Help with implementing EC reading

[ldan93]

Hello,
This issue is not directly related to YogaSMC. I'm kindly asking for some advice, your help would be very appreciated.

With @nekr0z and @profzei, we are trying to implement a battery conservation feature (charging thresholds) on the Huawei Matebook X Pro : nekr0z/matebook-applet#26 . @nekr0z wrote an app that works on Catalina. It relies on ioio and ACPI_Debug.kext to call ACPI methods to set the thresholds, and to read the related EC fields.

Reading the thresholds is currently done by outputting EC values to system logs, and then we get them by parsing the result of the log stream --predicate 'senderImagePath contains "ACPIDebug"' command.
The problems are :

• Getting values this way doesn't sound very clean
• ACPI_Debug.kext seems to be partially broken on Big Sur : ACPI methods can still be called, but outputting text to system logs doesn't work anymore. So the app is broken on Big Sur since we can't read the current thresholds...

I see that YogaSMC implement EC field reading. We would like to have your insight on our issue : is there a simple and cleaner way than parsing the system logs to get the EC values ? What would you advise us to do ?

[zhen-zen]

I also used to dig variables using ACPIDebug and customized ACPI methods before I come up with this kext.

Try if #115 will attach to the HWMI interface. (Use the Alter one.)

[ldan93]

Thank you !
I've successfully built the mate-attach branch and I've loaded the Alter kext with kextload. But then, I'm not sure what I should do / be looking for about the HWMI interface you mentioned...

[zhen-zen]

You can get prebuilt binary at https://github.com/zhen-zen/YogaSMC/actions/runs/536369821 . Please check your ioreg if YogaVPC is attached. For usage, see https://github.com/zhen-zen/YogaSMC#ec-reading

[ldan93]

YogaVPC is not attached in my ioreg. But there are 2 mentions of YogaWMI.
Trying to read EC fields with ioio returns No service matching "YogaVPC"

[zhen-zen]

It seems that the driver couldn't match the interface by _UID. So I will just use AMW0 for now. The same name is also used by WMI reference code so it won't be merged into master in this way.

The driver also supports EC RW functionality through IOUserClient, which can be accessed directly from user-space and won't mess up with log format. Here is an example: 87074b4

[zhen-zen]

Please inject a fake device for YogaVPC to attach on unsupported models. Check the latest commit of linked PR for example.

[ldan93]

I've added SSDT-YVPC.dsl to my OpenCore. I don't understand what I'm supposed to do then to make the driver work on the matebook...

[zhen-zen]

Compile it first and add it to config.plist.

[zhen-zen]

Close it for now. I will continue working on #135 after receiving further response.