linux 驱动开发例子

以下是一个简单的Linux字符设备驱动开发示例：

一、基础概念

字符设备
- 是一种按字符顺序读写的设备，如键盘、鼠标等。在Linux中，字符设备通过设备文件来表示，通常位于/dev目录下。

驱动开发
- 是为特定的硬件设备编写软件代码，使得操作系统能够与该硬件进行交互。在Linux下，驱动程序通常以模块的形式存在，可以动态加载和卸载。

二、示例代码（简单的字符设备驱动）

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

#define DEVICE_NAME "my_char_device"
#define CLASS_NAME "my_char_class"

static int major_number;
static struct class* my_class = NULL;
static struct device* my_device = NULL;

// 设备操作函数
static ssize_t device_read(struct file* filp, char* buffer, size_t length, loff_t* offset)
{
    printk(KERN_INFO "Read function called
");
    // 简单返回一个固定字符串
    const char* msg = "Hello from my char device";
    int len = strlen(msg);
    if (*offset >= len)
        return 0;
    if (*offset + length > len)
        length = len - *offset;
    if (copy_to_user(buffer, msg + *offset, length))
        return -EFAULT;
    *offset += length;
    return length;
}

static ssize_t device_write(struct file* filp, const char* buffer, size_t length, loff_t* offset)
{
    printk(KERN_INFO "Write function called
");
    // 这里简单打印写入的数据长度
    printk(KERN_INFO "Written data length: %zu
", length);
    return length;
}

static struct file_operations fops = {
   .read = device_read,
   .write = device_write,
};

// 模块初始化函数
static int __init my_driver_init(void)
{
    major_number = register_chrdev(0, DEVICE_NAME, &fops);
    if (major_number < 0) {
        printk(KERN_ALERT "Failed to register device, error code: %d
", major_number);
        return major_number;
    }
    printk(KERN_INFO "Registered correctly with major number %d
", major_number);

    my_class = class_create(THIS_MODULE, CLASS_NAME);
    if (IS_ERR(my_class)) {
        unregister_chrdev(major_number, DEVICE_NAME);
        printk(KERN_ALERT "Failed to create class
");
        return PTR_ERR(my_class);
    }
    printk(KERN_INFO "Class created successfully
");

    my_device = device_create(my_class, NULL, MKDEV(major_number, 0), NULL, DEVICE_NAME);
    if (IS_ERR(my_device)) {
        class_destroy(my_class);
        unregister_chrdev(major_number, DEVICE_NAME);
        printk(KERN_ALERT "Failed to create device
");
        return PTR_ERR(my_device);
    }
    printk(KERN_INFO "Device created successfully
");
    return 0;
}

// 模块退出函数
static void __exit my_driver_exit(void)
{
    device_destroy(my_class, MKDEV(major_number, 0));
    class_unregister(my_class);
    class_destroy(my_class);
    unregister_chrdev(major_number, DEVICE_NAME);
    printk(KERN_INFO "Goodbye, driver!
");
}

module_init(my_driver_init);
module_exit(my_driver_exit);

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

三、优势