V4L/DVB: V4L: Events: Support event handling in do_ioctl

Add support for event handling to do_ioctl.

Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/v4l2-fh.c b/drivers/media/video/v4l2-fh.c
index aab2fb6..d78f184 100644
--- a/drivers/media/video/v4l2-fh.c
+++ b/drivers/media/video/v4l2-fh.c
@@ -34,7 +34,16 @@
 	INIT_LIST_HEAD(&fh->list);
 	set_bit(V4L2_FL_USES_V4L2_FH, &fh->vdev->flags);
 
-	return v4l2_event_init(fh);
+	/*
+	 * fh->events only needs to be initialized if the driver
+	 * supports the VIDIOC_SUBSCRIBE_EVENT ioctl.
+	 */
+	if (vdev->ioctl_ops && vdev->ioctl_ops->vidioc_subscribe_event)
+		return v4l2_event_init(fh);
+
+	fh->events = NULL;
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(v4l2_fh_init);