On Wed, 11 Mar 2026 17:41:53 +0100 Théo Lebrun wrote:

+	struct macb *bp = netdev_priv(netdev);
+	unsigned int old_count = bp->num_queues;
+	unsigned int count = ch->combined_count;
+	int ret = 0;

unnecessary init

+	/*
+	 * 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;
+
+	if (count == old_count)
+		return 0;

should we reorder this with the running() check?