HID: wacom: Handle failing HID_DG_CONTACTMAX requests

Hardware may not respond to a request for the HID_DG_CONTACTMAX feature and
we should be tolerant of such a failure. This is especially true when using
hid-replay where the hardware doesn't exist, but also for devices attached
to a flaky bus. This patch increases the number of allowable retries to
match other calls to 'wacom_get_report' and also provides a fallback which
forces 'touch_max = 16' (enough for any Wacom device seen so far).

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_sys.c

@@ -125,9 +125,16 @@ static void wacom_feature_mapping(struct hid_device *hdev,
 				break;
 			data[0] = field->report->id;
 			ret = wacom_get_report(hdev, HID_FEATURE_REPORT,
-						data, 2, 0);
-			if (ret == 2)
+						data, 2, WAC_CMD_RETRIES);
+			if (ret == 2) {
 				features->touch_max = data[1];
+			} else {
+				features->touch_max = 16;
+				hid_warn(hdev, "wacom_feature_mapping: "
+					 "could not get HID_DG_CONTACTMAX, "
+					 "defaulting to %d\n",
+					  features->touch_max);
+			}
 			kfree(data);
 		}
 		break;