On Thu, 12 Sep 2024 10:51:22 +0800 Jijie Shao wrote:

+static int hbg_net_change_mtu(struct net_device *netdev, int new_mtu)
+{
+	struct hbg_priv *priv = netdev_priv(netdev);
+	bool is_running = netif_running(netdev);
+
+	if (is_running)
+		hbg_net_stop(netdev);
+
+	hbg_change_mtu(priv, new_mtu);
+	WRITE_ONCE(netdev->mtu, new_mtu);
+
+	dev_dbg(&priv->pdev->dev,
+		"change mtu from %u to %u\n", netdev->mtu, new_mtu);
+	if (is_running)
+		hbg_net_open(netdev);

What if open() fails? You either have to pre-allocate the new resources
or find a way of resetting without reallocating memory. Or return -EBUSY
if interface is running