Scroll lock doesn't toggle keyboard backlights after upgrade

fgallois · 2024-06-17 00:57:07

Hello, everyone

I have an issue where my keyboard backlights aren't turning on when I press the Scroll Lock key, even though it used to behave like that since some weeks ago.

I have done some tests with xev that prove that the key events are being picked up:

KeyPress event, serial 38, synthetic NO, window 0x600001,
    root 0x374, subw 0x600002, time 23858337, (36,37), root:(86,156),
    state 0x10, keycode 78 (keysym 0xff14, Scroll_Lock), same_screen YES,
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyRelease event, serial 38, synthetic NO, window 0x600001,
    root 0x374, subw 0x600002, time 23858409, (36,37), root:(86,156),
    state 0x10, keycode 78 (keysym 0xff14, Scroll_Lock), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

I've also figured out that I can manually turn the backlights on by using the following command, which I got from here:

sudo bash -c "echo 1 > /sys/class/leds/input3::scrolllock/brightness"

Some recent upgrade must have caused the issue, but I haven't figured out how to pinpoint where it is coming from.

My keyboard is a Cooler Master Devastator II.

seth · 2024-06-17 05:57:00

If the keys are printed in xev that means they're not bound to any global shortcut.
You could add one to toggle the brightness and bind it to the scroll-lock key.

As for what could have changed:
- Fn lock
- Dual boot condition (is there a parallel windows?)
- Kernel "regression" (while an ancient relic, the scroll-lock actually does something in the userspace that might conflict with the desire to just abuse it to toggle the scroll-lock LED)
- the "3" there (bb. that the input number is subject to change when the keyboard re-attaches, you want to glob it if you're adding a shortcut)
- Did you change the display server (x11/wayland)?

fgallois · 2024-06-17 19:06:11

Hi! Sorry for the delay.

About your suggestions:

As for what could have changed:
- Fn lock

My keyboard doesn't have a Fn key.

- Dual boot condition (is there a parallel windows?)

I'm not dual-booting either.

- Did you change the display server (x11/wayland)?

No, I have been using Wayland since installation. I tried changing my session type to X11 and setting

xmodmap -e 'add mod3 = Scroll_Lock'

, which actually made scroll-lock work as expected, but I really wanted a solution that worked with Wayland.

Also, I have tried binding the scroll-lock key as in this post, but I didn't succeed. Instead, it just messed with my keyboard layout.

seth · 2024-06-17 19:23:38

xev under wayland isn't all that authorative - also "wayland" isn't really a thing, which compositor specifically?
Also, are you using multiple layouts and "grp_led:scroll" ?

fgallois · 2024-06-17 20:11:26

My compositor is Mutter.
I am using both br and us layouts, with grp_led:scroll.

seth · 2024-06-17 20:20:48

I am using both br and us layouts, with grp_led:scroll.

In case the cold guess wasn't indicative enough: what if you don't?

fahim.chuchu · 2026-07-10 15:56:32

Use Scroll Lock to turn on/off Keyboard Backlight

Finally, I have got the exact solution after suffering and trying many methods for 2 years. This method works on XFCE system without any problem. For other DEs, try and see if it works.

Install numlockx:
Ubuntu / Debian / Mint:

sudo apt install numlockx

Fedora / RHEL:

sudo dnf install numlockx

Arch / Manjaro:

sudo pacman -S numlockx

Paste the script:

cd /usr/local/bin/

sudo nano toggle_led.sh

#!/bin/bash
if xset q | grep -q "Scroll Lock: off"; then
    xset led named "Scroll Lock"
    numlockx on
else
    xset -led named "Scroll Lock"
    numlockx on
fi

Bind Keyboard Shortcut:
- Goto Keyboard
- Add
```
/usr/local/bin/toggle_led.sh
```
- Press Scroll Lock
- Keep the Startup Notification turned off.
Log out & Relogin your session.

Now, pressing the Scroll Lock will turn on/off the keyboard light.

Extra Note: numlockx is required to keep the numpad working after executing

xset led

command. If you don't have numpad in your keyboard, you can skip the Step-1 and also remove the

numlockx on

lines from the script.

ewaller · 2026-07-10 17:59:48

Using this opportunity to close this old thread

Arch Linux

#1 2024-06-17 00:57:07

Scroll lock doesn't toggle keyboard backlights after upgrade

#2 2024-06-17 05:57:00

Re: Scroll lock doesn't toggle keyboard backlights after upgrade

#3 2024-06-17 19:06:11

Re: Scroll lock doesn't toggle keyboard backlights after upgrade

#4 2024-06-17 19:23:38

Re: Scroll lock doesn't toggle keyboard backlights after upgrade

#5 2024-06-17 20:11:26

Re: Scroll lock doesn't toggle keyboard backlights after upgrade

#6 2024-06-17 20:20:48

Re: Scroll lock doesn't toggle keyboard backlights after upgrade

#7 2026-07-10 15:56:32

Re: Scroll lock doesn't toggle keyboard backlights after upgrade

Use Scroll Lock to turn on/off Keyboard Backlight

#8 2026-07-10 17:59:48

Re: Scroll lock doesn't toggle keyboard backlights after upgrade

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