#include<linux/module.h>
#include<linux/kernel.h>
#include<linux/fs.h>
#include<linux/init.h>
#include<asm/uaccess.h>

#define MAGIC 'z'
#define GET_DATA _IOR(MAGIC, 1, int *)
#define SET_DATA _IOW(MAGIC, 2, int *)
#define GET_SIZE _IOR(MAGIC, 3, int *)

struct file_operations fops;
static char array[80] = "HelloWorld";
static int major;

int Mydevice_init_module(void)
{
	printk("In init module");
	major = register_chrdev(0,"Mydevice",&fops);
	printk("\nThe device is registered by Major no: %d",major);
	if(major == -1)
		printk("\nError in registering the module");
	else
		printk("\n");
	return 0;
}


void Mydevice_cleanup_module(void)
{
	unregister_chrdev(major,"Mydevice");
	printk("In cleanup module");
}


static int my_open(struct inode *inode, struct file *file)
{
	printk("\nMydevice: open");
	return 0;
}


static int my_release(struct inode *inode, struct file *file)
{
	printk("\nMydevide: release");
	return 0;
}

static ssize_t my_read(struct file *file, char *buff, size_t n,loff_t *offset)
{
	int position = (long)*offset;
	printk("\nMydevice: read");
	copy_to_user(buff,array+position,n);
	return 0;
}


static ssize_t my_write(struct file *file, const char *buff, size_t n, loff_t *offset)
{
	int position = (long)*offset;
	printk("\nMydevice: write");
	copy_from_user(array+position,buff,n);
	return 0;	
}

static loff_t my_lseek(struct file *file,loff_t offset,int whence)
{
	printk("\nMydevice: lseek");
	switch(whence)
	{
		case 0: file->f_pos = offset;      //SEEK_SET
			break;
		case 1: file->f_pos = (file->f_pos) + offset;  //SEEK_CUR
			break;
		case 2: file->f_pos = sizeof(array) - offset;  //SEEK_END
			break;
	}
	return file->f_pos;
}


static int my_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
	switch(cmd)
	{
		case GET_DATA:
			printk("\nMydevice: ioctl: GET_DATA");
			copy_to_user((char *)arg, array, 80);
			break;
		case SET_DATA:
			printk("\nMydevice: ioctl: SET_DATA");
			copy_from_user(array, (char *)arg, 80);
			break;
		case GET_SIZE:
			printk("\nMydevice: ioctl: GET_SIZE");
			*(int *) arg = sizeof(array);
			break;			
	}
	return 0;
}


struct file_operations fops =  
{
	open: my_open,
	release: my_release,
	read: my_read,
	write: my_write,
	llseek: my_lseek,
	ioctl: my_ioctl,
};


module_init(Mydevice_init_module);
module_exit(Mydevice_cleanup_module);
MODULE_LICENSE("GPL");