Re: [PATCH] drm/i915: Fix clang -Wimplicit-fallthrough in intel_async_flip_check_hw()

Nick Desaulniers
2023-05-26T16:51:38Z

On Thu, May 25, 2023 at 1:30 PM Matthieu Baerts
<matthieu.baerts@tessares.net> wrote:
>
> Hi Nick,
>
> On 24/05/2023 20:56, Nick Desaulniers wrote:
> > On Wed, May 24, 2023 at 11:41 AM Nathan Chancellor <nathan@kernel.org> wrote:
> >>
> >> On Wed, May 24, 2023 at 11:32:32AM -0700, Nick Desaulniers wrote:
> >>> On Wed, May 24, 2023 at 8:38 AM Nathan Chancellor <nathan@kernel.org> wrote:
> >>>>
> >>>> Clang warns:
> >>>>
> >>>> drivers/gpu/drm/i915/display/intel_display.c:6012:3: error: unannotated fall-through between switch labels [-Werror,-Wimplicit-fallthrough]
> >>>> case I915_FORMAT_MOD_X_TILED:
> >>>> ^
> >>>> drivers/gpu/drm/i915/display/intel_display.c:6012:3: note: insert 'break;' to avoid fall-through
> >>>> case I915_FORMAT_MOD_X_TILED:
> >>>> ^
> >>>> break;
> >>>> 1 error generated.
> >>>>
> >>>> Clang is a little more pedantic than GCC, which does not warn when
> >>>> falling through to a case that is just break or return. Clang's version
> >>>> is more in line with the kernel's own stance in deprecated.rst, which
> >>>> states that all switch/case blocks must end in either break,
> >>>> fallthrough, continue, goto, or return. Add the missing break to silence
> >>>> the warning.
> >>>>
> >>>> Fixes: 937859485aef ("drm/i915: Support Async Flip on Linear buffers")
> >>>> Reported-by: kernel test robot <lkp@intel.com>
> >>>> Closes: https://lore.kernel.org/202305241902.UvHtMoxa-lkp@intel.com/
> >>>> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> >>>> Closes: https://lore.kernel.org/CA+G9fYv68V3ewK0Qj-syQj7qX-hQr0H1MFL=QFNuDoE_J2Zu-g@mail.gmail.com/
> >>>> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> >>>
> >>> Thanks for the patch! I've never seen the closes tag before, that's
> >>> new to me. Can you tell me more about it?
> >>
> >> It is new to me (at least in the context of the kernel) as well. I only
> >> used it over Link: because checkpatch.pl told me to:
> >>
> >> WARNING: Reported-by: should be immediately followed by Closes: with a URL to the report
> >> #26:
> >> Reported-by: kernel test robot <lkp@intel.com>
> >> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> >>
> >> WARNING: Reported-by: should be immediately followed by Closes: with a URL to the report
> >> #27:
> >> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> >> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> >>
> >> It was Link: for a bit but commit 44c31888098a ("checkpatch: allow
> >> Closes tags with links") changed it to Closes:. Looks odd to me but
> >> whatever the linter says I suppose.
> >>
> >> Thanks for the review!
> >>
> >> Cheers,
> >> Nathan
> >>
> >>> A few more tags
> >>>
> >>> Reported-by: Tom Rix <trix@redhat.com>
> >>> Link: https://lore.kernel.org/all/20230523125116.1669057-1-trix@redhat.com/
> >>> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> >
> > Ah then I guess my link tag should have been
> >
> > Closes: https://lore.kernel.org/all/20230523125116.1669057-1-trix@redhat.com/
> >
> > I hope the author of
> > commit 44c31888098a ("checkpatch: allow Closes tags with links")
> > has coordinated with the maintainer of b4, so that b4 recognizes Closes tags.
> > b4 v0.12.2 does not pick up Closes tags.
>
> I'm sorry for the troubles caused by this series, that was not the
> intension.
>
> When looking at modifying b4 to support the Closes tag, I realised the
> Link tag from your previous message [1] was not taken as well. Was it
> just me?

oh? good find!

>
> If no, I just sent patches for b4, see [2]. I hope it will help!

appreciated! Thank you.

>
> Cheers,
> Matt
>
> [1]
> https://lore.kernel.org/all/CAKwvOd=jZJouuNMd3Rvc--goA0EXPHcf6cHXUA6W1kXJg2ay2w@mail.gmail.com/
> [2]
> https://lore.kernel.org/tools/20230525-closes-tags-v1-0-ed41b1773cb6@tessares.net/T/
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--
Thanks,
~Nick Desaulniers