HID: handle all multitouch devices through hid-multitouch

When the quirk HID_QUIRK_MULTITOUCH is present and when hid-multitouch
is loaded, let's pass the device to hid-multitouch even if it has
not been registered in hid-multitouch.

If any other driver wants to take precedence over hid-multitouch,
the usual way of adding it to hid_have_special_driver will work as
the quirk HID_QUIRK_MULTITOUCH won't be set by the generic hid layer.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@enac.fr>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 2088ab4..a61ba42 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -637,10 +637,12 @@
 	struct mt_device *td;
 	struct mt_class *mtclass = mt_classes; /* MT_CLS_DEFAULT */
 
-	for (i = 0; mt_classes[i].name ; i++) {
-		if (id->driver_data == mt_classes[i].name) {
-			mtclass = &(mt_classes[i]);
-			break;
+	if (id) {
+		for (i = 0; mt_classes[i].name ; i++) {
+			if (id->driver_data == mt_classes[i].name) {
+				mtclass = &(mt_classes[i]);
+				break;
+			}
 		}
 	}
 
@@ -648,6 +650,7 @@
 	 * that emit events over several HID messages.
 	 */
 	hdev->quirks |= HID_QUIRK_NO_INPUT_SYNC;
+	hdev->quirks &= ~HID_QUIRK_MULTITOUCH;
 
 	td = kzalloc(sizeof(struct mt_device), GFP_KERNEL);
 	if (!td) {