Merge branch 'net-dsa-Multi-CPU-ground-work'

Florian Fainelli says:

====================
net: dsa: Multi-CPU ground work (v4)

This patch series prepares the ground for adding mutliple CPU port support to
DSA, and starts by removing redundant pieces of information such as
master_netdev which is cpu_dp->ethernet. Finally drivers are moved away from
directly accessing ds->dst->cpu_dp and use appropriate helper functions.

Note that if you have Device Tree blobs/platform configurations that are
currently listing multiple CPU ports, the proposed behavior in
dsa_ds_get_cpu_dp() will be to return the last bit set in ds->cpu_port_mask.

Future plans include:
- making dst->cpu_dp a flexible data structure (array, list, you name it)
- having the ability for drivers to return a default/preferred CPU port (if
  necessary)

Changes in v4:

- fixed build warning with NETPOLL enabled

Changes in v3:

- removed the last patch since it causes problems with bcm_sf2/b53 in a
  dual-CPU case (root cause known, proper fix underway)

- removed dsa_ds_get_cpu_dp()

Changes in v2:

- added Reviewed-by tags
- assign port->cpu_dp earlier before ops->setup() has run
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/bcm_sf2.c

@@ -806,7 +806,7 @@ static int bcm_sf2_sw_resume(struct dsa_switch *ds)
 static void bcm_sf2_sw_get_wol(struct dsa_switch *ds, int port,
 			       struct ethtool_wolinfo *wol)
 {
-	struct net_device *p = ds->dst[ds->index].master_netdev;
+	struct net_device *p = ds->dst[ds->index].cpu_dp->netdev;
 	struct bcm_sf2_priv *priv = bcm_sf2_to_priv(ds);
 	struct ethtool_wolinfo pwol;
 
@@ -829,7 +829,7 @@ static void bcm_sf2_sw_get_wol(struct dsa_switch *ds, int port,
 static int bcm_sf2_sw_set_wol(struct dsa_switch *ds, int port,
 			      struct ethtool_wolinfo *wol)
 {
-	struct net_device *p = ds->dst[ds->index].master_netdev;
+	struct net_device *p = ds->dst[ds->index].cpu_dp->netdev;
 	struct bcm_sf2_priv *priv = bcm_sf2_to_priv(ds);
 	s8 cpu_port = ds->dst->cpu_dp->index;
 	struct ethtool_wolinfo pwol;

drivers/net/dsa/mt7530.c

@@ -912,11 +912,11 @@ mt7530_setup(struct dsa_switch *ds)
 	struct device_node *dn;
 	struct mt7530_dummy_poll p;
 
-	/* The parent node of master_netdev which holds the common system
+	/* The parent node of cpu_dp->netdev which holds the common system
 	 * controller also is the container for two GMACs nodes representing
 	 * as two netdev instances.
 	 */
-	dn = ds->master_netdev->dev.of_node->parent;
+	dn = ds->dst->cpu_dp->netdev->dev.of_node->parent;
 	priv->ethernet = syscon_node_to_regmap(dn);
 	if (IS_ERR(priv->ethernet))
 		return PTR_ERR(priv->ethernet);

include/net/dsa.h

@@ -122,24 +122,12 @@ struct dsa_switch_tree {
 	 */
 	struct dsa_platform_data	*pd;
 
-	/*
-	 * Reference to network device to use, and which tagging
-	 * protocol to use.
-	 */
-	struct net_device	*master_netdev;
-
 	/* Copy of tag_ops->rcv for faster access in hot path */
 	struct sk_buff *	(*rcv)(struct sk_buff *skb,
 				       struct net_device *dev,
 				       struct packet_type *pt,
 				       struct net_device *orig_dev);
 
-	/*
-	 * Original copy of the master netdev ethtool_ops
-	 */
-	struct ethtool_ops	master_ethtool_ops;
-	const struct ethtool_ops *master_orig_ethtool_ops;
-
 	/*
 	 * The switch port to which the CPU is attached.
 	 */
@@ -183,12 +171,18 @@ struct dsa_port {
 	struct dsa_switch	*ds;
 	unsigned int		index;
 	const char		*name;
+	struct dsa_port		*cpu_dp;
 	struct net_device	*netdev;
 	struct device_node	*dn;
 	unsigned int		ageing_time;
 	u8			stp_state;
 	struct net_device	*bridge_dev;
 	struct devlink_port	devlink_port;
+	/*
+	 * Original copy of the master netdev ethtool_ops
+	 */
+	struct ethtool_ops	ethtool_ops;
+	const struct ethtool_ops *orig_ethtool_ops;
 };
 
 struct dsa_switch {
@@ -226,11 +220,6 @@ struct dsa_switch {
 	 */
 	s8		rtable[DSA_MAX_SWITCHES];
 
