Re: [PARPORT] Re: ftape with Trakker parallel port

From: Jeremy Elson (
Date: Fri Jul 07 2000 - 11:51:50 EDT

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    "Jochen Hoenicke" writes:
    >It is not easy to autodetect the irq number for parallel ports. AFAIK
    >only ECP makes it possible to detect the interrupt. You should always
    >use the "irq=" option of parport_pc.

    I have noticed that with some parallel port hardware (when in normal
    bi-dir PS/2 mode), a single spurious interrupt is generated when I
    turn on the IRQ-enable bit in the control register. I have never
    found any documentation of this "feature" but I think it may be
    there to aid in IRQ autodetection. In particular I know my Dell
    Optiplex GX1 at work does this.

    I don't think the kernel tries using this trick to detect IRQ
    interrupts currently... I keep meaning to write a patch.


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