linux-kernel - Re: [PATCH v2 17/36] media: test-drivers: Fix misuse of min_buffers

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Message-ID: <5bc3e0e7-36b4-4553-8a2a-353fe533fe78@xs4all.nl>
Date:   Mon, 4 Dec 2023 15:42:26 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        mchehab@...nel.org, tfiga@...omium.org, m.szyprowski@...sung.com,
        matt.ranostay@...sulko.com
Cc:     linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-staging@...ts.linux.dev, kernel@...labora.com,
        Shuah Khan <skhan@...uxfoundation.org>,
        Kieran Bingham <kieran.bingham@...asonboard.com>
Subject: Re: [PATCH v2 17/36] media: test-drivers: Fix misuse of
 min_buffers_needed field

On 04/12/2023 14:23, Benjamin Gaignard wrote:
> 'min_buffers_needed' is suppose to be used to indicate the number
> of buffers needed by DMA engine to start streaming.
> Obvious test-drivers don't use DMA engine and just want to specify
> the minimum number of buffers to allocate when calling VIDIOC_REQBUFS.
> That 'min_reqbufs_allocation' field purpose so use it.
> While at it rename function parameter.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
> CC: Shuah Khan <skhan@...uxfoundation.org>
> CC: Kieran Bingham <kieran.bingham@...asonboard.com>
> ---
>  drivers/media/test-drivers/vimc/vimc-capture.c | 2 +-
>  drivers/media/test-drivers/vivid/vivid-core.c  | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/test-drivers/vimc/vimc-capture.c b/drivers/media/test-drivers/vimc/vimc-capture.c
> index aa944270e716..97693561f1e4 100644
> --- a/drivers/media/test-drivers/vimc/vimc-capture.c
> +++ b/drivers/media/test-drivers/vimc/vimc-capture.c
> @@ -432,7 +432,7 @@ static struct vimc_ent_device *vimc_capture_add(struct vimc_device *vimc,
>  	q->mem_ops = vimc_allocator == VIMC_ALLOCATOR_DMA_CONTIG
>  		   ? &vb2_dma_contig_memops : &vb2_vmalloc_memops;
>  	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> -	q->min_buffers_needed = 2;
> +	q->min_reqbufs_allocation = 2;
>  	q->lock = &vcapture->lock;
>  	q->dev = v4l2_dev->dev;
>  

That's OK.

> diff --git a/drivers/media/test-drivers/vivid/vivid-core.c b/drivers/media/test-drivers/vivid/vivid-core.c
> index 353f035fcd19..b4e888ac6016 100644
> --- a/drivers/media/test-drivers/vivid/vivid-core.c
> +++ b/drivers/media/test-drivers/vivid/vivid-core.c
> @@ -861,7 +861,7 @@ static const struct media_device_ops vivid_media_ops = {
>  static int vivid_create_queue(struct vivid_dev *dev,
>  			      struct vb2_queue *q,
>  			      u32 buf_type,
> -			      unsigned int min_buffers_needed,
> +			      unsigned int min_reqbufs_allocation,
>  			      const struct vb2_ops *ops)
>  {
>  	if (buf_type == V4L2_BUF_TYPE_VIDEO_CAPTURE && dev->multiplanar)
> @@ -898,7 +898,7 @@ static int vivid_create_queue(struct vivid_dev *dev,
>  	q->mem_ops = allocators[dev->inst] == 1 ? &vb2_dma_contig_memops :
>  						  &vb2_vmalloc_memops;
>  	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> -	q->min_buffers_needed = supports_requests[dev->inst] ? 0 : min_buffers_needed;
> +	q->min_reqbufs_allocation = supports_requests[dev->inst] ? 0 : min_reqbufs_allocation;

But here you can simplify this to:

	q->min_reqbufs_allocation = min_reqbufs_allocation;

The 'supports_requests' restriction is only relevant for q->min_buffers_needed.

Regards,

	Hans

>  	q->lock = &dev->mutex;
>  	q->dev = dev->v4l2_dev.dev;
>  	q->supports_requests = supports_requests[dev->inst];