net: devlink: introduce devlink_compat_switch_id_get() helper

Introduce devlink_compat_switch_id_get() helper which fills up switch_id
according to passed netdev pointer. Call it directly from
dev_get_port_parent_id() as a fallback when ndo_get_port_parent_id
is not defined for given netdev.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/devlink.h

@@ -743,6 +743,8 @@ void devlink_compat_running_version(struct net_device *dev,
 int devlink_compat_flash_update(struct net_device *dev, const char *file_name);
 int devlink_compat_phys_port_name_get(struct net_device *dev,
 				      char *name, size_t len);
+int devlink_compat_switch_id_get(struct net_device *dev,
+				 struct netdev_phys_item_id *ppid);
 
 #else
 
@@ -764,6 +766,13 @@ devlink_compat_phys_port_name_get(struct net_device *dev,
 	return -EOPNOTSUPP;
 }
 
+static inline int
+devlink_compat_switch_id_get(struct net_device *dev,
+			     struct netdev_phys_item_id *ppid)
+{
+	return -EOPNOTSUPP;
+}
+
 #endif
 
 #endif /* _NET_DEVLINK_H_ */

net/core/dev.c

@@ -7900,13 +7900,20 @@ int dev_get_port_parent_id(struct net_device *dev,
 	struct netdev_phys_item_id first = { };
 	struct net_device *lower_dev;
 	struct list_head *iter;
-	int err = -EOPNOTSUPP;
+	int err;
+
+	if (ops->ndo_get_port_parent_id) {
+		err = ops->ndo_get_port_parent_id(dev, ppid);
+		if (err != -EOPNOTSUPP)
+			return err;
+	}
 
-	if (ops->ndo_get_port_parent_id)
-		return ops->ndo_get_port_parent_id(dev, ppid);
+	err = devlink_compat_switch_id_get(dev, ppid);
+	if (!err || err != -EOPNOTSUPP)
+		return err;
 
 	if (!recurse)
-		return err;
+		return -EOPNOTSUPP;
 
 	netdev_for_each_lower_dev(dev, lower_dev, iter) {
 		err = dev_get_port_parent_id(lower_dev, ppid, recurse);

net/core/devlink.c

@@ -6508,6 +6508,25 @@ int devlink_compat_phys_port_name_get(struct net_device *dev,
 	return __devlink_port_phys_port_name_get(devlink_port, name, len);
 }
 
+int devlink_compat_switch_id_get(struct net_device *dev,
+				 struct netdev_phys_item_id *ppid)
+{
+	struct devlink_port *devlink_port;
+
+	/* RTNL mutex is held here which ensures that devlink_port
+	 * instance cannot disappear in the middle. No need to take
+	 * any devlink lock as only permanent values are accessed.
+	 */
+	ASSERT_RTNL();
+	devlink_port = netdev_to_devlink_port(dev);
+	if (!devlink_port || !devlink_port->attrs.switch_port)
+		return -EOPNOTSUPP;
+
+	memcpy(ppid, &devlink_port->attrs.switch_id, sizeof(*ppid));
+
+	return 0;
+}
+
 static int __init devlink_init(void)
 {
 	return genl_register_family(&devlink_nl_family);