キャラクタデバイスのデバイスドライバ例

#include <linux/fs.h>    // file_operations, inode
#include <asm/uaccess.h> // copy_to_user
#include <linux/module.h>
#include <linux/kernel.h>


static int devmajor = 77;
static char devname[] = "logdev";
static char devbuf[] = "this is my message.\n";

static int
logdev_read(struct file *filp, char *buf, size_t count, loff_t *pos)
{
  int copy_len = sizeof(devbuf);

  copy_to_user(buf, devbuf, copy_len);

  return copy_len;
}


static struct file_operations logdev_fops = {
  .read = logdev_read,
};


int
init_module(void)
{
  register_chrdev(devmajor, devname, &logdev_fops);
  printk(KERN_INFO "logdev init\n");

  return 0;
}

void
cleanup_module(void)
{
  unregister_chrdev(devmajor, devname);
  printk(KERN_INFO "logdev clean\n");
}

MODULE_DESCRIPTION( "sample char device driver" );

$ ls -l /dev/logdev
crw-r--r-- 1 root root 77, 0  /dev/logdev