#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>       // 包含 file_operations 和 register_chrdev 函数
#include <linux/cdev.h>     // 包含 cdev 相关结构和函数

#define DEVICE_NAME "charDevice3"

// 文件操作函数声明
static int dev_open(struct inode *inode, struct file *file);
static int dev_release(struct inode *inode, struct file *file);
static ssize_t dev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos);
static ssize_t dev_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos);

// 文件操作结构
static struct file_operations fops = {
    .owner = THIS_MODULE,
    .open = dev_open,
    .release = dev_release,
    .read = dev_read,
    .write = dev_write,
};

// 文件操作函数的实现
static int dev_open(struct inode *inode, struct file *file) {
    pr_info("Device opened\n");
    return 0;
}

static int dev_release(struct inode *inode, struct file *file) {
    pr_info("Device closed\n");
    return 0;
}

static ssize_t dev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) {
    pr_info("Reading from device\n");
    return 0; // 假设返回 0 表示读到文件结尾
}

static ssize_t dev_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) {
    pr_info("Writing to device\n");
    return count; // 返回写入的字节数
}

static int __init helloworld_init(void) {
    int retvalue;

    // 注册字符设备，使用主设备号 200
    retvalue = register_chrdev(200, DEVICE_NAME, &fops);
    if (retvalue < 0) {
        pr_err("Failed to register char device\n");
        return -EIO;
    }

    pr_info("Hello world initialization!\n");
    return 0;
}

static void __exit helloworld_exit(void) {
    // 注销字符设备驱动
    unregister_chrdev(200, DEVICE_NAME);
    pr_info("Hello world exit\n");
}

module_init(helloworld_init);
module_exit(helloworld_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("John Madieu <john.madieu@gmail.com>");
MODULE_DESCRIPTION("Linux kernel module skeleton");