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 <yannick.fertre@foss.st.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Philippe Cornu <philippe.cornu@foss.st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220222152045.484610-1-nathan@kernel.org

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 5eeb32c9c9ce65cb7c8cfc9e785f67bdbe19cca4..c9bc4ccb6d43369713c99173b57159f4118b55f6 100644 (file)
--- 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 */