == MotorId::HP2300) {
+        return;
+    }
+
+  /* MD6471/G2410/HP2300 and XP200 read/write data from an undocumented memory area which
+   * is after the second slope table */
+  switch (sensor.optical_res)
+    {
+    case 600:
+      addr = 0x08200;
+      break;
+    case 1200:
+      addr = 0x10200;
+      break;
+    case 2400:
+      addr = 0x1fa00;
+      break;
+    default:
+        throw SaneException("failed to compute control address");
+    }
+
+  /* XP200 sets dpi, what other scanner put is unknown yet */
+  switch (dev->model->motor_id)
+    {
+        case MotorId::XP200:
+      /* we put scan's dpi, not motor one */
+            control[0] = resolution & 0xff;
+            control[1] = (resolution >> 8) & 0xff;
+      control[2] = dev->control[4];
+      control[3] = dev->control[5];
+      break;
+        case MotorId::HP3670:
+        case MotorId::HP2400:
+        case MotorId::MD_5345:
+        default:
+      control[0] = dev->control[2];
+      control[1] = dev->control[3];
+      control[2] = dev->control[4];
+      control[3] = dev->control[5];
+      break;
+    }
+
+  DBG(DBG_info, "%s: control write=0x%02x 0x%02x 0x%02x 0x%02x\n", __func__, control[0], control[1],
+      control[2], control[3]);
+    dev->interface->write_buffer(0x3c, addr, control, 4);
+}
+
+/**
+ * search for a full width black or white strip.
+ * @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 CommandSetGl646::search_strip(Genesys_Device* dev, const Genesys_Sensor& sensor, bool forward,
+                                   bool black) const
+{
+    DBG_HELPER(dbg);
+    (void) sensor;
+
+  Genesys_Settings settings;
+  int res = get_closest_resolution(dev->model->sensor_id, 75, 1);
+  unsigned int pass, count, found, x, y;
+  char title[80];
+
+    const auto& calib_sensor = sanei_genesys_find_sensor(dev, res, 1, ScanMethod::FLATBED);
+
+  /* we set up for a lowest available resolution color grey scan, full width */
+    settings.scan_method = dev->model->default_method;
+  settings.scan_mode = ScanColorMode::GRAY;
+  settings.xres = res;
+  settings.yres = res;
+  settings.tl_x = 0;
+  settings.tl_y = 0;
+    settings.pixels = static_cast<unsigned>((dev->model->x_size * res) / MM_PER_INCH);
+    settings.pixels /= calib_sensor.get_ccd_size_divisor_for_dpi(res);
+    settings.requested_pixels = settings.pixels;
+
+  /* 15 mm at at time */
+    settings.lines = static_cast<unsigned>((15 * settings.yres) / MM_PER_INCH);
+  settings.depth = 8;
+  settings.color_filter = ColorFilter::RED;
+
+  settings.disable_interpolation = 0;
+  settings.threshold = 0;
+
+  /* signals if a strip of the given color has been found */
+  found = 0;
+
+  /* detection pass done */
+  pass = 0;
+
+  std::vector<uint8_t> data;
+
+  /* loop until strip is found or maximum pass number done */
+  while (pass < 20 && !found)
+    {
+        // scan a full width strip
+        simple_scan(dev, calib_sensor, settings, true, forward, false, data, "search_strip");
+
+        if (is_testing_mode()) {
+            return;
+        }
+
+      if (DBG_LEVEL >= DBG_data)
+	{
+            std::sprintf(title, "gl646_search_strip_%s%02d.pnm", forward ? "fwd" : "bwd", pass);
+          sanei_genesys_write_pnm_file (title, data.data(), settings.depth, 1,
+					settings.pixels, settings.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 < settings.lines && !found; y++)
+	    {
+	      count = 0;
+	      /* count of white/black pixels depending on the color searched */
+	      for (x = 0; x < settings.pixels; x++)
+		{
+		  /* when searching for black, detect white pixels */
+		  if (black && data[y * settings.pixels + x] > 90)
+		    {
+		      count++;
