Messages in this thread | | | Date | Thu, 25 Jul 2019 07:04:48 -0700 | From | Christoph Hellwig <> | Subject | Re: [PATCH v6 4/5] dma-buf: heaps: Add CMA heap to dmabuf heaps |
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On Thu, Jul 25, 2019 at 09:31:50AM -0400, Andrew F. Davis wrote: > But that's just it, dma-buf does not assume buffers are backed by normal > kernel managed memory, it is up to the buffer exporter where and when to > allocate the memory. The memory backed by this SRAM buffer does not have > the normal struct page backing. So moving the map, sync, etc functions > to common code would fail for this and many other heap types. This was a > major problem with Ion that prompted this new design.
The code clearly shows it has page backing, e.g. this:
+ sg_set_page(table->sgl, pfn_to_page(PFN_DOWN(buffer->paddr)), buffer->len, 0);
and the fact that it (and the dma-buf API) uses scatterlists, which requires pages.
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