diff --git a/backend/genesys.cc b/backend/genesys.cc
index 8e98fb1f8..71ef6cbd4 100644
--- a/backend/genesys.cc
+++ b/backend/genesys.cc
@@ -779,7 +779,7 @@ void sanei_genesys_create_default_gamma_table(Genesys_Device* dev,
 {
     int size = 0;
     int max = 0;
-    if (dev->model->asic_type == GENESYS_GL646) {
+    if (dev->model->asic_type == AsicType::GL646) {
         if (dev->model->flags & GENESYS_FLAG_14BIT_GAMMA) {
             size = 16384;
         } else {
@@ -1644,11 +1644,11 @@ static void genesys_dark_shading_calibration(Genesys_Device* dev, const Genesys_
         return;
     }
 
-    // FIXME: the current calculation is likely incorrect on non-GENESYS_GL843 implementations,
+    // FIXME: the current calculation is likely incorrect on non-GL843 implementations,
     // but this needs checking
     if (dev->calib_total_bytes_to_read > 0) {
         size = dev->calib_total_bytes_to_read;
-    } else if (dev->model->asic_type == GENESYS_GL843) {
+    } else if (dev->model->asic_type == AsicType::GL843) {
         size = channels * 2 * pixels_per_line * dev->calib_lines;
     } else {
         size = channels * 2 * pixels_per_line * (dev->calib_lines + 1);
@@ -1828,11 +1828,11 @@ static void genesys_white_shading_calibration(Genesys_Device* dev, const Genesys
   dev->white_average_data.clear();
   dev->white_average_data.resize(channels * 2 * out_pixels_per_line);
 
-    // FIXME: the current calculation is likely incorrect on non-GENESYS_GL843 implementations,
+    // FIXME: the current calculation is likely incorrect on non-GL843 implementations,
     // but this needs checking
     if (dev->calib_total_bytes_to_read > 0) {
         size = dev->calib_total_bytes_to_read;
-    } else if (dev->model->asic_type == GENESYS_GL843) {
+    } else if (dev->model->asic_type == AsicType::GL843) {
         size = channels * 2 * pixels_per_line * dev->calib_lines;
     } else {
         size = channels * 2 * pixels_per_line * (dev->calib_lines + 1);
@@ -2873,6 +2873,7 @@ static void genesys_save_calibration(Genesys_Device* dev, const Genesys_Sensor&
   found_cache_it->white_average_data = dev->white_average_data;
 
   found_cache_it->used_setup = dev->current_setup;
+  found_cache_it->params = dev->session.params;
   found_cache_it->frontend = dev->frontend;
   found_cache_it->sensor = sensor;
 
@@ -3503,9 +3504,8 @@ static void genesys_fill_line_interp_buffer(Genesys_Device* dev, uint8_t* work_b
       while (count < size)
 	{
           /* line counter */
-          /* dev->line_interp holds the number of lines scanned for one line of data sent */
-          if(((dev->line_count/dev->current_setup.channels) % dev->line_interp)==0)
-            {
+        // dev->line_interp holds the number of lines scanned for one line of data sent
+        if (((dev->line_count / dev->session.params.channels) % dev->line_interp) == 0) {
 	      /* copy pixel when line matches */
               work_buffer_dst[count] = dev->oe_buffer.get_read_pos()[dev->cur];
               count++;
@@ -3724,11 +3724,11 @@ static void genesys_read_ordered_data(Genesys_Device* dev, SANE_Byte* destinatio
     }
 
     debug_dump(DBG_info, dev->current_setup);
+    debug_dump(DBG_info, dev->session.params);
 
   /* prepare conversion */
-  /* current settings */
-  channels = dev->current_setup.channels;
-  depth = dev->current_setup.depth;
+    channels = dev->session.params.channels;
+    depth = dev->session.params.depth;
 
   src_pixels = dev->current_setup.pixels;
 
@@ -4135,12 +4135,12 @@ static void calc_parameters(Genesys_Scanner* s)
 
   /* we need an even pixels number
    * TODO invert test logic or generalize behaviour across all ASICs */
-  if ((s->dev->model->flags & GENESYS_FLAG_SIS_SENSOR)
-      || s->dev->model->asic_type == GENESYS_GL847
-      || s->dev->model->asic_type == GENESYS_GL124
-      || s->dev->model->asic_type == GENESYS_GL845
-      || s->dev->model->asic_type == GENESYS_GL846
-      || s->dev->model->asic_type == GENESYS_GL843)
+    if ((s->dev->model->flags & GENESYS_FLAG_SIS_SENSOR) ||
+        s->dev->model->asic_type == AsicType::GL847 ||
+        s->dev->model->asic_type == AsicType::GL124 ||
+        s->dev->model->asic_type == AsicType::GL845 ||
+        s->dev->model->asic_type == AsicType::GL846 ||
+        s->dev->model->asic_type == AsicType::GL843)
     {
       if (s->dev->settings.xres <= 1200)
         s->params.pixels_per_line = (s->params.pixels_per_line/4)*4;
@@ -4150,12 +4150,10 @@ static void calc_parameters(Genesys_Scanner* s)
 
   /* corner case for true lineart for sensor with several segments
    * or when xres is doubled to match yres */
-  if (s->dev->settings.xres >= 1200
-      && (    s->dev->model->asic_type == GENESYS_GL124
-           || s->dev->model->asic_type == GENESYS_GL847
-           || s->dev->current_setup.xres < s->dev->current_setup.yres
-         )
-     )
+    if (s->dev->settings.xres >= 1200 && (
+                s->dev->model->asic_type == AsicType::GL124 ||
+                s->dev->model->asic_type == AsicType::GL847 ||
+                s->dev->current_setup.xres < s->dev->session.params.yres))
     {
       s->params.pixels_per_line = (s->params.pixels_per_line/16)*16;
     }
@@ -4232,9 +4230,9 @@ static void calc_parameters(Genesys_Scanner* s)
   /* hardware lineart works only when we don't have interleave data
    * for GL847 scanners, ie up to 600 DPI, then we have to rely on
    * dynamic_lineart */
-  if(s->dev->settings.xres > 600
-     && s->dev->model->asic_type==GENESYS_GL847
-     && s->dev->settings.scan_mode == ScanColorMode::LINEART)
+    if (s->dev->settings.xres > 600 &&
+        s->dev->model->asic_type==AsicType::GL847 &&
+        s->dev->settings.scan_mode == ScanColorMode::LINEART)
    {
       s->dev->settings.dynamic_lineart = SANE_TRUE;
    }
@@ -4296,8 +4294,7 @@ init_gamma_vector_option (Genesys_Scanner * scanner, int option)
   scanner->opt[option].cap |= SANE_CAP_INACTIVE | SANE_CAP_ADVANCED;
   scanner->opt[option].unit = SANE_UNIT_NONE;
   scanner->opt[option].constraint_type = SANE_CONSTRAINT_RANGE;
-  if (scanner->dev->model->asic_type == GENESYS_GL646)
-    {
+    if (scanner->dev->model->asic_type == AsicType::GL646) {
       if ((scanner->dev->model->flags & GENESYS_FLAG_14BIT_GAMMA) != 0)
 	{
 	  scanner->opt[option].size = 16384 * sizeof (SANE_Word);
@@ -4768,8 +4765,8 @@ static void init_options(Genesys_Scanner* s)
   s->disable_dynamic_lineart = false;
 
   /* fastmod is required for hw lineart to work */
-  if ((s->dev->model->asic_type == GENESYS_GL646)
-    &&(s->dev->model->motor_type != MOTOR_XP200))
+    if ((s->dev->model->asic_type == AsicType::GL646) &&
+        (s->dev->model->motor_type != MOTOR_XP200))
     {
       s->opt[OPT_DISABLE_DYNAMIC_LINEART].cap = SANE_CAP_INACTIVE;
     }
@@ -4796,8 +4793,7 @@ static void init_options(Genesys_Scanner* s)
   s->opt[OPT_COLOR_FILTER].type = SANE_TYPE_STRING;
   s->opt[OPT_COLOR_FILTER].constraint_type = SANE_CONSTRAINT_STRING_LIST;
   /* true gray not yet supported for GL847 and GL124 scanners */
-  if(!model->is_cis || model->asic_type==GENESYS_GL847 || model->asic_type==GENESYS_GL124)
-    {
+    if (!model->is_cis || model->asic_type==AsicType::GL847 || model->asic_type==AsicType::GL124) {
       s->opt[OPT_COLOR_FILTER].size = max_string_size (color_filter_list);
       s->opt[OPT_COLOR_FILTER].constraint.string_list = color_filter_list;
       s->color_filter = s->opt[OPT_COLOR_FILTER].constraint.string_list[1];
@@ -4810,9 +4806,8 @@ static void init_options(Genesys_Scanner* s)
       s->color_filter = s->opt[OPT_COLOR_FILTER].constraint.string_list[3];
     }
 
-  /* no support for color filter for cis+gl646 scanners */
-  if (model->asic_type == GENESYS_GL646 && model->is_cis)
-    {
+    // no support for color filter for cis+gl646 scanners
+    if (model->asic_type == AsicType::GL646 && model->is_cis) {
       DISABLE (OPT_COLOR_FILTER);
     }
 
