#!/bin/sh

readonly SAVEFILE_PREFIX

do_stop() {
	local label=$1 knob=$2 max=$3 file=$SAVEFILE_PREFIX${1:+.$1}
	test -e "$knob" || return 0

	# If the backlight is off, don't save to avoid blank display after
	# reboot. See Devuan #617.
	test "$(cat $knob)" -eq 0 && return 0

	cat "$knob" >"$file"

	return $?
}

rv=0

# ACPI (without explicit label)
do_stop '' \
    /sys/class/backlight/acpi_video0/brightness \
    /sys/class/backlight/acpi_video0/max_brightness
rc=$?
test $rc -lt $rv || rv=$rc

# Intel
do_stop intel \
    /sys/class/backlight/intel_backlight/brightness \
    /sys/class/backlight/intel_backlight/max_brightness
rc=$?
test $rc -lt $rv || rv=$rc

# could insert others using the same scheme here
return $rv
