/*
 * Apple Macbook Pro LCD backlight control
 *
 * Copyright (C) 2006 Nicolas Boichat <nicolas@boichat.ch>
 * Copyright (C) 2006 Felipe Alfaro Solana <felipe_alfaro@linuxmail.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

#include <stdio.h>
#include <sys/io.h>
#include <stdlib.h>

void init()
{
  if (ioperm(0xB2, 0xB3, 1) < 0)
    {
      perror("ioperm failed (you should be root).");
      exit(2);
    }
}

int get_current_value()
{
  outb(0x03, 0xB3);
  outb(0xBF, 0xB2);
  char t = inb(0xB3) >> 4;
  return t;
}

int calculate_new_value(const char *arg)
{
  int val, new = atoi(arg);

  if (arg[0] == '+' || arg[0] == '-')
    val = new + get_current_value();
  else
    val = new;

  if (val > 15)
    val = 15;
  else if (val < 1)
    val = 1;

  return val;
}

int main(int argc, char** argv)
{
  if (argc > 2)
    {
      printf("Usage:\n");
      printf("%s : read current value\n", argv[0]);
      printf("%s value : write value [0-15]\n", argv[0]);
      exit(1);
    }

  init();
  
  if (argc < 2)
    {
      printf("Current value : %d\n", get_current_value());
      exit(0);
    }

  if (argc == 2)
    {
      int value = calculate_new_value(argv[1]);
      outb(0x04 | (value << 4), 0xB3);
      outb(0xBF, 0xB2);
      printf("new value: %d\n", value);
    }

  return 0;
}