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Message-Id: <20100826230139Y.fujita.tomonori@lab.ntt.co.jp>
Date: Thu, 26 Aug 2010 23:03:01 +0900
From: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To: fernando.lugo@...com
Cc: fujita.tomonori@....ntt.co.jp, linux-omap@...r.kernel.org,
linux-kernel@...r.kernel.org, ohad@...ery.com,
hiroshi.doyu@...ia.com, ameya.palande@...ia.com,
felipe.contreras@...ia.com
Subject: RE: [PATCH 8/9] dspbridge: add map support for big buffers
On Thu, 26 Aug 2010 08:16:24 -0500
"Guzman Lugo, Fernando" <fernando.lugo@...com> wrote:
> >From a quick look, arch/arm/plat-omap/iovmm.c does nothing wrong about
> >scatter gather chaining. arm/arm/mm/dma-mapping.c looks fine too about
> >it. Maybe just defining ARCH_HAS_SG_CHAIN works?
>
> I can try, but it looks tricky for me. Maybe someone else can tell us why
> SG chain is not supported for ARM or if there is a problem just defining
> ARCH_HAS_SG_CHAIN.
I suppose that nobody in ARM has been interested in the feature. It
was invented to improve I/O performance with large I/O requests. No
wonder embeded people aren't interested in it.
fujita@...e:~/git/linux-2.6$ find arch -name 'scatterlist.h'|xargs grep HAS_SG
arch/x86/include/asm/scatterlist.h:#define ARCH_HAS_SG_CHAIN
arch/ia64/include/asm/scatterlist.h:#define ARCH_HAS_SG_CHAIN
arch/sparc/include/asm/scatterlist.h:#define ARCH_HAS_SG_CHAIN
arch/powerpc/include/asm/scatterlist.h:#define ARCH_HAS_SG_CHAIN
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