[linux-audio-user] Setting IRQ on intel8x0-card

[Paul Davis]

On Mon, 2006-10-09 at 20:13 +0200, Mathias Friman wrote:
> Hi list.
> 
> I have a question regarding IRQ-assignment for an on-board card identified as an Intel 82801DB-ICH4.
> 
> It is a crappy card, I know, and you probably ask yourselves why on earth I would want to put any effort
> in configuring such sub-standard equipment. The question, fortunately, is a bit broader than that. I'm writing some swedish docs
> on how to set up a Linux-system as a DAW, and see the need to do it thoroughly. :)
> 
> As of now the card shares IRQ with the eth0-card, which isn't super if one is to set RT-prio 99 on it.
> 
> Is there a simple way in setting a specific IRQ without the need for a super-BIOS that does it for you? Since I have
> a laptop the option of shuffling the PCI-cards isn't really viable. :)
> 
> I think I remember from my early days of kernel-hacking that it is possible to set IRQ with modprobe options, but it
> was a while ago. I searched through the kernel tree in the /sound/pci/intel_8x0.c file to no avail.

its basically not possible. PC architecture has changed quite a lot in
the last few years, and AFAIK you can no longer get the kernel to change
IRQ assignments. it seems stupid, i know, but i dug into this rather
deeply a year or so back, and basically the kernel picks up the IO-APIC
routings and does not modify them, even with the many flags that appear
to be related to possibly modifying them :( there is a really cool perl
script that actually analyses IO-APIC routings via the /proc filesystem,
and it confirmed for me what i was worried about.

if your BIOS doesn't allow it, you're out of luck *AFAIK*. if i am
wrong, i will be happy to hear more, since i face similar issues on my
laptop.

--p