add rewind function to command set

backend/genesys_gl124.c

@@ -3926,6 +3926,7 @@ static Genesys_Command_Set gl124_cmd_set = {
   gl124_led_calibration,
 
   gl124_slow_back_home,
+  NULL,
 
   sanei_genesys_bulk_write_register,
   NULL,

backend/genesys_gl646.c

@@ -5767,6 +5767,7 @@ static Genesys_Command_Set gl646_cmd_set = {
   gl646_led_calibration,
 
   gl646_slow_back_home,
+  NULL,
 
   gl646_bulk_write_register,
   gl646_bulk_write_data,

backend/genesys_gl841.c

@@ -6352,6 +6352,7 @@ static Genesys_Command_Set gl841_cmd_set = {
   gl841_led_calibration,
 
   gl841_slow_back_home,
+  NULL,
 
   gl841_bulk_write_register,
   gl841_bulk_write_data,

backend/genesys_gl843.c

@@ -4446,6 +4446,7 @@ static Genesys_Command_Set gl843_cmd_set = {
   gl843_led_calibration,
 
   gl843_slow_back_home,
+  NULL,
 
   sanei_genesys_bulk_write_register,
   gl843_bulk_write_data,

backend/genesys_gl846.c

@@ -3680,6 +3680,7 @@ static Genesys_Command_Set gl846_cmd_set = {
   gl846_led_calibration,
 
   gl846_slow_back_home,
+  NULL,
 
   sanei_genesys_bulk_write_register,
   NULL,

backend/genesys_gl847.c

@@ -3753,6 +3753,7 @@ static Genesys_Command_Set gl847_cmd_set = {
   gl847_led_calibration,
 
   gl847_slow_back_home,
+  NULL,
 
   sanei_genesys_bulk_write_register,
   NULL,

backend/genesys_low.h

@@ -509,8 +509,8 @@ typedef struct Genesys_Command_Set
     SANE_Status (*coarse_gain_calibration) (Genesys_Device * dev, int dpi);
     SANE_Status (*led_calibration) (Genesys_Device * dev);
 
-    SANE_Status (*slow_back_home) (Genesys_Device * dev,
-				   SANE_Bool wait_until_home);
+    SANE_Status (*slow_back_home) (Genesys_Device * dev, SANE_Bool wait_until_home);
+    SANE_Status (*rewind) (Genesys_Device * dev);
 
     SANE_Status (*bulk_write_register) (Genesys_Device * dev,
 					Genesys_Register_Set * reg,