net: ibm/emac: allocate dummy net_device dynamically

Embedding net_device into structures prohibits the usage of flexible
arrays in the net_device structure. For more details, see the discussion
at [1].

Un-embed the net_device from the private struct by converting it
into a pointer. Then use the leverage the new alloc_netdev_dummy()
helper to allocate and initialize dummy devices.

[1] https://lore.kernel.org/all/20240229225910.79e224cf@kernel.org/Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ibm/emac/mal.c

@@ -605,9 +605,13 @@ static int mal_probe(struct platform_device *ofdev)
 	INIT_LIST_HEAD(&mal->list);
 	spin_lock_init(&mal->lock);
 
-	init_dummy_netdev(&mal->dummy_dev);
+	mal->dummy_dev = alloc_netdev_dummy(0);
+	if (!mal->dummy_dev) {
+		err = -ENOMEM;
+		goto fail_unmap;
+	}
 
-	netif_napi_add_weight(&mal->dummy_dev, &mal->napi, mal_poll,
+	netif_napi_add_weight(mal->dummy_dev, &mal->napi, mal_poll,
 			      CONFIG_IBM_EMAC_POLL_WEIGHT);
 
 	/* Load power-on reset defaults */
@@ -637,7 +641,7 @@ static int mal_probe(struct platform_device *ofdev)
 					  GFP_KERNEL);
 	if (mal->bd_virt == NULL) {
 		err = -ENOMEM;
-		goto fail_unmap;
+		goto fail_dummy;
 	}
 
 	for (i = 0; i < mal->num_tx_chans; ++i)
@@ -703,6 +707,8 @@ static int mal_probe(struct platform_device *ofdev)
 	free_irq(mal->serr_irq, mal);
  fail2:
 	dma_free_coherent(&ofdev->dev, bd_size, mal->bd_virt, mal->bd_dma);
+ fail_dummy:
+	free_netdev(mal->dummy_dev);
  fail_unmap:
 	dcr_unmap(mal->dcr_host, 0x100);
  fail:
@@ -734,6 +740,8 @@ static void mal_remove(struct platform_device *ofdev)
 
 	mal_reset(mal);
 
+	free_netdev(mal->dummy_dev);
+
 	dma_free_coherent(&ofdev->dev,
 			  sizeof(struct mal_descriptor) *
 			  (NUM_TX_BUFF * mal->num_tx_chans +

drivers/net/ethernet/ibm/emac/mal.h

@@ -205,7 +205,7 @@ struct mal_instance {
 	int			index;
 	spinlock_t		lock;
 
-	struct net_device	dummy_dev;
+	struct net_device	*dummy_dev;
 
 	unsigned int features;
 };