Input: mt: add input_mt_is_used

This patch extracts the test (slot->frame == mt->frame) so that it can
be used in third party drivers.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Reviewed-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/input/input-mt.c

@@ -247,7 +247,7 @@ void input_mt_sync_frame(struct input_dev *dev)
 
 	if (mt->flags & INPUT_MT_DROP_UNUSED) {
 		for (s = mt->slots; s != mt->slots + mt->num_slots; s++) {
-			if (s->frame == mt->frame)
+			if (input_mt_is_used(mt, s))
 				continue;
 			input_mt_slot(dev, s - mt->slots);
 			input_event(dev, EV_ABS, ABS_MT_TRACKING_ID, -1);

include/linux/input/mt.h

@@ -69,6 +69,12 @@ static inline bool input_mt_is_active(const struct input_mt_slot *slot)
 	return input_mt_get_value(slot, ABS_MT_TRACKING_ID) >= 0;
 }
 
+static inline bool input_mt_is_used(const struct input_mt *mt,
+				    const struct input_mt_slot *slot)
+{
+	return slot->frame == mt->frame;
+}
+
 int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots,
 			unsigned int flags);
 void input_mt_destroy_slots(struct input_dev *dev);