linux-kernel - Re: [PATCH v2 03/36] media: microchip: Remove useless setting of min_buffers

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Message-ID: <ab06b2c0-a290-46cd-9d97-3f9f6e3bbb36@xs4all.nl>
Date:   Mon, 4 Dec 2023 15:03:19 +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,
        Eugen Hristev <eugen.hristev@...labora.com>
Subject: Re: [PATCH v2 03/36] media: microchip: Remove useless setting of
 min_buffers_needed

On 04/12/2023 14:22, 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: Eugen Hristev <eugen.hristev@...labora.com>
> ---
>  drivers/media/platform/microchip/microchip-isc-base.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/media/platform/microchip/microchip-isc-base.c b/drivers/media/platform/microchip/microchip-isc-base.c
> index 3fba0e2844b6..63c39981f47a 100644
> --- a/drivers/media/platform/microchip/microchip-isc-base.c
> +++ b/drivers/media/platform/microchip/microchip-isc-base.c
> @@ -1821,7 +1821,6 @@ static int isc_async_complete(struct v4l2_async_notifier *notifier)
>  	q->mem_ops		= &vb2_dma_contig_memops;
>  	q->timestamp_flags	= V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
>  	q->lock			= &isc->lock;
> -	q->min_buffers_needed	= 1;

I don't think this can be dropped. Looking at the isc_start_streaming() function
it expects to have at least one buffer queued.

Regards,

	Hans

>  	q->dev			= isc->dev;
>  
>  	ret = vb2_queue_init(q);