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frederik-h / acer-wmi-battery

A linux kernel driver for the Acer WMI battery health control interface
GNU General Public License v2.0
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Not working on Acer Extensa 2519 #54

Closed dusxmt closed 3 months ago

dusxmt commented 3 months ago

Hey there,

I just tried this kernel module, as I've replaced the battery on my laptop and want it to last longer than the previous one, and while this module does recognize the WMI battery interface, the battery status output buffer is 4 bytes on my machine instead of 8 bytes:

[ 163.603854] acer_wmi_battery: WMI battery status call returned a buffer of unexpected length 4

I got this laptop back in 2017, so it's possible that it has an earlier version of the battery health interface. I see that the 4 bytes at the end of the structure are function status bytes, with 0 being the health mode and 1 being the calibration mode. I only have 0 available, so perhaps that means that only health mode adjustment is available

Is it reasonable to think that it may be possible to get the module running with limited functionality, allowing it to configure just the health mode?

Thanks, Marek

dusxmt commented 3 months ago

Out of curiosity, I decided to dump what the WMI interface is returning for method 20:

ret.uFunctionList: 0x00, ret.uReturn[0,1] = { 0x00, 0x01 }, ret.uFunctionStatus[0] = 0x00

I tried to also call method 21 to set health mode, but it seems to not do anything, the data returned by method 20 are still the same, and the battery still charges to 100%. The method 21 runs successfully, but returns 0. I tried to change the input size from 8 bytes to 4, getting rid of the 4 trailing reserved bytes, but it didn't change anything.

I tried to see if I could extract some information about the interface from the DSDT, but unfortunately, there are no mentions of 79772EC5-04B1-4bfd-843C-61E7F77B6CC9 in the _WDG section or in the WDQQ BMF. I also tried the fwts tool, and it sees that the interface exists, but it doesn't have a BMF:

\_SB_.PCI0.WMID._WDG (4 of 11)
  GUID: 79772EC6-04B1-4BFD-843C-61E7F77B6CC9
  WMI Method:
    Flags          : 0x02 (Method)
    Object ID      : BF
    Instance       : 0x01
FAILED [LOW] WMIMissingMethod: Test 1, GUID 79772EC6-04B1-4BFD-843C-61E7F77B6CC9 should have an associated method WMBF defined, however this does not seem to exist.
PASSED: Test 1, 79772EC6-04B1-4BFD-843C-61E7F77B6CC9 has more than zero instances

So unfortunately, it seems that this earlier version of the Acer Battery WMI interface has a different input/output argument format, and my DSDT doesn't contain any information about it.

frederik-h commented 3 months ago

Thanks for sharing the results of your investigation!