Re: [PATCH v5.1 1/2] vb2: add requires_requests bit for stateless codecs

[Mauro Carvalho Chehab <mchehab+samsung@kernel.org>]

Em Wed, 20 Mar 2019 13:33:04 +0100
hverkuil-cisco@xs4all.nl escreveu:

> From: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> 
> Stateless codecs require the use of the Request API as opposed of it
> being optional.
> 
> So add a bit to indicate this and let vb2 check for this.
> 
> If an attempt is made to queue a buffer without an associated request,
> then the EBADR error is returned to userspace.
> 
> Doing this check in the vb2 core simplifies drivers, since they
> don't have to check for this, they can just set this flag.
> 
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> ---
>  Documentation/media/uapi/v4l/vidioc-qbuf.rst    | 4 ++++
>  drivers/media/common/videobuf2/videobuf2-core.c | 9 +++++++++
>  drivers/media/common/videobuf2/videobuf2-v4l2.c | 4 ++++
>  include/media/videobuf2-core.h                  | 3 +++
>  4 files changed, 20 insertions(+)
> 
> diff --git a/Documentation/media/uapi/v4l/vidioc-qbuf.rst b/Documentation/media/uapi/v4l/vidioc-qbuf.rst
> index c138d149faea..5739c3676062 100644
> --- a/Documentation/media/uapi/v4l/vidioc-qbuf.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-qbuf.rst
> @@ -189,6 +189,10 @@ EACCES
>      The ``V4L2_BUF_FLAG_REQUEST_FD`` flag was set but the device does not
>      support requests for the given buffer type.
>  
> +EBADR
> +    The ``V4L2_BUF_FLAG_REQUEST_FD`` flag was not set but the device requires
> +    that the buffer is part of a request.
> +

Hmm... IMO, you should replace the previous text instead:

	EACCES
	    The ``V4L2_BUF_FLAG_REQUEST_FD`` flag was set but the device does not
	    support requests for the given buffer type.

Also, I would replace:

	device -> device driver

As this ia a device driver limitation of the current implementation, 
with may or may not reflect a hardware limitation.

>  EBUSY
>      The first buffer was queued via a request, but the application now tries
>      to queue it directly, or vice versa (it is not permitted to mix the two
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 678a31a2b549..b98ec6e1a222 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -1507,6 +1507,12 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
>  
>  	vb = q->bufs[index];
>  
> +	if (!req && vb->state != VB2_BUF_STATE_IN_REQUEST &&
> +	    q->requires_requests) {
> +		dprintk(1, "qbuf requires a request\n");
> +		return -EBADR;
> +	}
> +
>  	if ((req && q->uses_qbuf) ||
>  	    (!req && vb->state != VB2_BUF_STATE_IN_REQUEST &&
>  	     q->uses_requests)) {
> @@ -2238,6 +2244,9 @@ int vb2_core_queue_init(struct vb2_queue *q)
>  	    WARN_ON(!q->ops->buf_queue))
>  		return -EINVAL;
>  
> +	if (WARN_ON(q->requires_requests && !q->supports_requests))
> +		return -EINVAL;
> +

Shouldn't it also be EBADR?

>  	INIT_LIST_HEAD(&q->queued_list);
>  	INIT_LIST_HEAD(&q->done_list);
>  	spin_lock_init(&q->done_lock);
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index 74d3abf33b50..84de18b30a95 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -381,6 +381,10 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
>  		return 0;
>  
>  	if (!(b->flags & V4L2_BUF_FLAG_REQUEST_FD)) {
> +		if (q->requires_requests) {
> +			dprintk(1, "%s: queue requires requests\n", opname);
> +			return -EBADR;
> +		}
>  		if (q->uses_requests) {
>  			dprintk(1, "%s: queue uses requests\n", opname);
>  			return -EBUSY;
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index c02af6370e9b..fe010ad62b90 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -482,6 +482,8 @@ struct vb2_buf_ops {
>   *              has not been called. This is a vb1 idiom that has been adopted
>   *              also by vb2.
>   * @supports_requests: this queue supports the Request API.
> + * @requires_requests: this queue requires the Request API. If this is set to 1,
> + *		then supports_requests must be set to 1 as well.
>   * @uses_qbuf:	qbuf was used directly for this queue. Set to 1 the first
>   *		time this is called. Set to 0 when the queue is canceled.
>   *		If this is 1, then you cannot queue buffers from a request.
> @@ -556,6 +558,7 @@ struct vb2_queue {
>  	unsigned			allow_zero_bytesused:1;
>  	unsigned		   quirk_poll_must_check_waiting_for_buffers:1;
>  	unsigned			supports_requests:1;
> +	unsigned			requires_requests:1;
>  	unsigned			uses_qbuf:1;
>  	unsigned			uses_requests:1;
>  



Thanks,
Mauro