net: dsa: integrate with SWITCHDEV for HW bridging

In order to support bridging offloads in DSA switch drivers, select
NET_SWITCHDEV to get access to the port_stp_update and parent_get_id
NDOs that we are required to implement.

To facilitate the integratation at the DSA driver level, we implement 3
types of operations:

- port_join_bridge
- port_leave_bridge
- port_stp_update

DSA will resolve which switch ports that are currently bridge port
members as some Switch hardware/drivers need to know about that to limit
the register programming to just the relevant registers (especially for
slow MDIO buses).

We also take care of setting the correct STP state when slave network
devices are brought up/down while being bridge members.

Finally, when a port is leaving the bridge, we make sure we set in
BR_STATE_FORWARDING state, otherwise the bridge layer would leave it
disabled as a result of having left the bridge.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/dsa.c

@@ -826,6 +826,10 @@ static struct packet_type dsa_pack_type __read_mostly = {
 	.func	= dsa_switch_rcv,
 };
 
+static struct notifier_block dsa_netdevice_nb __read_mostly = {
+	.notifier_call	= dsa_slave_netdevice_event,
+};
+
 #ifdef CONFIG_PM_SLEEP
 static int dsa_suspend(struct device *d)
 {
@@ -884,6 +888,8 @@ static int __init dsa_init_module(void)
 {
 	int rc;
 
+	register_netdevice_notifier(&dsa_netdevice_nb);
+
 	rc = platform_driver_register(&dsa_driver);
 	if (rc)
 		return rc;
@@ -896,6 +902,7 @@ module_init(dsa_init_module);
 
 static void __exit dsa_cleanup_module(void)
 {
+	unregister_netdevice_notifier(&dsa_netdevice_nb);
 	dev_remove_pack(&dsa_pack_type);
 	platform_driver_unregister(&dsa_driver);
 }