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    SubjectRe: interrupt handling w/o handler?
    Mark Lord wrote:
    > Jes Sorensen wrote:
    > >
    > > >>>>> "Jeff" == Jeff Garzik <> writes:
    > >
    > > Jeff> Is there a function available to drivers that allows something
    > > Jeff> like: ... interruptible_sleep_on_irq (9); /* wait on IRQ 9 */
    > ..
    > > You have to register a handler for thaat, otherwise how are you
    > > guaranteed that the interrupt is handled and the hardware doesn't keep
    > > reasserting the same interrupt over and over again.
    > I think Jeff might be looking for a function such as:
    > interruptable_sleep_on_irq(n):
    > -- allocate unused irq(n), bind in generic_irqhandler(n)
    > -- save PID in wakeuptable(n)
    > -- unmask irq(n)
    > -- sleep until woken up by generic_irqhandler(n)
    > -- deallocate irq(n)
    > -- exit
    > generic_irqhandler(n):
    > -- permanently mask irq(n)
    > -- wakeup(wakeuptable(n))
    > -- exit
    > Those two functions could then be made available to user-level
    > either through /proc or a newsyscall, thereby permitting *user-level*
    > interrupt handling ("virtual device drivers" from userland).


    It seems to me that many drivers do not need a specific interrupt
    handler, they simply use interrupts to wait until an event occurs. I
    think a simple, generic interrupt handler that simply lets you know that
    an event occurred would be very useful.

    Specifically in video drivers, one can do

    do {
    status = read_fifo_register() & mask;
    } while (!status); /* poll for fifo */


    interruptible_sleep_on_irq (video_irq);
    /* FIFO is ready, proceed... */

    Now I _could_ write an interrupt handler to do this sort of thing, but a
    generic method seems much more useful, and keeps the code much, much
    cleaner. There might be a generic "register_generic_irq_handler()" step
    at video driver init, if needed.

    I hadn't thought about IRQ handling from userland, that _is_ an added



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    foul up, there's no law against whacking them around a little.
    -- Joe Martin

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