Loading custom DSDT

Alan Cox alan at redhat.com
Tue Oct 25 14:51:19 UTC 2005


On Tue, Oct 25, 2005 at 12:32:13PM +0100, Richard Hughes wrote:
> But some of the ACPI tables out there are *so* broken... The best way to
> do this surely is to grab the fixed dsdt from
> http://acpi.sourceforge.net/ dump that in /boot, and reboot (I think
> this is the way Ubuntu deals with dsdt updates, i.e. build it into the
> initrd automatically) and not have to worry about rebuilding a custom
> kernel.

There are several problems with that

1.	ACPI tables are software and provided by the vendor with licenses
that forbid modification, redistribution etc.
2.	For that matter if you live in the USSA then they probably disallow
disassembly
3.	Its not something the average user can do

> So what do I tell my helpless user? 
> 1. Start hacking kernel acpi internals, sending patches to lkml that
> have kludges for specific laptop models.
> 2. Rebuild their kernel with the updated dsdt.
> 3. Email your laptop vendor to release a new bios for a 5 year old
> laptop. I'm pretty certain this will be ignored as it "works in
> windows".

If the DSDT bug is known then it becomes practical to look at the problem
and make the Linux code bug compatible with Windows - and a fair bit of that
has occurred, or to blacklist the ACPI support using the dmi table.

That much becomes workable for users because it then just works out of the box.

The other approach in the US is probably the "you said it supports ACPI but
it's invalid class action lawsuit" approach. But I doubt that really fixes
anything but the lawyers swimming pool.

Alan




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