Re: [PATCH] ACPI / button: Add DMI quirk for Acer Switch 10 SW5-032 lid-switch

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Tue, Nov 19, 2019 at 04:38:52PM +0100, Hans de Goede wrote:
> Hi,
> 
> On 19-11-2019 13:57, Mika Westerberg wrote:
> > 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.
> 
> I would love to have something like this, but I'm afraid that the distros
> cannot just distribute modified DSDT's. I know we ask people to upload
> acpidump's to bugzilla, etc. all the time. But one can reasonably argue
> that that is fair-use (IANAL, TINLA). OTOH for something to be distributed
> by distros we are going to need something a lot less handwavy wrt
> re-dsitribution of these files, which AFAIK is impossible to get.

Good point.

> I had a discussion about this a while ago at my local hackerspace (*),
> and someone there suggested to distribute patch files and have some
> scripts which automatically generate an overlay by doing acpidump +
> acpixtract + iasl -d + apply-patch + iasl -ta. This would then automatically
> run at boot so that the next boot will have a fixed DSDT. Which is an
> interesting concept if anyone is willing to work on it ...

Indeed interesting idea. Not volunteering to work on it though ;-)