linux-kernel - Re: CPU_BIG_ENDIAN in generic code (was: Re: [PATCH v3 3/7] arch/sparc: Define config parameter CPU_BIG

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Date:   Thu, 25 May 2017 22:09:24 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Babu Moger <babu.moger@...cle.com>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        "David S. Miller" <davem@...emloft.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        sparclinux <sparclinux@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
Subject: Re: CPU_BIG_ENDIAN in generic code (was: Re: [PATCH v3 3/7]
 arch/sparc: Define config parameter CPU_BIG_ENDIAN)

On Thu, May 25, 2017 at 4:51 PM, Babu Moger <babu.moger@...cle.com> wrote:
> On 5/24/2017 5:18 AM, Arnd Bergmann wrote:

>>> I guess the time is ripe for adding (both) symbols to all architectures?
>>
>> Good idea. I think we can do most of this by adding a few lines to
>> arch/Kconfig:
>>
>> config CPU_BIG_ENDIAN
>>          bool
>>
>> config CPU_LITTLE_ENDIAN
>>         def_bool !CPU_BIG_ENDIAN
>>
>> This way, we only need to add 'select CPU_BIG_ENDIAN' to the
>> architectures that are always big-endian, and we don't need to
>> change anything for the ones that have a single 'CPU_BIG_ENDIAN'
>> option.
>>
>> The three architectures that have a 'choice' statement (mips, ppc and
>> sh) will have to convert, and m32r will have to replace the
>
>
> what to you mean by "(mips, ppc andsh) will have to convert"?  Do you expect
> any changes here?
>

Kconfig does not allow you to have the same symbol as both a regular
'bool' and also 'bool within choice', so those three have to replace the
choice with a user-visible 'config CPU_BIG_ENDIAN' option like the
other ones have.

I also notice that  for arch/s390/Kconfig you now have both the
'select CPU_BIG_ENDIAN' and the 'config CPU_BIG_ENDIAN
def_bool y', I'd remove the second one in the same patch.

       Arnd