Backlight control script via sysfs and other hacky methods

poormans-backlight.py

#!/usr/bin/python

# This script can control a laptop's backlight via the sysfs interface /sys/class/backlight/intel_backlight
# (and others you add yourself ;)
#
# I use it on my Asus zenbook UX305LA since no other method or kernel parameters got the backlight control
# keys working. It probably works with any Intel HD graphics based graphics.
# 
# To use, put it somewhere on your disk and give yourself sudo rights for this single file. The sysfs
# interface is only writable by root. Bind any key combination of your window manager to it. Naturally 
# BrightnessDown and Up, if the key produces a keycode on your laptop. Doesn't on the UX305LA. As of kernel
# 4.10 it does! So no more use for this hacky method.
#
# decreases brghtness by 10%
# 
# sudo poormans-backlight.py -t intel -d 10
# 
# increases brightness by 10%
#
# sudo poormans-backlight.py -t intel -i 10
# 
# License
# 
# This code is public domain. No copyright whatsoever, no warranty.

from __future__ import division
from __future__ import print_function
import argparse
import os

class GenericIntel:
	sysfs_path = '/sys/class/backlight/intel_backlight'

	def get_max_brightness(self):
		f = open(os.path.join(self.sysfs_path, 'max_brightness'), 'r')
		max_brightness = int(f.readline().rstrip())
		return max_brightness

	def get_brightness(self):
		f = open(os.path.join(self.sysfs_path, 'brightness'), 'r')
		brightness = int(f.readline().rstrip())
		return brightness

	def set_brightness(self, value):
		f = open(os.path.join(self.sysfs_path, 'brightness'), 'w')
		print(value, file=f)


parser = argparse.ArgumentParser(description='Poor man\'s backlight control.')
parser.add_argument('-i', '--increase', help='Increase by percentage.', type=int)
parser.add_argument('-d', '--decrease', help='Decrease by percentage.', type=int)
parser.add_argument('-t', '--type', help='Hardware type.')
args = parser.parse_args()

if args.increase != None and args.decrease != None:
	print("boom!")
	exit(-1)

if args.type == 'intel':
	backlight = GenericIntel()
else:
	print("Unknown backlight type.")
	exit(-1)

if args.increase == None:
	# Decrease backlight
	max_brightness = backlight.get_max_brightness()
	pct = args.decrease / 100
	delta = int(max_brightness * pct)
	brightness = backlight.get_brightness()
	new_brightness = brightness - delta
	if new_brightness < 0:
		new_brightness = 0
	print(new_brightness)
	backlight.set_brightness(new_brightness)
else:
	# Increase backlight
	max_brightness = backlight.get_max_brightness()
	pct = args.increase / 100
	delta = int(max_brightness * pct)
	brightness = backlight.get_brightness()
	new_brightness = brightness + delta
	if new_brightness > max_brightness:
		new_brightness = max_brightness
	print(new_brightness)
	backlight.set_brightness(new_brightness)