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

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

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.

Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Acked-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>      # for v3.17 and up
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>

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

---

http://git.linuxtv.org/cgit.cgi/media_tree.git/commit/?id=4623e5967448444a4ea1e77beb58898c4af48693

diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c
index 27b4b9e..502984c 100644
--- a/drivers/media/v4l2-core/videobuf2-v4l2.c
+++ b/drivers/media/v4l2-core/videobuf2-v4l2.c
@@ -822,10 +822,10 @@ unsigned int vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait)
 		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)) {
--
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