genesys: Add a way to override logical HW dpi

backend/genesys_sensor.h

@@ -279,6 +279,10 @@ struct Genesys_Sensor {
     // resolution. The value zero does not set the override.
     unsigned register_dpihw_override = 0;
 
+    // The scanner may be setup to use a custom logical dpihw that does not correspond to any actual
+    // resolution. The value zero does not set the override.
+    unsigned logical_dpihw_override = 0;
+
     // The scanner may be setup to use a custom dpiset value that does not correspond to any actual
     // resolution. The value zero does not set the override.
     unsigned dpiset_override = 0;

backend/genesys_tables_sensor.cc

@@ -47,6 +47,9 @@
 
 inline unsigned default_get_logical_hwdpi(const Genesys_Sensor& sensor, unsigned xres)
 {
+    if (sensor.logical_dpihw_override)
+        return sensor.logical_dpihw_override;
+
     // can't be below 600 dpi
     if (xres <= 600) {
         return 600;