-	/*
-	 * The lower device this switch uses to talk to the host
-	 */
-	struct net_device *master_netdev;
-
 	/*
 	 * Slave mii_bus and devices for the individual ports.
 	 */

net/dsa/dsa.c

@@ -118,18 +118,16 @@ int dsa_cpu_port_ethtool_setup(struct dsa_port *cpu_dp)
 	struct net_device *master;
 	struct ethtool_ops *cpu_ops;
 
-	master = ds->dst->master_netdev;
-	if (ds->master_netdev)
-		master = ds->master_netdev;
+	master = cpu_dp->netdev;
 
 	cpu_ops = devm_kzalloc(ds->dev, sizeof(*cpu_ops), GFP_KERNEL);
 	if (!cpu_ops)
 		return -ENOMEM;
 
-	memcpy(&ds->dst->master_ethtool_ops, master->ethtool_ops,
+	memcpy(&cpu_dp->ethtool_ops, master->ethtool_ops,
 	       sizeof(struct ethtool_ops));
-	ds->dst->master_orig_ethtool_ops = master->ethtool_ops;
-	memcpy(cpu_ops, &ds->dst->master_ethtool_ops,
+	cpu_dp->orig_ethtool_ops = master->ethtool_ops;
+	memcpy(cpu_ops, &cpu_dp->ethtool_ops,
 	       sizeof(struct ethtool_ops));
 	dsa_cpu_port_ethtool_init(cpu_ops);
 	master->ethtool_ops = cpu_ops;
@@ -139,14 +137,7 @@ int dsa_cpu_port_ethtool_setup(struct dsa_port *cpu_dp)
 
 void dsa_cpu_port_ethtool_restore(struct dsa_port *cpu_dp)
 {
-	struct dsa_switch *ds = cpu_dp->ds;
-	struct net_device *master;
-
-	master = ds->dst->master_netdev;
-	if (ds->master_netdev)
-		master = ds->master_netdev;
-
-	master->ethtool_ops = ds->dst->master_orig_ethtool_ops;
+	cpu_dp->netdev->ethtool_ops = cpu_dp->orig_ethtool_ops;
 }
 
 void dsa_cpu_dsa_destroy(struct dsa_port *port)

net/dsa/dsa2.c

@@ -337,7 +337,7 @@ static int dsa_ds_apply(struct dsa_switch_tree *dst, struct dsa_switch *ds)
 		return err;
 
 	if (ds->ops->set_addr) {
-		err = ds->ops->set_addr(ds, dst->master_netdev->dev_addr);
+		err = ds->ops->set_addr(ds, dst->cpu_dp->netdev->dev_addr);
 		if (err < 0)
 			return err;
 	}
@@ -444,7 +444,7 @@ static int dsa_dst_apply(struct dsa_switch_tree *dst)
 	 * sent to the tag format's receive function.
 	 */
 	wmb();
-	dst->master_netdev->dsa_ptr = dst;
+	dst->cpu_dp->netdev->dsa_ptr = dst;
 	dst->applied = true;
 
 	return 0;
@@ -458,7 +458,7 @@ static void dsa_dst_unapply(struct dsa_switch_tree *dst)
 	if (!dst->applied)
 		return;
 
-	dst->master_netdev->dsa_ptr = NULL;
+	dst->cpu_dp->netdev->dsa_ptr = NULL;
 
 	/* If we used a tagging format that doesn't have an ethertype
 	 * field, make sure that all packets from this point get sent
@@ -490,6 +490,8 @@ static int dsa_cpu_parse(struct dsa_port *port, u32 index,
 	enum dsa_tag_protocol tag_protocol;
 	struct net_device *ethernet_dev;
 	struct device_node *ethernet;
+	struct dsa_port *p;
+	unsigned int i;
 
 	if (port->dn) {
 		ethernet = of_parse_phandle(port->dn, "ethernet", 0);
@@ -504,14 +506,19 @@ static int dsa_cpu_parse(struct dsa_port *port, u32 index,
 	if (!ethernet_dev)
 		return -EPROBE_DEFER;
 
