/*
Compile and load the GFN driver module by using the commands,
cc -Wall -O1 -c -DMODULE -D__KERNEL__ gfn3.c
rmmod gfn  - to remove the existing one
insmod gfn.o
*/


#include <linux/malloc.h>
#include <linux/module.h>
#include <asm/io.h>
#include <linux/poll.h>   

#define	GFN_MAJOR	60

#define	BASE		0x378
#define	DATAPORT	(BASE)
#define	STATPORT	(BASE+1)
#define	CONPORT		(BASE+2)
#define	IRQENBIT	0x10
#define	IRQBIT	0x40


static DECLARE_WAIT_QUEUE_HEAD(my_wait_queue);  


static ssize_t 
gfn_write(struct file *file, const char *buf, size_t count, loff_t *ppos)
{
u8 data;

printk("WRITE: Waking up the process Put to sleep by READ\n");
wake_up_interruptible(&my_wait_queue);

if (copy_from_user(&data, buf, sizeof(data)))
   return -EFAULT; 

printk("Data from user %x hex\n", data);
outb(data, CONPORT);
return 0;
}

static ssize_t gfn_read(struct file *file, char *buffer, size_t count, loff_t *ppos)
{
u8 data;

data = inb(STATPORT);			// read the printer status port

printk("Process put to Sleep in READ\n");	// for debugging only
interruptible_sleep_on(&my_wait_queue); 

printk("Woken up. data = %x hex\n", data);	// for debugging only
	      
// transfer data from kernel address space to user address space

if(copy_to_user( buffer, &data, sizeof(u8))) return -EFAULT;    

return 0;
}

static int gfn_open(struct inode * inode, struct file * file)
{
printk("GFN open: Usage = %d\n", MOD_IN_USE);
MOD_INC_USE_COUNT;
return 0;
}

static int gfn_release(struct inode * inode, struct file * file)
{
MOD_DEC_USE_COUNT;
printk("GFN release: Usage = %d\n", MOD_IN_USE);
return 0;
}

struct file_operations gfn_fops = {
	owner: THIS_MODULE,
	open:    gfn_open,
	release: gfn_release,
	write:  gfn_write,
	read:   gfn_read
      };
      
      

int init_module(void)
{
if (register_chrdev(GFN_MAJOR,"gfn",&gfn_fops)) {
	printk("gfn: Failed to get major %d\n", GFN_MAJOR);
	return -EIO;
	}
printk("Registered device gfn: major %d\n",GFN_MAJOR);
return 0;
}

void cleanup_module(void)
{
printk("Freed resources: MOD_IN_USE = %d\n", MOD_IN_USE); 
unregister_chrdev(GFN_MAJOR,"gfn");
printk("Unregistered device gfn: major %d\n",GFN_MAJOR);
}