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

#define DEVNAME "hello"
static dev_t dev;
static struct class *hello_class;
static struct cdev *hello_cdev;

static int hello_open(struct inode *inode,struct file *flp)
{
 return 0;
}

static int hello_close(struct inode *inode,struct file *flp)
{
  return 0;
}
static struct file_operations hello_fops={
  .owner=THIS_MODULE,
  .open =hello_open,
  .release=hello_close,
 };

static int __init hello_init(void)
{
    int error;

    error = alloc_chrdev_region(&dev, 0, 2, "hello");
    if (error)
    {
        printk("hello: alloc_chardev_region failed! ");
        goto out;
    }
    hello_cdev = cdev_alloc();
    if (hello_cdev == NULL)
    {
        printk("hello: alloc cdev failed! ");
        error = -ENOMEM;
        goto out_chrdev;
    }
    hello_cdev->ops = &hello_fops;
    hello_cdev->owner = THIS_MODULE;
    error = cdev_add(hello_cdev, dev, 1);
    if (error)
    {
        printk("hello: cdev_add failed! ");
        goto out_cdev;
    }
    hello_class = class_create(THIS_MODULE, DEVNAME);
    if (IS_ERR(hello_class))
    {
        error = PTR_ERR(hello_class);
        goto out_chrdev;
    }
    device_create(hello_class, NULL, dev, NULL, DEVNAME);
    //memset (hello_buf, 0, sizeof(hello_buf));
    //memcpy(hello_buf, DEFAULT_MSG, sizeof(DEFAULT_MSG));
    printk("hello: Hello World! ");
    return 0;

out_cdev:
    cdev_del(hello_cdev);
out_chrdev:
    unregister_chrdev_region(hello_cdev->dev, 2);
out:
    return error;
}
static void __exit hello_exit(void)
{
    device_destroy(hello_class, dev);
    class_destroy(hello_class);
    unregister_chrdev_region(hello_cdev->dev, 2);
    cdev_del(hello_cdev);
    printk("hello: Goodbye World ");
}

module_init(hello_init);
module_exit(hello_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("YWW");
MODULE_DESCRIPTION("HELLO_CLASS_AUTO_DEV");

/sys/class  /dev  /proc/devices可以看到hello裝置