linux-kernel - Re: [RFC] arm: use built-in byte swap function

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Message-ID: <20130131213327.GB5050@pd.tnic>
Date:	Thu, 31 Jan 2013 22:33:27 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Kim Phillips <kim.phillips@...escale.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	"Woodhouse, David" <david.woodhouse@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Santos <daniel.santos@...ox.com>,
	David Rientjes <rientjes@...gle.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <robherring2@...il.com>
Subject: Re: [RFC] arm: use built-in byte swap function

On Thu, Jan 31, 2013 at 02:59:47PM -0600, Kim Phillips wrote:
> - add new ARCH_DEFINES_BUILTIN_BSWAP (see Kconfig help).
>   - if set, generic compiler header does not set HAVE_BUILTIN_BSWAPxx
>   - not too sure about this having to be a new CONFIG_, but it's hard
>     to find a place for it given linux/compiler.h doesn't include any
>     arch-specific files.

Yeah, me neither. It seems to me the whole deal can be simplified even
further without introducing CONFIG_ARCH_DEFINES_BUILTIN_BSWAP.

And, we don't even want to use CONFIG_ARCH_USE_BUILTIN_BSWAP on arm due
to different compiler versions supporting it (correct me if I'm wrong
here) vs the generic thing in include/linux/compiler-gcc4.h which we
want off.

If so, you'd need to simply put the following from below in
arch/arm/include/asm/swab.h

#if GCC_VERSION >= 40600
#define __HAVE_BUILTIN_BSWAP32__
#define __HAVE_BUILTIN_BSWAP64__
#if GCC_VERSION >= 40800
#define __HAVE_BUILTIN_BSWAP16__
#endif /* GCC_VERSION >= 40800 */
#endif /* GCC_VERSION >= 40600 */

and that's it.

Makes sense or am I over-simplifying this?

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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