有時為了除錯方便，需要建立一個檔案節點，供上層呼叫，下面是一個較簡單的例子；

可以在其基礎上，稍加修改名字，即可使用。

static ssize_t usb_hnp_show(struct file *file, char __user *user_buf,
				     size_t count, loff_t *ppos)
{
//	char *buf;
	ssize_t ret;
	struct usb_device *udev = global_usb_device;

	if (udev == NULL)
	{
		printk(KERN_ERR "%s:the usb_device is NULL\n", __func__);
		return -EFAULT;
	}

	dev_err(&udev->dev, "zsm %s\n", __func__);

	return ret;
}

static ssize_t usb_hnp_store(struct file *file,
				      const char __user *user_buf, size_t count,
				      loff_t *ppos)
{
	char buf[32];
	ssize_t buf_size;
	struct usb_device *udev = global_usb_device;

	if (udev == NULL)
	{
		printk(KERN_ERR "%s:the usb_device is NULL\n", __func__);
		return -EFAULT;
	}

	dev_err(&udev->dev, "zsm %s\n", __func__);

	buf_size = min(count, (size_t)(sizeof(buf)-1));
	if (copy_from_user(buf, user_buf, buf_size)) {
		dev_err(&udev->dev, "Failed to copy from user\n");
		return -EFAULT;
	}
	buf[buf_size] = 0;

	return buf_size;
}

static const struct file_operations usb_hnp_node_fops = {
	.owner = THIS_MODULE,
	.open = simple_open,
	.read = usb_hnp_show,
	.write = usb_hnp_store,
};
 

	struct dentry *usb_hnp_dentry;

	usb_hnp_dentry = debugfs_create_file("enable_usb_hnp",
					S_IRUGO, NULL, NULL, &usb_hnp_node_fops);

編譯執行後，生成的目錄在

/sys/kernel/debug/ 下。