HID: wacom: generic: Add support for vendor-defined "Distance" usage

The vendor-defined 0xFF0D01032 ("Distance") usage is nearly equivalent to
HID_GD_Z, except that the axis direction is inverted. Unlike HID_GD_Z which
increases in value as the pen-to-surface distance is decreased, this usage
decreases. Treat this usage as a special case to ensure we don't invert the
scale to be ABS_DISTANCE compatible like we do for HID_GD_Z.

Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/wacom_wac.c

@@ -1442,7 +1442,8 @@ static int wacom_equivalent_usage(int usage)
 		int subusage = (usage & 0xFF);
 
 		if (subpage == WACOM_HID_SP_DIGITIZER ||
-		    subpage == WACOM_HID_SP_DIGITIZERINFO) {
+		    subpage == WACOM_HID_SP_DIGITIZERINFO ||
+		    usage == WACOM_HID_WD_DISTANCE) {
 			return usage;
 		}
 
@@ -1502,6 +1503,7 @@ static void wacom_wac_pen_usage_mapping(struct hid_device *hdev,
 	case HID_GD_Y:
 		wacom_map_usage(input, usage, field, EV_ABS, ABS_Y, 4);
 		break;
+	case WACOM_HID_WD_DISTANCE:
 	case HID_GD_Z:
 		wacom_map_usage(input, usage, field, EV_ABS, ABS_DISTANCE, 0);
 		break;

drivers/hid/wacom_wac.h

@@ -88,6 +88,7 @@
 #define WACOM_HID_SP_DIGITIZER          0x000d0000
 #define WACOM_HID_SP_DIGITIZERINFO      0x00100000
 #define WACOM_HID_WD_DIGITIZER          (WACOM_HID_UP_WACOMDIGITIZER | 0x01)
+#define WACOM_HID_WD_DISTANCE           (WACOM_HID_UP_WACOMDIGITIZER | 0x0132)
 #define WACOM_HID_WD_DATAMODE           (WACOM_HID_UP_WACOMDIGITIZER | 0x1002)
 #define WACOM_HID_UP_G9                 0xff090000
 #define WACOM_HID_G9_PEN                (WACOM_HID_UP_G9 | 0x02)