From: Arnd Bergmann <arnd@arndb.de>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH][RFC] asm-generic:remove calling flush_write_buffers() in dma_sync_*_for_cpu
Date: Tue, 30 Jun 2009 15:38:43 +0200
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Cc: Joerg Roedel <joerg.roedel@amd.com>, tom.leiming@gmail.com,
       fujita.tomonori@lab.ntt.co.jp, linux-kernel@vger.kernel.org,
       akpm@linux-foundation.org
References: <1246199959-6548-1-git-send-email-tom.leiming@gmail.com> <200906301448.55064.arnd@arndb.de> <20090630140945.0784e174@lxorguk.ukuu.org.uk>
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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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