2.4.2-ac16 PIIX4 ACPI getting wrong IRQ?

2.4.2-ac16 PIIX4 ACPI getting wrong IRQ?

[Thomas Hood]

With 2.4.3-pre1, /proc/pci contained:
>   Bus  0, device   7, function  3:
>     Bridge: Intel Corporation 82371AB PIIX4 ACPI (rev 1).

With 2.4.2-ac16, /proc/pci contains:
>  Bus  0, device   7, function  3:
>    Bridge: Intel Corporation 82371AB PIIX4 ACPI (rev 1).
>      IRQ 9.

So the ACPI function of the PIIX4 is now being given
IRQ 9.  I don't want this.  I was using IRQ 9 for a
PCMCIA device.

So I tried booting the kernel with "acpi=off" and
"pci=irqmask=0x0800", but the result was the same.

Documentation/kernel-parameters.txt says that
"pci=irqmask=0xMMMM ... sets a bit mask of IRQs allowed
to be assigned".  This parameter is being ignored.

[... searches through kernel sources ...]

Well I see that this is the result of a change to
/usr/src/linux-2.4.2-ac16/arch/i386/kernel/pci_pc.c
which looks deliberate:

< static void __init pci_fixup_piix4_acpi(struct pci_dev *d)
< {
< 	/*
< 	 * PIIX4 ACPI device: hardwired IRQ9
< 	 */
< 	d->irq = 9;
< }

What's going on?

Thomas Hood
jdthood_AT_yahoo.co.uk

Re: 2.4.2-ac16 PIIX4 ACPI getting wrong IRQ?

[Alan Cox]

> With 2.4.2-ac16, /proc/pci contains:
> >  Bus  0, device   7, function  3:
> >    Bridge: Intel Corporation 82371AB PIIX4 ACPI (rev 1).
> >      IRQ 9.
> 
> So the ACPI function of the PIIX4 is now being given
> IRQ 9.  I don't want this.  I was using IRQ 9 for a
> PCMCIA device.

It was always being given IRQ 9, now we correctly handle this. 

Re: 2.4.2-ac16 PIIX4 ACPI getting wrong IRQ?

[Thomas Hood]

Alan Cox wrote:
> > So the ACPI function of the PIIX4 is now being given
> > IRQ 9.  I don't want this.  I was using IRQ 9 for a
> > PCMCIA device.
> 
> It was always being given IRQ 9, now we correctly handle this. 

Okay, but.  IRQs are scarce.  With previous kernels I was able
to use IRQ 9 for other things without any obvious problems.
Perhaps this is only because I don't have ACPI support enabled.
Still, if I disable ACPI support then shouldn't I be able to use
IRQ 9 for other things?  If so, shouldn't the kernel to refrain
from reserving this IRQ?

Thomas Hood
jdthood_AT_yahoo.co.uk