par.c

/* Necessary includes for drivers */
#include <linux/init.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,const char *buf, size_t count, loff_t *f_pos);
ssize_t parlelport_write(struct file *filp,const char *buf, size_t count, loff_t *f_pos);
static void parlelport_exit(void);
static int parlelport_init(void);

/* Structure that declares the common */
/* file access fcuntions */
static struct file_operations parlelport_fops = {
read: parlelport_read,  
write: parlelport_write, /* line 30 */
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;
  }
  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");
  printk(KERN_DEBUG "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,const char *buf,
  size_t count, loff_t *f_pos) {
  /* Buffer to read the device */
  char parlelport_buffer;
  /* 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,const 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);
  return 1;
}