wifi: ath12k: 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 struct ath12k_ext_irq_grp by converting it
into a pointer. Then use the leverage alloc_netdev_dummy() to allocate
the net_device object at ath12k_pci_ext_irq_config().

The free of the device occurs at ath12k_pci_free_ext_irq().

Link: https://lore.kernel.org/all/20240229225910.79e224cf@kernel.org/ [1]
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240508095410.1923198-1-leitao@debian.org

drivers/net/wireless/ath/ath12k/core.h

@@ -146,7 +146,7 @@ struct ath12k_ext_irq_grp {
 	u32 grp_id;
 	u64 timestamp;
 	struct napi_struct napi;
-	struct net_device napi_ndev;
+	struct net_device *napi_ndev;
 };
 
 struct ath12k_smbios_bdf {

drivers/net/wireless/ath/ath12k/pci.c

@@ -350,6 +350,7 @@ static void ath12k_pci_free_ext_irq(struct ath12k_base *ab)
 			free_irq(ab->irq_num[irq_grp->irqs[j]], irq_grp);
 
 		netif_napi_del(&irq_grp->napi);
+		free_netdev(irq_grp->napi_ndev);
 	}
 }
 
@@ -560,8 +561,9 @@ static irqreturn_t ath12k_pci_ext_interrupt_handler(int irq, void *arg)
 static int ath12k_pci_ext_irq_config(struct ath12k_base *ab)
 {
 	struct ath12k_pci *ab_pci = ath12k_pci_priv(ab);
-	int i, j, ret, num_vectors = 0;
+	int i, j, n, ret, num_vectors = 0;
 	u32 user_base_data = 0, base_vector = 0, base_idx;
+	struct ath12k_ext_irq_grp *irq_grp;
 
 	base_idx = ATH12K_PCI_IRQ_CE0_OFFSET + CE_COUNT_MAX;
 	ret = ath12k_pci_get_user_msi_assignment(ab, "DP",
@@ -572,13 +574,18 @@ static int ath12k_pci_ext_irq_config(struct ath12k_base *ab)
 		return ret;
 
 	for (i = 0; i < ATH12K_EXT_IRQ_GRP_NUM_MAX; i++) {
-		struct ath12k_ext_irq_grp *irq_grp = &ab->ext_irq_grp[i];
+		irq_grp = &ab->ext_irq_grp[i];
 		u32 num_irq = 0;
 
 		irq_grp->ab = ab;
 		irq_grp->grp_id = i;
-		init_dummy_netdev(&irq_grp->napi_ndev);
-		netif_napi_add(&irq_grp->napi_ndev, &irq_grp->napi,
+		irq_grp->napi_ndev = alloc_netdev_dummy(0);
+		if (!irq_grp->napi_ndev) {
+			ret = -ENOMEM;
+			goto fail_allocate;
+		}
+
+		netif_napi_add(irq_grp->napi_ndev, &irq_grp->napi,
 			       ath12k_pci_ext_grp_napi_poll);
 
 		if (ab->hw_params->ring_mask->tx[i] ||
@@ -611,13 +618,23 @@ static int ath12k_pci_ext_irq_config(struct ath12k_base *ab)
 			if (ret) {
 				ath12k_err(ab, "failed request irq %d: %d\n",
 					   vector, ret);
-				return ret;
+				goto fail_request;
 			}
 		}
 		ath12k_pci_ext_grp_disable(irq_grp);
 	}
 
 	return 0;
+
+fail_request:
+	/* i ->napi_ndev was properly allocated. Free it also */
+	i += 1;
+fail_allocate:
+	for (n = 0; n < i; n++) {
+		irq_grp = &ab->ext_irq_grp[n];
+		free_netdev(irq_grp->napi_ndev);
+	}
+	return ret;
 }
 
 static int ath12k_pci_set_irq_affinity_hint(struct ath12k_pci *ab_pci,