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

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Message-ID: <1359703995.23531.6.camel@shinybook.infradead.org>
Date:	Fri, 1 Feb 2013 07:33:17 +0000
From:	"Woodhouse, David" <david.woodhouse@...el.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Kim Phillips <kim.phillips@...escale.com>,
	Borislav Petkov <bp@...en8.de>,
	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 Fri, 2013-02-01 at 01:17 +0000, Russell King - ARM Linux wrote:
> 
> > I've tried both gcc 4.6.3 [1] and 4.6.4 [2].  If you can point me to
> > a 4.5.x, I'll try that, too, but as it stands now, if one moves the
> > code added to swab.h below outside of its armv6 protection,
> > gcc adds calls to __bswapsi2.
> 
> Take a look at the message I sent on the 29th towards the beginning of
> this thread for details of gcc 4.5.4 behaviour.

I'd like to see a comment (with PR# if appropriate) explaining clearly
*why* it isn't enabled for <ARMv6 even with a bleeding-edge compiler.

Russell's test also seemed to indicate that the 32-bit and 64-bit swap
support was present and functional in GCC 4.5.4 (as indeed it should
have been since 4.4), so I'm still not quite sure why you require 4.6
for that.

-- 
                   Sent with MeeGo's ActiveSync support.

David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation




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