//----------------------------------------------------------------
//	dos.c
//
//	This character-mode Linux device-driver supports mapping
//	of the conventional MS-DOS memory areas into user space. 
//
//	NOTE: Written and tested w/ Linux kernel version 2.4.21.
//
//	programmer: ALLAN CRUSE
//	written on: 06 DEC 2003
//----------------------------------------------------------------

#define __KERNEL__
#define   MODULE

#include <linux/module.h>	// for init_module()
#include <linux/mm.h>		
#include <linux/fs.h>

#define	SUCCESS		0

static char modname[] = "dos";
static int my_major = 86;
static unsigned long mm_base = 0x000000000;
static unsigned long mm_size = 0x000110000;

static int my_mmap( struct file *file, struct vm_area_struct *vma )
{
	unsigned long	region_length = vma->vm_end - vma->vm_start;
	unsigned long	region_origin = vma->vm_pgoff * PAGE_SIZE;
	unsigned long	phys_address = mm_base + region_origin;
	unsigned long	virt_address = vma->vm_start;

	// sanity check: mapped region cannot extend beyond device 
	if ( region_origin + region_length > mm_size ) return -EINVAL;

	// let the kernel know not to try swapping out this region
	vma->vm_flags |= VM_RESERVED;

	// tell the kernel to exclude this region from core dumps
	vma->vm_flags |= VM_IO;

	if ( io_remap_page_range( virt_address, phys_address,
		region_length, vma->vm_page_prot ) ) return -EAGAIN;

	return	SUCCESS;
}


static struct file_operations 
my_fops =	{
		owner:		THIS_MODULE,
		mmap:		my_mmap,
		};


int init_module( void )
{
	printk( "<1>\nInstalling \'%s\' module ", modname );
	printk( "(major=%d) \n", my_major );
	printk( "  base=%08X  size=%08X \n", mm_base, mm_size );
	
	return	register_chrdev( my_major, modname, &my_fops );
}


void cleanup_module( void )
{
	unregister_chrdev( my_major, modname );
	printk( "<1>Removing \'%s\' module\n", modname );
}

MODULE_LICENSE( "GPL" );