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

Trigger a switchdev event whenever the bridge's MST mode is
enabled/disabled. This allows constituent ports to either perform any
required hardware config, or refuse the change if it not supported.
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

@@ -27,6 +27,7 @@ enum switchdev_attr_id {
 	SWITCHDEV_ATTR_ID_BRIDGE_VLAN_PROTOCOL,
 	SWITCHDEV_ATTR_ID_BRIDGE_MC_DISABLED,
 	SWITCHDEV_ATTR_ID_BRIDGE_MROUTER,
+	SWITCHDEV_ATTR_ID_BRIDGE_MST,
 	SWITCHDEV_ATTR_ID_MRP_PORT_ROLE,
 };
 
@@ -48,6 +49,7 @@ struct switchdev_attr {
 		clock_t ageing_time;			/* BRIDGE_AGEING_TIME */
 		bool vlan_filtering;			/* BRIDGE_VLAN_FILTERING */
 		u16 vlan_protocol;			/* BRIDGE_VLAN_PROTOCOL */
+		bool mst;				/* BRIDGE_MST */
 		bool mc_disabled;			/* MC_DISABLED */
 		u8 mrp_port_role;			/* MRP_PORT_ROLE */
 	} u;

net/bridge/br_mst.c

@@ -7,6 +7,7 @@
  */
 
 #include <linux/kernel.h>
+#include <net/switchdev.h>
 
 #include "br_private.h"
 
@@ -102,8 +103,14 @@ void br_mst_vlan_init_state(struct net_bridge_vlan *v)
 int br_mst_set_enabled(struct net_bridge *br, bool on,
 		       struct netlink_ext_ack *extack)
 {
+	struct switchdev_attr attr = {
+		.id = SWITCHDEV_ATTR_ID_BRIDGE_MST,
+		.orig_dev = br->dev,
+		.u.mst = on,
+	};
 	struct net_bridge_vlan_group *vg;
 	struct net_bridge_port *p;
+	int err;
 
 	list_for_each_entry(p, &br->port_list, list) {
 		vg = nbp_vlan_group(p);
@@ -119,6 +126,10 @@ int br_mst_set_enabled(struct net_bridge *br, bool on,
 	if (br_opt_get(br, BROPT_MST_ENABLED) == on)
 		return 0;
 
+	err = switchdev_port_attr_set(br->dev, &attr, extack);
+	if (err && err != -EOPNOTSUPP)
+		return err;
+
 	if (on)
 		static_branch_enable(&br_mst_used);
 	else