[RFC] ARM: dma_map|unmap_sg plus iommu

['Joerg Roedel']

On Fri, Jul 29, 2011 at 12:14:25PM +0200, Marek Szyprowski wrote:
> > This sounds rather hacky. How about partitioning the address space for
> > the device and give the dma-api only a part of it. The other parts can
> > be directly mapped using the iommu-api then.
> 
> Well, I'm not convinced that iommu-api should be used by the device drivers 
> directly. If possible we should rather extend dma-mapping than use such hacks.

Building this into dma-api would turn it into an iommu-api. The line
between the apis are clear. The iommu-api provides direct mapping
of bus-addresses to system-addresses while the dma-api puts a memory
manager on-top which deals with bus-address allocation itself.
So if you want to map bus-addresses directly the iommu-api is the way to
go. This is in no way a hack.

Regards,

	Joerg