[PATCH net-next v4] switchdev: fix stp update API to work with layered netdevices

[roopa@cumulusnetworks.com]

From: Roopa Prabhu <roopa@cumulusnetworks.com>

make it same as the netdev_switch_port_bridge_setlink/dellink
api (ie traverse lowerdevs to get to the switch port).

removes "WARN_ON(!ops->ndo_switch_parent_id_get)" because
direct bridge ports can be stacked netdevices (like bonds
and team of switch ports) which may not imeplement this ndo.

v2 to v3:
	- remove changes to bond and team. Bring back the
	transparently following lowerdevs like i initially
	had for setlink/getlink
	(http://www.spinics.net/lists/netdev/msg313436.html)
	dave and scott feldman also seem to prefer it be that
	way and move to non-transparent way of doing things
	if we see a problem down the lane.

v3 to v4:
	- fix ret initialization

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
---
 net/switchdev/switchdev.c |   20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
index c9bfa00..e593b59 100644
--- a/net/switchdev/switchdev.c
+++ b/net/switchdev/switchdev.c
@@ -47,11 +47,23 @@ EXPORT_SYMBOL_GPL(netdev_switch_parent_id_get);
 int netdev_switch_port_stp_update(struct net_device *dev, u8 state)
 {
 	const struct swdev_ops *ops = dev->swdev_ops;
+	struct net_device *lower_dev;
+	struct list_head *iter;
+	int ret = -EOPNOTSUPP, err;
 
-	if (!ops || !ops->swdev_port_stp_update)
-		return -EOPNOTSUPP;
-	WARN_ON(!ops->swdev_parent_id_get);
-	return ops->swdev_port_stp_update(dev, state);
+	if (!(dev->features & NETIF_F_HW_SWITCH_OFFLOAD))
+		return ret;
+
+	if (ops && ops->swdev_port_stp_update)
+		return ops->swdev_port_stp_update(dev, state);
+
+	netdev_for_each_lower_dev(dev, lower_dev, iter) {
+		err = netdev_switch_port_stp_update(lower_dev, state);
+		if (err && err != -EOPNOTSUPP)
+			ret = err;
+	}
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(netdev_switch_port_stp_update);
 
-- 
1.7.10.4