Fn Lock light does not come on to indicate when Fn Lock is enabled

[pauldoo]

I have a Lenovo E595 running Ubuntu 20.04. The "Fn Lock" feature on the keyboard works in terms of how it modifies subsequent presses of the F1-F12 keys, but the little light on the Esc key doesn't show the current state.

Example:
1. I press F5 a few times, and the screen brightness is adjusted.
2. I press Fn+Esc, and "Fn Lock" is now on, but the light hasn't changed.
3. I press F5 again, or several times, and it acts as a normal F5 (ie my browser might refresh the page).
4. I press Fn+Esc again, and "Fn Lock" is now off, but again the light hasn't changed.

So, "Fn Lock" works in the sense that it modifies what keypresses do, but the little light on the Esc key doesn't come on. Under Windows the light does toggle, to show the current status.

The behaviour is the same on Xorg and Wayland.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-generic 5.4.0.31.36
ProcVersionSignature: Ubuntu 5.4.0-31.35-generic 5.4.34
Uname: Linux 5.4.0-31-generic x86_64
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: paul 2138 F.... pulseaudio
 /dev/snd/controlC0: paul 2138 F.... pulseaudio
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Wed May 27 21:37:47 2020
InstallationDate: Installed on 2020-05-13 (14 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
MachineType: LENOVO 20NFCTO1WW
ProcFB: 0 EFI VGA
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.4.0-31-generic root=UUID=f7c34228-ee6f-4043-931c-f4752ad503c8 ro quiet splash nomodeset vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-5.4.0-31-generic N/A
 linux-backports-modules-5.4.0-31-generic N/A
 linux-firmware 1.187
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/30/2020
dmi.bios.vendor: LENOVO
dmi.bios.version: R11ET36W (1.16 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20NFCTO1WW
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.modalias: dmi:bvnLENOVO:bvrR11ET36W(1.16):bd03/30/2020:svnLENOVO:pn20NFCTO1WW:pvrThinkPadE595:rvnLENOVO:rn20NFCTO1WW:rvrNotDefined:cvnLENOVO:ct10:cvrNone:
dmi.product.family: ThinkPad E595
dmi.product.name: 20NFCTO1WW
dmi.product.sku: LENOVO_MT_20NF_BU_Think_FM_ThinkPad E595
dmi.product.version: ThinkPad E595
dmi.sys.vendor: LENOVO

[pauldoo (paul-richards)]

( I also posted this to Ask Ubuntu: https://askubuntu.com/questions/1243284/how-do-i-get-the-lenovo-fn-lock-light-to-work-under-ubuntu )

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.

[AaronMa (mapengyu)]

This led status is controlled by BIOS, not OS.

[pauldoo (paul-richards)]

Here is some more information that I collected.

I tried toggling fn-lock while at different stages of booting.

* In the grub menu, the light does not toggle.
* If I choose to boot windows, then while windows is booting, the light does not toggle. (ie, during the "swirling dots" screen.)
* Once windows gets to the login screen, the light does toggle. This implies the light only works once windows has loaded a driver or similar.
* If I instead choose to boot Ubuntu, then the light does not toggle. Not during boot, at the login screen, or after logged in.
* If I enter the BIOS setup, then the light does toggle there. If I exit and boot into Ubuntu then the light no longer toggles.

I strongly suspect there is at least some OS involvement with the fn-lock LED working.

[pauldoo (paul-richards)]

Kernel bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=207841

[pauldoo (paul-richards)]

A code fix has been identified, and I confirm that it works on my Lenovo E595 when I build my own kernel with the fix included. See the Kernel bugzilla for details: https://bugzilla.kernel.org/show_bug.cgi?id=207841

What are the next steps to getting this upstreamed and/or included in the Ubuntu 20.04 kernels?

[Esteve Varela Colominas (mid-kid)]

The relevant patch was upstreamed in the following kernel versions:
* 5.12-rc5
* 5.11.13
* 5.10.29
* 5.4.111
* 4.19.186
* 4.14.230

I recently got an email from an ubuntu user having this issue, and it's a shame to see that the patch hasn't been picked up by ubuntu yet, even in its new 21.04 release or its HWE kernels. Could it be added?
For reference, the patch in question is: https://lore.kernel<email address hidden>/

[pauldoo (paul-richards)]

My Ubuntu 20.04 which uses the HWE kernel has recently updated to the following kernel version:

$ uname -a
Linux len 5.8.0-55-generic #62~20.04.1-Ubuntu SMP Wed Jun 2 08:55:04 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

I can confirm that the Fn Lock LED is working properly now. It looks like the fix was merged into the Ubuntu kernel here:

https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/focal/commit/?h=hwe-5.8&id=0fc59e1aac5ebb0b10e0e242417fc45065259f2d

Thanks!