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    SubjectRe: raw memory & PCI bus access
    pavel@rts.loniis.ru wrote:
    >
    > Hi all
    >
    > Say I have a driver that realizes a "virtual irq" (/dev/irq).

    I think Pavel Machek may have already written something like this?


    > User application waits for interrupts by calling select() for
    > that device. Obviously such a driver doesn't need much of code.
    > What a maximum latency between irq occurance and
    > userapp reaction I should expect?

    In modern machines it shouldn't be too bad -- but if you are concerned
    about it, a better course may be to at least put your interrupt handler
    in kernel space.

    Another possibility is have your user space driver pass information to
    /dev/irq, which tells the generic /dev/irq how to acknowledge
    interrupts, read data into a buffer, and other simple operations like
    that.

    Jeff

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