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/* Necessary includes for drivers */
#include <linux/init.h>
#include <linux/config.h>
#include <linux/module.h>
#include <linux/kernel.h> /* printk() */
#include <linux/slab.h> /* kmalloc() */
#include <linux/fs.h> /* everything... */
#include <linux/errno.h> /* error codes */
#include <linux/types.h> /* size_t */
#include <linux/proc_fs.h>
#include <linux/fcntl.h> /* O_ACCMODE */
#include <linux/ioport.h>
#include <asm/system.h> /* cli(), *_flags */
#include <asm/uaccess.h> /* copy_from/to_user */
#include <asm/io.h> /* inb, outb */
 
MODULE_LICENSE("Dual BSD/GPL");
 
/* Function declaration of parlelport.c */ 
int parlelport_open(struct inode *inode, struct file *filp); 
int parlelport_release(struct inode *inode, struct file *filp); 
ssize_t parlelport_read(struct file *filp, char *buf, 
                       size_t count, loff_t *f_pos); 
ssize_t parlelport_write(struct file *filp, char *buf, 
                       size_t count, loff_t *f_pos); 
void parlelport_exit(void);
int parlelport_init(void);
 
/* Structure that declares the common */
/* file access fcuntions */
struct file_operations parlelport_fops = { 
  read: parlelport_read,
  write: parlelport_write,
  open: parlelport_open,
  release: parlelport_release
};
 
/* Driver global variables */
/* Major number */
int parlelport_major = 61;
 
/* Control variable for memory */ 
/* reservation of the parallel port*/
int port;
 
module_init(parlelport_init);
module_exit(parlelport_exit);
 
int parlelport_init(void) { 
  int result;
 
  /* Registering device */
  result = register_chrdev(parlelport_major, "parlelport", 
      &parlelport_fops);
  if (result < 0) { 
    printk(
      "<1>parlelport: cannot obtain major number %d\n",
      parlelport_major); 
    return result; 
  } 
 
  <parlelport modified init module>
 
  printk("<1>Inserting parlelport module\n"); 
  return 0;
 
  fail: 
    parlelport_exit(); 
    return result;
}
 
void parlelport_exit(void) {
 
  /* Make major number free! */
  unregister_chrdev(parlelport_major, "parlelport");
 
  <parlelport modified exit module>
 
  printk("<1>Removing parlelport module\n");
}
 
int parlelport_open(struct inode *inode, struct file *filp) {
 
  /* Success */
  return 0;
 
}
 
int parlelport_release(struct inode *inode, struct file *filp) {
 
  /* Success */
  return 0; 
}
 
ssize_t parlelport_read(struct file *filp, char *buf, 
  size_t count, loff_t *f_pos) {
 
  /* Buffer to read the device */
  char parlelport_buffer;
 
  <parlelport inport>
 
  /* We transfer data to user space */
  copy_to_user(buf,&parlelport_buffer,1); 
 
  /* We change the reading position as best suits */
  if (*f_pos == 0) { 
    *f_pos+=1; 
    return 1; 
  } else { 
    return 0; 
  }
}
 
ssize_t parlelport_write( struct file *filp, char *buf, 
  size_t count, loff_t *f_pos) {
 
  char *tmp;
 
  /* Buffer writing to the device */
  char parlelport_buffer;
 
  tmp=buf+count-1;
  copy_from_user(&parlelport_buffer,tmp,1);
 
  <parlelport outport>
 
  return 1; 
}