net: dsa: Add support for DSA specific notifiers

In preparation for communicating a given DSA network device's port
number and switch index, create a specialized DSA notifier and two
events: DSA_PORT_REGISTER and DSA_PORT_UNREGISTER that communicate: the
slave network device (slave_dev), port number and switch number in the
tree.

This will be later used for network device drivers like bcmsysport which
needs to cooperate with its DSA network devices to set-up queue mapping
and scheduling.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -471,4 +471,49 @@ static inline int dsa_switch_resume(struct dsa_switch *ds)
 }
 #endif /* CONFIG_PM_SLEEP */
 
+enum dsa_notifier_type {
+	DSA_PORT_REGISTER,
+	DSA_PORT_UNREGISTER,
+};
+
+struct dsa_notifier_info {
+	struct net_device *dev;
+};
+
+struct dsa_notifier_register_info {
+	struct dsa_notifier_info info;	/* must be first */
+	struct net_device *master;
+	unsigned int port_number;
+	unsigned int switch_number;
+};
+
+static inline struct net_device *
+dsa_notifier_info_to_dev(const struct dsa_notifier_info *info)
+{
+	return info->dev;
+}
+
+#if IS_ENABLED(CONFIG_NET_DSA)
+int register_dsa_notifier(struct notifier_block *nb);
+int unregister_dsa_notifier(struct notifier_block *nb);
+int call_dsa_notifiers(unsigned long val, struct net_device *dev,
+		       struct dsa_notifier_info *info);
+#else
+static inline int register_dsa_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int unregister_dsa_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int call_dsa_notifiers(unsigned long val, struct net_device *dev,
+				     struct dsa_notifier_info *info)
+{
+	return NOTIFY_DONE;
+}
+#endif
+
 #endif

net/dsa/dsa.c

@@ -14,6 +14,7 @@
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/module.h>
+#include <linux/notifier.h>
 #include <linux/of.h>
 #include <linux/of_mdio.h>
 #include <linux/of_platform.h>
@@ -261,6 +262,28 @@ bool dsa_schedule_work(struct work_struct *work)
 	return queue_work(dsa_owq, work);
 }
 
+static ATOMIC_NOTIFIER_HEAD(dsa_notif_chain);
+
+int register_dsa_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_register(&dsa_notif_chain, nb);
+}
+EXPORT_SYMBOL_GPL(register_dsa_notifier);
+
+int unregister_dsa_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_unregister(&dsa_notif_chain, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_dsa_notifier);
+
+int call_dsa_notifiers(unsigned long val, struct net_device *dev,
+		       struct dsa_notifier_info *info)
+{
+	info->dev = dev;
+	return atomic_notifier_call_chain(&dsa_notif_chain, val, info);
+}
+EXPORT_SYMBOL_GPL(call_dsa_notifiers);
+
 static int __init dsa_init_module(void)
 {
 	int rc;

net/dsa/slave.c

@@ -1116,6 +1116,7 @@ int dsa_slave_resume(struct net_device *slave_dev)
 
 int dsa_slave_create(struct dsa_port *port, const char *name)
 {
+	struct dsa_notifier_register_info rinfo = { };
 	struct dsa_switch *ds = port->ds;
 	struct net_device *master;
 	struct net_device *slave_dev;
@@ -1177,6 +1178,12 @@ int dsa_slave_create(struct dsa_port *port, const char *name)
 		goto out_free;
 	}
 
+	rinfo.info.dev = slave_dev;
+	rinfo.master = master;
+	rinfo.port_number = p->dp->index;
+	rinfo.switch_number = p->dp->ds->index;
+	call_dsa_notifiers(DSA_PORT_REGISTER, slave_dev, &rinfo.info);
+
 	ret = register_netdev(slave_dev);
 	if (ret) {
 		netdev_err(master, "error %d registering interface %s\n",
@@ -1200,6 +1207,7 @@ int dsa_slave_create(struct dsa_port *port, const char *name)
 void dsa_slave_destroy(struct net_device *slave_dev)
 {
 	struct dsa_slave_priv *p = netdev_priv(slave_dev);
+	struct dsa_notifier_register_info rinfo = { };
 	struct device_node *port_dn;
 
 	port_dn = p->dp->dn;
@@ -1211,6 +1219,11 @@ void dsa_slave_destroy(struct net_device *slave_dev)
 		if (of_phy_is_fixed_link(port_dn))
 			of_phy_deregister_fixed_link(port_dn);
 	}
+	rinfo.info.dev = slave_dev;
+	rinfo.master = p->dp->cpu_dp->netdev;
+	rinfo.port_number = p->dp->index;
+	rinfo.switch_number = p->dp->ds->index;
+	call_dsa_notifiers(DSA_PORT_UNREGISTER, slave_dev, &rinfo.info);
 	unregister_netdev(slave_dev);
 	free_percpu(p->stats64);
 	free_netdev(slave_dev);