Thinkpad keyboard light - solved (ex. thinkpad T14 Gen 2)

[siladi]

Attaching a patch to get keyboard backlight working on new-ish(?) thinkpads , such as Thinkpad T14 Gen2. Probably works on other newer thinkpad models.

Patch is based on https://reviews.freebsd.org/D14103 which seems to be in limbo since 2019. The keyboard stuff backported and tested on FreeBSD 15.1RC1.

Quick usage instructions:
In /usr/src/sys/dev/acpi_support patch acpi_ibm.c
In /usr/src/sys/modules/acpi/acpi_ibm build and install
Unload acpi_ibm and load the new one from /boot/modules (kldload /boot/modules/acpi_ibm.ko)

sysctl dev.acpi_ibm.0.kbd_backlight=1

Now you can type with confidense.

 

[greyunix]

Attaching a patch to get keyboard backlight working on new-ish(?) thinkpads , such as Thinkpad T14 Gen2. Probably works on other newer thinkpad models.

Patch is based on https://reviews.freebsd.org/D14103 which seems to be in limbo since 2019. The keyboard stuff backported and tested on FreeBSD 15.1RC1.

Quick usage instructions:
In /usr/src/sys/dev/acpi_support patch acpi_ibm.c
In /usr/src/sys/modules/acpi/acpi_ibm build and install
Unload acpi_ibm and load the new one from /boot/modules (kldload /boot/modules/acpi_ibm.ko)

sysctl dev.acpi_ibm.0.kbd_backlight=1

Now you can type with confidense.

Hi ,

I feel a little silly asking this as you have added usage instructions, but can you explain how I use this patch ? I see your patch attachment , where should I place this file ?

 

[siladi]

You place it at the location of the file you want to patch (ex. /usr/src/sys/dev/acpi_support) , inside your kernel source tree . If you do not have the src tree already, you checkout the src with git. You use the patch command (man patch) to apply it , then after it applies cleanly, you efectively build the module (.ko file) by using the Makefile at the corresponding location (ex. /usr/src/sys/modules/acpi/acpi_ibm) . This new patched module (/boot/module) that has the new functionality should be the one loaded on boot , to superseed the already existing one (/boot/kernel/).
The FreeBSD handbook has more detailed information for managing and tracking the source tree and loads more.

 

[T-Daemon]

If you do not have the src tree already, you checkout the src with git. You use the patch command (man patch) to apply it ,

If using git to checkout the src tree, why not use git-apply(1) instead of patch(1) to apply the patch?

then after it applies cleanly,

Hmm ...

# cd /usr/src

# git status
On branch releng/15.1
Your branch is up to date with 'origin/releng/15.1'.

nothing to commit, working tree clean

# git  apply  /tmp/fbsd15.1rc1-acpi_ibm.patch
/tmp/fbsd15.1rc1-acpi_ibm.patch:10: trailing whitespace.
 * Copyright (c) 2018 Michael Gmelin <grembo@FreeBSD.org>
/tmp/fbsd15.1rc1-acpi_ibm.patch:31: trailing whitespace.
 
/tmp/fbsd15.1rc1-acpi_ibm.patch:97: trailing whitespace.
 
warning: 3 lines add whitespace errors.

 

[SirDice]

trailing whitespace

My linter nemesis, I always have a tonne of these.

 

[greyunix]

Followed all the instructions, thanks everyone. Unfortunately I couldn't get it to work. After sysctl dev.acpi_ibm.0.kbd_backlight=1 I get

sysctl: unknown oid 'dev.acpi_ibm.0.kbd_backlight'

I tried the git apply method and the patch method, kldstat shows the module is loaded, but no luck.

 

[siladi]

You need to unload the old driver and load the new one. The patched driver exposes that oid. You do have a thinkpad T14 gen2 yes?

kldunload acpi_ibm
kldload /boot/modules/acpi_ibm.ko
sysctl dev.acpi_ibm.0.kbd_backlight=1

 

[greyunix]

You need to unload the old driver and load the new one. The patched driver exposes that oid. You do have a thinkpad T14 gen2 yes?

kldunload acpi_ibm
kldload /boot/modules/acpi_ibm.ko
sysctl dev.acpi_ibm.0.kbd_backlight=1

Embarrassingly, I'm starting to think I don't have a T14s. Its a second hand laptop and after digging in to it, I think I have a T490s in a T14s case. The CPU is a i5-8265u. I think the earliest T14s has a 10 series CPU. Don't get me wrong the laptop was cheap , works well and was bought exclusively for FreeBSD, so I not disappointed, but it has caused a simple issue like this not working.