Re: [PATCH] drm/i915: Replace "cc-option -Wno-foo" with "cc-disable-warning foo"

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Oct 30, 2017 at 05:29:27PM +0000, Chris Wilson wrote:
> To quote kbuild/makefiles.txt:
> 
>     cc-disable-warning checks if gcc supports a given warning and returns
>     the commandline switch to disable it. This special function is needed,
>     because gcc 4.4 and later accept any unknown -Wno-* option and only
>     warn about it if there is another warning in the source file.
> 
> This is exactly what we were trying to achieve with cc-option -Wno-foo and
> failed miserably.
> 
> Reported-by: kbuild-all@01.org
> Fixes: 39bf4de89ff7 ("drm/i915: Add -Wall -Wextra to our build, set warnings to full")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/Makefile | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index 7750be8e27a6..1bbc5440db40 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -12,15 +12,15 @@
>  # will most likely get a sudden build breakage... Hopefully we will fix
>  # new warnings before CI updates!
>  subdir-ccflags-y := -Wall -Wextra
> -subdir-ccflags-y += $(call cc-option,-Wno-unused-parameter,)
> -subdir-ccflags-y += $(call cc-option,-Wno-type-limits,)
> -subdir-ccflags-y += $(call cc-option,-Wno-missing-field-initializers,)
> -subdir-ccflags-y += $(call cc-option,-Wno-implicit-fallthrough,)
> +subdir-ccflags-y += $(call cc-disable-warning, unused-parameter)
> +subdir-ccflags-y += $(call cc-disable-warning, type-limits)
> +subdir-ccflags-y += $(call cc-disable-warning, missing-field-initializers)
> +subdir-ccflags-y += $(call cc-disable-warning, implicit-fallthrough)
>  subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
>  
>  # Fine grained warnings disable
> -CFLAGS_i915_pci.o = $(call cc-option,-Wno-override-init,)
> -CFLAGS_intel_fbdev.o = $(call cc-option,-Wno-override-init,)
> +CFLAGS_i915_pci.o = $(call cc-disable-warning, override-init)
> +CFLAGS_intel_fbdev.o = $(call cc-disable-warning, override-init)

Looks correct to me.
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

>  
>  subdir-ccflags-y += \
>  	$(call as-instr,movntdqa (%eax)$(comma)%xmm0,-DCONFIG_AS_MOVNTDQA)
> -- 
> 2.15.0.rc2
> 
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-- 
Ville Syrjälä
Intel OTC
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