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    SubjectRe: [PATCHv8 00/12] Contiguous Memory Allocator
    On Thu, Dec 23, 2010 at 11:58:08AM +0100, Marek Szyprowski wrote:
    > Actually this contiguous memory allocator is a better replacement for
    > alloc_pages() which is used by dma_alloc_coherent(). It is a generic
    > framework that is not tied only to ARM architecture.

    ... which is open to abuse. What I'm trying to find out is - if it
    can't be used for DMA, what is it to be used for?

    Or are we inventing an everything-but-ARM framework?

    > > In other words, do we _actually_ have a use for this which doesn't
    > > involve doing something like allocating 32MB of memory from it,
    > > remapping it so that it's DMA coherent, and then performing DMA
    > > on the resulting buffer?
    >
    > This is an arm specific problem, also related to dma_alloc_coherent()
    > allocator. To be 100% conformant with ARM specification we would
    > probably need to unmap all pages used by the dma_coherent allocator
    > from the LOW MEM area. This is doable, but completely not related
    > to the CMA and this patch series.

    You've already been told why we can't unmap pages from the kernel
    direct mapping.

    Okay, so I'm just going to assume that CMA has _no_ _business_ being
    used on ARM, and is not something that should interest anyone in the
    ARM community.


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