net: bridge: mst: Notify switchdev drivers of MST state changes

Generate a switchdev notification whenever an MST state changes. This
notification is keyed by the VLANs MSTI rather than the VID, since
multiple VLANs may share the same MST instance.
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/switchdev.h

@@ -19,6 +19,7 @@
 enum switchdev_attr_id {
 	SWITCHDEV_ATTR_ID_UNDEFINED,
 	SWITCHDEV_ATTR_ID_PORT_STP_STATE,
+	SWITCHDEV_ATTR_ID_PORT_MST_STATE,
 	SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS,
 	SWITCHDEV_ATTR_ID_PORT_PRE_BRIDGE_FLAGS,
 	SWITCHDEV_ATTR_ID_PORT_MROUTER,
@@ -32,6 +33,11 @@ enum switchdev_attr_id {
 	SWITCHDEV_ATTR_ID_VLAN_MSTI,
 };
 
+struct switchdev_mst_state {
+	u16 msti;
+	u8 state;
+};
+
 struct switchdev_brport_flags {
 	unsigned long val;
 	unsigned long mask;
@@ -50,6 +56,7 @@ struct switchdev_attr {
 	void (*complete)(struct net_device *dev, int err, void *priv);
 	union {
 		u8 stp_state;				/* PORT_STP_STATE */
+		struct switchdev_mst_state mst_state;	/* PORT_MST_STATE */
 		struct switchdev_brport_flags brport_flags; /* PORT_BRIDGE_FLAGS */
 		bool mrouter;				/* PORT_MROUTER */
 		clock_t ageing_time;			/* BRIDGE_AGEING_TIME */

net/bridge/br_mst.c

@@ -30,13 +30,31 @@ static void br_mst_vlan_set_state(struct net_bridge_port *p, struct net_bridge_v
 int br_mst_set_state(struct net_bridge_port *p, u16 msti, u8 state,
 		     struct netlink_ext_ack *extack)
 {
+	struct switchdev_attr attr = {
+		.id = SWITCHDEV_ATTR_ID_PORT_MST_STATE,
+		.orig_dev = p->dev,
+		.u.mst_state = {
+			.msti = msti,
+			.state = state,
+		},
+	};
 	struct net_bridge_vlan_group *vg;
 	struct net_bridge_vlan *v;
+	int err;
 
 	vg = nbp_vlan_group(p);
 	if (!vg)
 		return 0;
 
+	/* MSTI 0 (CST) state changes are notified via the regular
+	 * SWITCHDEV_ATTR_ID_PORT_STP_STATE.
+	 */
+	if (msti) {
+		err = switchdev_port_attr_set(p->dev, &attr, extack);
+		if (err && err != -EOPNOTSUPP)
+			return err;
+	}
+
 	list_for_each_entry(v, &vg->vlan_list, vlist) {
 		if (v->brvlan->msti != msti)
 			continue;