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

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.