基于Linux C编程语言，生成ioctl函数的样例代码，要求代码可以正常运行

在Linux系统中，ioctl (Input/Output Control) 是一种用于驱动程序与用户空间应用程序通信的方式。它允许你在设备文件上执行低级别的操作，这些操作通常不在标准的输入/输出函数内。下面是一个简单的基于C的ioctl函数的样例代码片段：

#include <linux/fs.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>

#define DRIVER_NAME "example_driver"
#define IOCTL_CMD_READ  FIONREAD
#define IOCTL_CMD_WRITE FIO_WRITE

static int driver_open(struct inode *inode, struct file *file)
{
    printk(KERN_INFO "%s: open\n", DRIVER_NAME);
    return 0;
}

static int driver_release(struct inode *inode, struct file *file)
{
    printk(KERN_INFO "%s: release\n", DRIVER_NAME);
    return 0;
}

static ssize_t driver_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
    if (!count)
        return -EINVAL;

    // 在这里处理实际的读取操作，并将数据写入用户空间
    char *data = kmalloc(count, GFP_KERNEL);  // 假设成功读取了数据
    // ... 实现数据读取逻辑 ...

    return copy_to_user(buf, data, count) ? -EFAULT : count;
}

static ssize_t driver_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
    if (!count)
        return -EINVAL;

    // 在这里处理实际的写入操作，并从用户空间获取数据
    char *data = kmalloc(count, GFP_KERNEL);
    if (copy_from_user(data, buf, count)) {
        printk(KERN_ERR "%s: write failed due to user space error\n", DRIVER_NAME);
        return -EFAULT;
    }

    // ... 实现数据写入逻辑 ...
    kfree(data);

    return count;
}

static long driver_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    switch (cmd) {
    case IOCTL_CMD_READ:
        return doIOCRead(file, (void __user *)arg);
    case IOCTL_CMD_WRITE:
        return doIOWrite(file, (void __user *)arg);
    default:
        return -ENOTTY;  // 指定未知命令的错误代码
    }
}

static const struct file_operations fops = {
    .open     = driver_open,
    .release  = driver_release,
    .read     = driver_read,
    .write    = driver_write,
    .unlocked_ioctl = driver_ioctl,   // 允许无锁的ioctl操作
};

int register_driver(void)
{
    struct cdev dev;
    struct class *cls = class_create(THIS_MODULE, DRIVER_NAME);
    
    cdev_init(&dev, &fops);
    dev.ops = &fops;
    minor_count = alloc_chrdev_region(&dev_num, 0, 1, DRIVER_NAME);
    if (minor_count < 0) {
        pr_err("Failed to allocate device number: %d\n", minor_count);
        goto err_alloc_dev_num;
    }

    cdev_add(&dev, MKDEV(MAJOR(dev_num), 0), 1);  // 添加设备节点到系统
    device_create(cls, NULL, MKDEV(MAJOR(dev_num), 0), NULL, DRIVER_NAME);

    return 0;
err_alloc_dev_num:
    class_destroy(cls);
    return minor_count;
}

module_init(register_driver);
module_exit(driver_unregister);