[LAU] rtirq, kernels >= 3.2 and udev

[Fernando Lopez-Lezcano]

Hi all (and Rui),

As noted in another thread I found out that the naming of the irq 
processes of pci soundcards has changed with kernels >= 3.2 to be 
uniform and predictable. That made it possible to change rtirq so that 
(at least for pci cards) only the irq process that corresponds to the 
soundcard gets an elevated priority - this was not completely reliable 
before.

Another nice (very nice I'd say) side effect of this change is that now 
udev can be trivially used to change the priorities of soundcards 
dynamically. I tested this while running 3.2.16-rt27 on a Fedora 14 
system. I removed "snd" and "usb" of the rtirq sysconfig file so that it 
would not touch those and rebooted. My hda_intel got the priority I 
wanted, inserting (or removing) a usb or a pci-express card with a 
Multiface II worked as well. Right now my simple script does not try to 
order priorities, it just sets them to a fixed one. But well, it is a 
start... Code attached (the udev rule goes into /etc/udev/rules.d/ in my 
system)...

This simple script also returns the priority of the usb irq for the 
soundcard to 50 (the default) when the card is unplugged, but it does 
not check for multiple cards (ie: even if another soundcard is still 
using the same irq process it downgrades its priority), this should be 
fixed.

Feedback appreciated.
-- Fernando

PS: Another rtirq script in /etc/pm/sleep.d/ could save the current 
priorities before a suspend and restore them after a resume - that does 
not happen currently.
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