@@ -6111,10 +6106,9 @@ set_option_value (Genesys_Scanner * s, int option, void *val,
 	  ENABLE (OPT_THRESHOLD);
 	  ENABLE (OPT_THRESHOLD_CURVE);
 	  DISABLE (OPT_BIT_DEPTH);
-          if (s->dev->model->asic_type != GENESYS_GL646 || !s->dev->model->is_cis)
-            {
-	      ENABLE (OPT_COLOR_FILTER);
-            }
+                if (s->dev->model->asic_type != AsicType::GL646 || !s->dev->model->is_cis) {
+                    ENABLE(OPT_COLOR_FILTER);
+                }
 	  ENABLE (OPT_DISABLE_DYNAMIC_LINEART);
 	}
       else
@@ -6124,10 +6118,9 @@ set_option_value (Genesys_Scanner * s, int option, void *val,
 	  DISABLE (OPT_DISABLE_DYNAMIC_LINEART);
           if (s->mode == SANE_VALUE_SCAN_MODE_GRAY)
 	    {
-              if (s->dev->model->asic_type != GENESYS_GL646 || !s->dev->model->is_cis)
-                {
-	          ENABLE (OPT_COLOR_FILTER);
-                }
+                    if (s->dev->model->asic_type != AsicType::GL646 || !s->dev->model->is_cis) {
+                        ENABLE(OPT_COLOR_FILTER);
+                    }
 	      create_bpp_list (s, s->dev->model->bpp_gray_values);
 	    }
 	  else
diff --git a/backend/genesys_calibration.h b/backend/genesys_calibration.h
index 54b4165ce..579cc4e39 100644
--- a/backend/genesys_calibration.h
+++ b/backend/genesys_calibration.h
@@ -54,6 +54,7 @@ struct Genesys_Calibration_Cache
 
     // used to check if entry is compatible
     Genesys_Current_Setup used_setup;
+    SetupParams params;
     time_t last_calibration = 0;
 
     Genesys_Frontend frontend;
@@ -68,6 +69,7 @@ struct Genesys_Calibration_Cache
     bool operator==(const Genesys_Calibration_Cache& other) const
     {
         return used_setup == other.used_setup &&
+            params == other.params &&
             last_calibration == other.last_calibration &&
             frontend == other.frontend &&
             sensor == other.sensor &&
@@ -84,6 +86,8 @@ void serialize(Stream& str, Genesys_Calibration_Cache& x)
 {
     serialize(str, x.used_setup);
     serialize_newline(str);
+    serialize(str, x.params);
+    serialize_newline(str);
     serialize(str, x.last_calibration);
     serialize_newline(str);
     serialize(str, x.frontend);
diff --git a/backend/genesys_device.h b/backend/genesys_device.h
index cedd0229a..4005b9808 100644
--- a/backend/genesys_device.h
+++ b/backend/genesys_device.h
@@ -92,8 +92,7 @@ struct Genesys_Model
     const char* model = nullptr;
     unsigned model_id = 0;
 
-    // ASIC type gl646 or gl841
-    unsigned asic_type = 0;
+    AsicType asic_type = AsicType::UNKNOWN;
 
     // possible x resolutions
     std::vector<unsigned> xdpi_values;
@@ -288,6 +287,8 @@ struct Genesys_Device
 
     // contains the real used values
     Genesys_Current_Setup current_setup;
+    // contains computed data for the current setup
+    ScanSession session;
 
     // look up table used in dynamic rasterization
     unsigned char lineart_lut[256] = {};
diff --git a/backend/genesys_devices.cc b/backend/genesys_devices.cc
index 085ddfb5f..94c423e91 100644
--- a/backend/genesys_devices.cc
+++ b/backend/genesys_devices.cc
@@ -3015,7 +3015,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "UMAX";
     model.model = "Astra 4500";
     model.model_id = MODEL_UMAX_ASTRA_4500;
-    model.asic_type = GENESYS_GL646;
+    model.asic_type = AsicType::GL646;
 
     model.xdpi_values = { 1200, 600, 300, 150, 75 };
     model.ydpi_values = { 2400, 1200, 600, 300, 150, 75 };
@@ -3067,7 +3067,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "LiDE 35/40/50";
     model.model_id = MODEL_CANON_LIDE_50;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 1200, 600, 400, 300, 240, 200, 150, 75 };
     model.ydpi_values = { 2400, 1200, 600, 400, 300, 240, 200, 150, 75 };
@@ -3126,7 +3126,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Panasonic";
     model.model = "KV-SS080";
     model.model_id = MODEL_PANASONIC_KV_SS080;
-    model.asic_type = GENESYS_GL843;
+    model.asic_type = AsicType::GL843;
 
     model.xdpi_values = { 600, /* 500, 400,*/ 300, 200, 150, 100, 75 };
     model.ydpi_values = { 1200, 600, /* 500, 400, */ 300, 200, 150, 100, 75 };
@@ -3181,7 +3181,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Hewlett Packard";
     model.model = "ScanJet 4850C";
     model.model_id = MODEL_HP_SCANJET_4850C;
-    model.asic_type = GENESYS_GL843;
+    model.asic_type = AsicType::GL843;
 
     model.xdpi_values = { 2400, 1200, 600, 400, 300, 200, 150, 100 };
     model.ydpi_values = { 2400, 1200, 600, 400, 300, 200, 150, 100 };
@@ -3237,7 +3237,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Hewlett Packard";
     model.model = "ScanJet G4010";
     model.model_id = MODEL_HP_SCANJET_G4010;
-    model.asic_type = GENESYS_GL843;
+    model.asic_type = AsicType::GL843;
 
     model.xdpi_values = { 2400, 1200, 600, 400, 300, 200, 150, 100 };
     model.ydpi_values = { 2400, 1200, 600, 400, 300, 200, 150, 100 };
@@ -3293,7 +3293,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Hewlett Packard";
     model.model = "ScanJet G4050";
     model.model_id = MODEL_HP_SCANJET_G4050;
-    model.asic_type = GENESYS_GL843;
+    model.asic_type = AsicType::GL843;
 
     model.xdpi_values = { 2400, 1200, 600, 400, 300, 200, 150, 100 };
     model.ydpi_values = { 2400, 1200, 600, 400, 300, 200, 150, 100 };
@@ -3350,7 +3350,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "Canoscan 4400f";
     model.model_id = MODEL_CANON_CANOSCAN_4400F;
-    model.asic_type = GENESYS_GL843;
+    model.asic_type = AsicType::GL843;
 
     model.xdpi_values = { 4800, 2400, 1200, 600, 400, 300, 200, 150, 100 };
     model.ydpi_values = { 4800, 2400, 1200, 600, 400, 300, 200, 150, 100 };
@@ -3409,7 +3409,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "Canoscan 8400f";
     model.model_id = MODEL_CANON_CANOSCAN_8400F;
-    model.asic_type = GENESYS_GL843;
+    model.asic_type = AsicType::GL843;
 
     model.xdpi_values = { 4800, 2400, 1200, 600, 400, 300, 200, 150, 100 };
     model.ydpi_values = { 4800, 2400, 1200, 600, 400, 300, 200, 150, 100 };
@@ -3470,7 +3470,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "Canoscan 8600f";
     model.model_id = MODEL_CANON_CANOSCAN_8600F;
-    model.asic_type = GENESYS_GL843;
+    model.asic_type = AsicType::GL843;
 
     model.xdpi_values = { 4800, 2400, 1200, 600, 400, 300 }; // TODO: resolutions for non-XPA mode
     model.ydpi_values = { 4800, 2400, 1200, 600, 400, 300 }; // TODO: resolutions for non-XPA mode
@@ -3531,7 +3531,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "LiDE 100";
     model.model_id = MODEL_CANON_LIDE_100;
-    model.asic_type = GENESYS_GL847;
+    model.asic_type = AsicType::GL847;
 
     model.xdpi_values = { 4800, 2400, 1200, 600, 300, 200, 150, 100, 75 };
     model.ydpi_values = { 4800, 2400, 1200, 600, 300, 200, 150, 100, 75 };
@@ -3591,7 +3591,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "LiDE 110";
     model.model_id = MODEL_CANON_LIDE_110;
-    model.asic_type = GENESYS_GL124;
+    model.asic_type = AsicType::GL124;
 
     model.xdpi_values = { 4800, 2400, 1200, 600, /* 400,*/ 300, 150, 100, 75 };
     model.ydpi_values = { 4800, 2400, 1200, 600, /* 400,*/ 300, 150, 100, 75 };
@@ -3649,7 +3649,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "LiDE 120";
     model.model_id = MODEL_CANON_LIDE_120;
-    model.asic_type = GENESYS_GL124;
+    model.asic_type = AsicType::GL124;
 
     model.xdpi_values = { 4800, 2400, 1200, 600, 300, 150, 100, 75 };
     model.ydpi_values = { 4800, 2400, 1200, 600, 300, 150, 100, 75 };
@@ -3706,7 +3706,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "LiDE 210";
     model.model_id = MODEL_CANON_LIDE_210;
-    model.asic_type = GENESYS_GL124;
+    model.asic_type = AsicType::GL124;
 
     model.xdpi_values = { 4800, 2400, 1200, 600, /* 400,*/ 300, 150, 100, 75 };
     model.ydpi_values = { 4800, 2400, 1200, 600, /* 400,*/ 300, 150, 100, 75 };
@@ -3766,7 +3766,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "LiDE 220";
     model.model_id = MODEL_CANON_LIDE_220;
-    model.asic_type = GENESYS_GL124; // or a compatible one
+    model.asic_type = AsicType::GL124; // or a compatible one
 
     model.xdpi_values = { 4800, 2400, 1200, 600, 300, 150, 100, 75 };
     model.ydpi_values = { 4800, 2400, 1200, 600, 300, 150, 100, 75 };
@@ -3825,7 +3825,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "5600F";
     model.model_id = MODEL_CANON_CANOSCAN_5600F;
-    model.asic_type = GENESYS_GL847;
+    model.asic_type = AsicType::GL847;
 
