linux-kernel - Re: [PATCH v6 13/13] media: platform: mtk-mdp3: fix uninitialized variable in mdp_path

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Date:   Mon, 2 Oct 2023 12:57:14 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Moudy Ho <moudy.ho@...iatek.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Ping-Hsun Wu <ping-hsun.wu@...iatek.com>,
        daoyuan huang <daoyuan.huang@...iatek.com>
Cc:     linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v6 13/13] media: platform: mtk-mdp3: fix uninitialized
 variable in mdp_path_config()

On 22/09/2023 09:41, Moudy Ho wrote:
> Fix the build warnings that were detected by the linux-media
> build scripts tool:
> 
> drivers/media/platform/mediatek/mdp3/mtk-mdp3-cmdq.c:
> 	In function 'mdp_path_config.isra':
> drivers/media/platform/mediatek/mdp3/mtk-mdp3-cmdq.c:443:51:
> 	warning: 'ctx' may be used uninitialized [-Wmaybe-uninitialized]
>   443 |                    out = CFG_COMP(MT8195, ctx->param, outputs[0]);
>       |                                           ~~~^~~~~~~
> drivers/media/platform/mediatek/mdp3/mtk-img-ipi.h:137:25: note:
> 	in definition of macro 'CFG_COMP'
>   137 |         (IS_ERR_OR_NULL(comp) ? 0 : _CFG_COMP(plat, comp, mem))
>       |                         ^~~~
> drivers/media/platform/mediatek/mdp3/mtk-mdp3-cmdq.c:396:30:
> 	note: 'ctx' was declared here
>   396 |         struct mdp_comp_ctx *ctx;
>       |
> 
> Fixes: 61890ccaefaf ("media: platform: mtk-mdp3: add MediaTek MDP3 driver")
> Signed-off-by: Moudy Ho <moudy.ho@...iatek.com>
> ---
>  drivers/media/platform/mediatek/mdp3/mtk-mdp3-cmdq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-cmdq.c b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-cmdq.c
> index 15a0b944745e..4a8d941178aa 100644
> --- a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-cmdq.c
> +++ b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-cmdq.c
> @@ -436,13 +436,13 @@ static int mdp_path_config(struct mdp_dev *mdp, struct mdp_cmdq_cmd *cmd,
>  		if (mdp_cfg_comp_is_dummy(path->mdp_dev, inner_id))
>  			continue;
>  
> +		ctx = &path->comps[index];
>  		if (CFG_CHECK(MT8183, p_id))
>  			out = CFG_COMP(MT8183, ctx->param, outputs[0]);
>  		else if (CFG_CHECK(MT8195, p_id))
>  			out = CFG_COMP(MT8195, ctx->param, outputs[0]);
>  
>  		compose = path->composes[out];
> -		ctx = &path->comps[index];
>  		ret = call_op(ctx, config_frame, cmd, compose);
>  		if (ret)
>  			return ret;

Hmm, this patch really should be a separate patch on top of the media
staging branch: it is wrong there as well, except you don't get a build
warning. Other changes in this patch series caused this warning to appear,
but the actual bug is already present in the current staging code.

Regards,

	Hans