-	if (!ds->master_netdev)
-		ds->master_netdev = ethernet_dev;
+	if (!dst->cpu_dp) {
+		dst->cpu_dp = port;
+		dst->cpu_dp->netdev = ethernet_dev;
 
-	if (!dst->master_netdev)
-		dst->master_netdev = ethernet_dev;
+		for (i = 0; i < ds->num_ports; i++) {
+			p = &ds->ports[i];
+			if (!dsa_port_is_valid(p) ||
+			    i == index)
+				continue;
 
-	if (!dst->cpu_dp)
-		dst->cpu_dp = port;
+			p->cpu_dp = port;
+		}
+	}
 
 	tag_protocol = ds->ops->get_tag_protocol(ds);
 	dst->tag_ops = dsa_resolve_tag_protocol(tag_protocol);
@@ -578,7 +585,7 @@ static int dsa_dst_parse(struct dsa_switch_tree *dst)
 			return err;
 	}
 
-	if (!dst->master_netdev) {
+	if (!dst->cpu_dp->netdev) {
 		pr_warn("Tree has no master device\n");
 		return -EINVAL;
 	}

net/dsa/dsa_priv.h

@@ -183,4 +183,14 @@ extern const struct dsa_device_ops qca_netdev_ops;
 /* tag_trailer.c */
 extern const struct dsa_device_ops trailer_netdev_ops;
 
+static inline struct net_device *dsa_master_netdev(struct dsa_slave_priv *p)
+{
+	return p->dp->cpu_dp->netdev;
+}
+
+static inline struct dsa_port *dsa_get_cpu_port(struct dsa_switch_tree *dst)
+{
+	return dst->cpu_dp;
+}
+
 #endif

net/dsa/legacy.c

@@ -101,9 +101,12 @@ static int dsa_switch_setup_one(struct dsa_switch *ds, struct device *parent)
 	struct dsa_switch_tree *dst = ds->dst;
 	struct dsa_chip_data *cd = ds->cd;
 	bool valid_name_found = false;
+	struct net_device *master;
 	int index = ds->index;
 	int i, ret;
 
+	master = dst->cpu_dp->netdev;
+
 	/*
 	 * Validate supplied switch configuration.
 	 */
@@ -116,7 +119,7 @@ static int dsa_switch_setup_one(struct dsa_switch *ds, struct device *parent)
 
 		if (!strcmp(name, "cpu")) {
 			if (dst->cpu_dp) {
-				netdev_err(dst->master_netdev,
+				netdev_err(master,
 					   "multiple cpu ports?!\n");
 				return -EINVAL;
 			}
@@ -126,6 +129,7 @@ static int dsa_switch_setup_one(struct dsa_switch *ds, struct device *parent)
 			ds->dsa_port_mask |= 1 << i;
 		} else {
 			ds->enabled_port_mask |= 1 << i;
+			ds->ports[i].cpu_dp = dst->cpu_dp;
 		}
 		valid_name_found = true;
 	}
@@ -168,7 +172,7 @@ static int dsa_switch_setup_one(struct dsa_switch *ds, struct device *parent)
 		return ret;
 
 	if (ops->set_addr) {
-		ret = ops->set_addr(ds, dst->master_netdev->dev_addr);
+		ret = ops->set_addr(ds, master->dev_addr);
 		if (ret < 0)
 			return ret;
 	}
@@ -195,14 +199,14 @@ static int dsa_switch_setup_one(struct dsa_switch *ds, struct device *parent)
 
 		ret = dsa_slave_create(ds, parent, i, cd->port_names[i]);
 		if (ret < 0)
-			netdev_err(dst->master_netdev, "[%d]: can't create dsa slave device for port %d(%s): %d\n",
+			netdev_err(master, "[%d]: can't create dsa slave device for port %d(%s): %d\n",
 				   index, i, cd->port_names[i], ret);
 	}
 
