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06.01.2005 00:26

Woozy Numbat on my notebook, part 1

I ran into a problem while trying to upgrade to Linux 2.6.10 on my notebook (ASUS M2400N). ALSA didn't find any soundcards during boot, although it should (2.6.9 did).

0000:00:1f.5 Multimedia audio controller: Intel Corp. 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) AC'97 Audio Controller (rev 03)

After searching through the kernel source and trying various other things, including building the driver as module, loading with special parameters, forced loading, many ugly hacks...
Needless to say, none of my approaches lead to a working soundcard. After a while I recognized that with 2.6.10, my parport device got an IRQ assigned to it, IRQ 7. My soundcard also wants to occupy this IRQ but that shouldn't be the problem, I thought, because in times, where we have IRQ sharing and request_irq's SA_SHIRQ parameter, two devices per IRQ could easily be done.
Anyhow, I rebooted to view the IRQ-table in 2.6.9 but I didn't see the parport device listed there. This was the time, when I knew, that I know absolutely not enough about the parport implementation in the linux kernel. After reading the parport documentation, everything was much clearer to me.
parport doesn't need an interrupt, to work properly. 2.6.10 was the first kernel, that assigned one to it - maybe because of the new PNP ACPI feature?
Appending one additional parameter to the kernel's cmdline solved the problem by restoring the old behaviour: not assigning an interrupt to the parport driver.
LILO: 2.6.10 parport=0x378,-1

The -1 means, that no IRQ should be assigned to the parport driver. Now everything is fine:
  0:    3864839          XT-PIC  timer
  1:      11674          XT-PIC  i8042
  2:          0          XT-PIC  cascade
  4:          1          XT-PIC  ehci_hcd
  5:     120838          XT-PIC  yenta, uhci_hcd, uhci_hcd, uhci_hcd, eth0, eth1
  7:          0          XT-PIC  snd-intel8x0
  9:       7641          XT-PIC  acpi
 12:      95168          XT-PIC  i8042
 14:      24773          XT-PIC  ide0
 15:         13          XT-PIC  ide1
NMI:          0
ERR:          0

There are also other issues with 2.6.10 on my system, but that's another story, maybe in another entry...