i915 enables a wider set of warnings with '-Wall -Wextra' then disables several with cc-disable-warning. If an unknown flag gets added to KBUILD_CFLAGS when building with clang, all subsequent calls to cc-{disable-warning,option} will fail, meaning that all of these warnings do not get disabled [1].
A separate series will address the root cause of the issue by not adding these flags when building with clang [2]; however, the symptom of these extra warnings appearing can be addressed separately by just removing the calls to cc-disable-warning, which makes the build ever so slightly faster because the compiler does not need to be called as much before building.
The following warnings are supported by GCC 4.9 and clang 10.0.1, which are the minimum supported versions of these compilers so the call to cc-disable-warning is not necessary. Masahiro cleaned this up for the reset of the kernel in commit 4c8dd95a723d ("kbuild: add some extra warning flags unconditionally").
* -Wmissing-field-initializers * -Wsign-compare * -Wtype-limits * -Wunused-parameter
-Wunused-but-set-variable was implemented in clang 13.0.0 and -Wframe-address was implemented in clang 12.0.0 so the cc-disable-warning calls are kept for these two warnings.
Lastly, -Winitializer-overrides is clang's version of -Woverride-init, which is disabled for the specific files that are problematic. clang added a compatibility alias in clang 8.0.0 so -Winitializer-overrides can be removed.
[1]: https://lore.kernel.org/r/202108210311.CBtcgoUL-lkp@intel.com/ [2]: https://lore.kernel.org/r/20210824022640.2170859-1-nathan@kernel.org/
Signed-off-by: Nathan Chancellor nathan@kernel.org ---
NOTE: This is based on my series to enable -Wsometimes-initialized here:
https://lore.kernel.org/r/20210824225427.2065517-1-nathan@kernel.org/
I sent it separately as this can go into whatever release but I would like for that series to go into 5.15.
drivers/gpu/drm/i915/Makefile | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile index 335ba9f43d8f..6b38547543b1 100644 --- a/drivers/gpu/drm/i915/Makefile +++ b/drivers/gpu/drm/i915/Makefile @@ -13,13 +13,11 @@ # 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-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 += -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 += $(call cc-disable-warning, unused-but-set-variable) -# clang warnings -subdir-ccflags-y += $(call cc-disable-warning, sign-compare) -subdir-ccflags-y += $(call cc-disable-warning, initializer-overrides) subdir-ccflags-y += $(call cc-disable-warning, frame-address) subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
base-commit: fb43ebc83e069625cfeeb2490efc3ffa0013bfa4 prerequisite-patch-id: 31c28450ed7e8785dce967a16db6d52eff3d7d6d prerequisite-patch-id: 372dfa0e07249f207acc1942ab0e39b13ff229b2 prerequisite-patch-id: 1a585fa6cda50c32ad1e3ac8235d3cff1b599978