#include <linux/types.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/cdev.h>

dev_t hello_dev_id;
struct cdev hello_cdev;
int hello_major = 0;
int hello_minor;

uint8_t kernel_buffer[1024] = { 0 };
static struct class *hello_driver_class;

static int hello_driver_open(struct inode *inode, struct file *file)
{
	printk("hello_driver_open\r\n");
	return 0;
}

static int hello_driver_release(struct inode *inode, struct file *file)
{
	printk("hello_driver_release\r\n");
	return 0;
}

static ssize_t hello_driver_read(struct file *file, char __user *buffer, size_t size, loff_t *ppos)
{
	printk("hello_driver_read size=%ld\r\n", size);
	copy_to_user(buffer, kernel_buffer, size);
	return size;
}

static ssize_t hello_driver_write(struct file *file, const char __user *buffer, size_t size, loff_t *ppos)
{
	printk("hello_driver_write size=%ld\r\n", size);
	copy_from_user(kernel_buffer, buffer, size);
	return size;
}

static const struct file_operations hello_driver_fops = {
	.owner   = THIS_MODULE,
	.open    = hello_driver_open,
	.release = hello_driver_release,
	.read    = hello_driver_read,
	.write   = hello_driver_write,
};

static int __init hello_driver_init(void)
{
	printk("hello_driver_init\r\n");

	/* automatically apply for device number */
	alloc_chrdev_region(&hello_dev_id, 0, 1, "hello_driver");
	hello_major = MAJOR(hello_dev_id);
	hello_minor = MINOR(hello_dev_id);
	printk("hello_driver: major=%d, minor=%d\r\n", hello_major, hello_minor);

	hello_cdev.owner = THIS_MODULE;
	cdev_init(&hello_cdev, &hello_driver_fops);
	cdev_add(&hello_cdev, hello_dev_id, 1);
	// ret = register_chrdev(CHRDEVBASE_MAJOR, "hello_driver", &hello_driver_fops);

	/* automatically add device node file */
	hello_driver_class = class_create("hello_driver_class");
	device_create(hello_driver_class, NULL, hello_dev_id, NULL, "hello_driver_device");

	return 0;
}

static void __exit hello_driver_exit(void)
{
	printk("hello_driver_exit\r\n");

	cdev_del(&hello_cdev);
	unregister_chrdev_region(hello_dev_id, 1);

	device_destroy(hello_driver_class, hello_dev_id);
	class_destroy(hello_driver_class);
	// unregister_chrdev(CHRDEVBASE_MAJOR, "hello_driver");
}

module_init(hello_driver_init);
module_exit(hello_driver_exit);
MODULE_LICENSE("GPL");