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drm/i915: Ensure _print_param() builds with Clang

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When building the kernel with Clang with defconfig and CONFIG_64BIT
disabled, vmlinux fails to link because of the BUILD_BUG in
_print_param.

ld: drivers/gpu/drm/i915/i915_params.o: in function `i915_params_dump':
i915_params.c:(.text+0x56): undefined reference to
`__compiletime_assert_191'

This function is semantically invalid unless the code is first inlined
then constant folded, which doesn't work for Clang because semantic
analysis happens before optimization/inlining.

[The above written by Nathan Chancellor <natechancellor@gmail.com>]

Use WARN_ONCE() instead of BUILD_BUG() to avoid the problem. The
WARN_ONCE() should get optimized away unless there's a type that's not
handled by _print_param().

References: https://github.com/ClangBuiltLinux/linux/issues/191
References: http://mid.mail-archive.com/20181009171401.14980-1-natechancellor@gmail.com
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181016122938.18757-1-jani.nikula@intel.com
This commit is contained in:
Jani Nikula 2018-10-16 15:29:37 +03:00
parent 046c9bca3d
commit 7b3e51dd43
1 changed files with 2 additions and 1 deletions
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3
drivers/gpu/drm/i915/i915_params.c
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@ -184,7 +184,8 @@ static __always_inline void _print_param(struct drm_printer *p,
else if (!__builtin_strcmp(type, "char *"))
drm_printf(p, "i915.%s=%s\n", name, *(const char **)x);
else
BUILD_BUG();
WARN_ONCE(1, "no printer defined for param type %s (i915.%s)\n",
type, name);
}
/**