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

[Philippe CORNU]

On 2/7/22 8:44 PM, Nick Desaulniers wrote:
> On Mon, Feb 7, 2022 at 8:53 AM Nathan Chancellor <nathan@xxxxxxxxxx> 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@xxxxxxxxxx>
> > ---
> >   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);
>
> This is fine, but in the future you should add an explicit
> #include <drm/drm_print.h>
> to avoid implicit header dependencies (like the ones that Mingo is
> trying to detangle) for the declaration of drm_err. `drm_vprintf`
> needs it, too.
>
> Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>

Hi Nick,
and thank you for having pointing this.

Hi Nathan,
May I ask you please to update your patch changing drm_err(plane->dev, ) 
with DRM_ERROR().


Big thank you,

Philippe :-)



> > +               return;
> >          }
> >
> >          /* Enable limited range */
> >
> > base-commit: 542898c5aa5c6a3179dffb1d1606884a63f75fed
> > --
> > 2.35.1