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    SubjectRe: DMA API issues
    James Bottomley wrote:

    >On Fri, 2004-06-18 at 19:14, Ian Molton wrote:
    >
    >
    >>On 18 Jun 2004 19:04:11 -0500
    >>James Bottomley <James.Bottomley@SteelEye.com> wrote:
    >>
    >>
    >>
    >>>Because the piece of memory you wish to access is bus remote.
    >>>
    >>>
    >>No, its *not*
    >>
    >>my CPU can write there directly.
    >>
    >>no strings attached.
    >>
    >>the DMA API just only understands how to map from RAM, not anything
    >>else.
    >>
    >>
    >
    >I think you'll actually find that it is. OHCI is a device (representing
    >a USB hub), it's attached to the system by some interface that
    >constitutes a bus (the bus interface transforming the CPU access cycles
    >to device access cycles, translating interrupts etc.).
    >
    >
    >
    Bus remote is a red herring in this case. The only difference between
    this case and the ones supported by the coherent_dma_mask is that the
    constraint on placement of the allocated memory cannot be encoded as a
    bitmask.

    Jamey

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