linux-kernel - Re: MMIO and gcc re-ordering issue

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Message-ID: <20080602101102.0d8979c5@hskinnemo-gx745.norway.atmel.com>
Date:	Mon, 2 Jun 2008 10:11:02 +0200
From:	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	benh@...nel.crashing.org, Matthew Wilcox <matthew@....cx>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>, linux-arch@...r.kernel.org,
	scottwood@...escale.com, linuxppc-dev@...abs.org,
	alan@...rguk.ukuu.org.uk, linux-kernel@...r.kernel.org,
	tpiepho@...escale.com
Subject: Re: MMIO and gcc re-ordering issue

Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Fri, 30 May 2008, Haavard Skinnemoen wrote:
> > Maybe we need another interface that does not do byteswapping but
> > provides stronger ordering guarantees?
> 
> The byte swapping depends on the device/bus.

Of course. But isn't it reasonable to assume that a device integrated
on the same silicon as the CPU is connected to a somewhat sane bus
which doesn't require any byte swapping?

> So what happened to the old idea of putting the accessor function pointers
> in the device/bus structure?

Don't know. I think it sounds like overkill to replace a simple load or
store with an indirect function call.

Haavard
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