//-------------------------------------------------------------------
//	sischip.c
//
//	This module demonstrates the creation of a '/proc' file that 
//	has both read-and-write capabilities.  Applications may read
//	or write the value of the Screen Start-Address Offset in the
//	SiS 315 VGA Graphics Display hardware used in our classroom.
//	
//	NOTE: Written and tested using Linux kernel version 2.4.20.
//
//	programmer: ALLAN CRUSE
//	written on: 08 MAY 2003
//-------------------------------------------------------------------

#define	__KERNEL__
#define	  MODULE  

#include <linux/module.h>	// for init_module() 
#include <linux/proc_fs.h>	// for create_proc_entry() 
#include <linux/pci.h>		// for pci_find_device()
#include <asm/uaccess.h>	// copy_to_user()

#define	SUCCESS	0
#define	PROC_DIR	NULL
#define	PROC_MODE	0666
#define VENDOR_ID PCI_VENDOR_ID_SI
#define DEVICE_ID	0x6325
#define VGA_SEQN_PORT	0x3C4
#define VGA_CRTC_PORT	0x3D4

static char modname[] = "sischip";
static struct pci_dev *devp = NULL;
static unsigned long fb_base;
static unsigned long fb_size = (32<<20);

static unsigned long sis_get_start_address_offset( void )
{
	unsigned long	temp, start_offset = 0;
	
	// bits 23..16
	outb( 13, VGA_SEQN_PORT );
	temp = inw( VGA_SEQN_PORT );
	start_offset |= ((temp>>8)<<16);
	
	// bits 15..8
	outb( 12, VGA_CRTC_PORT );
	temp = inw( VGA_CRTC_PORT );
	start_offset |= ((temp>>8)<<8);
	
	// bits 7..0
	outb( 13, VGA_CRTC_PORT );
	temp = inw( VGA_CRTC_PORT );
	start_offset |= ((temp>>8)<<0);

	return	start_offset;	
}

static void sis_set_start_address_offset( unsigned long start_offset )
{
	unsigned short	temp;

	// bits 7..0
	temp = ((start_offset>>0)&0xFF)<<8;
	temp |= 13;	
	outw( temp, VGA_CRTC_PORT );

	// bits 15..8
	temp = ((start_offset>>8)&0xFF)<<8;
	temp |= 12;	
	outw( temp, VGA_CRTC_PORT );
	
	// bits 23..16
	temp = ((start_offset>>16)&0xFF)<<8;
	temp |= 13;	
	outw( temp, VGA_SEQN_PORT );
}

static ssize_t
my_write( struct file *file, const char *buf, size_t len, loff_t *pos )
{
	unsigned long	start_address_offset;
	int		more;

	more = copy_from_user( &start_address_offset, buf, 4 );
	sis_set_start_address_offset( start_address_offset );

	return	len;
}

static ssize_t
my_read( struct file *file, char *buf, size_t len, loff_t *pos )
{
	unsigned long	start_address_offset;
	int		more;

	start_address_offset = sis_get_start_address_offset();
	more = copy_to_user( buf, &start_address_offset, 4 );
	if ( more ) return -EFAULT;

	return	len;
}


static struct file_operations 
my_fops =	{
		owner:		THIS_MODULE,
		write:		my_write,
		read:		my_read,
		};





int init_module( void )
{
	struct proc_dir_entry	*entry;

	printk( "<1>\nInstalling \'%s\' module\n", modname );

	devp = pci_find_device( VENDOR_ID, DEVICE_ID, devp );
	if ( !devp ) return -ENODEV;
	printk( "<1>  %s \n", devp->name );

	fb_base = pci_resource_start( devp, 0 );

	entry = create_proc_entry( modname, PROC_MODE, PROC_DIR );
	entry->proc_fops = &my_fops;
	return	SUCCESS;
}


void cleanup_module( void )
{
	remove_proc_entry( modname, PROC_DIR );

	printk( "<1>Removing \'%s\' module\n", modname );
}

MODULE_LICENSE("GPL");