linux-kernel - Re: [PATCH] fb.h: ARM uses __raw

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Date:	Mon, 13 Jun 2011 13:00:04 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	H Hartley Sweeten <hartleys@...ionengravers.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	ARM Kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-fbdev@...r.kernel.org, Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH] fb.h: ARM uses __raw_{read/write}

On Fri, Jun 10, 2011 at 05:31:08PM -0700, H Hartley Sweeten wrote:
> ARM provides __raw_{read/write}* functions for memory access. These
> should be used instead of the default '(*(volatile' stuff to make sure the
> memory accesses are typesafe (void __iomem *).
> 
> This also fixes a number of sparse warning like:
> 
>   warning: cast removes address space of expression
> 
> Signed-off-by: H Hartley Sweeten <hsweeten@...ionengravers.com>
> Cc: Paul Mundt <lethal@...ux-sh.org>
> Cc: Russell King <linux@....linux.org.uk>
> 
I'm not sure what semantics are desirable for ARM here, so I'll wait for
Russell to reply.

This wrapping will basically mean that the fb_read/write ops are using
__raw_xxx variants while the memset and memcpy wrappers will be using the
regular read/write[bwl] routines which contain __iormb() calls. Given
that ioread/write and friends all wrap in to the normal versions with the
barriers, I would suppose that this is the default behaviour that is
desired, as opposed to wrapping in to the __raw_xxx variants directly.
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