Custom DSDT not loading with kernel 2.6.22-6-generic

[Brad Peters]

Binary package hint: linux-source-2.6.22

My laptop has a weird DSDT which is not supported out of the box. Under Feisty, I could load a custom DSDT that would enable sound on my laptop. Since my upgrade this morning, I noticed I did not have sound. I checked /var/log/messages and noted the following:

fubar@fry:~$ cat /var/log/messages | grep DSDT
Jun 20 08:49:58 localhost kernel: [ 20.165245] ACPI: Looking for DSDT in initramfs... successfully read 31951 bytes from /DSDT.aml.
Jun 20 08:49:58 localhost kernel: [ 20.165305] ACPI (tbget-0297): Table [DSDT] replaced by host OS [20060707]
Jun 20 11:07:27 localhost kernel: [ 0.000000] ACPI: DSDT 7FE9311A, 8A9C (r1 TOSQCI Denver 6040000 MSFT 3000001)
Jun 20 12:12:45 localhost kernel: [ 0.000000] ACPI: DSDT 7FE9311A, 8A9C (r1 TOSQCI Denver 6040000 MSFT 3000001)

The upgrade occurred around 11am. As you can see, prior to the upgrade the DSDT was loaded correctly, however now it is not loaded. I hope this functionality was not done away with, as I have no other options that I'm aware of to get sound working.

[Kyle McMartin (kyle)]

Which kernel version were you running before and after the upgrade?

[Brad Peters (thefubar)]

2.6.20-16-generic prior to the upgrade

2.6.22-6-generic after the upgrade

[Nikolaus Filus (nfilus)]

I can confirm for 2.6.22-7-i386
There is no more
    CONFIG_ACPI_CUSTOM_DSDT_INITRD=y
in /boot/config-2.6.22-7-386 and my custom DSDT is not loaded anymore (even not present in initrd.img). I need the DSDT for reducing the fan trippoints and enabling C3/C4 states for my CPU.
I'm on feisty, with upgraded kernel to gutsy. The laptop is Samsung P35

[Brad Peters (thefubar)]

Indeed, 2.6.22-7 also exhibits the same behavior. If there's any patches I can test, please let me know :)

[Ben Collins (ben-collins)]

DSDT patch isn't in the tree yet. Should be added post tribe-3 though. I believe Amit said he was going to integrate this.

[MyName (rk.)]

2.6.22-8-generic #1 SMP Thu Jul 12 15:59:45 GMT 2007 i686 GNU/Linux

still no custom DSDT

[Amit Kucheria (amitk)]

I have just committed the patch from http://gaugusch.at/kernel.shtml to allow loading of custom DSDTs. If all goes well, you should be able to roll your own initramfs in Gutsy Tribe 4 CD/next kernel release.

[Amit Kucheria (amitk)]

DSDT patch committed to git tree

[Brad Peters (thefubar)]

Thanks so much for the work on this. Can't wait to give it a test, and I'll definitely let you know how it goes.

[Martin Pitt (pitti)]

Too late for a full kernel upload now, unless this is an unintrusive one and does not break ABI.

[Brad Peters (thefubar)]

It looks like the loading now works, however, the custom DSDT that I had used in Feisty no longer works in Gutsy. I attempted to load a couple other DSDTs which caused my system to hardlock until I removed them and rebuild the initrd, which is how I know the loading functionality works. My guess is that something in the kernel changed between 2.6.20 and 2.6.22 that's causing these issues.