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    SubjectRe: DMA mapping

    > I have a nice piece of hardware, that manages state (32-bit handle)
    > for me. It is just a shame that I will have to hack further state
    > tracking on top.

    I had the same problem for the Qlogic cards- they return, either in a
    response queue entry or in two 16 bit registers, a 32 bit handle that
    identifies a completing command. But this was always sorta busted for alpha &&
    ultrasparc to try and figure out from this what the real address of the
    original command block was, so I just began using the handle as an index into
    a an array of pointers- turns out this is much cleaner and safer because a lot
    of times the Qlogic f/w is confused and returns garbage instead of the correct
    handle- it's much easier to detect this when you have an index in the range of
    0 to 1024 rather than assume what you get back from the card is a valid

    Moral: it's a bad practice to take candy from strangers (i.e., trust
    CPU pointers as returned out of I/O cards).

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      Last update: 2005-03-22 13:56    [W:0.038 / U:65.224 seconds]
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