嵌入式linux高级编程

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

// 设备号
static dev_t dev_num;
// 设备文件名
static const char *device_name = "my_char_device";
// 设备结构体
static struct cdev my_cdev;

// 打开设备文件
static int my_open(struct inode *inode, struct file *file)
{
    printk(KERN_INFO "Device opened
");
    return 0;
}

// 关闭设备文件
static int my_release(struct inode *inode, struct file *file)
{
    printk(KERN_INFO "Device closed
");
    return 0;
}

// 设备文件操作结构体
static struct file_operations fops = {
    .owner = THIS_MODULE,
    .open = my_open,
    .release = my_release,
};

// 模块加载函数
static int __init my_init(void)
{
    int ret;
    // 分配设备号
    ret = alloc_chrdev_region(&dev_num, 0, 1, device_name);
    if (ret < 0) {
        printk(KERN_ERR "Failed to allocate device number
");
        return ret;
    }
    // 初始化字符设备
    cdev_init(&my_cdev, &fops);
    my_cdev.owner = THIS_MODULE;
    // 添加字符设备
    ret = cdev_add(&my_cdev, dev_num, 1);
    if (ret < 0) {
        printk(KERN_ERR "Failed to add character device
");
        unregister_chrdev_region(dev_num, 1);
        return ret;
    }
    printk(KERN_INFO "Device registered successfully
");
    return 0;
}

// 模块卸载函数
static void __exit my_exit(void)
{
    cdev_del(&my_cdev);
    unregister_chrdev_region(dev_num, 1);
    printk(KERN_INFO "Device unregistered successfully
");
}

module_init(my_init);
module_exit(my_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("A simple character device driver example");