 	/* Perform configuration of the CPU and DSA ports */
 	ret = dsa_cpu_dsa_setups(ds, parent);
 	if (ret < 0)
-		netdev_err(dst->master_netdev, "[%d] : can't configure CPU and DSA ports\n",
+		netdev_err(master, "[%d] : can't configure CPU and DSA ports\n",
 			   index);
 
 	ret = dsa_cpu_port_ethtool_setup(ds->dst->cpu_dp);
@@ -217,6 +221,7 @@ dsa_switch_setup(struct dsa_switch_tree *dst, int index,
 		 struct device *parent, struct device *host_dev)
 {
 	struct dsa_chip_data *cd = dst->pd->chip + index;
+	struct net_device *master = dst->cpu_dp->netdev;
 	const struct dsa_switch_ops *ops;
 	struct dsa_switch *ds;
 	int ret;
@@ -228,11 +233,11 @@ dsa_switch_setup(struct dsa_switch_tree *dst, int index,
 	 */
 	ops = dsa_switch_probe(parent, host_dev, cd->sw_addr, &name, &priv);
 	if (!ops) {
-		netdev_err(dst->master_netdev, "[%d]: could not detect attached switch\n",
+		netdev_err(master, "[%d]: could not detect attached switch\n",
 			   index);
 		return ERR_PTR(-EINVAL);
 	}
-	netdev_info(dst->master_netdev, "[%d]: detected a %s switch\n",
+	netdev_info(master, "[%d]: detected a %s switch\n",
 		    index, name);
 
 
@@ -575,7 +580,7 @@ static int dsa_setup_dst(struct dsa_switch_tree *dst, struct net_device *dev,
 	unsigned configured = 0;
 
 	dst->pd = pd;
-	dst->master_netdev = dev;
+	dst->cpu_dp->netdev = dev;
 
 	for (i = 0; i < pd->nr_chips; i++) {
 		struct dsa_switch *ds;
@@ -671,7 +676,7 @@ static void dsa_remove_dst(struct dsa_switch_tree *dst)
 {
 	int i;
 
-	dst->master_netdev->dsa_ptr = NULL;
+	dst->cpu_dp->netdev->dsa_ptr = NULL;
 
 	/* If we used a tagging format that doesn't have an ethertype
 	 * field, make sure that all packets from this point get sent
@@ -688,7 +693,7 @@ static void dsa_remove_dst(struct dsa_switch_tree *dst)
 
 	dsa_cpu_port_ethtool_restore(dst->cpu_dp);
 
-	dev_put(dst->master_netdev);
+	dev_put(dst->cpu_dp->netdev);
 }
 
 static int dsa_remove(struct platform_device *pdev)

net/dsa/slave.c

@@ -66,7 +66,7 @@ static int dsa_slave_get_iflink(const struct net_device *dev)
 {
 	struct dsa_slave_priv *p = netdev_priv(dev);
 
-	return p->dp->ds->dst->master_netdev->ifindex;
+	return dsa_master_netdev(p)->ifindex;
 }
 
 static int dsa_slave_open(struct net_device *dev)
@@ -74,7 +74,7 @@ static int dsa_slave_open(struct net_device *dev)
 	struct dsa_slave_priv *p = netdev_priv(dev);
 	struct dsa_port *dp = p->dp;
 	struct dsa_switch *ds = dp->ds;
-	struct net_device *master = ds->dst->master_netdev;
+	struct net_device *master = dsa_master_netdev(p);
 	u8 stp_state = dp->bridge_dev ? BR_STATE_BLOCKING : BR_STATE_FORWARDING;
 	int err;
 
@@ -127,7 +127,7 @@ out:
 static int dsa_slave_close(struct net_device *dev)
 {
 	struct dsa_slave_priv *p = netdev_priv(dev);
-	struct net_device *master = p->dp->ds->dst->master_netdev;
+	struct net_device *master = dsa_master_netdev(p);
 	struct dsa_switch *ds = p->dp->ds;
 
 	if (p->phy)
@@ -154,7 +154,7 @@ static int dsa_slave_close(struct net_device *dev)
 static void dsa_slave_change_rx_flags(struct net_device *dev, int change)
 {
 	struct dsa_slave_priv *p = netdev_priv(dev);
-	struct net_device *master = p->dp->ds->dst->master_netdev;
+	struct net_device *master = dsa_master_netdev(p);
 
