cdevインターフェイスを使用した書き替え

実験(10)で作成したdio_drv.cを書き直すと次のようになる。

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

#define DRIVERNAME "dio_drv"
#define DEV_COUNT 1

MODULE_LICENSE("GPL");

static dev_t dev_num;

static struct cdev char_dev;

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

int __init dio_init(void)
{
  int ret;
  int baseminor = 0;

  printk("initialize the dio_device\n");

  ret = alloc_chrdev_region(&dev_num, baseminor, DEV_COUNT, DRIVERNAME);
  if (ret < 0) {
     printk(DRIVERNAME ": Touroku Shippai\n");
     goto err1;
  }
  cdev_init(&char_dev, &dio_fops);
  char_dev.owner = THIS_MODULE;
  ret = cdev_add(&char_dev, dev_num, DEV_COUNT);
  if (ret < 0) {
      goto err2;
  }
  printk(DRIVERNAME ": Touroku Seikou. Major Number=%d\n", MAJOR(dev_num));
  return 0;

err2:
  cdev_del(&char_dev);
  unregister_chrdev_region(dev_num, DEV_COUNT);

err1:
  return ret;
}

void __exit dio_cleanup(void)
{
  printk("cleanup the dio_device\n");
   
  cdev_del(&char_dev);
  unregister_chrdev_region(dev_num, DEV_COUNT);
  printk(DRIVERNAME ": Sakujo Seikou. Major Number=%d\n", MAJOR(dev_num));
}

module_init(dio_init);
module_exit(dio_cleanup);