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    SubjectRe: can device drivers return non-ram via vm_ops->nopage?
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    On Sat, 2004-03-20 at 14:45 -0800, William Lee Irwin III wrote:
    > This is the exact opposite of what I'd hoped come of this discussion.
    > ISTR something about remap_area_pages() missing several pieces, but
    > I pretty much need some kind of clarification to know what. Well, that,
    > and I presumed your fixups for ALSA were headed toward mainline
    > regardless after coping with whatever issue dwmw2 had (e.g. returning
    > pfn's or something).

    My request was that we shouldn't assume an architecture will have a
    'struct page' corresponding to whatever it chooses to return from
    dma_alloc_coherent().

    There are machines where DMA to/from main memory _cannot_ be coherent
    but we have some memory elsewhere, perhaps some SRAM which itself is
    hanging off an I/O bus somewhere, which can be used. One of my toys is
    currently running with dma_alloc_coherent() giving out memory from a PCI
    video card, in fact.

    Using a PFN should be OK.

    --
    dwmw2


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