HID: multitouch: Release all touch slots on reset_resume

When resetting a device (especially after power loss) it is unlikely
that the firmware will keep the contact tracking data for the previous
touches and will be able to reconcile it with the new contacts, so
let's release all slots on reset resume as start anew.

Signed-off-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-multitouch.c

@@ -1150,8 +1150,30 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
 }
 
 #ifdef CONFIG_PM
+static void mt_release_contacts(struct hid_device *hid)
+{
+	struct hid_input *hidinput;
+
+	list_for_each_entry(hidinput, &hid->inputs, list) {
+		struct input_dev *input_dev = hidinput->input;
+		struct input_mt *mt = input_dev->mt;
+		int i;
+
+		if (mt) {
+			for (i = 0; i < mt->num_slots; i++) {
+				input_mt_slot(input_dev, i);
+				input_mt_report_slot_state(input_dev,
+							   MT_TOOL_FINGER,
+							   false);
+			}
+			input_sync(input_dev);
+		}
+	}
+}
+
 static int mt_reset_resume(struct hid_device *hdev)
 {
+	mt_release_contacts(hdev);
 	mt_set_maxcontacts(hdev);
 	mt_set_input_mode(hdev);
 	return 0;