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

[Hans de Goede <hdegoede@redhat.com>]

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.

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 ...

Regards,

Hans




*) While working on fixing something which needed a DSDT override IIRC