linux-kernel - Re: [PATCH] drm/stm: Avoid using val uninitialized in ltdc_set_ycbcr

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Message-ID: <aea58d59-9b1c-608b-7212-1d64ce2f07db@foss.st.com>
Date:   Tue, 8 Feb 2022 16:44:16 +0100
From:   yannick Fertre <yannick.fertre@...s.st.com>
To:     Nathan Chancellor <nathan@...nel.org>,
        Philippe Cornu <philippe.cornu@...s.st.com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>
CC:     Nick Desaulniers <ndesaulniers@...gle.com>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <llvm@...ts.linux.dev>
Subject: Re: [PATCH] drm/stm: Avoid using val uninitialized in
 ltdc_set_ycbcr_config()

Hi Nathan,
Thenks for the patch.

Acked-by: Yannick Fertre <yannick.fertre@...s.st.com>

Best regards

On 2/7/22 17:53, Nathan Chancellor wrote:
> Clang warns:
> 
>    drivers/gpu/drm/stm/ltdc.c:625:2: warning: variable 'val' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
>            default:
>            ^~~~~~~
>    drivers/gpu/drm/stm/ltdc.c:635:2: note: uninitialized use occurs here
>            val |= LxPCR_YCEN;
>            ^~~
>    drivers/gpu/drm/stm/ltdc.c:600:9: note: initialize the variable 'val' to silence this warning
>            u32 val;
>                   ^
>                    = 0
>    1 warning generated.
> 
> Use a return instead of break in the default case to fix the warning.
> Add an error message so that this return is not silent, which could hide
> issues in the future.
> 
> Fixes: 484e72d3146b ("drm/stm: ltdc: add support of ycbcr pixel formats")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1575
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>   drivers/gpu/drm/stm/ltdc.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index 5eeb32c9c9ce..447ddde1786c 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -624,7 +624,8 @@ static inline void ltdc_set_ycbcr_config(struct drm_plane *plane, u32 drm_pix_fm
>   		break;
>   	default:
>   		/* RGB or not a YCbCr supported format */
> -		break;
> +		drm_err(plane->dev, "Unsupported pixel format: %u\n", drm_pix_fmt);
> +		return;
>   	}
>   
>   	/* Enable limited range */
> 
> base-commit: 542898c5aa5c6a3179dffb1d1606884a63f75fed