//-------------------------------------------------------------------
//	mmap8139.c
//
//	This module implements a character device-driver that lets 
//	an application map the RTL-8139 registers into user-space.  
//
//	NOTE: Written and tested with Linux kernel version 2.6.10.
//
//	programmer: ALLAN CRUSE
//	written on: 04 APR 2005 
//	revised on: 24 OCT 2006 -- as Vladimir Neyelov suggested
//-------------------------------------------------------------------

#include <linux/module.h>	// for init_module() 
#include <linux/pci.h>		// for pci_find_device()

#define VENDOR_ID  0x10EC	// RealTek Semiconductor Corp
#define	DEVICE_ID  0x8139 	// RTL-8139 Network Processor

char modname[] = "mmap8139";	// for displaying module name
char devname[] = "nic";		// for registering the driver 
int my_major = 98;		// static major-ID assignment
unsigned long mmio_base;	// registers physical address 	
unsigned long mmio_size;	// size of the registers bank


int my_mmap( struct file *file, struct vm_area_struct *vma )
{
	unsigned long	region_origin = vma->vm_pgoff * PAGE_SIZE;
	unsigned long	region_length = vma->vm_end - vma->vm_start;
	unsigned long	physical_addr = mmio_base + region_origin;
	unsigned long	user_virtaddr = vma->vm_start;

	// determine page-offset -- Vladimir Neyelov's suggestion
	unsigned long	phys_page_off = physical_addr & ~PAGE_MASK;

	// sanity check: mapped region is confined to just one page 
	if ( region_length > PAGE_SIZE ) return -EINVAL;

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

	// tell the kernel that this region maps io memory
	vma->vm_flags |= VM_IO;

	// ask the kernel to set up the required page-tables
	if ( io_remap_page_range( vma, user_virtaddr, physical_addr,
		region_length, vma->vm_page_prot ) ) return -EAGAIN;	

	// add page offset to virtual page start -- Vladimir Neyelov
	vma->vm_start += phys_page_off;

	return	0;  // SUCCESS
}


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


int init_module( void )
{
	struct pci_dev	*devp = NULL; 

	printk( "<1>\nInstalling \'%s\' module\n", modname );
	printk( "  device-file is \'/dev/%s\' ", devname );
	printk( "(major=%d) \n", my_major ); 

	devp = pci_find_device( VENDOR_ID, DEVICE_ID, devp );
	if ( !devp ) return -ENODEV;

	mmio_base = pci_resource_start( devp, 1 );
	mmio_size = pci_resource_len( devp, 1 );
	printk( "  RealTek 8139 Network Interface:" ); 
	printk( "  %08lX-%08lX \n", mmio_base, mmio_base+mmio_size );

	register_chrdev( my_major, devname, &my_fops );
	return	0;  // SUCCESS
}


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

MODULE_LICENSE("GPL");

//---------------------------------------------------------------------
// We owe thanks to Vladimir Neyelov for proposing the changes that are
// incorporated into the 'my_mmap' function here, so that applications,
// such as our 'nicregs.cpp' demo, which allow the kernel to select the
// base-address for the requested memory-mapping, may nevertheless work
// correctly in cases where the kernel's address is not 'page-aligned'.
//					-- Allan Cruse, 24 October 2006
//---------------------------------------------------------------------