#include  <linux/module.h>
#include  <linux/init.h>
#include  <linux/fs.h>
#include  <linux/types.h>
#include  <linux/cdev.h>

#define  DEVICE_NAME  "test"
#define  MODULE_NAME  "test"

static dev_t Devno;
static struct cdev test_cdev;
static struct mutex test_mutex;

static ssize_t test_read(struct file *filp, char *buff, size_t len,
			 loff_t *whence)
{
	return 1;
}

static ssize_t test_write(struct file *filp, const char *buff,
			  size_t len, loff_t *whence)
{
	return 1;
}

static int test_open(struct inode *ino, struct file *filp)
{
	if (mutex_lock_interruptible(&test_mutex))
		return -ERESTARTSYS;
	printk("%s: test device is open.\n", MODULE_NAME);
	return 0;
}

static int test_close(struct inode *ino, struct file *filp)
{
	printk("%s: test device is closed.\n", MODULE_NAME);
	mutex_unlock(&test_mutex);
	return 0;
}

static struct file_operations Fops  =  { .owner   = THIS_MODULE,
				         .read    = test_read,
				         .write   = test_write,
				         .open    = test_open,
				         .release = test_close    };

static int __init test_init(void)
{
	int rc;
	rc = alloc_chrdev_region(&Devno, 0, 1, DEVICE_NAME);
	if (rc < 0)
	{
		printk("%s: Registration failed...\n",MODULE_NAME);
		return rc;
	}
	printk("%s: Registration %s at major number %d\n", MODULE_NAME,
				DEVICE_NAME, MAJOR(Devno));
	cdev_init(&test_cdev, &Fops);
	test_cdev.owner = THIS_MODULE;
	rc = cdev_add(&test_cdev, Devno, 1);
	if (rc < 0) {
		printk("%s: Device object not added!\n", MODULE_NAME);
		unregister_chrdev_region(Devno, 1);
		return rc;
	}
	printk("%s: Device added.\n", MODULE_NAME);
	mutex_init(&test_mutex);
	return 0;
}

static void __exit test_exit(void)
{
	cdev_del(&test_cdev);
	unregister_chrdev_region(Devno, 1);
	printk("%s: Module removed.\n", MODULE_NAME);
}

module_init(test_init);
module_exit(test_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Frank");
MODULE_DESCRIPTION("Simple char driver.");