linux-kernel - Re: [PATCH 2/2] asm-generic: io: don't perform swab during {in,out} string functions

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Message-ID: <20120427165919.GD14743@mudshark.cambridge.arm.com>
Date:	Fri, 27 Apr 2012 17:59:19 +0100
From:	Will Deacon <will.deacon@....com>
To:	Mike Frysinger <vapier@...too.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"uclinux-dist-devel@...ckfin.uclinux.org" 
	<uclinux-dist-devel@...ckfin.uclinux.org>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 2/2] asm-generic: io: don't perform swab during {in,out}
 string functions

On Fri, Apr 27, 2012 at 05:18:58PM +0100, Mike Frysinger wrote:
> On Friday 27 April 2012 06:42:56 Will Deacon wrote:
> > The {in,out}s{b,w,l} functions are designed to operate on a stream of
> > bytes and therefore should not perform any byte-swapping, regardless of
> > the CPU byte order.
> 
> says who ?  where's the agreed upon documentation for this ?

This specific case is actually documented in Linux Device Drivers, but I
appreciate that it's not especially clear. I had some offline discussion
with Arnd where we agreed on this -- it also means that asm-generic/io.h
matches what is done by bi-endian architectures providing their own
accessors.

Will
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