虚拟平台设备开发指南

本章将带领您学习如何在QEMU虚拟环境中创建自定义硬件设备，并为其编写专业的Linux内核驱动程序。通过这个项目，您将掌握虚拟设备开发的完整流程。

QEMU设备创建

使用QEMU的-device参数可以在虚拟机中动态添加虚拟硬件设备：

qemu-system-x86_64 \
    -kernel bzImage \
    -append "console=ttyS0 root=/dev/sda" \
    -device edu,id=my_edu_device \
    -drive file=rootfs.ext4,format=raw \
    -nographic

设备驱动架构

简单的字符设备驱动

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

#define DEVICE_NAME "qemu_edu"
#define CLASS_NAME "qedu"

static int major_num;
static struct class* edu_class = NULL;
static struct device* edu_device = NULL;

static int edu_open(struct inode *inodep, struct file *filep) {
    printk(KERN_INFO "QEMU EDU device opened\n");
    return 0;
}

static ssize_t edu_read(struct file *filep, char *buffer, size_t len, loff_t *offset) {
    printk(KERN_INFO "QEMU EDU device read operation\n");
    return 0;
}

static struct file_operations fops = {
    .open = edu_open,
    .read = edu_read,
};

static int __init edu_init(void) {
    printk(KERN_INFO "QEMU EDU driver initialized\n");
    
    major_num = register_chrdev(0, DEVICE_NAME, &fops);
    if (major_num < 0) {
        printk(KERN_ALERT "Failed to register device\n");
        return major_num;
    }
    
    edu_class = class_create(THIS_MODULE, CLASS_NAME);
    if (IS_ERR(edu_class)) {
        unregister_chrdev(major_num, DEVICE_NAME);
        return PTR_ERR(edu_class);
    }
    
    edu_device = device_create(edu_class, NULL, MKDEV(major_num, 0), NULL, DEVICE_NAME);
    if (IS_ERR(edu_device)) {
        class_destroy(edu_class);
        unregister_chrdev(major_num, DEVICE_NAME);
        return PTR_ERR(edu_device);
    }
    
    return 0;
}

static void __exit edu_exit(void) {
    device_destroy(edu_class, MKDEV(major_num, 0));
    class_unregister(edu_class);
    class_destroy(edu_class);
    unregister_chrdev(major_num, DEVICE_NAME);
    printk(KERN_INFO "QEMU EDU driver unloaded\n");
}

module_init(edu_init);
module_exit(edu_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("嵌入式系统课");
MODULE_DESCRIPTION("QEMU EDU Device Driver");

obj-m += qemu_edu.o

all:
    make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
    make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

设备加载与测试步骤

1. 编译驱动模块：make
2. 加载模块：insmod qemu_edu.ko
3. 检查设备节点：ls -l /dev/qemu_edu
4. 查看内核日志：dmesg | tail
5. 测试设备访问：cat /dev/qemu_edu
6. 卸载模块：rmmod qemu_edu

支持的特性列表

• DMA数据传输
• 中断处理机制
• IO端口和内存映射
• 多设备实例支持
• 电源管理功能
• 热插拔支持