dsa: implement ndo_get_devlink_port

In order for devlink compat functions to work, implement
ndo_get_devlink_port. Legacy slaves does not have devlink port instances
created for themselves.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/slave.c

@@ -1096,6 +1096,13 @@ int dsa_legacy_fdb_del(struct ndmsg *ndm, struct nlattr *tb[],
 	return dsa_port_fdb_del(dp, addr, vid);
 }
 
+static struct devlink_port *dsa_slave_get_devlink_port(struct net_device *dev)
+{
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+
+	return dp->ds->devlink ? &dp->devlink_port : NULL;
+}
+
 static const struct net_device_ops dsa_slave_netdev_ops = {
 	.ndo_open	 	= dsa_slave_open,
 	.ndo_stop		= dsa_slave_close,
@@ -1119,6 +1126,7 @@ static const struct net_device_ops dsa_slave_netdev_ops = {
 	.ndo_get_port_parent_id	= dsa_slave_get_port_parent_id,
 	.ndo_vlan_rx_add_vid	= dsa_slave_vlan_rx_add_vid,
 	.ndo_vlan_rx_kill_vid	= dsa_slave_vlan_rx_kill_vid,
+	.ndo_get_devlink_port	= dsa_slave_get_devlink_port,
 };
 
 static struct device_type dsa_type = {