#!/bin/sh
# Backlight control.
#
# keylaunch binds "Held XF86PowerDown" to `bl toggle`, but no `bl` exists in
# this rootfs -- it came from the familiar/iPAQ tools, not from GPE or
# Debian, and is not in Psion's tree either. The binding was therefore dead.
#
# The interface is not guesswork: minilite, the frontlight applet already
# installed here, drives the backlight through
#   /sys/class/backlight/<dev>/brightness   (and .../max_brightness)
#   /sys/class/lcd/<dev>/power
#   /proc/driver/backlight
# so this uses the same paths, preferring sysfs and falling back to procfs.
#
# ipaq-sleep drives this directly -- it runs "/usr/bin/bl <n>" to dim and
# "/usr/bin/bl off" to blank, using dim_level from /etc/ipaq-sleep.conf,
# which Psion ship set to 2. familiar's bl took a small device level rather
# than a percentage, so a bare number of 10 or less is treated as a level on
# a 0-10 scale and anything larger as a percentage.
#
# Usage: bl [toggle|on|off|up|down|<level 0-10 | percent 11-100>]

DEV=$(ls /sys/class/backlight 2>/dev/null | head -1)
LCD=$(ls /sys/class/lcd 2>/dev/null | head -1)

sys_max() { cat "/sys/class/backlight/$DEV/max_brightness" 2>/dev/null || echo 255; }
sys_get() { cat "/sys/class/backlight/$DEV/brightness" 2>/dev/null || echo 0; }
sys_set() { echo "$1" > "/sys/class/backlight/$DEV/brightness" 2>/dev/null; }

if [ -n "$DEV" ]; then
  MAX=$(sys_max); CUR=$(sys_get)
  case "${1:-toggle}" in
    toggle) if [ "$CUR" -gt 0 ]; then
              echo "$CUR" > /var/run/bl.last 2>/dev/null; sys_set 0
            else
              sys_set "$(cat /var/run/bl.last 2>/dev/null || echo "$MAX")"
            fi ;;
    on)     sys_set "$MAX" ;;
    off)    echo "$CUR" > /var/run/bl.last 2>/dev/null; sys_set 0 ;;
    up)     v=$((CUR + MAX/8)); [ "$v" -gt "$MAX" ] && v=$MAX; sys_set "$v" ;;
    down)   v=$((CUR - MAX/8)); [ "$v" -lt 0 ] && v=0; sys_set "$v" ;;
    ''|*[!0-9]*) echo "usage: bl [toggle|on|off|up|down|0-100]" >&2; exit 1 ;;
    *)      if [ "$1" -le 10 ]; then sys_set $(( $1 * MAX / 10 ))
            else sys_set $(( $1 * MAX / 100 )); fi ;;
  esac
  [ -n "$LCD" ] && [ "$(sys_get)" -gt 0 ] && echo 0 > "/sys/class/lcd/$LCD/power" 2>/dev/null
  exit 0
fi

# no sysfs backlight: fall back to the older procfs node minilite also knows
if [ -w /proc/driver/backlight ]; then
  case "${1:-toggle}" in
    off)   echo 0   > /proc/driver/backlight ;;
    on)    echo 100 > /proc/driver/backlight ;;
    toggle) if [ "$(cat /proc/driver/backlight 2>/dev/null)" = "0" ]; then
              echo 100 > /proc/driver/backlight
            else
              echo 0 > /proc/driver/backlight
            fi ;;
    *)     if [ "$1" -le 10 ] 2>/dev/null; then echo $(( $1 * 10 )) > /proc/driver/backlight
           else echo "${1}" > /proc/driver/backlight; fi ;;
  esac
  exit 0
fi

echo "bl: no backlight control found" >&2
exit 1