Linux-kernel mailing list archive 1997-11,: Re: [2.1.65] New patch for serial port IRQ setup.

# Re: [2.1.65] New patch for serial port IRQ setup.

Rogier Wolff (R.E.Wolff@BitWizard.nl)
Mon, 24 Nov 1997 13:02:42 +0100 (MET)

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Alan Cox wrote:
>
> > I've been made aware that some manufacturers of internal modems recommend
> > using irq 2 for COM 4, while other recommende using irq 9. I've made this
> > a configuration option.
>
> You cannot share ISA interrupts between two standard seperate ISA cards
> in general. The way the cards are wired means that whoever has the strongest
> drivers sets the interrupt level.

Talking about sharing ISA interrupts, has PNP changed any of this?
This would've been a good time to change that situation: specify that
when in level triggered interrupt mode each card provides a pull-up,
and an active-low (if the lines are active-low). The pullup should be
specified to be 1/5th of the minimum requires sink current, allowing
upto 5 pull-up resistors in series: 5 cards can share an interrrupt.

Roger.

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