Openwrt/target/linux/generic/backport-5.4/774-v5.12-net-dsa-exit-early-in-dsa_slave_switchdev_event-if-w.patch

From 5fb4a451a87d8ed3363d28b63a3295399373d6c4 Mon Sep 17 00:00:00 2001
From: Vladimir Oltean <vladimir.oltean@nxp.com>
Date: Wed, 6 Jan 2021 11:51:34 +0200
Subject: [PATCH] net: dsa: exit early in dsa_slave_switchdev_event if we can't
 program the FDB

Right now, the following would happen for a switch driver that does not
implement .port_fdb_add or .port_fdb_del.

dsa_slave_switchdev_event returns NOTIFY_OK and schedules:
-> dsa_slave_switchdev_event_work
   -> dsa_port_fdb_add
      -> dsa_port_notify(DSA_NOTIFIER_FDB_ADD)
         -> dsa_switch_fdb_add
            -> if (!ds->ops->port_fdb_add) return -EOPNOTSUPP;
   -> an error is printed with dev_dbg, and
      dsa_fdb_offload_notify(switchdev_work) is not called.

We can avoid scheduling the worker for nothing and say NOTIFY_DONE.
Because we don't call dsa_fdb_offload_notify, the static FDB entry will
remain just in the software bridge.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/dsa/slave.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1655,6 +1655,9 @@ static int dsa_slave_switchdev_event(str
 
 		dp = dsa_slave_to_port(dev);
 
+		if (!dp->ds->ops->port_fdb_add || !dp->ds->ops->port_fdb_del)
+			return NOTIFY_DONE;
+
 		switchdev_work = kzalloc(sizeof(*switchdev_work), GFP_ATOMIC);
 		if (!switchdev_work)
 			return NOTIFY_BAD;