2022-02-22 17:16:29

by Nathan Chancellor

Subject: [PATCH v2] drm/stm: Avoid using val uninitialized in ltdc_set_ycbcr_config()

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 <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Reviewed-by: Raphael Gallais-Pou <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---

v1 -> v2: https://lore.kernel.org/r/[email protected]/

* Use DRM_ERROR() instead of drm_err() (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
--
2.35.1

2022-02-25 13:41:21

by Philippe CORNU

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 <[email protected]>
> Reviewed-by: Nick Desaulniers <[email protected]>
> Reviewed-by: Raphael Gallais-Pou <[email protected]>
> Signed-off-by: Nathan Chancellor <[email protected]>
> ---
>
> v1 -> v2: https://lore.kernel.org/r/[email protected]/
>
> * 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