oled-brightness.sh

#!/bin/bash
# Smooth brightness control

readonly PROGNAME="$(basename "$0")"
readonly PROGDIR="$(readlink -m "$(dirname "$0")")"
readonly ARGS="$@"



function main {
  export  DISPLAY=$(who | grep ':' |  awk '{print $2}')
  local USER=$(who | grep ':' |  awk '{print $1}')
  local USER_ID=$(id -u lriutzel)

  if [ -f run/user/$USER_ID/gdm/Xauthority ]; then
    export XAUTHORITY=/run/user/$USER_ID/gdm/Xauthority
  else
    export XAUTHORITY=/home/$USER/.Xauthority
  fi
  
  
  
  OLED_BR=`xrandr --verbose | grep -i brightness | cut -f2 -d ' '`
  CURR=`LC_ALL=C /usr/bin/printf "%.*f" 1 $OLED_BR`
  
  MIN=0
  MAX=1.2
  
  if [ "$1" == "up" ]; then
      VAL=`echo "scale=1; $CURR+0.1" | bc`
  else
      VAL=`echo "scale=1; $CURR-0.1" | bc`
  fi
  
  if (( `echo "$VAL < $MIN" | bc -l` )); then
      VAL=$MIN
  elif (( `echo "$VAL > $MAX" | bc -l` )); then
      VAL=$MAX
  else
      if [ "$1" == "up" ]; then
          for I in {1..10..1}; do xrandr --output eDP1 --brightness `echo "scale=2; $I/100+$CURR" | bc` 2>&1 >/dev/null | logger -t oled-brightness; done
      else
          for I in {1..10..1}; do xrandr --output eDP1 --brightness `echo "scale=2; $CURR-$I/100" | bc` 2>&1 >/dev/null | logger -t oled-brightness; done
      fi
  fi
  
  # Set Intel backlight to fake value
  # to sync OSD brightness indicator to actual brightness
  INTEL_PANEL="/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight"
  if [ -d "$INTEL_PANEL" ]; then
      PERCENT=`echo "scale=4; $VAL/$MAX" | bc -l`
      INTEL_MAX=$(cat "$INTEL_PANEL/max_brightness")
      INTEL_BRIGHTNESS=`echo "scale=4; $PERCENT*$INTEL_MAX" | bc -l`
      INTEL_BRIGHTNESS=`LC_ALL=C /usr/bin/printf "%.*f" 0 $INTEL_BRIGHTNESS`
      echo $INTEL_BRIGHTNESS > "$INTEL_PANEL/brightness"
  fi
}

main $ARGS

unfortunately, Xrandr is no longer supported on Chromium OS. are there any alternatives?