On 02/19/2015 04:40 PM, Kamil Debski wrote:
> The vb2: fix bytesused == 0 handling (8a75ffb) patch changed the behavior
> of __fill_vb2_buffer function, so that if bytesused is 0 it is set to the
> size of the buffer. However, bytesused set to 0 is used by older codec
> drivers as as indication used to mark the end of stream.
>
> To keep backward compatibility, this patch adds a flag passed to the
> vb2_queue_init function - allow_zero_bytesused. If the flag is set upon
> initialization of the queue, the videobuf2 keeps the value of bytesused
> intact in the OUTPUT queue and passes it to the driver.
>
> Reported-by: Nicolas Dufresne <[email protected]>
> Signed-off-by: Kamil Debski <[email protected]>
> ---
> drivers/media/v4l2-core/videobuf2-core.c | 29 +++++++++++++++++++++++------
> include/media/videobuf2-core.h | 2 ++
> 2 files changed, 25 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/videobuf2-core.c
> b/drivers/media/v4l2-core/videobuf2-core.c
> index 5cd60bf..b8a30d5 100644
> --- a/drivers/media/v4l2-core/videobuf2-core.c
> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> @@ -1276,13 +1276,22 @@ static void __fill_vb2_buffer(struct vb2_buffer *vb,
> const struct v4l2_buffer *b
> * userspace clearly never bothered to set it and
> * it's a safe assumption that they really meant to
> * use the full plane sizes.
> + *
> + * Some drivers, e.g. old codec drivers, use bytesused
> + * == 0 as a way to indicate that streaming is finished.
> + * In that case, the driver should use the
> + * allow_zero_bytesused flag to keep old userspace
> + * applications working.
> */
> for (plane = 0; plane < vb->num_planes; ++plane) {
> struct v4l2_plane *pdst = &v4l2_planes[plane];
> struct v4l2_plane *psrc = &b->m.planes[plane];
>
> - pdst->bytesused = psrc->bytesused ?
> - psrc->bytesused : pdst->length;
> + if (vb->vb2_queue->allow_zero_bytesused)
> + pdst->bytesused = psrc->bytesused;
> + else
> + pdst->bytesused = psrc->bytesused ?
> + psrc->bytesused : pdst->length;
> pdst->data_offset = psrc->data_offset;
> }
> }
> @@ -1295,6 +1304,11 @@ static void __fill_vb2_buffer(struct vb2_buffer *vb,
> const struct v4l2_buffer *b
> *
> * If bytesused == 0 for the output buffer, then fall back
> * to the full buffer size as that's a sensible default.
> + *
> + * Some drivers, e.g. old codec drivers, use bytesused * == 0 as
> + * a way to indicate that streaming is finished. In that case,
> + * the driver should use the allow_zero_bytesused flag to keep
> + * old userspace applications working.
> */
> if (b->memory == V4L2_MEMORY_USERPTR) {
> v4l2_planes[0].m.userptr = b->m.userptr;
> @@ -1306,10 +1320,13 @@ static void __fill_vb2_buffer(struct vb2_buffer *vb,
> const struct v4l2_buffer *b
> v4l2_planes[0].length = b->length;
> }
>
> - if (V4L2_TYPE_IS_OUTPUT(b->type))
> - v4l2_planes[0].bytesused = b->bytesused ?
> - b->bytesused : v4l2_planes[0].length;
> - else
> + if (V4L2_TYPE_IS_OUTPUT(b->type)) {
> + if (vb->vb2_queue->allow_zero_bytesused)
> + v4l2_planes[0].bytesused = b->bytesused;
I would really prefer to see a pr_warn_once here telling end-users that this
is deprecated, replaced by DEC_CMD_STOP and that it will be removed in 201X.
Actually, I think something like this will work well:
if (WARN_ON_ONCE(b->bytesused == 0)) {
pr_warn_once("use of bytesused == 0 is
deprecated and will be removed in 2017,\n");
if (vb->vb2_queue->allow_zero_bytesused)
pr_warn_once("use
VIDIOC_DECODER_CMD(V4L2_DEC_CMD_STOP) instead.\n");
else
pr_warn_once("use the actual size
instead.\n");
}
I believe both the coda and s5p-mfc drivers support V4L2_DEC_CMD_STOP as
a working alternative to this?
Regards,
Hans
> + else
> + v4l2_planes[0].bytesused = b->bytesused ?
> + b->bytesused : v4l2_planes[0].length;
> + } else
> v4l2_planes[0].bytesused = 0;
>
> }
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index e49dc6b..a5790fd 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -337,6 +337,7 @@ struct v4l2_fh;
> * @io_modes: supported io methods (see vb2_io_modes enum)
> * @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
> * @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
> @@ -388,6 +389,7 @@ struct vb2_queue {
> unsigned int io_modes;
> unsigned fileio_read_once:1;
> unsigned fileio_write_immediately:1;
> + unsigned allow_zero_bytesused:1;
>
> struct mutex *lock;
> struct v4l2_fh *owner;
>
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