On Tue, Nov 19, 2019 at 02:44:11PM +0200, Andy Shevchenko wrote:
> On Tue, Nov 19, 2019 at 12:12:35PM +0100, Hans de Goede wrote:
> > On 19-11-2019 09:26, Mika Westerberg wrote:
> > > On Mon, Nov 18, 2019 at 04:35:56PM +0100, Hans de Goede wrote:
>
> > Working around this is not impossible, but it will be quite ugly and given
> > the age of the machine IMHO not worth it. I've also found out that I need a
> > DSDT override to be able to control the LCD backlight, this is controlled by
> > the 1st PWM controller in the SoC LPSS block, which is normally enumerated
> > through ACPI but the entire Device (PWM1) {} block is missing from the
> > DSDT :| Adding it from similar hardware fixes things and makes the backlight
> > controllable. TL;DR: it seems that this is one of the rare cased where
> > people who want to run Linux will need to do a manual DSDT override :|
>
> If it's missing it's easy to inject entire block from EFI variable or using
> ConfigFS (see meta-acpi project [1] for details).
>
> > When they do that override they can also fix the _LID method and
> > then re-enable LID functionality on the kernel commandline overriding
> > this DMI quirk.
>
> Yes, if you override entire DSDT it can be fixed for many bugs at once.
>
> > I will probably do a blog post on this (some people have asked me
> > to do some blogposts about how to analyze DSDT-s, this will be a nice
> > example) and add a link to the DSDT override to the blogpost, I believe
> > that this is the best we can do for users of this device.
>
> Perhaps above mentioned project somehow can be extended to keep DSDT ASL code
> for overriding? Mika?
>
> [1]: https://github.com/westeri/meta-acpi/
No objections.
Maybe we should have a mechanism in the kernel that allows you to have
ACPI table quirks like this for multiple different systems (based on DMI
indentifiers perhaps) inside a single initrd and the kernel then loads
tables only matching the running system. That would allow distros to
ship these for broken systems.
