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/openbmc/linux/drivers/usb/musb/
H A Dmusb_gadget_ep0.c93578a25d4e21603518daf27a5f9caa4bf79de68 Thu Oct 08 17:28:49 CDT 2020 Gustavo A. R. Silva <gustavoars@kernel.org> usb: musb: gadget: Use fallthrough pseudo-keyword

In order to enable -Wimplicit-fallthrough for Clang[1], replace the
existing /* FALLTHROUGH */ comment with the new pseudo-keyword
macro fallthrough[2].

[1] https://git.kernel.org/linus/e2079e93f562c7f7a030eb7642017ee5eabaaa10
[2] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20201008222849.GA18634@embeddedor
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
/openbmc/linux/drivers/net/wireless/ti/wlcore/
H A Dmain.ca821e3858e4dec2d6505258fea46e020af8532c6 Thu Oct 08 17:09:05 CDT 2020 Gustavo A. R. Silva <gustavoars@kernel.org> wlcore: Use fallthrough pseudo-keyword

In order to enable -Wimplicit-fallthrough for Clang[1], replace the
existing /* fall-through */ comments with the new pseudo-keyword
macro fallthrough[2].

[1] https://git.kernel.org/linus/e2079e93f562c7f7a030eb7642017ee5eabaaa10
[2] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201008220905.GA8040@embeddedor
/openbmc/linux/
H A DMakefilee2079e93f562c7f7a030eb7642017ee5eabaaa10 Mon Aug 26 19:41:55 CDT 2019 Nathan Chancellor <natechancellor@gmail.com> kbuild: Do not enable -Wimplicit-fallthrough for clang for now

This functionally reverts commit bfd77145f35c ("Makefile: Convert
-Wimplicit-fallthrough=3 to just -Wimplicit-fallthrough for clang").

clang enabled support for -Wimplicit-fallthrough in C in r369414 [1],
which causes a lot of warnings when building the kernel for two reasons:

1. Clang does not support the /* fall through */ comments. There seems
to be a general consensus in the LLVM community that this is not
something they want to support. Joe Perches wrote a script to convert
all of the comments to a "fallthrough" keyword that will be added to
compiler_attributes.h [2] [3], which catches the vast majority of the
comments. There doesn't appear to be any consensus in the kernel
community when to do this conversion.

2. Clang and GCC disagree about falling through to final case statements
with no content or cases that simply break:

https://godbolt.org/z/c8csDu

This difference contributes at least 50 warnings in an allyesconfig
build for x86, not considering other architectures. This difference
will need to be discussed to see which compiler is right [4] [5].

[1]: https://github.com/llvm/llvm-project/commit/1e0affb6e564b7361b0aadb38805f26deff4ecfc
[2]: https://lore.kernel.org/lkml/61ddbb86d5e68a15e24ccb06d9b399bbf5ce2da7.camel@perches.com/
[3]: https://lore.kernel.org/lkml/1d2830aadbe9d8151728a7df5b88528fc72a0095.1564549413.git.joe@perches.com/
[4]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91432
[5]: https://github.com/ClangBuiltLinux/linux/issues/636

Given these two problems need discussion and coordination, do not enable
-Wimplicit-fallthrough with clang right now. Add a comment to explain
what is going on as well. This commit should be reverted once these two
issues are fully flushed out and resolved.

Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>