linux-kernel - Re: [PATCH v14 26/56] media: i2c: video-i2c: Stop direct calls to queue num

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Date:   Thu, 9 Nov 2023 11:18:48 +0100
From:   Andrzej Pietrasiewicz <andrzej.p@...labora.com>
To:     Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        mchehab@...nel.org, tfiga@...omium.org, m.szyprowski@...sung.com,
        ming.qian@....com, ezequiel@...guardiasur.com.ar,
        p.zabel@...gutronix.de, gregkh@...uxfoundation.org,
        hverkuil-cisco@...all.nl, nicolas.dufresne@...labora.com
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, linux-staging@...ts.linux.dev,
        kernel@...labora.com, Matt Ranostay <matt.ranostay@...sulko.com>
Subject: Re: [PATCH v14 26/56] media: i2c: video-i2c: Stop direct calls to
 queue num_buffers field

Hi Benjamin,

W dniu 31.10.2023 o 17:30, Benjamin Gaignard pisze:
> Use vb2_get_num_buffers() to avoid using queue num_buffers field directly.
> This allows us to change how the number of buffers is computed in the
> future.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
> CC: Matt Ranostay <matt.ranostay@...sulko.com>
> ---
>   drivers/media/i2c/video-i2c.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/i2c/video-i2c.c b/drivers/media/i2c/video-i2c.c
> index 178bd06cc2ed..ebf2ac98a068 100644
> --- a/drivers/media/i2c/video-i2c.c
> +++ b/drivers/media/i2c/video-i2c.c
> @@ -405,9 +405,10 @@ static int queue_setup(struct vb2_queue *vq,
>   {
>   	struct video_i2c_data *data = vb2_get_drv_priv(vq);
>   	unsigned int size = data->chip->buffer_size;
> +	unsigned int q_num_bufs = vb2_get_num_buffers(vq);
>   
> -	if (vq->num_buffers + *nbuffers < 2)
> -		*nbuffers = 2;
> +	if (q_num_bufs + *nbuffers < 2)
> +		*nbuffers = 2 - q_num_bufs;

This actually changes the logic. Maybe it has already been discussed and
the result of that discussion is this change in logic? Looking at other
drivers *nbuffers = 2 - q_num_bufs; seems the right thing to do.
But then at least the commit message body IMO should mention this change.
Or, preferably, the change in logic should be a separate patch to be applied
before this one.

Regards,

Andrzej

>   
>   	if (*nplanes)
>   		return sizes[0] < size ? -EINVAL : 0;