// Set the brightness of the Griffin Powermate's LED.
// By Phil Endecott, 2008.
// I hereby place this code in the public domain.
// You can get the latest version of this code from
//   http://svn.chezphil.org/utils/trunk/gpsetled.c

// See also
//   http://sowerbutts.com/powermate/
// which I discovered after writing this.

#include <linux/input.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>


void usage()
{
  fprintf(stderr,"Usage: gpsetled <device> off|on|<brightness 0-255>\n");
}


int main(int argc, char* argv[])
{
  if (argc!=3) {
    usage();
    exit(1);
  }

  const char* dev_fn = argv[1];
  const char* brightness_s = argv[2];

  int fd = open(dev_fn,O_WRONLY);
  if (fd==-1) {
    perror("open()");
    exit(1);
  }

  int brightness;
  if (strcmp(brightness_s,"on")==0) {
    brightness=255;
  } else if (strcmp(brightness_s,"off")==0) {
    brightness=0;
  } else {
    brightness = strtoul(brightness_s,NULL,0);
  }

  struct input_event ev;
  ev.type = EV_MSC;
  ev.code = MSC_PULSELED;
  ev.value = brightness;

  ssize_t b = write(fd,&ev,sizeof(ev));
  if (b != sizeof(ev)) {
    perror("write()");
    exit(1);
  }

  exit(0);
}