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SubjectRe: [PATCH 3/3] dma_buf: Add documentation for the new cpu access support
On Sat, Mar 3, 2012 at 01:23, Sakari Ailus <> 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

Yours, Daniel
Daniel Vetter - +41 (0) 79 365 57 48 -

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