Subject: Re: [PATCH] powerpc: Kconfig.cputype: Disallow TUNE_CELL on LE systems

From: Thomas Huth <[email-masked]>
Date: Mon, 21 Sep 2015 12:07:27 +0200

On 21/09/15 09:18, Michael Ellerman wrote:
> On Fri, 2015-09-18 at 16:17 +0200, Thomas Huth wrote:
>> It looks somewhat weird that you can enable TUNE_CELL on little
>> endian systems, so let's disable this option with CPU_LITTLE_ENDIAN.
>>
>> Signed-off-by: Thomas Huth <[email-masked]>
>> ---
>>  I first thought that it might be better to make this option depend
>>  on PPC_CELL instead ... but I guess it's a bad idea to depend a
>>  CPU option on a platform option? Alternatively, would it make
>>  sense to make it depend on (GENERIC_CPU || CELL_CPU) instead?
> 
> Hmm, it's a little backward, but I think it would be fine, and less confusing
> for users. Both PS3 and Cell select PPC_CELL, so it would work in both those
> cases.

It's just that when you step through the kernel config (e.g. with "make
menuconfig"), you normally step through the "Processor support" first,
and then later do the "Platform support". I think most users won't look
back into "Processor support" again once they already reached the
"Platform support" section, so this TUNE_CELL option then might appear
unnoticed when you enable a Cell platform under "Platform support".

That's why thought that CPU_LITTLE_ENDIAN or (GENERIC_CPU || CELL_CPU)
might be the better option here... but if you think PPC_CELL is the
better way to go, I'm also fine to change my patch to use this instead
(in the end, TUNE_CELL is likely hardly used anymore nowadays, so it
should not be that bad if it does not appear "immediately" to the user).

 Thomas