I recently bought a Jedel K510 gaming keyboard and found that keyboard LEDs are not working on my Arch Linux laptop. By default extra LEDS are disabled on most of linux distributions for power saving purposes. However I enabled it and found that LED toggle button is also not working. But finally I managed to make all things work.
Linux is allowing users to control all hardware items by a virtual
file system called sys. You can find out whats in the sys directory
by running ls /sys command. As per the official linux
doc LED
controllers are in the /sys/class/leds and we can control LEDs by
running following commands.
# Turn on LEDS on a specific device
$ echo 1 > /sys/class/leds/<led-name>/brightness
# Turn off LEDS on s specific device
$ echo 0 > /sys/class/leds/<led-name>/brightness
But there are multiple LED names in the /sys/class/leds/
directory and we need to find the exact LED name for our device.
To find out the LED name, first we should know the device id. To find
the device id we can use our friendly lsusb command.
$ lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 005: ID 0bda:b00a Realtek Semiconductor Corp. Realtek Bluetooth 4.2 Adapter
Bus 001 Device 004: ID 04f2:b626 Chicony Electronics Co., Ltd HP TrueVision HD Camera
Bus 001 Device 003: ID 2a7a:9587 CASUE USB KB
Bus 001 Device 002: ID 1bcf:08a0 Sunplus Innovation Technology Inc. Gaming mouse [Philips SPK9304]
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
In this example my device id is 2a7a:9587 which vendor id is 2a7a
and the product id is 9587.
Now we can find the LED name by running following command in your bash/sh terminal.
$ for led in $(ls -1 /sys/class/leds/); do echo "LED Name:- $led Device Id:- $(cat /sys/class/leds/$led/device/id/vendor):$(cat /sys/class/leds/$led/device/id/product)"; done | grep 2a7a:9587
Replace 2a7a:9587 with your device id. Now you can see an output like
below.
LED Name:- input8::capslock Device Id:- 2a7a:9587
LED Name:- input8::compose Device Id:- 2a7a:9587
LED Name:- input8::kana Device Id:- 2a7a:9587
LED Name:- input8::numlock Device Id:- 2a7a:9587
LED Name:- input8::scrolllock Device Id:- 2a7a:9587
I know in Jedel K510 keyboard, all LEDs mapped to Scroll Lock button. Because it mentioned in the keyboard casing. If you are trying with another keyboard, Run bellow command for each LED names and check which LED name is making your LEDs turn on.
$ su # Logging as root user
$ echo 1 > /sys/class/leds/<led-name>/brightness
For some keyboards this LED name is permanent and not for some keyboards. You can run below command after re-plug your keyboard to check the weather the LED name changed.
$ for led in $(ls -1 /sys/class/leds/); do echo "LED Name:- $led Device Id:- $(cat /sys/class/leds/$led/device/id/vendor):$(cat /sys/class/leds/$led/device/id/product)"; done | grep 2a7a:9587
I made a simple script to toggle keyboard backlight when we pass
vendor id and product id obtained by lsusb command. Change VENDOR,
PRODUCT variables with your vendor id and product id. And also change
BUTTON with your LED name suffix.
# ~/.local/bin/kbb.sh
#!/usr/bin/bash
VENDOR=2a7a
PRODUCT=9587
BUTTON="scrolllock"
MODE=$1
for led in $(ls -1 /sys/class/leds/)
do
productId=$(cat /sys/class/leds/$led/device/id/product)
vendorId=$(cat /sys/class/leds/$led/device/id/vendor)
if [ "$VENDOR:$PRODUCT" = "$vendorId:$productId" -a "${led##*::}" = "$BUTTON" ]
then
if [ "$#" -ne 1 ]; then
if [ "0" = $(cat /sys/class/leds/$led/brightness) ]; then
MODE="1"
else
MODE="0"
fi
fi
echo "MODE" > /sys/class/leds/$led/brightness
fi
done
I made this script for keyboards with dynamic LED names. If your LED
name is a constant, remove additional for loops and make it simple
like below. Replace LEDNAME variable with the name of the LED.
