V4L/DVB (11021): v4l2-device: add a notify callback.

Add a notify callback to v4l2_device to let sub-devices notify their
parent of special events.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 05b6965..1b97a2c 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -191,4 +191,9 @@
 	(!(sd) ? -ENODEV : (((sd) && (sd)->ops->o && (sd)->ops->o->f) ?	\
 		(sd)->ops->o->f((sd) , ##args) : -ENOIOCTLCMD))
 
+/* Send a notification to v4l2_device. */
+#define v4l2_subdev_notify(sd, notification, arg)			   \
+	((!(sd) || !(sd)->v4l2_dev || !(sd)->v4l2_dev->notify) ? -ENODEV : \
+	 (sd)->v4l2_dev->notify((sd), (notification), (arg)))
+
 #endif