linux-kernel - Re: [PATCH] xtensa: move CONFIG_CPU_*

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Message-ID: <CAK7LNASb4wDk4p7Qk28nNbu0fr9kNa_PaDq-RXRzB_qiJedzQg@mail.gmail.com>
Date:   Sat, 13 Mar 2021 21:03:17 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Max Filippov <jcmvbkbc@...il.com>
Cc:     Chris Zankel <chris@...kel.net>,
        "open list:TENSILICA XTENSA PORT (xtensa)" 
        <linux-xtensa@...ux-xtensa.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] xtensa: move CONFIG_CPU_*_ENDIAN defines to Kconfig

On Sat, Mar 13, 2021 at 5:57 PM Max Filippov <jcmvbkbc@...il.com> wrote:
>
> On Fri, Mar 12, 2021 at 7:14 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
> >
> > Move the definition of CONFIG_CPU_*_ENDIAN to Kconfig, the best place
> > for CONFIG options.
> >
> > I slightly simplified the test code. You can use the -P option to suppress
> > linemarker generation. The grep command is unneeded.
> >
> >   $ echo __XTENSA_EB__ | xtensa-linux-gcc -E -
> >   # 1 "<stdin>"
> >   # 1 "<built-in>"
> >   # 1 "<command-line>"
> >   # 1 "<stdin>"
> >   1
> >
> >   $ echo __XTENSA_EB__ | xtensa-linux-gcc -E -P -
> >   1
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> > ---
>
> > If I understood correctly, xtensa compilers can support either
> > big-endian or little-endian. We cannot change it via a command option.
> > Actually, it does not understand -mbig-endian or -mlittle-endian.
> > (Is this correct?)
>
> This is correct. The idea is that specific xtensa core has fixed endianness,
> but it can be either little or big. The toolchain is configured for the specific
> xtensa core at build time, so there's no need for a runtime endian switch.
>
> >   $ xtensa-linux-gcc   -mbig-endian  /dev/null  -c -o /dev/null
> >   xtensa-linux-gcc: error: unrecognized command-line option '-mbig-endian'
> >
> > I see -mbig-endian / -mlittle-endian in old GCC manual.
> >   https://gcc.gnu.org/onlinedocs/gcc-3.3.5/gcc/Xtensa-Options.html
> > But, I cannot see them in recent gcc manuals.
> > So, I have no idea better than checking __XTENSA_EB__ or __XTENSA_EL__.
> > I just moved the logic to Kconfig from Makefile.
> >
> >
> >  arch/xtensa/Kconfig  | 6 ++++++
> >  arch/xtensa/Makefile | 9 +--------
> >  2 files changed, 7 insertions(+), 8 deletions(-)
>
> Acked-by: Max Filippov <jcmvbkbc@...il.com>
> Please let me know if I should take it into the xtensa tree or you will
> carry it in the kbuild tree.


Please apply it to the xtensa tree.


I also submitted 3 patches to clean up xtensa syscall table generation.

https://lore.kernel.org/patchwork/project/lkml/list/?series=487007

They should go to the xtensa tree as well.



-- 
Best Regards
Masahiro Yamada