Messages in this thread | | | Date | Tue, 16 Oct 2012 09:59:28 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [Linaro-mm-sig] [RFC 0/2] DMA-mapping & IOMMU - physically contiguous allocations |
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On Tue, Oct 16, 2012 at 09:04:34AM +0300, Hiroshi Doyu wrote: > In addition to those contiguous/discontiguous page allocation, is > there any way to _import_ anonymous pages allocated by a process to be > used in dma-mapping API later? > > I'm considering the following scenario, an user process allocates a > buffer by malloc() in advance, and then it asks some driver to convert > that buffer into IOMMU'able/DMA'able ones later. In this case, pages > are discouguous and even they may not be yet allocated at > malloc()/mmap().
That situation is covered. It's the streaming API you're wanting for that. dma_map_sg() - but you may need additional cache handling via flush_dcache_page() to ensure that your code is safe for all CPU cache architectures.
Remember that pages allocated into userspace will be cacheable, so a cache flush is required before they can be DMA'd. Hence the streaming API.
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