linux-kernel - Re: [PATCH] lib/atomic64_test: do not build on non-atomic64 systems

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Message-ID: <AANLkTim6AFDw_1V9rtF4e_2tmgctbKHziQa-1e3=q7og@mail.gmail.com>
Date:	Thu, 21 Oct 2010 19:04:36 -0400
From:	Mike Frysinger <vapier@...too.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Luca Barbieri <luca@...a-barbieri.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lib/atomic64_test: do not build on non-atomic64 systems

On Thu, Oct 21, 2010 at 18:55, Andrew Morton wrote:
> On Thu, 21 Oct 2010 18:23:37 -0400 Mike Frysinger wrote:
>> On Thursday, October 21, 2010 18:02:50 Andrew Morton wrote:
>> > On Sat, 16 Oct 2010 13:27:15 -0400 Mike Frysinger wrote:
>> > > If the arch doesn't provide atomic64 functionality (there are quite a
>> > > few), then don't bother trying to build this test.
>> >
>> > I don't get it.  If the arch doesn't implement atomic64 then this file
>> > will get zillions of build errors, won't it?
>>
>> ... which is why i added the ifdef protection
>
> So the changelog was poor.  Please write complete changelogs so I need
> to have this sort of conversation less often?

the changelog seems pretty clear to me.  arch doesnt provide atomic64,
so dont build code that uses atomic64.

> Why doesn't this cause lots of you-broke-my-build complaints?  Nobody's
> running allmodonfig?

that's how i noticed.  perhaps the other arches that dont provide
atomic64 arent doing as many build tests as i am.

>> > > diff --git a/lib/atomic64_test.c b/lib/atomic64_test.c
>> > > index 250ed11..0ac1a66 100644
>> > > --- a/lib/atomic64_test.c
>> > > +++ b/lib/atomic64_test.c
>> > > @@ -12,6 +12,8 @@
>> > >
>> > >  #include <linux/kernel.h>
>> > >  #include <asm/atomic.h>
>> > >
>> > > +#ifdef ATOMIC64_INIT
>> >
>> > hm, that's a bit lazy.  It should really use a CONFIG_HAVE_ thing.  What
>> > a pita.
>>
>> ATOMIC64_INIT is required for atomic64 headers to provide, and having a
>> Kconfig knob doesnt gain anything else
>
> I know that.  But the standard way for an architecture to indicate to
> the core that it impements a feature is for it to define CONFIG_HAVE_*.
> Picking some related #define which architectures happen to implement
> is atypical and unexpected.
>
> Will it cause problems?  Probably not, unless the arch goes and defines
> ATOMIC64_INIT without actually implementing atomic64.  But it's
> atypical and unexpected and, yes, lazy!

you can say "lazy" all you like.  i dont see the point in going that route.
-mike
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