linux-kernel - Re: [PATCH v2 15/36] media: pci: intel: ipu3: Remove useless setting of min_buffers

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Date:   Mon, 4 Dec 2023 15:36:21 +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,
        Yong Zhi <yong.zhi@...el.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Bingbu Cao <bingbu.cao@...el.com>,
        Dan Scally <djrscally@...il.com>,
        Tianshu Qiu <tian.shu.qiu@...el.com>
Subject: Re: [PATCH v2 15/36] media: pci: intel: ipu3: Remove useless setting
 of min_buffers_needed

On 04/12/2023 14:23, Benjamin Gaignard wrote:
> This driver uses min_buffers_needed which vb2 uses to ensure
> start_streaming is called when at least 'min_buffers_needed'
> buffers are queued. However, this driver doesn't need this,
> it can stream fine without any buffers queued.
> Just drop this unnecessary restriction.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
> CC: Yong Zhi <yong.zhi@...el.com>
> CC: Sakari Ailus <sakari.ailus@...ux.intel.com>
> CC: Bingbu Cao <bingbu.cao@...el.com>
> CC: Dan Scally <djrscally@...il.com>
> CC: Tianshu Qiu <tian.shu.qiu@...el.com>
> ---
>  drivers/media/pci/intel/ipu3/ipu3-cio2.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/media/pci/intel/ipu3/ipu3-cio2.c b/drivers/media/pci/intel/ipu3/ipu3-cio2.c
> index 5d3b0ffd3d08..7f72be686981 100644
> --- a/drivers/media/pci/intel/ipu3/ipu3-cio2.c
> +++ b/drivers/media/pci/intel/ipu3/ipu3-cio2.c
> @@ -1589,7 +1589,6 @@ static int cio2_queue_init(struct cio2_device *cio2, struct cio2_queue *q)
>  	vbq->mem_ops = &vb2_dma_sg_memops;
>  	vbq->buf_struct_size = sizeof(struct cio2_buffer);
>  	vbq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> -	vbq->min_buffers_needed = 1;
>  	vbq->drv_priv = cio2;
>  	vbq->lock = &q->lock;
>  	r = vb2_queue_init(vbq);

I can't really tell if this is needed or not. Definitely needs to be reviewed
by Sakari or someone else with sufficient knowledge of this driver.

Regards,

	Hans