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    SubjectRe: [PATCH 3/3] dma_buf: Add documentation for the new cpu access support
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    On Sat, Mar 3, 2012 at 01:23, Sakari Ailus <sakari.ailus@iki.fi> wrote:
    > Where it should be decided which operations are being done to the buffer
    > when it is passed to user space and back to kernel space?
    >
    > How about spliting these operations to those done on the first time the
    > buffer is passed to the user space (mapping to kernel address space, for
    > example) and those required every time buffer is passed from kernel to user
    > and back (cache flusing)?
    >
    > I'm asking since any unnecessary time-consuming operations, especially as
    > heavy as mapping the buffer, should be avoidable in subsystems dealing
    > with streaming video, cameras etc., i.e. non-GPU users.

    I'm a bit confused about your comments because this interface
    extension doesn't support userspace mmap. So userspace isn't even part
    of the picture. Adding mmap support is something entirely different
    imo, and I have no idea yet how we should handle cache coherency for
    that.

    Yours, Daniel
    --
    Daniel Vetter
    daniel.vetter@ffwll.ch - +41 (0) 79 365 57 48 - http://blog.ffwll.ch


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