+		    }
+		  /* when searching for white, detect black pixels */
+		  if (!black && data[y * settings.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) / settings.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\n", __func__, settings.pixels, count);
+		}
+	    }
+	}
+      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 < settings.lines; y++)
+	    {
+	      /* count of white/black pixels depending on the color searched */
+	      for (x = 0; x < settings.pixels; x++)
+		{
+		  /* when searching for black, detect white pixels */
+		  if (black && data[y * settings.pixels + x] > 60)
+		    {
+		      count++;
+		    }
+		  /* when searching for white, detect black pixels */
+		  if (!black && data[y * settings.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) / (settings.pixels * settings.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\n", __func__, settings.pixels, count);
+	    }
+	}
+      pass++;
+    }
+  if (found)
+    {
+      DBG(DBG_info, "%s: strip found\n", __func__);
+    }
+  else
+    {
+        throw SaneException(SANE_STATUS_UNSUPPORTED, "%s strip not found", black ? "black" : "white");
+    }
+}
+
+void CommandSetGl646::wait_for_motor_stop(Genesys_Device* dev) const
+{
+    (void) dev;
+}
+
+void CommandSetGl646::send_shading_data(Genesys_Device* dev, const Genesys_Sensor& sensor,
+                                        std::uint8_t* data, int size) const
+{
+    (void) dev;
+    (void) sensor;
+    (void) data;
+    (void) size;
+    throw SaneException("not implemented");
+}
+
+ScanSession CommandSetGl646::calculate_scan_session(const Genesys_Device* dev,
+                                                    const Genesys_Sensor& sensor,
+                                                    const Genesys_Settings& settings) const
+{
+    // compute distance to move
+    float move = 0;
+    // XXX STEF XXX MD5345 -> optical_ydpi, other base_ydpi => half/full step ? */
+    if (!dev->model->is_sheetfed) {
+        move = static_cast<float>(dev->model->y_offset);
+        // add tl_y to base movement
+    }
+    move += static_cast<float>(settings.tl_y);
+
+    if (move < 0) {
+        DBG(DBG_error, "%s: overriding negative move value %f\n", __func__, move);
+        move = 0;
+    }
+
+    move = static_cast<float>((move * dev->motor.optical_ydpi) / MM_PER_INCH);
+    float start = static_cast<float>(settings.tl_x);
+    if (settings.scan_method == ScanMethod::FLATBED) {
+        start += static_cast<float>(dev->model->x_offset);
+    } else {
+        start += static_cast<float>(dev->model->x_offset_ta);
+    }
+    start = static_cast<float>((start * sensor.optical_res) / MM_PER_INCH);
+
+    ScanSession session;
+    session.params.xres = settings.xres;
+    session.params.yres = settings.yres;
+    session.params.startx = static_cast<unsigned>(start);
+    session.params.starty = static_cast<unsigned>(move);
+    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 = dev->settings.scan_method;
+    session.params.scan_mode = settings.scan_mode;
+    session.params.color_filter = settings.color_filter;
+    session.params.flags = ScanFlag::USE_XCORRECTION;
+    if (settings.scan_method == ScanMethod::TRANSPARENCY) {
+        session.params.flags |= ScanFlag::USE_XPA;
+    }
+    compute_session(dev, session, sensor);
+
+    return session;
+}
+
+void CommandSetGl646::asic_boot(Genesys_Device *dev, bool cold) const
+{
+    (void) dev;
+    (void) cold;
+    throw SaneException("not implemented");
+}
+
+std::unique_ptr<CommandSet> create_gl646_cmd_set()
+{
+    return std::unique_ptr<CommandSet>(new CommandSetGl646{});
+}
+
+} // namespace gl646
+} // namespace genesys