 	if (change & IFF_ALLMULTI)
 		dev_set_allmulti(master, dev->flags & IFF_ALLMULTI ? 1 : -1);
@@ -165,7 +165,7 @@ static void dsa_slave_change_rx_flags(struct net_device *dev, int change)
 static void dsa_slave_set_rx_mode(struct net_device *dev)
 {
 	struct dsa_slave_priv *p = netdev_priv(dev);
-	struct net_device *master = p->dp->ds->dst->master_netdev;
+	struct net_device *master = dsa_master_netdev(p);
 
 	dev_mc_sync(master, dev);
 	dev_uc_sync(master, dev);
@@ -174,7 +174,7 @@ static void dsa_slave_set_rx_mode(struct net_device *dev)
 static int dsa_slave_set_mac_address(struct net_device *dev, void *a)
 {
 	struct dsa_slave_priv *p = netdev_priv(dev);
-	struct net_device *master = p->dp->ds->dst->master_netdev;
+	struct net_device *master = dsa_master_netdev(p);
 	struct sockaddr *addr = a;
 	int err;
 
@@ -375,7 +375,7 @@ static netdev_tx_t dsa_slave_xmit(struct sk_buff *skb, struct net_device *dev)
 	/* Queue the SKB for transmission on the parent interface, but
 	 * do not modify its EtherType
 	 */
-	nskb->dev = p->dp->ds->dst->master_netdev;
+	nskb->dev = dsa_master_netdev(p);
 	dev_queue_xmit(nskb);
 
 	return NETDEV_TX_OK;
@@ -520,14 +520,14 @@ static void dsa_cpu_port_get_ethtool_stats(struct net_device *dev,
 					   uint64_t *data)
 {
 	struct dsa_switch_tree *dst = dev->dsa_ptr;
-	struct dsa_switch *ds = dst->cpu_dp->ds;
-	s8 cpu_port = dst->cpu_dp->index;
+	struct dsa_port *cpu_dp = dsa_get_cpu_port(dst);
+	struct dsa_switch *ds = cpu_dp->ds;
+	s8 cpu_port = cpu_dp->index;
 	int count = 0;
 
-	if (dst->master_ethtool_ops.get_sset_count) {
-		count = dst->master_ethtool_ops.get_sset_count(dev,
-							       ETH_SS_STATS);
-		dst->master_ethtool_ops.get_ethtool_stats(dev, stats, data);
+	if (cpu_dp->ethtool_ops.get_sset_count) {
+		count = cpu_dp->ethtool_ops.get_sset_count(dev, ETH_SS_STATS);
+		cpu_dp->ethtool_ops.get_ethtool_stats(dev, stats, data);
 	}
 
 	if (ds->ops->get_ethtool_stats)
@@ -537,11 +537,12 @@ static void dsa_cpu_port_get_ethtool_stats(struct net_device *dev,
 static int dsa_cpu_port_get_sset_count(struct net_device *dev, int sset)
 {
 	struct dsa_switch_tree *dst = dev->dsa_ptr;
-	struct dsa_switch *ds = dst->cpu_dp->ds;
+	struct dsa_port *cpu_dp = dsa_get_cpu_port(dst);
+	struct dsa_switch *ds = cpu_dp->ds;
 	int count = 0;
 
-	if (dst->master_ethtool_ops.get_sset_count)
-		count += dst->master_ethtool_ops.get_sset_count(dev, sset);
+	if (cpu_dp->ethtool_ops.get_sset_count)
+		count += cpu_dp->ethtool_ops.get_sset_count(dev, sset);
 
 	if (sset == ETH_SS_STATS && ds->ops->get_sset_count)
 		count += ds->ops->get_sset_count(ds);
@@ -553,8 +554,9 @@ static void dsa_cpu_port_get_strings(struct net_device *dev,
 				     uint32_t stringset, uint8_t *data)
 {
 	struct dsa_switch_tree *dst = dev->dsa_ptr;
-	struct dsa_switch *ds = dst->cpu_dp->ds;
-	s8 cpu_port = dst->cpu_dp->index;
+	struct dsa_port *cpu_dp = dsa_get_cpu_port(dst);
+	struct dsa_switch *ds = cpu_dp->ds;
+	s8 cpu_port = cpu_dp->index;
 	int len = ETH_GSTRING_LEN;
 	int mcount = 0, count;
 	unsigned int i;
@@ -565,10 +567,9 @@ static void dsa_cpu_port_get_strings(struct net_device *dev,
 	/* We do not want to be NULL-terminated, since this is a prefix */
 	pfx[sizeof(pfx) - 1] = '_';
 
