null.c

#include <linux/module.h>
#include <linux/version.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/kdev_t.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/cdev.h>

static dev_t first;
static struct cdev c_dev;
static struct class *cl;
static int my_open(struct inode *i, struct file *f)
{
	printk(KERN_INFO "Driver: open()\n");
	return 0;
}
static int my_close(struct inode *i, struct file *f)
{
	printk(KERN_INFO "Driver: close()\n");
	return 0;
}
static ssize_t my_read(struct file *f, char __user *buf, size_t len, loff_t *off)
{
	printk(KERN_INFO "Driver: read()\n");
	return 0;
}
static ssize_t my_write(struct file *f, const char __user *buf,size_t len, loff_t *off)
{
	printk(KERN_INFO "Driver: write()\n");
	return len;
}
static struct file_operations pugs_fops ={
.owner=THIS_MODULE,
.open=my_open,
.release=my_close,
.read=my_read,
.write=my_write,
};
static int __init ofcd_init(void)
{
	printk(KERN_INFO "Hello: ofcd registered");
	if (alloc_chrdev_region(&first, 0, 1, "Ganesh") < 0)
	{
		return -1;
	}
	if ((cl = class_create(THIS_MODULE, "chardrv")) == NULL)
	{
		unregister_chrdev_region(first, 1);
		return -1;
	}
	if (device_create(cl, NULL, first, NULL, "mynull") == NULL)
	{
		class_destroy(cl);
		unregister_chrdev_region(first,1);
		return -1;
	}
	cdev_init(&c_dev, &pugs_fops);
	if (cdev_add(&c_dev, first, 1) == -1)
	{
		device_destroy(cl,first);
		class_destroy(cl);
		unregister_chrdev_region(first,1);
		return -1;
	}
return 0;
}

static void __exit ofcd_exit(void)
{
	cdev_del(&c_dev);
	device_destroy(cl,first);
	class_destroy(cl);
	unregister_chrdev_region(first,1);
	printk(KERN_INFO"Bye : ofcd unregistered");
}
module_init(ofcd_init);
module_exit(ofcd_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("GANESH");
MODULE_DESCRIPTION("First Character Driver");