     model.xdpi_values = { 1200, 600, 400, 300, 200, 150, 100, 75 };
     model.ydpi_values = { 1200, 600, 400, 300, 200, 150, 100, 75 };
@@ -3885,7 +3885,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "LiDE 700F";
     model.model_id = MODEL_CANON_LIDE_700F;
-    model.asic_type = GENESYS_GL847;
+    model.asic_type = AsicType::GL847;
 
     model.xdpi_values = { 4800, 2400, 1200, 600, 300, 200, 150, 100, 75 };
     model.ydpi_values = { 4800, 2400, 1200, 600, 300, 200, 150, 100, 75 };
@@ -3944,7 +3944,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "LiDE 200";
     model.model_id = MODEL_CANON_LIDE_200;
-    model.asic_type = GENESYS_GL847;
+    model.asic_type = AsicType::GL847;
 
     model.xdpi_values = { 4800, 2400, 1200, 600, 300, 200, 150, 100, 75 };
     model.ydpi_values = { 4800, 2400, 1200, 600, 300, 200, 150, 100, 75 };
@@ -4003,7 +4003,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "LiDE 60";
     model.model_id = MODEL_CANON_LIDE_60;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 1200, 600, 300, 150, 75 };
     model.ydpi_values = { 2400, 1200, 600, 300, 150, 75 };
@@ -4062,7 +4062,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "LiDE 80";
     model.model_id = MODEL_CANON_LIDE_80;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = {      1200, 600, 400, 300, 240, 150, 100, 75 };
     model.ydpi_values = { 2400, 1200, 600, 400, 300, 240, 150, 100, 75 };
@@ -4120,7 +4120,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Hewlett Packard";
     model.model = "ScanJet 2300c";
     model.model_id = MODEL_HP_SCANJET_2300C;
-    model.asic_type = GENESYS_GL646;
+    model.asic_type = AsicType::GL646;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 75 };
@@ -4177,7 +4177,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Hewlett Packard";
     model.model = "ScanJet 2400c";
     model.model_id = MODEL_HP_SCANJET_2400C;
-    model.asic_type = GENESYS_GL646;
+    model.asic_type = AsicType::GL646;
 
     model.xdpi_values = { 1200, 600, 300, 150, 100, 50 };
     model.ydpi_values = { 1200, 600, 300, 150, 100, 50 };
@@ -4235,7 +4235,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Visioneer";
     model.model = "Strobe XP200";
     model.model_id = MODEL_VISIONEER_STROBE_XP200;
-    model.asic_type = GENESYS_GL646;
+    model.asic_type = AsicType::GL646;
 
     model.xdpi_values = { 600, 300, 200, 100, 75 };
     model.ydpi_values = { 600, 300, 200, 100, 75 };
@@ -4292,7 +4292,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Hewlett Packard";
     model.model = "ScanJet 3670c";
     model.model_id = MODEL_HP_SCANJET_3670C;
-    model.asic_type = GENESYS_GL646;
+    model.asic_type = AsicType::GL646;
 
     model.xdpi_values = { 1200, 600, 300, 150, 100, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 100, 75 };
@@ -4350,7 +4350,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Plustek";
     model.model = "OpticPro ST12";
     model.model_id = MODEL_PLUSTEK_OPTICPRO_ST12;
-    model.asic_type = GENESYS_GL646;
+    model.asic_type = AsicType::GL646;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 75 };
@@ -4401,7 +4401,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Plustek";
     model.model = "OpticPro ST24";
     model.model_id = MODEL_PLUSTEK_OPTICPRO_ST24;
-    model.asic_type = GENESYS_GL646;
+    model.asic_type = AsicType::GL646;
 
     model.xdpi_values = { 1200, 600, 300, 150, 75 };
     model.ydpi_values = { 2400, 1200, 600, 300, 150, 75 };
@@ -4457,7 +4457,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Medion";
     model.model = "MD5345/MD6228/MD6471";
     model.model_id = MODEL_MEDION_MD5345;
-    model.asic_type = GENESYS_GL646;
+    model.asic_type = AsicType::GL646;
 
     model.xdpi_values = { 1200, 600, 400, 300, 200, 150, 100, 75, 50 };
     model.ydpi_values = { 2400, 1200, 600, 400, 300, 200, 150, 100, 75, 50 };
@@ -4518,7 +4518,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Visioneer";
     model.model = "Strobe XP300";
     model.model_id = MODEL_VISIONEER_STROBE_XP300;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 600, 300, 150, 75 };
@@ -4573,7 +4573,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Syscan/Ambir";
     model.model = "DocketPORT 665";
     model.model_id = MODEL_SYSCAN_DOCKETPORT_665;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 75 };
@@ -4628,7 +4628,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Visioneer";
     model.model = "Readwarrior";
     model.model_id = MODEL_VISIONEER_ROADWARRIOR;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 75 };
@@ -4683,7 +4683,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Syscan";
     model.model = "DocketPORT 465";
     model.model_id = MODEL_SYSCAN_DOCKETPORT_465;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 75 };
@@ -4739,7 +4739,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Visioneer";
     model.model = "XP100 Revision 3";
     model.model_id = MODEL_VISIONEER_STROBE_XP100_REVISION3;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 75 };
@@ -4794,7 +4794,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Pentax";
     model.model = "DSmobile 600";
     model.model_id = MODEL_PENTAX_DSMOBILE_600;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 75 };
@@ -4851,7 +4851,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Syscan";
     model.model = "DocketPORT 467";
     model.model_id = MODEL_SYSCAN_DOCKETPORT_467;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 75 };
@@ -4905,7 +4905,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Syscan/Ambir";
     model.model = "DocketPORT 685";
     model.model_id = MODEL_SYSCAN_DOCKETPORT_685;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 600, 300, 150, 75 };
@@ -4962,7 +4962,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Syscan/Ambir";
     model.model = "DocketPORT 485";
     model.model_id = MODEL_SYSCAN_DOCKETPORT_485;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 600, 300, 150, 75 };
@@ -5018,7 +5018,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "DCT";
     model.model = "DocketPORT 487";
     model.model_id = MODEL_DCT_DOCKETPORT_487;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 600, 300, 150, 75 };
@@ -5075,7 +5075,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Visioneer";
     model.model = "OneTouch 7100";
     model.model_id = MODEL_VISIONEER_7100;
-    model.asic_type = GENESYS_GL646;
+    model.asic_type = AsicType::GL646;
 
     model.xdpi_values = { 1200, 600, 400, 300, 200, 150, 100, 75, 50 };
     model.ydpi_values = { 2400, 1200, 600, 400, 300, 200, 150, 100, 75, 50 };
@@ -5136,7 +5136,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Xerox";
     model.model = "OneTouch 2400";
     model.model_id = MODEL_XEROX_2400;
-    model.asic_type = GENESYS_GL646;
+    model.asic_type = AsicType::GL646;
 
     model.xdpi_values = { 1200, 600, 400, 300, 200, 150, 100, 75, 50 };
     model.ydpi_values = { 2400, 1200, 600, 400, 300, 200, 150, 100, 75, 50 };
@@ -5197,7 +5197,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Xerox";
     model.model = "Travelscanner 100";
     model.model_id = MODEL_XEROX_TRAVELSCANNER_100;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
 
     model.xdpi_values = { 600, 300, 150, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 75 };
@@ -5253,7 +5253,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "PLUSTEK";
     model.model = "OpticBook 3600";
     model.model_id = MODEL_PLUSTEK_OPTICPRO_3600;
-    model.asic_type = GENESYS_GL841;
+    model.asic_type = AsicType::GL841;
     model.xdpi_values = { /*1200,*/ 600, 400, 300, 200, 150, 100, 75 };
     model.ydpi_values = { /*2400,*/ 1200, 600, 400, 300, 200, 150, 100, 75 };
     model.bpp_gray_values = { 16, 8 };
@@ -5309,7 +5309,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Hewlett Packard";
     model.model = "ScanJet N6310";
     model.model_id = MODEL_HP_SCANJET_N6310;
-    model.asic_type = GENESYS_GL847;
+    model.asic_type = AsicType::GL847;
 
     model.xdpi_values = { 2400, 1200, 600, 400, 300, 200, 150, 100, 75 };
     model.ydpi_values = { 2400, 1200, 600, 400, 300, 200, 150, 100, 75 };
@@ -5370,7 +5370,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "PLUSTEK";
     model.model = "OpticBook 3800";
     model.model_id = MODEL_PLUSTEK_OPTICBOOK_3800;
-    model.asic_type = GENESYS_GL845;
+    model.asic_type = AsicType::GL845;
 
     model.xdpi_values = { 1200, 600, 300, 150, 100, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 100, 75 };
@@ -5425,7 +5425,7 @@ void genesys_init_usb_device_tables()
     model.vendor = "Canon";
     model.model = "Image Formula 101";
     model.model_id = MODEL_CANON_IMAGE_FORMULA_101;
-    model.asic_type = GENESYS_GL846;
+    model.asic_type = AsicType::GL846;
 
     model.xdpi_values = { 1200, 600, 300, 150, 100, 75 };
     model.ydpi_values = { 1200, 600, 300, 150, 100, 75 };
diff --git a/backend/genesys_enums.h b/backend/genesys_enums.h
index 37ebd2b14..e1453fa10 100644
--- a/backend/genesys_enums.h
+++ b/backend/genesys_enums.h
@@ -286,4 +286,18 @@ enum Genesys_Motor_Type
     MOTOR_CANONLIDE120
 };
 
