[media] media: vb2: Fix regression on poll() for RW mode

When using a device is read/write mode, vb2 does not handle properly the
first select/poll operation.

The reason for this, is that when this code has been refactored, some of
the operations have changed their order, and now fileio emulator is not
started.

The reintroduced check to the core is enabled by a quirk flag, that
avoids this check by other subsystems like DVB.

Fixes: 49d8ab9feaf2 ("media] media: videobuf2: Separate vb2_poll()")

Reported-by: Dimitrios Katsaros <patcherwork@gmail.com>
Cc: Junghak Sung <jh1009.sung@samsung.com>
Cc: <stable@vger.kernel.org>      # for v4.5 and up
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 5342ff4d748f..88e3ab496e8f 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -404,6 +404,9 @@ struct vb2_buf_ops {
  * @fileio_read_once:		report EOF after reading the first buffer
  * @fileio_write_immediately:	queue buffer after each write() call
  * @allow_zero_bytesused:	allow bytesused == 0 to be passed to the driver
+ * @quirk_poll_must_check_waiting_for_buffers: Return POLLERR at poll when QBUF
+ *              has not been called. This is a vb1 idiom that has been adopted
+ *              also by vb2.
  * @lock:	pointer to a mutex that protects the vb2_queue struct. The
  *		driver can set this to a mutex to let the v4l2 core serialize
  *		the queuing ioctls. If the driver wants to handle locking
@@ -467,6 +470,7 @@ struct vb2_queue {
 	unsigned			fileio_read_once:1;
 	unsigned			fileio_write_immediately:1;
 	unsigned			allow_zero_bytesused:1;
+	unsigned		   quirk_poll_must_check_waiting_for_buffers:1;
 
 	struct mutex			*lock;
 	void				*owner;