[v2,2/2] drm/i915: enable W=1 warnings by default

Commit Message

Jani Nikula Oct. 11, 2023, 7:29 a.m. UTC

We enable a bunch more compiler warnings than the kernel
defaults. However, they've drifted to become a unique set of warnings,
and have increasingly fallen behind from the W=1 set.

Align with the W=1 warnings from scripts/Makefile.extrawarn for clarity,
by copy-pasting them with s/KBUILD_CFLAGS/subdir-ccflags-y/ to make it
easier to compare in the future.

Some of the -Wextra warnings do need to be disabled, just like in
Makefile.extrawarn, but take care to not disable them for W=2 or W=3
builds, depending on the warning.

v2: Add back some -Wextra warning disables (Nathan)

Cc: Arnd Bergmann <[e-mail]>
Cc: Nick Desaulniers <[e-mail]>
Cc: Nathan Chancellor <[e-mail]>
Cc: Masahiro Yamada <[e-mail]>
Reviewed-by: Nathan Chancellor <[e-mail]>
Signed-off-by: Jani Nikula <[e-mail]>
---
 drivers/gpu/drm/i915/Makefile | 42 ++++++++++++++++++++++-------------
 1 file changed, 27 insertions(+), 15 deletions(-)

Comments

Masahiro Yamada Oct. 11, 2023, 2:37 p.m. UTC | #1

On Wed, Oct 11, 2023 at 4:29 PM Jani Nikula <[e-mail]> wrote:
>
> We enable a bunch more compiler warnings than the kernel
> defaults. However, they've drifted to become a unique set of warnings,
> and have increasingly fallen behind from the W=1 set.
>
> Align with the W=1 warnings from scripts/Makefile.extrawarn for clarity,
> by copy-pasting them with s/KBUILD_CFLAGS/subdir-ccflags-y/ to make it
> easier to compare in the future.
>
> Some of the -Wextra warnings do need to be disabled, just like in
> Makefile.extrawarn, but take care to not disable them for W=2 or W=3
> builds, depending on the warning.
>
> v2: Add back some -Wextra warning disables (Nathan)
>
> Cc: Arnd Bergmann <[e-mail]>
> Cc: Nick Desaulniers <[e-mail]>
> Cc: Nathan Chancellor <[e-mail]>
> Cc: Masahiro Yamada <[e-mail]>
> Reviewed-by: Nathan Chancellor <[e-mail]>
> Signed-off-by: Jani Nikula <[e-mail]>

Reviewed-by: Masahiro Yamada <[e-mail]>

Jani Nikula Oct. 11, 2023, 8:54 p.m. UTC | #2

On Wed, 11 Oct 2023, Masahiro Yamada <[e-mail]> wrote:
> On Wed, Oct 11, 2023 at 4:29 PM Jani Nikula <[e-mail]> wrote:
>>
>> We enable a bunch more compiler warnings than the kernel
>> defaults. However, they've drifted to become a unique set of warnings,
>> and have increasingly fallen behind from the W=1 set.
>>
>> Align with the W=1 warnings from scripts/Makefile.extrawarn for clarity,
>> by copy-pasting them with s/KBUILD_CFLAGS/subdir-ccflags-y/ to make it
>> easier to compare in the future.
>>
>> Some of the -Wextra warnings do need to be disabled, just like in
>> Makefile.extrawarn, but take care to not disable them for W=2 or W=3
>> builds, depending on the warning.
>>
>> v2: Add back some -Wextra warning disables (Nathan)
>>
>> Cc: Arnd Bergmann <[e-mail]>
>> Cc: Nick Desaulniers <[e-mail]>
>> Cc: Nathan Chancellor <[e-mail]>
>> Cc: Masahiro Yamada <[e-mail]>
>> Reviewed-by: Nathan Chancellor <[e-mail]>
>> Signed-off-by: Jani Nikula <[e-mail]>
>
> Reviewed-by: Masahiro Yamada <[e-mail]>

Thanks for the reviews everyone...

...though we missed some s/KBUILD_CFLAGS/subdir-ccflags-y/ in v2. Fixed
while applying.

BR,
Jani.

Patch

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 623f81217442..94f84befa38f 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -3,22 +3,34 @@ 
 # Makefile for the drm device driver.  This driver provides support for the
 # Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
 
-# Add a set of useful warning flags and enable -Werror for CI to prevent
-# trivial mistakes from creeping in. We have to do this piecemeal as we reject
-# any patch that isn't warning clean, so turning on -Wextra (or W=1) we
-# need to filter out dubious warnings.  Still it is our interest
-# to keep running locally with W=1 C=1 until we are completely clean.
-#
-# Note the danger in using -Wextra is that when CI updates gcc we
-# will most likely get a sudden build breakage... Hopefully we will fix
-# new warnings before CI updates!
-subdir-ccflags-y := -Wextra
-subdir-ccflags-y += -Wno-unused-parameter
-subdir-ccflags-y += -Wno-type-limits
-subdir-ccflags-y += -Wno-missing-field-initializers
-subdir-ccflags-y += -Wno-sign-compare
-subdir-ccflags-y += -Wno-shift-negative-value
+# Unconditionally enable W=1 warnings locally
+# --- begin copy-paste W=1 warnings from scripts/Makefile.extrawarn
+subdir-ccflags-y += -Wextra -Wunused -Wno-unused-parameter
+subdir-ccflags-y += -Wmissing-declarations
+subdir-ccflags-y += $(call cc-option, -Wrestrict)
+subdir-ccflags-y += -Wmissing-format-attribute
+subdir-ccflags-y += -Wmissing-prototypes
+subdir-ccflags-y += -Wold-style-definition
+subdir-ccflags-y += -Wmissing-include-dirs
 subdir-ccflags-y += $(call cc-option, -Wunused-but-set-variable)
+subdir-ccflags-y += $(call cc-option, -Wunused-const-variable)
+subdir-ccflags-y += $(call cc-option, -Wpacked-not-aligned)
+subdir-ccflags-y += $(call cc-option, -Wformat-overflow)
+subdir-ccflags-y += $(call cc-option, -Wformat-truncation)
+subdir-ccflags-y += $(call cc-option, -Wstringop-overflow)
+subdir-ccflags-y += $(call cc-option, -Wstringop-truncation)
+# The following turn off the warnings enabled by -Wextra
+ifeq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
+KBUILD_CFLAGS += -Wno-missing-field-initializers
+KBUILD_CFLAGS += -Wno-type-limits
+KBUILD_CFLAGS += -Wno-shift-negative-value
+endif
+ifeq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
+KBUILD_CFLAGS += -Wno-sign-compare
+endif
+# --- end copy-paste
+
+# Enable -Werror in CI and development
 subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
 
 # Fine grained warnings disable