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    SubjectRe: parport - interrupt sharing possible?

    On Sun, Jul 11, 2004 at 10:51:19PM -0500, Ryan Underwood wrote:
    > Hi,
    > Does anyone know if the generic parport interrupt handler is okay (or not)
    > for sharing interrupts? The reason I ask is that I have a PCI parallel
    > card with two ports on it. Without a IRQ sharing capability, it is not
    > possible for both of them to operate in interrupt-driven mode. I tested
    > a quick hack to enable IRQ sharing:
    > and it seems to work okay with both ports in use. I'm hoping someone
    > more knowledgeable on the parallel port subject (Tim Waugh?) can shed
    > some light on whether this is acceptable or not. The interrupt handler
    > eventually ends up in parport_ieee1284_interrupt which really doesn't do
    > much besides wake up sleepers.
    > Thanks!
    > PS: Heh, the power just went out and back on as I wrote this. Giving thanks
    > for having multiple UPS units around!

    Hi Ryan,

    Quoting Tim Waugh:

    > 2) Allows PCI parallel port to share an IRQ if possible. In limited testing
    > this seems to be ok, but maybe the interrupt handler was not written for
    > sharing. Someone else will need to ok this.

    This seems dangerous to me. There are some issues with IRQs in
    parport, although I think they are known and there is a fix around:

    Incidentally, I have asked if there is anyone with more time than me
    who would like to maintain the paride/parport bits, but no-one has
    stepped forward. I see that Al Viro has fixed a lot of problems while
    I've been busy with other things.
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