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    SubjectRe: DMA from SCSI controller to PCI frame buffer memory.
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    Date
    > In theory you can mmap the frame buffer memory, then do O_DIRECT I/O
    > into it. In practice it will buffer (I hope it still does). One of the
    > problems is that there are huge lists of PCI->AGP DMA errata in
    > chipsets.

    I am not accessing the AGP bus as my frame buffer is located on the PCI
    bus.
    00:08.0 Multimedia video controller: Unknown device f1d0:efac
    Subsystem: Unknown device f1d0:efac
    Flags: bus master, stepping, medium devsel, latency 64, IRQ 10
    Memory at f4000000 (32-bit, non-prefetchable) [size=4K]
    Memory at f6000000 (32-bit, prefetchable) [size=16M]
    (I am working with the second memory address)

    Any recommendations on where to start hacking? Would it be a good idea
    to add O_DIRECT to a mmaped PCI space? The kernel should not be doing
    any buffering whatsoever, as we will be coming close to filling the pci
    bus up with transfers from direct disk->fb already. (We are already
    doing buffering on the FB card as well)

    Jason
    --
    Jason Howard

    Professional:
    SpectSoft, LLC
    http://www.spectsoft.com jason@spectsoft.com
    Phone: +1.209.847.7812 Fax: +1.209.847.7859
    Personal:
    http://www.psinux.org jason@psinux.org
    Cell: +1.209.968.1289
    Text Message: jasonsphone@psinux.org


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