# ~/.local/bin/kbb.sh
#!/usr/bin/bash
MODE=$1
LEDNAME="asuskb_backlight"
if [ "$#" -ne 1 ]; then
if [ "0" = $(cat /sys/class/leds/$LEDNAME/brightness) ]; then
MODE="1"
else
MODE="0"
fi
fi
echo "MODE" > /sys/class/leds/$LEDNAME/brightness
Now you can run the script like bellow.
# Giving executable permissions to file
$ chmod +x ~/.local/bin/kbb.sh
# Turn on LEDs
$ sudo ~/.local/bin/kbb.sh 1
# Turn off LEDs
$ sudo ~/.local/bin/kbb.sh 0
# Toggle LEDs
$ sudo ~/.local/bin/kbb.sh
By default non-root users do not have permission to edit the /sys/class
files. So we have to use sudo when running the command in terminal and
the sudo will ask for the password. But in auto-scripts, we do not have
a tty to interact with commands. So we have to avoid the interactions
when using sudo command. We can achieve this by adding a rule to
sudoers file.
Another issue is we can not redirect echo output to a file when using
sudo command. So we have to use tee command with sudo to write
output to /sys files.
# /etc/sudoers
# ...
ALL ALL = (ALL) NOPASSWD: /usr/bin/tee /sys/class/leds/*/brightness
After adding the above rule sudo command will not asking for a
password anymore when controlling LEDs.
Now we have to change our script to use tee instead echo.
$ ~/.local/bin/kbb.sh
# Change this
echo "MODE" > /sys/class/leds/$led/brightness
# to
echo "$MODE" | sudo /usr/bin/tee "/sys/class/leds/$device/brightness"
Now check our change by running the script without sudo
$ ~/.local/bin/kbb.sh
You can see your keyboard LEDs toggled. Next add the command to your
.profile file to run on startup
# ~/.profile
/home/ramesh/.local/bin/kbb.sh
To bind the scroll lock key to our script, we have to know the key id of the Scroll Lock key. First run below command and find the master id of your keyboard.
$ xinput list
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ HID 1bcf:08a0 Mouse id=8 [slave pointer (2)]
⎜ ↳ HID 1bcf:08a0 Keyboard id=9 [slave pointer (2)]
⎜ ↳ SynPS/2 Synaptics TouchPad id=16 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
↳ Power Button id=6 [slave keyboard (3)]
↳ Video Bus id=7 [slave keyboard (3)]
↳ HID 1bcf:08a0 id=10 [slave keyboard (3)]
↳ CASUE USB KB id=11 [slave keyboard (3)]
↳ CASUE USB KB System Control id=12 [slave keyboard (3)]
↳ CASUE USB KB Consumer Control id=13 [slave keyboard (3)]
↳ HP TrueVision HD Camera: HP Tru id=14 [slave keyboard (3)]
↳ AT Translated Set 2 keyboard id=15 [slave keyboard (3)]
↳ Wireless hotkeys id=17 [slave keyboard (3)]
↳ HP WMI hotkeys id=18 [slave keyboard (3)]
↳ HID 1bcf:08a0 Keyboard id=19 [slave keyboard (3)]
In this example, the master id of my keyboard is 11. Then run the below
command and press Scroll Lock key while running it. Replace 11 with
your master id.
$ xinput test 11
key release 36
key press 78
key release 78
key press 78
key release 78
key press 78
key release 78
key press 37
key press 54
^C
In this example the key id is 78 and it is the common key id of the
scroll key for every keyboard.
Now bind our script to the Scroll Key by editing i3 configuration file.
# ~/.config/i3/config
# Keyboard backlight
bindcode 78 exec --no-startup-id /home/ramesh/.local/bin/kbb.sh
Now reload the i3 configurations by pressing Cmd+Shift+R.
Check it by pressing the Scroll Lock key. Your keyboard backlight will be toggled.