drm/amd/amdgpu: enable W=1 for amdgpu

  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>
---
 drivers/gpu/drm/amd/amdgpu/Makefile | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)
  

+ 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
>
  

On Sat, Jun 10, 2023 at 5:17 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> + 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.



I believe this patch is the right way because
we will be able to add a new warning option to
scripts/Makefile.extrawarn without fixing any code.

I remember somebody argued that drivers should be
able to do
  subdir-ccflags-y += $(W1_FLAGS)

However, if a new flag, -Wfoo, emits warnings
for drivers/gpu/drm/{i915,amd},
you cannot add it to W=1 until fixing the code.

If many drivers start to do likewise,
W=1 warning will not be W=1 any more.



Another good thing for hard-coding warning options
is you can lift up a warning flag one by one.


Let's say you fixed the entire DRM subsystem so
it is -Wunused free now.

Then, you can move -Wunused to drivers/gpu/drm/Makefile,
while other warning options stay in drivers Makefiles.







>
> 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
> >
  

On Sat, 10 Jun 2023, Masahiro Yamada <masahiroy@kernel.org> wrote:
> On Sat, Jun 10, 2023 at 5:17 AM Nathan Chancellor <nathan@kernel.org> wrote:
>>
>> + 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.
>
>
>
> I believe this patch is the right way because
> we will be able to add a new warning option to
> scripts/Makefile.extrawarn without fixing any code.
>
> I remember somebody argued that drivers should be
> able to do
>   subdir-ccflags-y += $(W1_FLAGS)

Personally, I think this would be the viable way to make the kernel free
of W=1 warnings. Make it clean driver and subsystem at a time, with
constant progress. Currently, there's haphazard fixing of issues, with
new ones creeping back in, because kernel-wide W=1 is too verbose for
most developers. It's whac-a-mole.

> However, if a new flag, -Wfoo, emits warnings
> for drivers/gpu/drm/{i915,amd},
> you cannot add it to W=1 until fixing the code.

Or adding -Wno-foo where it breaks, until fixed.

> If many drivers start to do likewise,
> W=1 warning will not be W=1 any more.

I don't know, is the goal to fix the warnings, or keep adding stuff to
W=1 so that it'll always emit warnings? :p


BR,
Jani.

> Another good thing for hard-coding warning options
> is you can lift up a warning flag one by one.
>
>
> Let's say you fixed the entire DRM subsystem so
> it is -Wunused free now.
>
> Then, you can move -Wunused to drivers/gpu/drm/Makefile,
> while other warning options stay in drivers Makefiles.
>
>
>
>
>
>
>
>>
>> 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
>> >