[Bug 2081037] Re: LG Gram screen brightness hot keys and battery charge limit regression

I just upgraded to Ubuntu 24.10, and this issue seems to be fixed. It's
unfortunate that the bug affects the LTS release, but whatever the
underlying cause was, it seems to be solved going forwards.

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https://bugs.launchpad.net/bugs/2081037

Title:
LG Gram screen brightness hot keys and battery charge limit regression

Status in linux package in Ubuntu:
New

Bug description:
I'm running Xubuntu 24.04 with all packages up to date on an LG Gram
14ZD90Q. It's been upgraded in place since 23.04. When I first
installed it, Xubuntu supported the Fn+F2/Fn+F3 screen brightness hot
keys out of the box. They stopped working a couple of weeks ago. It's
hard to pin down an exact cause, but I did install a kernel update
around the same time. Some other Fn+FX hot keys still work (volume
controls and keyboard backlighting). The remaining Fn+FX hot keys
don't work, but I'm not sure whether that's a regression since I
wasn't using them before noticing this bug.

In addition, the battery charge limit threshold is no longer working.
Per the "Battery care limit" instructions at
https://docs.kernel.org/admin-guide/laptops/lg-laptop.html I had set
the charge limit to 80%. Now it no longer has any effect.

```sh
root@gram:~# cat /sys/class/power_supply/CMB0/charge_control_end_threshold
0
root@gram:~# echo 80 > /sys/class/power_supply/CMB0/charge_control_end_threshold
root@gram:~# cat /sys/class/power_supply/CMB0/charge_control_end_threshold
0
root@gram:~# echo 100 > /sys/class/power_supply/CMB0/charge_control_end_threshold
root@gram:~# cat /sys/class/power_supply/CMB0/charge_control_end_threshold
0
root@gram:~# echo 50 > /sys/class/power_supply/CMB0/charge_control_end_threshold
bash: echo: write error: Invalid argument
```

Both of the supported values 80 and 100 are accepted, but don't take
effect. An invalid value throws an error as previously.

This may be related to upstream bug https://bugzilla.kernel.org/show_bug.cgi?id=204913.
---
ProblemType: Bug
ApportVersion: 2.28.1-0ubuntu3.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/seq: pete 1564 F.... pipewire
/dev/snd/controlC0: pete 1564 F.... pipewire
pete 1566 F.... wireplumber
CRDA: N/A
CasperMD5CheckResult: pass
CurrentDesktop: XFCE
DistroRelease: Ubuntu 24.04
InstallationDate: Installed on 2023-03-25 (545 days ago)
InstallationMedia: Xubuntu 22.10 "Kinetic Kudu" - Release amd64 (20221018)
MachineType: LG Electronics 14ZD90Q-G.AX56A5
Package: linux (not installed)
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-6.8.0-45-generic root=UUID=e4fb412b-8244-40b5-90d3-b873747955a2 ro
ProcVersionSignature: Ubuntu 6.8.0-45.45-generic 6.8.12
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
linux-restricted-modules-6.8.0-45-generic N/A
linux-backports-modules-6.8.0-45-generic N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.3
Tags: noble
Uname: Linux 6.8.0-45-generic x86_64
UnreportableReason: This report is about a package that is not installed.
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip docker kvm libvirt lpadmin lxd plugdev sambashare sudo
_MarkForUpload: False
dmi.bios.date: 08/23/2022
dmi.bios.release: 0.1
dmi.bios.vendor: Phoenix Technologies Ltd.
dmi.bios.version: A1ZG0400 X64
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: 14Z90Q
dmi.board.vendor: LG Electronics
dmi.board.version: FAB1
dmi.chassis.asset.tag: Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LG Electronics
dmi.chassis.version: 0.1
dmi.ec.firmware.release: 33.0
dmi.modalias: dmi:bvnPhoenixTechnologiesLtd.:bvrA1ZG0400X64:bd08/23/2022:br0.1:efr33.0:svnLGElectronics:pn14ZD90Q-G.AX56A5:pvr0.1:rvnLGElectronics:rn14Z90Q:rvrFAB1:cvnLGElectronics:ct10:cvr0.1:sku:
dmi.product.family: LG gram PC
dmi.product.name: 14ZD90Q-G.AX56A5
dmi.product.version: 0.1
dmi.sys.vendor: LG Electronics

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