디바이스 드라이버를 설치해도 /dev 폴더에 장치가 생기지 않네요???

#define GPIO_USE_NAME "ftgpio_function"
 
static dev_t dev_num;
static struct cdev gpio_cdev;
static struct class *gpio_class = NULL;
static u32 open_cnt = 0;
static DECLARE_MUTEX(drv_sem);
 
//============================================
//      file operations
//============================================
static int gpio_open(struct inode *inode, struct file *filp)
{
    int ret = 0;
 
    down(&drv_sem);
    if (!open_cnt) {
        open_cnt++;
    } else {
        printk("request gpio functions fail\n");
        ret = -EINVAL;
    }
    up(&drv_sem);
    return ret;
}
 
static int gpio_release(struct inode *inode, struct file *filp)
{
    int ret = 0;
 
    down(&drv_sem);
    open_cnt--;
    up(&drv_sem);
 
    return ret;
}
 
static int gpio_ioctl(struct inode *inode, struct file *filp, unsigned int cmd, unsigned long arg)
{
    int ret = 0;
 
    if (_IOC_TYPE(cmd) != GPIO_IOC_MAGIC)
        return -ENOTTY;
    if (_IOC_NR(cmd) > GPIO_IOC_MAXNR)
        return -ENOTTY;
    if (_IOC_DIR(cmd) & _IOC_READ)
        ret = !access_ok(VERIFY_WRITE, (void __user *)arg, _IOC_SIZE(cmd));
    else if (_IOC_DIR(cmd) & _IOC_WRITE)
        ret = !access_ok(VERIFY_READ, (void __user *)arg, _IOC_SIZE(cmd));
    if (ret)
        return -EFAULT;
 
    switch (cmd) {
    case 1:
        break;
 
    case 2:
        break;
 
    case 3:
        break;
 
    default:
        break;
    }
    return ret;
}
 
struct file_operations gpio_fops = {
    .owner = THIS_MODULE,
    .open = gpio_open,
    .release = gpio_release,
    .ioctl = gpio_ioctl,
};
 
static int __init ftgpio_function_init(void)
{
    int ret = 0;
    ret = alloc_chrdev_region(&dev_num, 0, 1, GPIO_USE_NAME);
    if (unlikely(ret < 0)) {
        printk(KERN_ERR "%s:alloc_chrdev_region failed\n", __func__);
        goto err1;
    }
    cdev_init(&gpio_cdev, &gpio_fops);
    gpio_cdev.owner = THIS_MODULE;
    gpio_cdev.ops = &gpio_fops;
    ret = cdev_add(&gpio_cdev, dev_num, 1);
    if (unlikely(ret < 0)) {
        printk(KERN_ERR "%s:cdev_add failed\n", __func__);
        goto err3;
    }
    gpio_class = class_create(THIS_MODULE, GPIO_USE_NAME);
    if (IS_ERR(gpio_class)) {
        printk(KERN_ERR "%s:class_create failed\n", __func__);
        goto err2;
    }
    device_create(gpio_class, NULL, gpio_cdev.dev, NULL, GPIO_USE_NAME);
 
    printk(KERN_NOTICE "\nFTGPIO Functions Driver registered success\n");
  err1:
    return ret;
  err2:
    cdev_del(&gpio_cdev);
  err3:
    unregister_chrdev_region(dev_num, 1);
    return ret;
}
 
static void __exit ftgpio_function_exit(void)
{
    unregister_chrdev_region(dev_num, 1);
    cdev_del(&gpio_cdev);
    device_destroy(gpio_class, dev_num);
    class_destroy(gpio_class);
}
 
module_init(ftgpio_function_init);
module_exit(ftgpio_function_exit);
MODULE_AUTHOR("Test Corp.");
MODULE_DESCRIPTION("GPIO Function Driver");
MODULE_LICENSE("GPL");