-	if (dst->master_ethtool_ops.get_sset_count) {
-		mcount = dst->master_ethtool_ops.get_sset_count(dev,
-								ETH_SS_STATS);
-		dst->master_ethtool_ops.get_strings(dev, stringset, data);
+	if (cpu_dp->ethtool_ops.get_sset_count) {
+		mcount = cpu_dp->ethtool_ops.get_sset_count(dev, ETH_SS_STATS);
+		cpu_dp->ethtool_ops.get_strings(dev, stringset, data);
 	}
 
 	if (stringset == ETH_SS_STATS && ds->ops->get_strings) {
@@ -684,8 +685,7 @@ static int dsa_slave_netpoll_setup(struct net_device *dev,
 				   struct netpoll_info *ni)
 {
 	struct dsa_slave_priv *p = netdev_priv(dev);
-	struct dsa_switch *ds = p->dp->ds;
-	struct net_device *master = ds->dst->master_netdev;
+	struct net_device *master = dsa_master_netdev(p);
 	struct netpoll *netpoll;
 	int err = 0;
 
@@ -1141,11 +1141,11 @@ int dsa_slave_create(struct dsa_switch *ds, struct device *parent,
 	struct net_device *master;
 	struct net_device *slave_dev;
 	struct dsa_slave_priv *p;
+	struct dsa_port *cpu_dp;
 	int ret;
 
-	master = ds->dst->master_netdev;
-	if (ds->master_netdev)
-		master = ds->master_netdev;
+	cpu_dp = ds->dst->cpu_dp;
+	master = cpu_dp->netdev;
 
 	slave_dev = alloc_netdev(sizeof(struct dsa_slave_priv), name,
 				 NET_NAME_UNKNOWN, ether_setup);

net/dsa/tag_brcm.c

@@ -93,12 +93,11 @@ static struct sk_buff *brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 				    struct net_device *orig_dev)
 {
 	struct dsa_switch_tree *dst = dev->dsa_ptr;
-	struct dsa_switch *ds;
+	struct dsa_port *cpu_dp = dsa_get_cpu_port(dst);
+	struct dsa_switch *ds = cpu_dp->ds;
 	int source_port;
 	u8 *brcm_tag;
 
-	ds = dst->cpu_dp->ds;
-
 	if (unlikely(!pskb_may_pull(skb, BRCM_TAG_LEN)))
 		return NULL;
 

net/dsa/tag_ksz.c

@@ -75,12 +75,11 @@ static struct sk_buff *ksz_rcv(struct sk_buff *skb, struct net_device *dev,
 			       struct net_device *orig_dev)
 {
 	struct dsa_switch_tree *dst = dev->dsa_ptr;
-	struct dsa_switch *ds;
+	struct dsa_port *cpu_dp = dsa_get_cpu_port(dst);
+	struct dsa_switch *ds = cpu_dp->ds;
 	u8 *tag;
 	int source_port;
 
-	ds = dst->cpu_dp->ds;
-
 	tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN;
 
 	source_port = tag[0] & 7;

net/dsa/tag_qca.c

@@ -67,6 +67,7 @@ static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 				   struct net_device *orig_dev)
 {
 	struct dsa_switch_tree *dst = dev->dsa_ptr;
+	struct dsa_port *cpu_dp = dsa_get_cpu_port(dst);
 	struct dsa_switch *ds;
 	u8 ver;
 	int port;
@@ -95,7 +96,7 @@ static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 	/* This protocol doesn't support cascading multiple switches so it's
 	 * safe to assume the switch is first in the tree
 	 */
-	ds = dst->cpu_dp->ds;
+	ds = cpu_dp->ds;
 	if (!ds)
 		return NULL;
 

net/dsa/tag_trailer.c

@@ -61,12 +61,11 @@ static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev,
 				   struct net_device *orig_dev)
 {
 	struct dsa_switch_tree *dst = dev->dsa_ptr;
-	struct dsa_switch *ds;
+	struct dsa_port *cpu_dp = dsa_get_cpu_port(dst);
+	struct dsa_switch *ds = cpu_dp->ds;
 	u8 *trailer;
 	int source_port;
 
-	ds = dst->cpu_dp->ds;
-
 	if (skb_linearize(skb))
 		return NULL;