linux-kernel - Re: [PATCH v3 17/24] media: rkvdec: h264: Fix reference frame

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Date:   Fri, 22 Apr 2022 09:43:27 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     kernel@...labora.com, linux-kernel@...r.kernel.org,
        Jonas Karlman <jonas@...boo.se>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Sebastian Fricke <sebastian.fricke@...labora.com>,
        linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-staging@...ts.linux.dev
Subject: Re: [PATCH v3 17/24] media: rkvdec: h264: Fix reference frame_num
 wrap for second field

On 05/04/2022 22:44, Nicolas Dufresne wrote:
> From: Jonas Karlman <jonas@...boo.se>
> 
> When decoding the second field in a complementary field pair the second
> field is sharing the same frame_num with the first field.
> 
> Currently the frame_num for the first field is wrapped when it matches the
> field being decoded, this cause issues to decode the second field in a

cause issues to decode -> caused issues decoding

> complementary field pair.
> 
> Fix this by using inclusive comparison, less than or equal.

I would change this last sentence to:

	Fix this by using inclusive comparison: 'less than or equal'.

It makes it a bit easier to parse.

> 
> Signed-off-by: Jonas Karlman <jonas@...boo.se>
> Signed-off-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
> Reviewed-by: Ezequiel Garcia <ezequiel@...labora.com>
> Reviewed-by: Sebastian Fricke <sebastian.fricke@...labora.com>
> ---
>  drivers/staging/media/rkvdec/rkvdec-h264.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/media/rkvdec/rkvdec-h264.c b/drivers/staging/media/rkvdec/rkvdec-h264.c
> index f081b476340f..60eaf06b6e25 100644
> --- a/drivers/staging/media/rkvdec/rkvdec-h264.c
> +++ b/drivers/staging/media/rkvdec/rkvdec-h264.c
> @@ -781,7 +781,7 @@ static void assemble_hw_rps(struct rkvdec_ctx *ctx,
>  			continue;
>  
>  		if (dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM ||
> -		    dpb[i].frame_num < dec_params->frame_num) {
> +		    dpb[i].frame_num <= dec_params->frame_num) {

I wonder if a comment should be added here, explaining the reason for '<='.

It doesn't seem obvious to me. Up to you, though.

>  			p[i] = dpb[i].frame_num;
>  			continue;
>  		}

Regards,

	Hans