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Date:   Fri, 9 Jun 2023 13:17:54 -0700
From:   Nathan Chancellor <nathan@kernel.org>
To:     Hamza Mahfooz <hamza.mahfooz@amd.com>
Cc:     amd-gfx@lists.freedesktop.org,
        Alex Deucher <alexander.deucher@amd.com>,
        Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        "Pan, Xinhui" <Xinhui.Pan@amd.com>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Hawking Zhang <Hawking.Zhang@amd.com>, Le Ma <le.ma@amd.com>,
        Tao Zhou <tao.zhou1@amd.com>,
        YiPeng Chai <YiPeng.Chai@amd.com>,
        James Zhu <James.Zhu@amd.com>,
        Xiaojian Du <Xiaojian.Du@amd.com>,
        Lijo Lazar <lijo.lazar@amd.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Masahiro Yamada <masahiroy@kernel.org>,
        linux-kbuild@vger.kernel.org
Subject: Re: [PATCH] drm/amd/amdgpu: enable W=1 for amdgpu
Message-ID: <20230609201754.GA3961359@dev-arch.thelio-3990X>
References: <20230609164207.430377-1-hamza.mahfooz@amd.com>
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+ Masahiro and linux-kbuild

On Fri, Jun 09, 2023 at 12:42:06PM -0400, Hamza Mahfooz wrote:
> We have a clean build with W=1 as of
> commit 12a15dd589ac ("drm/amd/display/amdgpu_dm/amdgpu_dm_helpers: Move
> SYNAPTICS_DEVICE_ID into CONFIG_DRM_AMD_DC_DCN ifdef"). So, let's enable
> these checks unconditionally for the entire module to catch these errors
> during development.
> 
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>

I think this is fine, especially since it will help catch issues in
amdgpu quickly and hopefully encourage developers to fix their problems
before they make it to a tree with wider impact lika -next.

However, this is now the third place that W=1 has been effectively
enabled (i915 and btrfs are the other two I know of) and it would be
nice if this was a little more unified, especially since it is not
uncommon for the warnings under W=1 to shift around and keeping them
unified will make maintainence over the longer term a little easier. I
am not sure if this has been brought up in the past and I don't want to
hold up this change but I suspect this sentiment of wanting to enable
W=1 on a per-subsystem basis is going to continue to grow.

Regardless, for clang 11.1.0 to 16.0.5, I see no warnings when building
drivers/gpu/drm/amd/amdgpu/ with Arch Linux's configuration or
allmodconfig.

Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  drivers/gpu/drm/amd/amdgpu/Makefile | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/Makefile b/drivers/gpu/drm/amd/amdgpu/Makefile
> index 86b833085f19..8d16f280b695 100644
> --- a/drivers/gpu/drm/amd/amdgpu/Makefile
> +++ b/drivers/gpu/drm/amd/amdgpu/Makefile
> @@ -40,7 +40,18 @@ ccflags-y := -I$(FULL_AMD_PATH)/include/asic_reg \
>  	-I$(FULL_AMD_PATH)/amdkfd
>  
>  subdir-ccflags-y := -Wextra
> -subdir-ccflags-y += $(call cc-option, -Wunused-but-set-variable)
> +subdir-ccflags-y += -Wunused
> +subdir-ccflags-y += -Wmissing-prototypes
> +subdir-ccflags-y += -Wmissing-declarations
> +subdir-ccflags-y += -Wmissing-include-dirs
> +subdir-ccflags-y += -Wold-style-definition
> +subdir-ccflags-y += -Wmissing-format-attribute
> +# Need this to avoid recursive variable evaluation issues
> +cond-flags := $(call cc-option, -Wunused-but-set-variable) \
> +	$(call cc-option, -Wunused-const-variable) \
> +	$(call cc-option, -Wstringop-truncation) \
> +	$(call cc-option, -Wpacked-not-aligned)
> +subdir-ccflags-y += $(cond-flags)
>  subdir-ccflags-y += -Wno-unused-parameter
>  subdir-ccflags-y += -Wno-type-limits
>  subdir-ccflags-y += -Wno-sign-compare
> -- 
> 2.40.1
>