[media] videobuf: only start streaming in poll() if so requested by the poll mask

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/videobuf-core.c

@@ -1129,6 +1129,7 @@ unsigned int videobuf_poll_stream(struct file *file,
 				  struct videobuf_queue *q,
 				  poll_table *wait)
 {
+	unsigned long req_events = poll_requested_events(wait);
 	struct videobuf_buffer *buf = NULL;
 	unsigned int rc = 0;
 
@@ -1137,7 +1138,7 @@ unsigned int videobuf_poll_stream(struct file *file,
 		if (!list_empty(&q->stream))
 			buf = list_entry(q->stream.next,
 					 struct videobuf_buffer, stream);
-	} else {
+	} else if (req_events & (POLLIN | POLLRDNORM)) {
 		if (!q->reading)
 			__videobuf_read_start(q);
 		if (!q->reading) {