+enum class AsicType : unsigned
+{
+    UNKNOWN = 0,
+    GL646,
+    GL841,
+    GL843,
+    GL845,
+    GL846,
+    GL847,
+    GL848,
+    GL123,
+    GL124,
+};
+
 #endif // BACKEND_GENESYS_ENUMS_H
diff --git a/backend/genesys_gl124.cc b/backend/genesys_gl124.cc
index 8cfc6593d..77c3426c8 100644
--- a/backend/genesys_gl124.cc
+++ b/backend/genesys_gl124.cc
@@ -1247,8 +1247,6 @@ static void gl124_init_scan_regs(Genesys_Device* dev, const Genesys_Sensor& sens
     oflags |= OPTICAL_FLAG_DISABLE_GAMMA;
   if (params.flags & SCAN_FLAG_DISABLE_LAMP)
     oflags |= OPTICAL_FLAG_DISABLE_LAMP;
-  if (params.flags & SCAN_FLAG_CALIBRATION)
-    oflags |= OPTICAL_FLAG_DISABLE_DOUBLE;
 
   if (dev->model->is_cis && dev->settings.true_gray)
     {
@@ -1316,15 +1314,12 @@ static void gl124_init_scan_regs(Genesys_Device* dev, const Genesys_Sensor& sens
   dev->read_active = SANE_TRUE;
 
 
-  dev->current_setup.params = params;
+    dev->session.params = params;
   dev->current_setup.pixels = (used_pixels * used_res) / optical_res;
   DBG(DBG_info, "%s: current_setup.pixels=%d\n", __func__, dev->current_setup.pixels);
   dev->current_setup.lines = lincnt;
-  dev->current_setup.depth = params.depth;
-  dev->current_setup.channels = params.channels;
   dev->current_setup.exposure_time = exposure_time;
   dev->current_setup.xres = used_res;
-  dev->current_setup.yres = params.yres;
   dev->current_setup.ccd_size_divisor = ccd_size_divisor;
   dev->current_setup.stagger = stagger;
   dev->current_setup.max_shift = max_shift + stagger;
@@ -1438,15 +1433,12 @@ gl124_calculate_current_setup (Genesys_Device * dev, const Genesys_Sensor& senso
   /* lincnt */
   lincnt = params.lines + max_shift + stagger;
 
-  dev->current_setup.params = params;
+    dev->session.params = params;
   dev->current_setup.pixels = (used_pixels * used_res) / optical_res;
   DBG (DBG_info, "%s: current_setup.pixels=%d\n", __func__, dev->current_setup.pixels);
   dev->current_setup.lines = lincnt;
-  dev->current_setup.depth = params.depth;
-  dev->current_setup.channels = params.channels;
   dev->current_setup.exposure_time = exposure_time;
   dev->current_setup.xres = used_res;
-  dev->current_setup.yres = params.yres;
   dev->current_setup.ccd_size_divisor = ccd_size_divisor;
   dev->current_setup.stagger = stagger;
   dev->current_setup.max_shift = max_shift + stagger;
@@ -2182,7 +2174,7 @@ static void gl124_send_shading_data(Genesys_Device* dev, const Genesys_Sensor& s
     {
       dev->binary=fopen("binary.pnm","wb");
         lines = dev->reg.get24(REG_LINCNT);
-      channels=dev->current_setup.channels;
+        channels = dev->session.params.channels;
       if(dev->binary!=NULL)
         {
           fprintf(dev->binary,"P5\n%d %d\n%d\n",(endpixel-strpixel)/factor*channels*dev->segnb,lines/channels,255);
diff --git a/backend/genesys_gl646.cc b/backend/genesys_gl646.cc
index 0107410fd..f6cc0bef8 100644
--- a/backend/genesys_gl646.cc
+++ b/backend/genesys_gl646.cc
@@ -943,15 +943,12 @@ static void gl646_setup_registers(Genesys_Device* dev,
   DBG(DBG_info, "%s: physical bytes to read = %lu\n", __func__, (u_long) dev->read_bytes_left);
   dev->read_active = SANE_TRUE;
 
-  dev->current_setup.params = params;
+    dev->session.params = params;
   dev->current_setup.pixels =
     ((endx - startx) * sensor_mst->xdpi) / sensor.optical_res;
   dev->current_setup.lines = linecnt;
-  dev->current_setup.depth = params.depth;
-  dev->current_setup.channels = params.channels;
   dev->current_setup.exposure_time = sensor_mst->exposure;
   dev->current_setup.xres = sensor_mst->xdpi;
-  dev->current_setup.yres = motor->ydpi;
   dev->current_setup.ccd_size_divisor = ccd_size_divisor;
   dev->current_setup.stagger = stagger;
   dev->current_setup.max_shift = max_shift + stagger;
@@ -1734,17 +1731,13 @@ static void gl646_detect_document_end(Genesys_Device* dev)
         sanei_genesys_read_valid_words(dev, &bytes_left);
 
       /* we add the number of lines needed to read the last part of the document in */
-      lines =
-	(SANE_UNFIX (dev->model->y_offset) * dev->current_setup.yres) /
-	MM_PER_INCH;
+        lines = (SANE_UNFIX(dev->model->y_offset) * dev->session.params.yres) / MM_PER_INCH;
       DBG(DBG_io, "%s: adding %d line to flush\n", __func__, lines);
       bytes_left += lines * dev->wpl;
-      if (dev->current_setup.depth > 8)
-	{
+        if (dev->session.params.depth > 8) {
 	  bytes_left = 2 * bytes_left;
 	}
-      if (dev->current_setup.channels > 1)
-	{
+        if (dev->session.params.channels > 1) {
 	  bytes_left = 3 * bytes_left;
 	}
       if (bytes_left < dev->read_bytes_left)
@@ -2256,7 +2249,7 @@ static void gl646_init_regs_for_shading(Genesys_Device* dev, const Genesys_Senso
 
   /* used when sending shading calibration data */
   dev->calib_pixels = settings.pixels;
-  dev->calib_channels = dev->current_setup.channels;
+    dev->calib_channels = dev->session.params.channels;
   if (dev->model->is_cis == SANE_FALSE)
     {
       dev->calib_channels = 3;
@@ -3857,36 +3850,31 @@ gl646_is_compatible_calibration (Genesys_Device * dev, const Genesys_Sensor& sen
    */
   if (dev->settings.scan_mode == ScanColorMode::COLOR_SINGLE_PASS)
     {
-      dev->current_setup.channels = 3;
-    }
-  else
-    {
-      dev->current_setup.channels = 1;
+        dev->session.params.channels = 3;
+    } else {
+        dev->session.params.channels = 1;
     }
   dev->current_setup.xres = dev->settings.xres;
 
-  DBG(DBG_io, "%s: requested=(%d,%f), tested=(%d,%f)\n", __func__, dev->current_setup.channels,
-      dev->current_setup.xres, cache->used_setup.channels, cache->used_setup.xres);
+    DBG(DBG_io, "%s: requested=(%d,%f), tested=(%d,%f)\n", __func__,
+        dev->session.params.channels, dev->current_setup.xres,
+        cache->params.channels, cache->used_setup.xres);
 
   /* a calibration cache is compatible if color mode and x dpi match the user
    * requested scan. In the case of CIS scanners, dpi isn't a criteria */
   if (dev->model->is_cis == SANE_FALSE)
     {
-      compatible =
-	((dev->current_setup.channels == cache->used_setup.channels)
-	 && (((int) dev->current_setup.xres) ==
-	     ((int) cache->used_setup.xres)));
+        compatible = (dev->session.params.channels == cache->params.channels) &&
+                      (((int) dev->current_setup.xres) == ((int) cache->used_setup.xres));
+    } else {
+        compatible = dev->session.params.channels == cache->params.channels;
     }
-  else
-    {
-      compatible =
-	(dev->current_setup.channels == cache->used_setup.channels);
-    }
-  if (dev->current_setup.params.scan_method != cache->used_setup.params.scan_method)
+
+  if (dev->session.params.scan_method != cache->params.scan_method)
     {
       DBG(DBG_io, "%s: current method=%d, used=%d\n", __func__,
-          static_cast<unsigned>(dev->current_setup.params.scan_method),
-          static_cast<unsigned>(cache->used_setup.params.scan_method));
+          static_cast<unsigned>(dev->session.params.scan_method),
+          static_cast<unsigned>(cache->params.scan_method));
       compatible = 0;
     }
   if (!compatible)
diff --git a/backend/genesys_gl646.h b/backend/genesys_gl646.h
index cabf7002b..1525757b9 100644
--- a/backend/genesys_gl646.h
+++ b/backend/genesys_gl646.h
@@ -269,7 +269,10 @@ typedef struct
   unsigned channels;
 
   /* settings */
-  SANE_Int ydpi;		/* real motor dpi, may be different from the resolution */
+
+    // real motor dpi, may be different from the resolution. For the currently known motors it's the
+    // same
+    SANE_Int ydpi;
   SANE_Int steptype;		/* 0=full, 1=half, 2=quarter */
   SANE_Bool fastmod;		/* fast scanning 0/1 */
   SANE_Bool fastfed;		/* fast fed slope tables */
diff --git a/backend/genesys_gl841.cc b/backend/genesys_gl841.cc
index 4afc13a33..b60c5280d 100644
--- a/backend/genesys_gl841.cc
+++ b/backend/genesys_gl841.cc
@@ -2038,14 +2038,11 @@ dummy \ scanned lines
   DBG(DBG_info, "%s: physical bytes to read = %lu\n", __func__, (u_long) dev->read_bytes_left);
   dev->read_active = SANE_TRUE;
 
