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SubjectRe: Define CONFIG_BOUNCE to avoid useless inclusion of bounce buffer logic.
On Wed, May 23, 2007 at 09:03:02PM -0700, Christoph Lameter wrote:
> On Thu, 24 May 2007, Paul Mackerras wrote:
> > Also there is the problem that some drivers use ZONE_DMA allocations
> > because their device can only generate addresses below some limit, but
> > on a platform with an IOMMU there is in fact no restriction on what
> > memory the device can access.
> That problem is to some extend addressed by switching ZONE_DMA off which
> results in GFP_DMA becoming meaningless. And if GFP_DMA and ZONE_DMA is
> gone from a platform then the MAX_DMA_ADDRESS inconsistencies are solved
> since the cause of the inconsistencies has evaporated.

Suffice it to say then that with this approach ARM will _never_ be able
to have ZONE_DMA turned off, even on platforms where there are no DMA
restrictions. I guess that's something we'll just have to live with.

Russell King
Linux kernel 2.6 ARM Linux -
maintainer of:
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