Messages in this thread | | | From | Catalin Marinas <> | Date | Tue, 16 Oct 2012 11:04:29 +0100 | Subject | Re: [Linaro-mm-sig] [RFC 0/2] DMA-mapping & IOMMU - physically contiguous allocations |
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On 16 October 2012 09:59, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote: > 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.
For user-allocated pages you first need get_user_pages() to make sure they are in memory (and will stay there). This function also calls flush_dcache_page(). Then you can build the sg list for dma_map_sg().
-- Catalin
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