Patch "[media] vb2: fix a regression in poll() behavior for output,streams" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

[media] vb2: fix a regression in poll() behavior for output,streams

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
vb2-fix-a-regression-in-poll-behavior-for-output-streams.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Hans Verkuil <[email protected]>
Date: Thu, 29 Oct 2015 03:02:06 -0200
Subject: [media] vb2: fix a regression in poll() behavior for output,streams

From: Hans Verkuil <[email protected]>

commit 4623e5967448444a4ea1e77beb58898c4af48693 upstream.

In the 3.17 kernel the poll() behavior changed for output streams:
as long as not all buffers were queued up poll() would return that userspace can write. This is fine for the write() call, but when using stream I/O this changed the behavior since the expectation was that it would wait for buffers to become available for dequeuing.

This patch only enables the check whether you can queue buffers for file I/O only, and skips it for stream I/O.

---
 drivers/media/v4l2-core/videobuf2-v4l2.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -822,10 +822,10 @@ unsigned int vb2_poll(struct vb2_queue *
 		return res | POLLERR;
 
 	/*
-	 * For output streams you can write as long as there are fewer buffers
-	 * queued than there are buffers available.
+	 * For output streams you can call write() as long as there are fewer
+	 * buffers queued than there are buffers available.
 	 */
-	if (q->is_output && q->queued_count < q->num_buffers)
+	if (q->is_output && q->fileio && q->queued_count < q->num_buffers)
 		return res | POLLOUT | POLLWRNORM;
 
 	if (list_empty(&q->done_list)) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/vb2-fix-a-regression-in-poll-behavior-for-output-streams.patch