#include <linux/kernel.h>
#include <linux/module.h>
#include <asm/errno.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <linux/miscdevice.h>
#include <linux/pci.h>
#include <linux/delay.h>

static ssize_t doc_read (struct file *filp, char *buf, size_t count, loff_t *ptr);
static ssize_t doc_write (struct file *file, const char *buf, size_t count, loff_t *ppos);
static int doc_release(struct inode *inode, struct file *file);
static int doc_open(struct inode *inode, struct file *filp);

struct file_operations doc_fops={
	NULL,      /* llseek */
	doc_read,        /* read */
	doc_write,       /* write */
	NULL,           /* readdir */
	NULL,           /* poll */
       	NULL,       /* ioctl */
       	NULL,           /* mmap */
	doc_open,        /* open */
	NULL,           /* flush */
	doc_release,     /* release */
	NULL            /* fsync */
};


struct miscdevice doc_miscdev={
  157,
  "doc",
  &doc_fops
}; 

#define DOCLOC 0xd8000

unsigned long docptr=0;
int doccheck(unsigned long potential);

int init_module(void)
{
  int status;
  
  docptr=(unsigned long)ioremap(0xd8000, 0x2000);
  
  status=doccheck(docptr);
  
  if (status)
    {
      printk("DOC found at 0x%lx\n",docptr);
      misc_register (&doc_miscdev); 
      return 0;
    }
  else
    {
      printk("DOC not found at 0x%lx\n", docptr);
      return -ENXIO;
    }
}

void cleanup_module(void)
{
  
  if (docptr)
    iounmap((void *)docptr);
  docptr = 0;
  misc_deregister (&doc_miscdev); 
}

int doccheck(unsigned long potential)
{
  unsigned long window=potential;
  unsigned char tmp, tmp2;
  

  /* Routine copied from the Linux DOC driver */

  if (readb(window) != 0x55 || readb(window+1) != 0xaa)
    {
      printk ("Start of window not 0x55 0xaa: %2.2X %2.2X\n", (unsigned int)readb(window),(unsigned int)readb(window+1));
      return 0;
    }

  tmp2 = readb(window+0x1002);
  
  writeb(0x84, window+0x1002);
  writeb(0x84, window+0x1002);
  writeb(0x85, window+0x1002);
  writeb(0x85, window+0x1002);
  
  if (readb(window+0x1000) != 0x20)
    {
      writeb(tmp2, window+0x1002);
      return 0;
    }
  
  tmp = readb(window+0x1007) & 4;
  
  if ((readb(window+0x1007) & 4) != tmp)
    {
      return 1;
    }
  
  writeb(tmp2, window+0x1002);
  return 0;
}     


static ssize_t doc_read (struct file *filp, char *buf, size_t count, loff_t *ptr)
{
  size_t di;
  loff_t ofs = *ptr;
  
  di = 0;                                   
  
  for (ofs = *ptr; ofs < *ptr + count ; ofs++)
    {
      if (!(ofs & 0xf)) {                     
	
	writeb(0x1d, docptr+ 0x1004);              // Set to 'set address' mode?
	writew( 1+ readw(docptr + 0x1000), docptr + 0x1000);

	//writeb( ofs & 0xff, docptr+ 0x100d);
	writeb( ofs & 0xff, docptr+ 0x1800);
	
	//writeb( (ofs >> 8) & 0xff, docptr + 0x100d);
	writeb( (ofs >> 8) & 0xff, docptr + 0x1800);
	
	//writeb( (ofs >> 16) & 0xff, docptr + 0x100d);
	writeb( (ofs >> 16) & 0xff, docptr + 0x1800);
	
	writeb ( 0x19, docptr + 0x1004);           // Set to 'read' mode?
	writew( 1 + readw(docptr + 0x1000), docptr + 0x1000);   

	while ( !(readb(docptr + 0x1004) & 80) ) 
	  printk("waiting...\n");      // Wait for ack?
	(void)readw(docptr + 0x1004);
	
	/* The while() loop above never actually seems to wait.
	   We need this udelay() to get consistent results. */

	udelay(1);
      }

      //(void)readb(docptr + 0x100d);
      buf[di++] = readb(docptr + 0x1800);
    }
  
  *ptr = ofs;

  return count;
}

static ssize_t doc_write (struct file *file, const char *buf, size_t count, loff_t *ppos)
{
  return -EIO;
}


static int doc_release(struct inode *inode, struct file *file)
{
  return 0;
}

static int doc_open(struct inode *inode, struct file *filp)
{
  return 0;
}