genesys: Move setup of read buffer to a single function

backend/genesys_gl124.cc

@@ -951,9 +951,7 @@ static void gl124_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
   DBG (DBG_io2, "%s: pixels          =%d\n", __func__, session.optical_pixels);
   DBG (DBG_io2, "%s: depth           =%d\n", __func__, session.params.depth);
 
-    // BUG: we shouldn't multiply by channels here
-    dev->oe_buffer.clear();
-    dev->oe_buffer.alloc(session.output_line_bytes_raw * session.params.channels);
+    build_image_pipeline(dev, session);
 
     // MAXWD is expressed in 2 words unit
 

backend/genesys_gl843.cc

@@ -1301,8 +1301,7 @@ static void gl843_init_scan_regs(Genesys_Device* dev, const Genesys_Sensor& sens
     dev->out_buffer.clear();
     dev->out_buffer.alloc(session.buffer_size_out);
 
-    dev->oe_buffer.clear();
-    dev->oe_buffer.alloc(session.output_line_bytes_raw * 2);
+    build_image_pipeline(dev, session);
 
   dev->read_bytes_left_after_deseg = session.output_line_bytes * session.output_line_count;
 

backend/genesys_gl846.cc

@@ -821,9 +821,7 @@ static void gl846_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
   DBG (DBG_io2, "%s: pixels     =%d\n", __func__, session.optical_pixels);
   DBG (DBG_io2, "%s: depth      =%d\n", __func__, session.params.depth);
 
-    // BUG: we shouldn't multiply by channels here
-    dev->oe_buffer.clear();
-    dev->oe_buffer.alloc(session.output_line_bytes_raw * session.params.channels);
+    build_image_pipeline(dev, session);
 
   /* MAXWD is expressed in 4 words unit */
     // BUG: we shouldn't multiply by channels here

backend/genesys_gl847.cc

@@ -838,9 +838,7 @@ static void gl847_init_optical_regs_scan(Genesys_Device* dev, const Genesys_Sens
   DBG (DBG_io2, "%s: pixels     =%d\n", __func__, session.optical_pixels);
   DBG (DBG_io2, "%s: depth      =%d\n", __func__, session.params.depth);
 
-    // BUG: we shouldn't multiply by channels here
-    dev->oe_buffer.clear();
-    dev->oe_buffer.alloc(session.output_line_bytes_raw * session.params.channels);
+    build_image_pipeline(dev, session);
 
   /* MAXWD is expressed in 4 words unit */
     // BUG: we shouldn't multiply by channels here

backend/genesys_low.cc

@@ -1387,6 +1387,33 @@ void compute_session(Genesys_Device* dev, ScanSession& s, const Genesys_Sensor&
     compute_session_buffer_sizes(dev->model->asic_type, s);
 }
 
+static std::size_t get_usb_buffer_read_size(AsicType asic, const ScanSession& session)
+{
+    switch (asic) {
+        case AsicType::GL646:
+            // buffer not used on this chip set
+            return 1;
+
+        case AsicType::GL124:
+        case AsicType::GL846:
+        case AsicType::GL847:
+            // BUG: we shouldn't multiply by channels here
+            return session.output_line_bytes_raw * session.params.channels;
+
+        case AsicType::GL843:
+            return session.output_line_bytes_raw * 2;
+
+        default:
+            throw SaneException("Unknown asic type");
+    }
+}
+
+void build_image_pipeline(Genesys_Device* dev, const ScanSession& session)
+{
+    dev->oe_buffer.clear();
+    dev->oe_buffer.alloc(get_usb_buffer_read_size(dev->model->asic_type, session));
+}
+
 const SensorProfile& get_sensor_profile(AsicType asic_type, const Genesys_Sensor& sensor,
                                         unsigned dpi, unsigned ccd_size_divisor)
 {

backend/genesys_low.h

@@ -638,6 +638,8 @@ extern void sanei_genesys_generate_gamma_buffer(Genesys_Device* dev,
 
 void compute_session(Genesys_Device* dev, ScanSession& s, const Genesys_Sensor& sensor);
 
+void build_image_pipeline(Genesys_Device* dev, const ScanSession& session);
+
 void genesys_fill_segmented_buffer(Genesys_Device* dev, uint8_t* work_buffer_dst, size_t size);
 
 const SensorProfile& get_sensor_profile(AsicType asic_type, const Genesys_Sensor& sensor,