-  dev->current_setup.params = params;
+    dev->session.params = params;
   dev->current_setup.pixels = (used_pixels * used_res)/optical_res;
   dev->current_setup.lines = lincnt;
-  dev->current_setup.depth = params.depth;
-  dev->current_setup.channels =  params.channels;
   dev->current_setup.exposure_time = exposure_time;
   dev->current_setup.xres = used_res;
-  dev->current_setup.yres = params.yres;
     dev->current_setup.ccd_size_divisor = ccd_size_divisor;
   dev->current_setup.stagger = stagger;
   dev->current_setup.max_shift = max_shift + stagger;
@@ -2251,14 +2248,11 @@ dummy \ scanned lines
 
     lincnt = params.lines + max_shift + stagger;
 
-  dev->current_setup.params = params;
+    dev->session.params = params;
   dev->current_setup.pixels = (used_pixels * used_res)/optical_res;
   dev->current_setup.lines = lincnt;
-  dev->current_setup.depth = params.depth;
-  dev->current_setup.channels = params.channels;
   dev->current_setup.exposure_time = exposure_time;
   dev->current_setup.xres = used_res;
-  dev->current_setup.yres = params.yres;
     dev->current_setup.ccd_size_divisor = ccd_size_divisor;
   dev->current_setup.stagger = stagger;
   dev->current_setup.max_shift = max_shift + stagger;
@@ -4580,7 +4574,7 @@ static void gl841_send_shading_data(Genesys_Device* dev, const Genesys_Sensor& s
     {
       dev->binary=fopen("binary.pnm","wb");
         lines = dev->reg.get24(REG_LINCNT);
-      channels=dev->current_setup.channels;
+        channels = dev->session.params.channels;
       if(dev->binary!=NULL)
         {
           fprintf(dev->binary,"P5\n%d %d\n%d\n",(endpixel-strpixel)/factor*channels,lines/channels,255);
diff --git a/backend/genesys_gl843.cc b/backend/genesys_gl843.cc
index 53084b446..0edab7310 100644
--- a/backend/genesys_gl843.cc
+++ b/backend/genesys_gl843.cc
@@ -1243,53 +1243,6 @@ static void gl843_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
   r->value = sensor.dummy_pixel;
 }
 
-struct ScanSession {
-    SetupParams params;
-
-    // whether the session setup has been computed via gl843_compute_session()
-    bool computed = false;
-
-    // whether CCD operates as half-resolution or full resolution at a specific resolution
-    unsigned ccd_size_divisor = 1;
-
-    // the optical resolution of the scanner.
-    unsigned optical_resolution = 0;
-
-    // the number of pixels at the optical resolution.
-    unsigned optical_pixels = 0;
-
-    // the number of bytes in the output of a single line directly from scanner
-    unsigned optical_line_bytes = 0;
-
-    // the resolution of the output data.
-    unsigned output_resolution = 0;
-
-    // the number of pixels in output data
-    unsigned output_pixels = 0;
-
-    // the number of bytes in the output of a single line
-    unsigned output_line_bytes = 0;
-
-    // the number of lines in the output of the scanner. This must be larger than the user
-    // requested number due to line staggering and color channel shifting.
-    unsigned output_line_count = 0;
-
-    // the number of staggered lines (i.e. lines that overlap during scanning due to line being
-    // thinner than the CCD element)
-    unsigned num_staggered_lines = 0;
-
-    // the number of lines that color channels shift due to different physical positions of
-    // different color channels
-    unsigned max_color_shift_lines = 0;
-
-    void assert_computed() const
-    {
-        if (!computed) {
-            throw std::runtime_error("ScanSession is not computed");
-        }
-    }
-};
-
 static unsigned align_int_up(unsigned num, unsigned alignment)
 {
     unsigned mask = alignment - 1;
@@ -1307,16 +1260,12 @@ static void gl843_compute_session(Genesys_Device* dev, ScanSession& s,
 
     s.optical_resolution = sensor.optical_res / s.ccd_size_divisor;
 
-    if (s.params.flags & SCAN_FLAG_USE_OPTICAL_RES) {
+    // resolution is choosen from a fixed list and can be used directly
+    // unless we have ydpi higher than sensor's maximum one
+    if (s.params.xres > s.optical_resolution)
         s.output_resolution = s.optical_resolution;
-    } else {
-        // resolution is choosen from a fixed list and can be used directly
-        // unless we have ydpi higher than sensor's maximum one
-        if (s.params.xres > s.optical_resolution)
-            s.output_resolution = s.optical_resolution;
-        else
-            s.output_resolution = s.params.xres;
-    }
+    else
+        s.output_resolution = s.params.xres;
 
     // compute rounded up number of optical pixels
     s.optical_pixels = (s.params.pixels * s.optical_resolution) / s.params.xres;
@@ -1382,8 +1331,6 @@ static void gl843_init_scan_regs(Genesys_Device* dev, const Genesys_Sensor& sens
     oflags |= OPTICAL_FLAG_DISABLE_GAMMA;
   if (session.params.flags & SCAN_FLAG_DISABLE_LAMP)
     oflags |= OPTICAL_FLAG_DISABLE_LAMP;
-  if (session.params.flags & SCAN_FLAG_CALIBRATION)
-    oflags |= OPTICAL_FLAG_DISABLE_DOUBLE;
   if (session.num_staggered_lines)
     oflags |= OPTICAL_FLAG_STAGGER;
   if (session.params.flags & SCAN_FLAG_USE_XPA)
@@ -1502,15 +1449,12 @@ static void gl843_init_scan_regs(Genesys_Device* dev, const Genesys_Sensor& sens
   DBG(DBG_info, "%s: physical bytes to read = %lu\n", __func__, (u_long) dev->read_bytes_left);
   dev->read_active = SANE_TRUE;
 
-  dev->current_setup.params = session.params;
+    dev->session = session;
   dev->current_setup.pixels = session.output_pixels;
   DBG(DBG_info, "%s: current_setup.pixels=%d\n", __func__, dev->current_setup.pixels);
   dev->current_setup.lines = session.output_line_count;
-  dev->current_setup.depth = session.params.depth;
-  dev->current_setup.channels = session.params.channels;
   dev->current_setup.exposure_time = exposure;
   dev->current_setup.xres = session.output_resolution;
-  dev->current_setup.yres = session.params.yres;
   dev->current_setup.ccd_size_divisor = session.ccd_size_divisor;
   dev->current_setup.stagger = session.num_staggered_lines;
   dev->current_setup.max_shift = session.max_color_shift_lines + session.num_staggered_lines;
@@ -1649,15 +1593,12 @@ gl843_calculate_current_setup(Genesys_Device * dev, const Genesys_Sensor& sensor
   /* lincnt */
   lincnt = params.lines + max_shift + stagger;
 
-  dev->current_setup.params = params;
+    dev->session.params = params;
   dev->current_setup.pixels = (used_pixels * used_res) / optical_res;
   DBG(DBG_info, "%s: current_setup.pixels=%d\n", __func__, dev->current_setup.pixels);
   dev->current_setup.lines = lincnt;
-  dev->current_setup.depth = params.depth;
-  dev->current_setup.channels = params.channels;
   dev->current_setup.exposure_time = exposure;
   dev->current_setup.xres = used_res;
-  dev->current_setup.yres = params.yres;
   dev->current_setup.ccd_size_divisor = ccd_size_divisor;
   dev->current_setup.stagger = stagger;
   dev->current_setup.max_shift = max_shift + stagger;
@@ -1793,7 +1734,7 @@ static void gl843_detect_document_end(Genesys_Device* dev)
     DBG_HELPER(dbg);
   SANE_Bool paper_loaded;
   unsigned int scancnt = 0;
-  int flines, channels, depth, bytes_remain, sublines,
+  int flines, bytes_remain, sublines,
     bytes_to_flush, lines, sub_bytes, tmp, read_bytes_left;
 
     gl843_get_paper_sensor(dev, &paper_loaded);
@@ -1804,8 +1745,8 @@ static void gl843_detect_document_end(Genesys_Device* dev)
       DBG(DBG_info, "%s: no more document\n", __func__);
       dev->document = SANE_FALSE;
 
-      channels = dev->current_setup.channels;
-      depth = dev->current_setup.depth;
+        unsigned channels = dev->session.params.channels;
+        unsigned depth = dev->session.params.depth;
       read_bytes_left = (int) dev->read_bytes_left;
       DBG(DBG_io, "%s: read_bytes_left=%d\n", __func__, read_bytes_left);
 
@@ -1828,12 +1769,11 @@ static void gl843_detect_document_end(Genesys_Device* dev)
 
 	  DBG(DBG_io, "%s: %d scanned but not read lines\n", __func__, flines);
 
-      /* adjust number of bytes to read
-       * we need to read the final bytes which are word per line * number of last lines
-       * to have doc leaving feeder */
-      lines =
-	(SANE_UNFIX (dev->model->post_scan) * dev->current_setup.yres) /
-	MM_PER_INCH + flines;
+        // Adjust number of bytes to read. We need to read the final bytes which are word per
+        // line times number of last lines to have doc leaving feeder
+        lines = (SANE_UNFIX(dev->model->post_scan) * dev->session.params.yres) / MM_PER_INCH +
+            flines;
+
       DBG(DBG_io, "%s: adding %d line to flush\n", __func__, lines);
 
