Re: IRQ 2,9

Andrew Walker (
Wed, 12 Feb 1997 12:45:03 +0100 (MET)

. Tethys " SYSTEM ADMIN " X wrote:
> Hmmm. This reminds me. When I wanted to add a network card, I needed
> to find a free IRQ. I checked /proc/interrupts to see what was being
> used, but it didn't report all the currently used IRQs. Specifically,
> it missed out a serial port, parallel port, floppy controller and
> possibly a few others. I had to resort to MSD to find out what I was
> using where (and I don't entirely trust MSD anyway).
> So, is there a reason why this information is incomplete (as at 2.0.27
> on x86 -- I haven't checked since then)?
> Tet

Well, for the serial ports (yawn! have we got to say this again),
the interrupt isn't reserved unless the serial port is in use.
The driver won't grab irq 4 or 3 (or whatever) until it needs it.
That's a design feature, not a bug.

By default, the parallel printer driver doesn't use interrupts,
so it won't grab irq 7 or 5 (or whatever) unless you

a) load the lp driver - if its a module
b) tell it to use interrupts

That's another design feature, not a bug.


Andy Walker                              Kvaerner Engineering a.s.        P.O. Box 222, N-1324 Lysaker, Norway

......if the answer isn't violence, neither is your silence......

(pwei barmy army - oslo "filial")