linux-kernel - Re: [PATCH][RFC] asm-generic:remove calling flush_write_buffers() in dma_sync_*_for

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Date:	Tue, 30 Jun 2009 15:38:43 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Joerg Roedel <joerg.roedel@....com>, tom.leiming@...il.com,
	fujita.tomonori@....ntt.co.jp, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH][RFC] asm-generic:remove calling flush_write_buffers() in dma_sync_*_for_cpu

On Tuesday 30 June 2009, Alan Cox wrote:
> > > What about non x86 - this is asm-generic you are playing with and its the
> > > kind of change that causes evil really hard to track down and subtle
> > > corruptions and user data loss if you get it wrong.
> > 
> > Non-x86 is the real motivation for the patch, because the flush_write_buffers
> > call in this file is currently not implemented and causes build errors
> > on everything but x86, frv, ia64 and m32r, where the latter two implement
> > it as an empty macro.
> 
> Ok so the FRV would grow a similar no iommu patch to the x86.

Well, not even that. dma-mapping-common.h only makes sense on architectures
that have multiple dma-mapping implementations (parisc, mips, arm, powerpc,
sparc, ia64 and x86, possibly alpha). All others including frv only need a
nommu case anyway and would not use dma-mapping-common.h but could be
changed to use something like the dma-mapping-linear.h I worked on recently.

	Arnd <><
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