linux-kernel - Re: [PATCH v2] drm/stm: Avoid using val uninitialized in ltdc_set_ycbcr

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Message-ID: <c61d8a3f-6f19-48aa-ae69-e4f3670d4b16@foss.st.com>
Date:   Fri, 25 Feb 2022 14:19:50 +0100
From:   Philippe CORNU <philippe.cornu@...s.st.com>
To:     Nathan Chancellor <nathan@...nel.org>,
        Yannick Fertre <yannick.fertre@...s.st.com>
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>,
        Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>
Subject: Re: [PATCH v2] drm/stm: Avoid using val uninitialized in
 ltdc_set_ycbcr_config()



On 2/22/22 16:20, 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
> Acked-by: Yannick Fertre <yannick.fertre@...s.st.com>
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Reviewed-by: Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
> 
> v1 -> v2: https://lore.kernel.org/r/20220207165304.1046867-1-nathan@kernel.org/
> 
> * Use DRM_ERROR() instead of drm_err() (Philippe).

Hi Nathan,

Applied on drm-misc-next.
Many thanks for your patch,
Philippe :-)

> 
> * Collect tags from v1, as nothing substantial has changed.
> 
>   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..c9bc4ccb6d43 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_ERROR("Unsupported pixel format: %u\n", drm_pix_fmt);
> +		return;
>   	}
>   
>   	/* Enable limited range */
> 
> base-commit: 542898c5aa5c6a3179dffb1d1606884a63f75fed