[Intel-gfx] [PATCH 1/2] drm/i915: Ensure _print_param() builds with Clang

[Nick Desaulniers]

On Tue, Oct 16, 2018 at 8:18 AM Chris Wilson <chris at chris-wilson.co.uk> wrote:
>
> Quoting Jani Nikula (2018-10-16 13:29:37)
> > 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 at 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 at google.com>
> > Cc: Nathan Chancellor <natechancellor at gmail.com>
> > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > Reported-by: Nick Desaulniers <ndesaulniers at google.com>
> > Reported-by: Nathan Chancellor <natechancellor at gmail.com>
> > Signed-off-by: Jani Nikula <jani.nikula at intel.com>
>
> Fair enough,
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
> -Chris

Thanks for the fix, we appreciate it!
Reviewed-by: Nick Desaulniers <ndesaulniers at google.com>

-- 
Thanks,
~Nick Desaulniers