       /* number of bytes to read from scanner to get document out of it after
diff --git a/backend/genesys_gl843.h b/backend/genesys_gl843.h
index 1f936a20b..8306fc1ae 100644
--- a/backend/genesys_gl843.h
+++ b/backend/genesys_gl843.h
@@ -378,7 +378,6 @@
 #define SCAN_FLAG_DISABLE_GAMMA            0x004
 #define SCAN_FLAG_DISABLE_BUFFER_FULL_MOVE 0x008
 #define SCAN_FLAG_IGNORE_LINE_DISTANCE     0x010
-#define SCAN_FLAG_USE_OPTICAL_RES          0x020
 #define SCAN_FLAG_DISABLE_LAMP             0x040
 #define SCAN_FLAG_DYNAMIC_LINEART          0x080
 
diff --git a/backend/genesys_gl846.cc b/backend/genesys_gl846.cc
index c9701d02b..1ab6f5c43 100644
--- a/backend/genesys_gl846.cc
+++ b/backend/genesys_gl846.cc
@@ -218,8 +218,6 @@ static void gl846_setup_sensor(Genesys_Device * dev, const Genesys_Sensor& senso
   int dpihw;
   uint16_t exp;
 
-    dpihw = sensor.get_register_hwdpi(dpi);
-
     for (uint16_t addr = 0x16; addr < 0x1e; addr++) {
         regs->set8(addr, sensor.custom_regs.get_value(addr));
     }
@@ -1170,14 +1168,11 @@ static void gl846_init_scan_regs(Genesys_Device* dev, const Genesys_Sensor& sens
   DBG(DBG_info, "%s: physical bytes to read = %lu\n", __func__, (u_long) dev->read_bytes_left);
   dev->read_active = SANE_TRUE;
 
-  dev->current_setup.params = params;
+    dev->session.params = params;
   dev->current_setup.pixels = (used_pixels * used_res) / optical_res;
   dev->current_setup.lines = lincnt;
-  dev->current_setup.depth = params.depth;
-  dev->current_setup.channels = params.channels;
   dev->current_setup.exposure_time = exposure_time;
   dev->current_setup.xres = used_res;
-  dev->current_setup.yres = params.yres;
   dev->current_setup.ccd_size_divisor = ccd_size_divisor;
   dev->current_setup.stagger = stagger;
   dev->current_setup.max_shift = max_shift + stagger;
@@ -1309,14 +1304,11 @@ gl846_calculate_current_setup(Genesys_Device * dev, const Genesys_Sensor& sensor
   /* lincnt */
   lincnt = params.lines + max_shift + stagger;
 
-  dev->current_setup.params = params;
+    dev->session.params = params;
   dev->current_setup.pixels = (used_pixels * used_res) / optical_res;
   dev->current_setup.lines = lincnt;
-  dev->current_setup.depth = params.depth;
-  dev->current_setup.channels = params.channels;
   dev->current_setup.exposure_time = exposure_time;
   dev->current_setup.xres = used_res;
-  dev->current_setup.yres = params.yres;
     dev->current_setup.ccd_size_divisor = ccd_size_divisor;
   dev->current_setup.stagger = stagger;
   dev->current_setup.max_shift = max_shift + stagger;
@@ -1916,7 +1908,7 @@ static void gl846_send_shading_data(Genesys_Device* dev, const Genesys_Sensor& s
     DBG_HELPER_ARGS(dbg, "writing %d bytes of shading data", size);
   uint32_t addr, length, i, x, factor, pixels;
   uint32_t dpiset, dpihw, strpixel, endpixel;
-  uint32_t lines, channels;
+  uint32_t lines;
   uint8_t val,*ptr,*src;
 
   /* shading data is plit in 3 (up to 5 with IR) areas
@@ -1941,7 +1933,7 @@ static void gl846_send_shading_data(Genesys_Device* dev, const Genesys_Sensor& s
     {
       dev->binary=fopen("binary.pnm","wb");
         lines = dev->reg.get24(REG_LINCNT);
-      channels=dev->current_setup.channels;
+        unsigned channels = dev->session.params.channels;
       if(dev->binary!=NULL)
         {
           fprintf(dev->binary,"P5\n%d %d\n%d\n",(endpixel-strpixel)/factor*channels,lines/channels,255);
diff --git a/backend/genesys_gl847.cc b/backend/genesys_gl847.cc
index af15ac0bd..3cb351bac 100644
--- a/backend/genesys_gl847.cc
+++ b/backend/genesys_gl847.cc
@@ -1185,14 +1185,11 @@ static void gl847_init_scan_regs(Genesys_Device* dev, const Genesys_Sensor& sens
   DBG(DBG_info, "%s: physical bytes to read = %lu\n", __func__, (u_long) dev->read_bytes_left);
   dev->read_active = SANE_TRUE;
 
-  dev->current_setup.params = params;
+    dev->session.params = params;
   dev->current_setup.pixels = (used_pixels * used_res) / optical_res;
   dev->current_setup.lines = lincnt;
-  dev->current_setup.depth = params.depth;
-  dev->current_setup.channels = params.channels;
   dev->current_setup.exposure_time = exposure_time;
   dev->current_setup.xres = used_res;
-  dev->current_setup.yres = params.yres;
   dev->current_setup.ccd_size_divisor = ccd_size_divisor;
   dev->current_setup.stagger = stagger;
   dev->current_setup.max_shift = max_shift + stagger;
@@ -1325,14 +1322,11 @@ gl847_calculate_current_setup(Genesys_Device * dev, const Genesys_Sensor& sensor
   /* lincnt */
   lincnt = params.lines + max_shift + stagger;
 
-  dev->current_setup.params = params;
+    dev->session.params = params;
   dev->current_setup.pixels = (used_pixels * used_res) / optical_res;
   dev->current_setup.lines = lincnt;
-  dev->current_setup.depth = params.depth;
-  dev->current_setup.channels = params.channels;
   dev->current_setup.exposure_time = exposure_time;
   dev->current_setup.xres = used_res;
-  dev->current_setup.yres = params.yres;
   dev->current_setup.ccd_size_divisor = ccd_size_divisor;
   dev->current_setup.stagger = stagger;
   dev->current_setup.max_shift = max_shift + stagger;
@@ -1969,7 +1963,7 @@ static void gl847_send_shading_data(Genesys_Device* dev, const Genesys_Sensor& s
     DBG_HELPER_ARGS(dbg, "writing %d bytes of shading data", size);
   uint32_t addr, length, i, x, factor, pixels;
   uint32_t dpiset, dpihw, strpixel, endpixel;
-  uint32_t lines, channels;
+    uint32_t lines;
   uint8_t val,*ptr,*src;
 
   /* shading data is plit in 3 (up to 5 with IR) areas
@@ -1994,7 +1988,7 @@ static void gl847_send_shading_data(Genesys_Device* dev, const Genesys_Sensor& s
     {
       dev->binary=fopen("binary.pnm","wb");
         lines = dev->reg.get24(REG_LINCNT);
-      channels=dev->current_setup.channels;
+        unsigned channels = dev->session.params.channels;
       if(dev->binary!=NULL)
         {
           fprintf(dev->binary,"P5\n%d %d\n%d\n",(endpixel-strpixel)/factor*channels,lines/channels,255);
diff --git a/backend/genesys_low.cc b/backend/genesys_low.cc
index bf7f1f0ee..81e3939e3 100644
--- a/backend/genesys_low.cc
+++ b/backend/genesys_low.cc
@@ -68,13 +68,13 @@ void sanei_genesys_init_cmd_set(Genesys_Device* dev)
   DBG_INIT ();
     DBG_HELPER(dbg);
     switch (dev->model->asic_type) {
-        case GENESYS_GL646: dev->cmd_set = &gl646_cmd_set; break;
-        case GENESYS_GL841: dev->cmd_set = &gl841_cmd_set; break;
-        case GENESYS_GL843: dev->cmd_set = &gl843_cmd_set; break;
-        case GENESYS_GL845: // since only a few reg bits differs we handle both together
-        case GENESYS_GL846: dev->cmd_set = &gl846_cmd_set; break;
-        case GENESYS_GL847: dev->cmd_set = &gl847_cmd_set; break;
-        case GENESYS_GL124: dev->cmd_set = &gl124_cmd_set; break;
+        case AsicType::GL646: dev->cmd_set = &gl646_cmd_set; break;
+        case AsicType::GL841: dev->cmd_set = &gl841_cmd_set; break;
+        case AsicType::GL843: dev->cmd_set = &gl843_cmd_set; break;
+        case AsicType::GL845: // since only a few reg bits differs we handle both together
+        case AsicType::GL846: dev->cmd_set = &gl846_cmd_set; break;
+        case AsicType::GL847: dev->cmd_set = &gl847_cmd_set; break;
+        case AsicType::GL124: dev->cmd_set = &gl124_cmd_set; break;
         default: throw SaneException(SANE_STATUS_INVAL, "unknown ASIC type");
     }
 }
@@ -170,9 +170,10 @@ extern unsigned sanei_genesys_get_bulk_max_size(Genesys_Device * dev)
         b_size is the size of the ring buffer. By default it's 300*1024, so the
         packet is limited 61440 without any visibility to acquiring software.
     */
-    if (dev->model->asic_type == GENESYS_GL124 ||
-        dev->model->asic_type == GENESYS_GL846 ||
-        dev->model->asic_type == GENESYS_GL847) {
+    if (dev->model->asic_type == AsicType::GL124 ||
+        dev->model->asic_type == AsicType::GL846 ||
+        dev->model->asic_type == AsicType::GL847)
+    {
         return 0xeff0;
     }
     return 0xf000;
@@ -183,17 +184,17 @@ void sanei_genesys_bulk_read_data_send_header(Genesys_Device* dev, size_t len)
     DBG_HELPER(dbg);
 
     uint8_t outdata[8];
-    if (dev->model->asic_type == GENESYS_GL124 ||
-        dev->model->asic_type == GENESYS_GL846 ||
-        dev->model->asic_type == GENESYS_GL847)
+    if (dev->model->asic_type == AsicType::GL124 ||
+        dev->model->asic_type == AsicType::GL846 ||
+        dev->model->asic_type == AsicType::GL847)
     {
         // hard coded 0x10000000 address
         outdata[0] = 0;
         outdata[1] = 0;
         outdata[2] = 0;
         outdata[3] = 0x10;
-    } else if (dev->model->asic_type == GENESYS_GL841 ||
-               dev->model->asic_type == GENESYS_GL843) {
+    } else if (dev->model->asic_type == AsicType::GL841 ||
+               dev->model->asic_type == AsicType::GL843) {
         outdata[0] = BULK_IN;
         outdata[1] = BULK_RAM;
         outdata[2] = 0x82; //
@@ -226,9 +227,9 @@ void sanei_genesys_bulk_read_data(Genesys_Device * dev, uint8_t addr, uint8_t* d
 
     unsigned is_addr_used = 1;
     unsigned has_header_before_each_chunk = 0;
-    if (dev->model->asic_type == GENESYS_GL124 ||
-        dev->model->asic_type == GENESYS_GL846 ||
-        dev->model->asic_type == GENESYS_GL847)
+    if (dev->model->asic_type == AsicType::GL124 ||
+        dev->model->asic_type == AsicType::GL846 ||
+        dev->model->asic_type == AsicType::GL847)
     {
         is_addr_used = 0;
         has_header_before_each_chunk = 1;
@@ -304,7 +305,7 @@ void sanei_genesys_bulk_write_data(Genesys_Device* dev, uint8_t addr, uint8_t* d
         else
             size = len;
 
