Getting a backlight to work on a lenovo oled laptop

screen_brightness_hack.sh

#! /usr/bin/env bash
##
# A little hack that forces the brightness up and down on a specific `backlight`
# device - this is largely redundant but helps when you have a lenovo laptop 
# with an OLED and both an iGPU and a discrete GPU.
#
# This can be used in conjunction with keyboard shortcuts by creating a new 
# file and assigning the shortcut to it.
#
# Example 'up' bind your shortcut to:
# /bin/bash -c  "/home/scripts/bin/screen_brightness_up.sh up"

# Example 'down' bind your shortcut to:
# /bin/bash -c  "/home/scripts/bin/screen_brightness_up.sh down"
#
# refs: https://wiki.archlinux.org/title/Backlight
##

# The device to force the brightness to
export BRIGHTNESS_DEVICE_NAME="intel_backlight" 
# A temporary file to hold the brightness value to retain between rebuilds
export BRIGHTNESS_HACK_FILE="/tmp/.tmp.brightness_hack"

# Minvalue if you wanna play with it
export BRIGHTNESS_HACK_MIN=0
# Max value - this varies between screens, you can just override it
export BRIGHTNESS_HACK_MAX=`cat /sys/class/backlight/${BRIGHTNESS_DEVICE_NAME}/max_brightness`

# number of divisions
BRIGHTNESS_HACK_STEPS=10

# set the incrementor
export BRIGHTNESS_HACK_INC=$(( ($BRIGHTNESS_HACK_MAX - $BRIGHTNESS_HACK_MIN) / $BRIGHTNESS_HACK_STEPS ))

# if there's no tmp file, just make it now and at 50%
if [ ! -f "$BRIGHTNESS_HACK_FILE" ]; then
  echo $(( $BRIGHTNESS_HACK_MAX / 2 )) > $BRIGHTNESS_HACK_FILE
fi

#### Functions

# Turn up the brightness by adding the increment to the current value
brightness_hack_up() {
  BRIGHTNESS_HACK_VALUE=$(($BRIGHTNESS_HACK_VALUE + $BRIGHTNESS_HACK_INC))
  brightness_hack_check
  brightness_hack_write
}

# Turn down the brightness by subtracting the increment to the current value
brightness_hack_down() {
  BRIGHTNESS_HACK_VALUE=$(($BRIGHTNESS_HACK_VALUE - $BRIGHTNESS_HACK_INC))
  brightness_hack_check
  brightness_hack_write
}

# Check for overflowed values
brightness_hack_check() {
  if (( $BRIGHTNESS_HACK_VALUE > $BRIGHTNESS_HACK_MAX )); then
    BRIGHTNESS_HACK_VALUE=$BRIGHTNESS_HACK_MAX;
  fi

  if (( $BRIGHTNESS_HACK_VALUE < $BRIGHTNESS_HACK_MIN )); then
    BRIGHTNESS_HACK_VALUE=$BRIGHTNESS_HACK_MIN;
  fi
}

# Reads the last brightness value from the tmp file
brightness_hack_read() {
  export BRIGHTNESS_HACK_VALUE=`cat ${BRIGHTNESS_HACK_FILE}`
}

# Writes the last brightness value to the tmp file and forces the device to update
brightness_hack_write() {
  echo "setting brightness to ${BRIGHTNESS_HACK_VALUE}"
  echo $BRIGHTNESS_HACK_VALUE > ${BRIGHTNESS_HACK_FILE}
  sudo /bin/bash -c "echo $BRIGHTNESS_HACK_VALUE > /sys/class/backlight/${BRIGHTNESS_DEVICE_NAME}/brightness"
}

# Read the file
brightness_hack_read

# see if there's input
if [[ "${1}" == "up" ]]; then
  brightness_hack_up
fi

if [[ "${1}" == "down" ]]; then
  brightness_hack_down
fi

# Write the file and Var
if [[ -z "${1}" ]]; then
  brightness_hack_write
fi