Re: [RFCv3 2/2] dma-buf: add helpers for sharing attacher constraints with dma-parms

[Russell King - ARM Linux]

On Tue, Feb 03, 2015 at 09:04:03AM -0500, Rob Clark wrote:
> Since I'm stuck w/ an iommu, instead of built in mmu, my plan was to
> drop use of dma-mapping entirely (incl the current call to dma_map_sg,
> which I just need until we can use drm_cflush on arm), and
> attach/detach iommu domains directly to implement context switches.
> At that point, dma_addr_t really has no sensible meaning for me.

So how do you intend to import from a subsystem which only gives you
the dma_addr_t?

If you aren't passing system memory, you have no struct page.  You can't
fake up a struct page.  What this means is that struct scatterlist can't
represent it any other way.

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