-        if (dev->model->asic_type == GENESYS_GL841) {
+        if (dev->model->asic_type == AsicType::GL841) {
             outdata[0] = BULK_OUT;
             outdata[1] = BULK_RAM;
             // both 0x82 and 0x00 works on GL841.
@@ -417,11 +418,11 @@ void sanei_genesys_write_register(Genesys_Device* dev, uint16_t reg, uint8_t val
         return;
     }
 
-  /* route to gl847 function if needed */
-  if(dev->model->asic_type==GENESYS_GL847
-  || dev->model->asic_type==GENESYS_GL845
-  || dev->model->asic_type==GENESYS_GL846
-  || dev->model->asic_type==GENESYS_GL124)
+    // route to gl847 function if needed
+    if (dev->model->asic_type == AsicType::GL847 ||
+        dev->model->asic_type == AsicType::GL845 ||
+        dev->model->asic_type == AsicType::GL846 ||
+        dev->model->asic_type == AsicType::GL124)
     {
         sanei_genesys_write_gl847_register(dev, reg, val);
         return;
@@ -489,10 +490,10 @@ void sanei_genesys_read_register(Genesys_Device* dev, uint16_t reg, uint8_t* val
     }
 
     // route to gl847 function if needed
-    if (dev->model->asic_type==GENESYS_GL847
-        || dev->model->asic_type==GENESYS_GL845
-        || dev->model->asic_type==GENESYS_GL846
-        || dev->model->asic_type==GENESYS_GL124)
+    if (dev->model->asic_type == AsicType::GL847 ||
+        dev->model->asic_type == AsicType::GL845 ||
+        dev->model->asic_type == AsicType::GL846 ||
+        dev->model->asic_type == AsicType::GL124)
     {
         sanei_genesys_read_gl847_register(dev, reg, val);
         return;
@@ -517,10 +518,10 @@ void sanei_genesys_set_buffer_address(Genesys_Device* dev, uint32_t addr)
 {
     DBG_HELPER(dbg);
 
-  if(dev->model->asic_type==GENESYS_GL847
-  || dev->model->asic_type==GENESYS_GL845
-  || dev->model->asic_type==GENESYS_GL846
-  || dev->model->asic_type==GENESYS_GL124)
+    if (dev->model->asic_type==AsicType::GL847 ||
+        dev->model->asic_type==AsicType::GL845 ||
+        dev->model->asic_type==AsicType::GL846 ||
+        dev->model->asic_type==AsicType::GL124)
     {
       DBG(DBG_warn, "%s: shouldn't be used for GL846+ ASICs\n", __func__);
       return;
@@ -573,7 +574,7 @@ void sanei_genesys_fe_write_data(Genesys_Device* dev, uint8_t addr, uint16_t dat
   Genesys_Register_Set reg(Genesys_Register_Set::SEQUENTIAL);
 
     reg.init_reg(0x51, addr);
-    if (dev->model->asic_type == GENESYS_GL124) {
+    if (dev->model->asic_type == AsicType::GL124) {
         reg.init_reg(0x5d, (data / 256) & 0xff);
         reg.init_reg(0x5e, data & 0xff);
     } else {
@@ -593,7 +594,7 @@ void sanei_genesys_fe_write_data(Genesys_Device* dev, uint8_t addr, uint16_t dat
 void sanei_genesys_get_status(Genesys_Device* dev, uint8_t* status)
 {
     DBG_HELPER(dbg);
-    if (dev->model->asic_type == GENESYS_GL124) {
+    if (dev->model->asic_type == AsicType::GL124) {
         sanei_genesys_read_hregister(dev, 0x101, status);
         return;
     }
@@ -653,22 +654,22 @@ void sanei_genesys_read_valid_words(Genesys_Device* dev, unsigned int* words)
 
   switch (dev->model->asic_type)
     {
-    case GENESYS_GL124:
+    case AsicType::GL124:
             *words = dev->read_register(0x102) & 0x03;
             *words = *words * 256 + dev->read_register(0x103);
             *words = *words * 256 + dev->read_register(0x104);
             *words = *words * 256 + dev->read_register(0x105);
             break;
 
-    case GENESYS_GL845:
-    case GENESYS_GL846:
+    case AsicType::GL845:
+    case AsicType::GL846:
             *words = dev->read_register(0x42) & 0x02;
             *words = *words * 256 + dev->read_register(0x43);
             *words = *words * 256 + dev->read_register(0x44);
             *words = *words * 256 + dev->read_register(0x45);
             break;
 
-    case GENESYS_GL847:
+    case AsicType::GL847:
             *words = dev->read_register(0x42) & 0x03;
             *words = *words * 256 + dev->read_register(0x43);
             *words = *words * 256 + dev->read_register(0x44);
@@ -678,7 +679,7 @@ void sanei_genesys_read_valid_words(Genesys_Device* dev, unsigned int* words)
     default:
             *words = dev->read_register(0x44);
             *words += dev->read_register(0x43) * 256;
-            if (dev->model->asic_type == GENESYS_GL646) {
+            if (dev->model->asic_type == AsicType::GL646) {
                 *words += ((dev->read_register(0x42) & 0x03) * 256 * 256);
             } else {
                 *words += ((dev->read_register(0x42) & 0x0f) * 256 * 256);
@@ -695,8 +696,7 @@ void sanei_genesys_read_scancnt(Genesys_Device* dev, unsigned int* words)
 {
     DBG_HELPER(dbg);
 
-  if (dev->model->asic_type == GENESYS_GL124)
-    {
+    if (dev->model->asic_type == AsicType::GL124) {
         *words = (dev->read_register(0x10b) & 0x0f) << 16;
         *words += (dev->read_register(0x10c) << 8);
         *words += dev->read_register(0x10d);
@@ -705,7 +705,7 @@ void sanei_genesys_read_scancnt(Genesys_Device* dev, unsigned int* words)
     {
         *words = dev->read_register(0x4d);
         *words += dev->read_register(0x4c) * 256;
-        if (dev->model->asic_type == GENESYS_GL646) {
+        if (dev->model->asic_type == AsicType::GL646) {
             *words += ((dev->read_register(0x4b) & 0x03) * 256 * 256);
         } else {
             *words += ((dev->read_register(0x4b) & 0x0f) * 256 * 256);
@@ -776,8 +776,7 @@ void sanei_genesys_read_feed_steps(Genesys_Device* dev, unsigned int* steps)
 {
     DBG_HELPER(dbg);
 
-  if (dev->model->asic_type == GENESYS_GL124)
-    {
+    if (dev->model->asic_type == AsicType::GL124) {
         *steps = (dev->read_register(0x108) & 0x1f) << 16;
         *steps += (dev->read_register(0x109) << 8);
         *steps += dev->read_register(0x10a);
@@ -786,9 +785,9 @@ void sanei_genesys_read_feed_steps(Genesys_Device* dev, unsigned int* steps)
     {
         *steps = dev->read_register(0x4a);
         *steps += dev->read_register(0x49) * 256;
-        if (dev->model->asic_type == GENESYS_GL646) {
+        if (dev->model->asic_type == AsicType::GL646) {
             *steps += ((dev->read_register(0x48) & 0x03) * 256 * 256);
-        } else if (dev->model->asic_type == GENESYS_GL841) {
+        } else if (dev->model->asic_type == AsicType::GL841) {
             *steps += ((dev->read_register(0x48) & 0x0f) * 256 * 256);
         } else {
             *steps += ((dev->read_register(0x48) & 0x1f) * 256 * 256);
@@ -806,12 +805,12 @@ void sanei_genesys_set_lamp_power(Genesys_Device* dev, const Genesys_Sensor& sen
     if (set) {
         regs.find_reg(0x03).value |= REG03_LAMPPWR;
 
-        if (dev->model->asic_type == GENESYS_GL841) {
+        if (dev->model->asic_type == AsicType::GL841) {
             sanei_genesys_set_exposure(regs, sanei_genesys_fixup_exposure(sensor.exposure));
             regs.set8(0x19, 0x50);
         }
 
-        if (dev->model->asic_type == GENESYS_GL843) {
+        if (dev->model->asic_type == AsicType::GL843) {
             sanei_genesys_set_exposure(regs, sensor.exposure);
 
