Turn on or off the ThinkLight (or keyboard backlight) on various ThinkPad laptops

thinklight.go

package main

import (
	"flag"
	"log"
	"os"
)

func btoi(n bool) byte {
	if n {
		return 1
	} else {
		return 0
	}
}

func main() {
	const (
		off  byte = 0x03
		low  byte = 0x43
		high byte = 0x83
	)

	flag_off := flag.Bool("off", false, "turns off the keyboard backlight")
	flag_low := flag.Bool("low", false, "turns the keyboard backlight on low")
	flag_high := flag.Bool("high", false, "turns the keyboard backlight on high")
	flag.Parse()

	if !(*flag_off || *flag_low || *flag_high) {
		flag.Usage()
		os.Exit(1)
	} else if btoi(*flag_off)+btoi(*flag_low)+btoi(*flag_high) > 1 {
		log.Println("You must specify only one level.")
		flag.Usage()
		os.Exit(1)
	}

	f, err := os.OpenFile("/sys/kernel/debug/ec/ec0/io", os.O_RDWR, os.ModeDevice)
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	var level byte
	if *flag_off {
		level = off
	} else if *flag_low {
		level = low
	} else if *flag_high {
		level = high
	}

	_, err = f.WriteAt([]byte{level}, 0x0d)
	if err != nil {
		log.Fatal(err)
	}
}