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    SubjectRe: [PATCH v6 4/5] dma-buf: heaps: Add CMA heap to dmabuf heaps
    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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