#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/gpio.h>
#include <asm/uaccess.h>

static dev_t gpio_dev_nr;
static struct cdev *driver_object;
static struct class *gpio_class;
static struct device *gpio_dev;

static int driver_open( struct inode
    *geraete_datei,struct file *instanz)
{
  int err;

  err = gpio_request( 4, "rpi-gpio-4" );
  if (err) {
    printk("gpio_request %d\n",err);
    return -1;
  }
  err = gpio_direction_output( 4, 0 );
  if (err) {
    printk("gpio_dir_output %d\n", err);
    gpio_free( 4 );
    return -1;
  }
  printk("gpio 4 configured\n");
  return 0;
}

static int driver_close( struct inode
    *geraete_datei, struct file *instanz)
{
  printk( "driver_close called\n" );
  gpio_free( 4 );
  return 0;
}

static ssize_t driver_write( struct file
    *instanz, const char __user *user,
    size_t count, loff_t *offset )
{
  unsigned long not_copied, to_copy;
  u32 value=0;

  to_copy = min( count, sizeof(value) );
  not_copied=copy_from_user(&value,user,
      to_copy);
  if (value==1)
    gpio_set_value(4,1);
  else
    gpio_set_value(4,0);
  //gpio_set_value( 4, value?0:1 );
  return to_copy-not_copied;
}

static struct file_operations fops = {
  .owner= THIS_MODULE,
  .write= driver_write,
  .open= driver_open,
  .release= driver_close,
};

static int __init mod_init( void )
{
  if( alloc_chrdev_region(&gpio_dev_nr,
    0,1,"fastgpio4")<0 )
    return -EIO;
  driver_object = cdev_alloc();
  if( driver_object==NULL )
    goto free_device_number;
  driver_object->owner = THIS_MODULE;
  driver_object->ops = &fops;
  if( cdev_add(driver_object,
    gpio_dev_nr,1) )
    goto free_cdev;
  gpio_class = class_create( THIS_MODULE,
    "fastgpio4" );
  if( IS_ERR( gpio_class ) ) {
    pr_err("fastgpio4:no udev support\n");
    goto free_cdev;
  }
  gpio_dev=device_create(gpio_class,NULL,
    gpio_dev_nr,NULL,"%s","fastgpio4");
  dev_info(gpio_dev, "mod_init");
  return 0;
free_cdev:
  kobject_put( &driver_object->kobj );
free_device_number:
  unregister_chrdev_region(gpio_dev_nr,1);
  return -EIO;
}

static void __exit mod_exit( void )
{
  dev_info(gpio_dev, "mod_exit");
  device_destroy(gpio_class,gpio_dev_nr);
  class_destroy( gpio_class );
  cdev_del( driver_object );
  unregister_chrdev_region(gpio_dev_nr,1);
  return;
}

module_init( mod_init );
module_exit( mod_exit );
MODULE_LICENSE("GPL");