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    SubjectRe: [RFC][PATCH] add dma_reserve_coherent_memory()/dma_free_reserved_memory() API
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    On Sunday, October 10, 2010 05:08:22 pm FUJITA Tomonori wrote:
    > On Fri, 20 Aug 2010 14:50:12 +0300
    > Marin Mitov <mitov@issp.bas.bg> wrote:
    >
    > > On Friday, August 20, 2010 11:35:06 am FUJITA Tomonori wrote:
    > > > On Fri, 20 Aug 2010 11:13:45 +0300
    > > > Marin Mitov <mitov@issp.bas.bg> wrote:
    > > >
    > > > > > > This tric is already used in drivers/staging/dt3155v4l.c
    > > > > > > dt3155_alloc_coherent()/dt3155_free_coherent()
    > > > > > >
    > > > > > > Here proposed for general use by popular demand from video4linux folks.
    > > > > > > Helps for videobuf-dma-contig framework.
    > > > > >
    > > > > > What you guys exactly want to do? If you just want to pre-allocate
    > > > > > coherent memory for latter usage,
    > > > >
    > > > > Yes, just to preallocate not coherent, but rather contiguous memory for latter usage.
    > > > > We use coherent memory because it turns out to be contiguous.
    > > >
    > > > Hmm, you don't care about coherency? You just need contiguous memory?
    > >
    > > Yes. We just need contiguous memory. Coherency is important as far as when dma
    > > transfer finishes user land is able to see the new data. Could be done by something like
    > > dma_{,un}map_single()
    >
    > Anyone is working on this?

    I am not, sorry.

    >
    > KAMEZAWA posted a patch to improve the generic page allocator to
    > allocate physically contiguous memory. He said that he can push it
    > into mainline.

    I am waiting for the new videobuf2 framework to become part of the kernel.
    Then KAMEZAWA's improvements can help.

    Marin Mitov

    >
    > The approach enables us to solve this issue without adding any new
    > API.
    >


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