             // we don't actually turn on lamp on infrared scan
@@ -825,12 +824,12 @@ void sanei_genesys_set_lamp_power(Genesys_Device* dev, const Genesys_Sensor& sen
     } else {
         regs.find_reg(0x03).value &= ~REG03_LAMPPWR;
 
-        if (dev->model->asic_type == GENESYS_GL841) {
+        if (dev->model->asic_type == AsicType::GL841) {
             sanei_genesys_set_exposure(regs, {0x0101, 0x0101, 0x0101});
             regs.set8(0x19, 0xff);
         }
 
-        if (dev->model->asic_type == GENESYS_GL843) {
+        if (dev->model->asic_type == AsicType::GL843) {
             if (dev->model->model_id == MODEL_PANASONIC_KV_SS080 ||
                 dev->model->model_id == MODEL_HP_SCANJET_4850C ||
                 dev->model->model_id == MODEL_HP_SCANJET_G4010 ||
@@ -867,8 +866,8 @@ void sanei_genesys_bulk_write_register(Genesys_Device* dev, const Genesys_Regist
 {
     DBG_HELPER(dbg);
 
-    if (dev->model->asic_type == GENESYS_GL646 ||
-        dev->model->asic_type == GENESYS_GL841)
+    if (dev->model->asic_type == AsicType::GL646 ||
+        dev->model->asic_type == AsicType::GL841)
     {
         uint8_t outdata[8];
         std::vector<uint8_t> buffer;
@@ -883,7 +882,7 @@ void sanei_genesys_bulk_write_register(Genesys_Device* dev, const Genesys_Regist
         DBG(DBG_io, "%s (elems= %lu, size = %lu)\n", __func__, (u_long) reg.size(),
             (u_long) buffer.size());
 
-        if (dev->model->asic_type == GENESYS_GL646) {
+        if (dev->model->asic_type == AsicType::GL646) {
             outdata[0] = BULK_OUT;
             outdata[1] = BULK_REGISTER;
             outdata[2] = 0x00;
@@ -1476,11 +1475,11 @@ bool sanei_genesys_is_compatible_calibration(Genesys_Device * dev, const Genesys
            dev->current_setup.ccd_size_divisor, cache->used_setup.ccd_size_divisor);
       compatible = 0;
     }
-  if (dev->current_setup.params.scan_method != cache->used_setup.params.scan_method)
+  if (dev->session.params.scan_method != cache->params.scan_method)
     {
       DBG (DBG_io, "%s: current method=%d, used=%d\n", __func__,
-           static_cast<unsigned>(dev->current_setup.params.scan_method),
-           static_cast<unsigned>(cache->used_setup.params.scan_method));
+           static_cast<unsigned>(dev->session.params.scan_method),
+           static_cast<unsigned>(cache->params.scan_method));
       compatible = 0;
     }
   if (!compatible)
@@ -1711,19 +1710,15 @@ void debug_dump(unsigned level, const Genesys_Current_Setup& setup)
     DBG(level, "current_setup:\n"
         "Pixels: %d\n"
         "Lines: %d\n"
-        "Depth: %d\n"
-        "Channels: %d\n"
         "exposure_time: %d\n"
-        "Resolution X/Y: %g %g\n"
+        "Resolution X/Y: %g\n"
         "ccd_size_divisor: %d\n"
         "stagger: %d\n"
         "max_shift: %d\n",
         setup.pixels,
         setup.lines,
-        setup.depth,
-        setup.channels,
         setup.exposure_time,
-        setup.xres, setup.yres,
+        setup.xres,
         setup.ccd_size_divisor,
         setup.stagger,
         setup.max_shift);
diff --git a/backend/genesys_low.h b/backend/genesys_low.h
index 3708e7ed6..311955428 100644
--- a/backend/genesys_low.h
+++ b/backend/genesys_low.h
@@ -204,16 +204,6 @@
 #define MAX_RESOLUTIONS 13
 #define MAX_DPI 4
 
-#define GENESYS_GL646	 646
-#define GENESYS_GL841	 841
-#define GENESYS_GL843	 843
-#define GENESYS_GL845	 845
-#define GENESYS_GL846	 846
-#define GENESYS_GL847	 847
-#define GENESYS_GL848	 848
-#define GENESYS_GL123	 123
-#define GENESYS_GL124	 124
-
 /* Forward typedefs */
 struct Genesys_Scanner;
 typedef struct Genesys_Calibration_Cache  Genesys_Calibration_Cache;
@@ -395,7 +385,6 @@ typedef struct {
 #define OPTICAL_FLAG_DISABLE_SHADING        0x02 /**< disable shading correction */
 #define OPTICAL_FLAG_DISABLE_LAMP           0x04 /**< turn off lamp */
 #define OPTICAL_FLAG_ENABLE_LEDADD          0x08 /**< enable true CIS gray by enabling LED addition */
-#define OPTICAL_FLAG_DISABLE_DOUBLE         0x10 /**< disable automatic x-direction double data expansion */
 #define OPTICAL_FLAG_STAGGER                0x20 /**< disable stagger correction */
 #define OPTICAL_FLAG_USE_XPA                0x40 /**< use XPA lamp rather than regular one */
 
diff --git a/backend/genesys_settings.h b/backend/genesys_settings.h
index 683a4d243..55e311b97 100644
--- a/backend/genesys_settings.h
+++ b/backend/genesys_settings.h
@@ -174,26 +174,75 @@ void serialize(Stream& str, SetupParams& x)
     serialize(str, x.flags);
 }
 
-struct Genesys_Current_Setup
-{
-    // params used for this setup
+struct ScanSession {
     SetupParams params;
 
+    // whether the session setup has been computed via gl843_compute_session()
+    // gl843-only
+    bool computed = false;
+
+    // whether CCD operates as half-resolution or full resolution at a specific resolution
+    // gl843-only
+    unsigned ccd_size_divisor = 1;
+
+    // the optical resolution of the scanner.
+    // gl843-only
+    unsigned optical_resolution = 0;
+
+    // the number of pixels at the optical resolution.
+    // gl843-only
+    unsigned optical_pixels = 0;
+
+    // the number of bytes in the output of a single line directly from scanner
+    // gl843-only
+    unsigned optical_line_bytes = 0;
+
+    // the resolution of the output data.
+    // gl843-only
+    unsigned output_resolution = 0;
+
+    // the number of pixels in output data
+    // gl843-only
+    unsigned output_pixels = 0;
+
+    // the number of bytes in the output of a single line
+    // gl843-only
+    unsigned output_line_bytes = 0;
+
+    // the number of lines in the output of the scanner. This must be larger than the user
+    // gl843-only
+    // requested number due to line staggering and color channel shifting.
+    unsigned output_line_count = 0;
+
+    // the number of staggered lines (i.e. lines that overlap during scanning due to line being
+    // gl843-only
+    // thinner than the CCD element)
+    unsigned num_staggered_lines = 0;
+
+    // the number of lines that color channels shift due to different physical positions of
+    // gl843-only
+    // different color channels
+    unsigned max_color_shift_lines = 0;
+
+    void assert_computed() const
+    {
+        if (!computed) {
+            throw std::runtime_error("ScanSession is not computed");
+        }
+    }
+};
+
+struct Genesys_Current_Setup
+{
     // pixel count expected from scanner
     int pixels = 0;
     // line count expected from scanner
     int lines = 0;
-    // depth expected from scanner
-    int depth = 0;
-    // channel count expected from scanner
-    int channels = 0;
 
     // used exposure time
     int exposure_time = 0;
     // used xres
     float xres = 0;
-    // used yres
-    float yres = 0;
     // half ccd mode
     unsigned ccd_size_divisor = 1;
     SANE_Int stagger = 0;
@@ -202,14 +251,10 @@ struct Genesys_Current_Setup
 
     bool operator==(const Genesys_Current_Setup& other) const
     {
-        return params == other.params &&
-            pixels == other.pixels &&
+        return pixels == other.pixels &&
             lines == other.lines &&
-            depth == other.depth &&
-            channels == other.channels &&
             exposure_time == other.exposure_time &&
             xres == other.xres &&
-            yres == other.yres &&
             ccd_size_divisor == other.ccd_size_divisor &&
             stagger == other.stagger &&
             max_shift == other.max_shift;
@@ -219,15 +264,10 @@ struct Genesys_Current_Setup
 template<class Stream>
 void serialize(Stream& str, Genesys_Current_Setup& x)
 {
-    serialize(str, x.params);
-    serialize_newline(str);
     serialize(str, x.pixels);
     serialize(str, x.lines);
-    serialize(str, x.depth);
-    serialize(str, x.channels);
     serialize(str, x.exposure_time);
     serialize(str, x.xres);
-    serialize(str, x.yres);
     serialize(str, x.ccd_size_divisor);
     serialize(str, x.stagger);
     serialize(str, x.max_shift);
diff --git a/testsuite/backend/genesys/tests_calibration.cc b/testsuite/backend/genesys/tests_calibration.cc
index 95aee3c0e..bcc0623d9 100644
--- a/testsuite/backend/genesys/tests_calibration.cc
+++ b/testsuite/backend/genesys/tests_calibration.cc
@@ -36,6 +36,11 @@ Genesys_Calibration_Cache create_fake_calibration_entry()
     calib.used_setup.lines = 150;
     calib.used_setup.xres = 100.5;
 
+    calib.params.channels = 3;
+    calib.params.depth = 8;
+    calib.params.lines = 100;
+    calib.params.pixels = 200;
+
     GenesysFrontendLayout wolfson_layout;
     wolfson_layout.offset_addr = { 0x20, 0x21, 0x22 };
     wolfson_layout.gain_addr = { 0x28, 0x29, 0x2a };