On Tue, 17 Mar 2026 17:19:08 +0100 Théo Lebrun wrote:

+static int macb_set_channels(struct net_device *netdev,
+			     struct ethtool_channels *ch)
+{
+	struct macb *bp = netdev_priv(netdev);
+	unsigned int old_count = bp->num_queues;
+	unsigned int count = ch->combined_count;
+	int ret;
+
+	/*
+	 * MACB_CAPS_QUEUE_DISABLE means that the field QUEUE_DISABLE/BIT0 in
+	 * the per-queue RBQP register disables queue Rx. If we don't have that
+	 * capability we can have multiple queues but we must always run with
+	 * all enabled.
+	 */
+	if (!(bp->caps & MACB_CAPS_QUEUE_DISABLE))
+		return -EOPNOTSUPP;
+
+	/*
+	 * An ideal .set_channels() implementation uses upfront allocated
+	 * resources and swaps them in, bringing reliability under memory
+	 * pressure. However, here we implement it for memory savings in
+	 * setups with less than max number of queues active.
+	 *
+	 * Signal it by refusing .set_channels() once interface is opened.
+	 */
+	if (netif_running(bp->dev))
+		return -EBUSY;
+
+	ret = netif_set_real_num_queues(bp->dev, count, count);
+	if (ret)
+		return ret;
+
+	bp->num_queues = count;
+	return 0;
+}

Looks like some left over here:

drivers/net/ethernet/cadence/macb_main.c:4173:15: warning: unused variable 'old_count' [-Wunused-variable]
 4173 |         unsigned int old_count = bp->num_queues;
      |                      ^~~~~~~~~