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Subject: Re: FRV/ARM unaligned access question
From: Harvey Harrison <harvey.harrison@gmail.com>
To: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>
In-Reply-To: <20081008091055.GB19322@flint.arm.linux.org.uk>
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	 <20081008073519.GA19322@flint.arm.linux.org.uk>
	 <1223451379.8195.88.camel@brick>
	 <20081008091055.GB19322@flint.arm.linux.org.uk>
Content-Type: text/plain
Date: Wed, 08 Oct 2008 02:34:07 -0700
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On Wed, 2008-10-08 at 10:10 +0100, Russell King wrote:
> On Wed, Oct 08, 2008 at 12:36:19AM -0700, Harvey Harrison wrote:
> > On Wed, 2008-10-08 at 08:35 +0100, Russell King wrote:
> > > On Wed, Oct 08, 2008 at 12:26:13AM -0700, Harvey Harrison wrote:
> > > > I noticed that frv/arm are the only two arches that currently use open-coded
> > > > byteshifting routines for both the cpu endianness and the other endianness
> > > > whereas just about all the other arches use a packed-struct version for the
> > > > cpu-endian and then the byteshifting versions (lifted from arm) for the other
> > > > endianness.
> > > 
> > > I'm sorry, I think you're mistaken.  I've looked at x86, m68k and
> > > parisc, and they all use assembly for their swab functions in
> > > asm/byteorder.h.
> > > 
> > 
> > Sorry, not talking about byteorder at the moment, talking about
> > unaligned.h.
> 
> At the moment, I've no idea what effect it'll have.  I'd need to run
> some tests to discover what the effect will be.  Not sure when I'll
> get around to that.
> 
> If someone else can be found to evaluate what the effect would be...
> 

I don't have hardware to test with, but I'll do some cross-compiles to
investigate a bit.  I was just curious if there was any known issues on
arm, or a specific arm compiler that made you choose the implementation
you did.

Cheers,

Harvey

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