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Subject: Re: [PATCH] sparc: use asm-generic/scatterlist.h
From: David Miller <davem@davemloft.net>
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From: Arnd Bergmann <arnd@arndb.de>
Date: Tue, 2 Mar 2010 14:54:11 +0100

> Broken in the sense that arch/powerpc/Kconfig describes CONFIG_IOMMU_VMERGE:
> 
>        Cause IO segments sent to a device for DMA to be merged virtually
>        by the IOMMU when they happen to have been allocated contiguously.
>        This doesn't add pressure to the IOMMU allocator. However, some
>        drivers don't support getting large merged segments coming back
>        from *_map_sg().
> 
>        Most drivers don't have this problem; it is safe to say Y here.
> 
> I don't know if this comment still applies to any drivers in the mainline
> kernel, but it's possible.

That really has to be out of date these days.