backport: HID: wacom: Set a default resolution for older tablets

Some older tablets may not report physical maximum for X/Y
coordinates. Set a default to prevent undefined resolution.

Signed-off-by: Ping Cheng <[email protected]>
Signed-off-by: Benjamin Tissoires <[email protected]>
[[email protected]: Imported into input-wacom (08a46b4190)]
Signed-off-by: Ping Cheng <[email protected]>
[[email protected]: Backported from input-wacom (235fcdb)]
Signed-off-by: Ping Cheng <[email protected]>

Author: Ping Cheng

3.17/wacom_wac.c

@@ -1910,6 +1910,7 @@ static void wacom_map_usage(struct input_dev *input, struct hid_usage *usage,
 	int fmax = field->logical_maximum;
 	unsigned int equivalent_usage = wacom_equivalent_usage(usage->hid);
 	int resolution_code = code;
+	int resolution = hidinput_calc_abs_res(field, resolution_code);
 
 	if (equivalent_usage == HID_DG_TWIST ||
 	    equivalent_usage == WACOM_HID_WD_TOUCHRING) {
@@ -1931,8 +1932,15 @@ static void wacom_map_usage(struct input_dev *input, struct hid_usage *usage,
 	switch (type) {
 	case EV_ABS:
 		input_set_abs_params(input, code, fmin, fmax, fuzz, 0);
-		input_abs_set_res(input, code,
-				  hidinput_calc_abs_res(field, resolution_code));
+
+		/* older tablet may miss physical usage */
+		if ((code == ABS_X || code == ABS_Y) && !resolution) {
+			resolution = WACOM_INTUOS_RES;
+			hid_warn(input,
+				 "Wacom usage (%d) missing resolution \n",
+				 code);
+		}
+		input_abs_set_res(input, code, resolution);
 		break;
 	case EV_KEY:
 	case EV_MSC: