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    SubjectRe: [Alsa-devel] Re: [OT] ALSA userspace API complexity
    On Mon, Jan 09, 2006 at 04:29:45PM -0800, David Lang wrote:
    > On Tue, 10 Jan 2006, John Rigg wrote:
    >
    > >>does the CPU touch the data for these, or do you DMA directly from
    > >>userspace (i.e. "zero-copy")?
    > >
    > >The cards I mentioned use DMA. RME actually advertises that some of their
    > >cards can handle 52 channels with zero CPU load. Their onboard DSPs can
    > >also do routing and mixing, again without touching the CPU.
    >
    > I was under the (apparently mistaken) impression that you couldn't DMA
    > from userspace (something to do with the possibility that the userspace
    > memory pages could be swapped out in the middle of the DMA)

    Hmm. Maybe I've been paying too much attention to card vendors'
    sales talk :)

    John
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