#include<linux/kernel.h>
#include<linux/module.h>

#include<linux/fs.h>
#include<linux/kdev_t.h>
#include<asm/uaccess.h>

MODULE_LICENSE("GPL");

#include<linux/ioctl.h>

#define DEVICE_NAME "HJ"
#define HJ_LEN 32

#define HJ_MAGICNUM 254
#define HJ_READ  _IOR(HJ_MAGICNUM,0,char*) 	 
#define HJ_WRITE _IOW(HJ_MAGICNUM,1,char*)

static int HJ_Major=0;
static char HJ_block[HJ_LEN]="\0";

static int HJ_open(struct inode *inode, struct file *filp);
static int HJ_release(struct inode *inode, struct file *filp);
static int HJ_ioctl(struct inode *inode, struct file *filp, unsigned int cmd, unsigned long arg);

struct file_operations HJ_fops={
	open: 		HJ_open,
	release: 	HJ_release,
	ioctl: 		HJ_ioctl,
};

int init_module(void)
{
	printk("Loading HJ Device Driver... \n");

	if((HJ_Major=register_chrdev(0,DEVICE_NAME,&HJ_fops))<0){
		printk(DEVICE_NAME" : Device registration failed (%d)\n", HJ_Major);
		return HJ_Major;
	}
	printk(DEVICE_NAME" : Device Driver registeration OK with Major Number = %d\n\n", HJ_Major);

	return 0;
}

void cleanup_module(void)
{
	int nRetCode;

	printk("Unloading HJ Device Driver.. \n");

	if((nRetCode=unregister_chrdev(HJ_Major,DEVICE_NAME))<0)
		printk(DEVICE_NAME" : Device unregisteration failed (%d)\n",nRetCode);
	else printk(DEVICE_NAME" : Device unregistration OK\n");
}

int HJ_open(struct inode *inode, struct file *flip)
{
	MOD_INC_USE_COUNT;
	printk(DEVICE_NAME" : Device open OK (%d, %d)\n\n",MAJOR(inode->i_rdev),MINOR(inode->i_rdev));
 	return 0;
}

int HJ_release(struct inode *inode, struct file *flip)
{
	MOD_DEC_USE_COUNT;
	printk(DEVICE_NAME" : Device close OK(%d, %d)\n\n",MAJOR(inode->i_rdev),MINOR(inode->i_rdev));
	return 0;
}
	
int HJ_ioctl(struct inode *inodep, struct file *filp, unsigned int cmd, unsigned long arg)
{
	int count;
	int length;
	char *buffer = (char *)arg;
	count=0;

	switch(cmd){	
		case HJ_READ:
			length = strlen(HJ_block);	
 			printk("READ : length= %d \n ",count);	
	       		while(count<length){
        	       		put_user(HJ_block[count],buffer);
               			buffer++; count++;
					if(count>=HJ_LEN) break; 
	       		}
 			printk("READ : length= %d \n ",count);	
			break;
		case HJ_WRITE:
			length = strlen(buffer);
        		while(count<length){
                		get_user(HJ_block[count],buffer);
                		buffer++; count++;
                		if(count>=HJ_LEN) break;
        		}
        		printk("WRITE : length= %d \n",count);
			break;
	}
	return 0;
}