register_chrdevとunregister_chrdevの使用例

前回の実験(10)で作成したdio_drv.cは次の通りであった。

  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/fs.h>

  #define DRIVERNAME "dio_drv"
  int dio_major = 0;

  MODULE_LICENSE("GPL");

  struct file_operations dio_fops = {
    .owner   = NULL,
    .read    = NULL,
    .write   = NULL,
    .ioctl   = NULL,
    .open    = NULL,
    .release = NULL,
  };

  int __init dio_init(void)
  {
    int ret;

    printk("initialize the dio_device \n");
    ret = register_chrdev(dio_major, DRIVERNAME, &dio_fops);

    if (ret < 0)
       return ret;

    if (dio_major == 0) 
       dio_major = ret;

    return 0;
  }

  void __exit dio_cleanup(void)
  {
    printk("cleanup the dio_device \n");
    unregister_chrdev(dio_major, DRIVERNAME);
  }

  module_init(dio_init);
  module_exit(dio_cleanup);