i3c: Add support for bus enumeration & notification

This allows other drivers to be notified when new i3c busses are
attached, referring to a whole i3c bus as opposed to individual
devices.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/i3c/master.c

@@ -22,6 +22,7 @@
 static DEFINE_IDR(i3c_bus_idr);
 static DEFINE_MUTEX(i3c_core_lock);
 static int __i3c_first_dynamic_bus_num;
+static BLOCKING_NOTIFIER_HEAD(i3c_bus_notifier);
 
 /**
  * i3c_bus_maintenance_lock - Lock the bus for a maintenance operation
@@ -453,6 +454,36 @@ static int i3c_bus_init(struct i3c_bus *i3cbus, struct device_node *np)
 	return 0;
 }
 
+void i3c_for_each_bus_locked(int (*fn)(struct i3c_bus *bus, void *data),
+			     void *data)
+{
+	struct i3c_bus *bus;
+	int id;
+
+	mutex_lock(&i3c_core_lock);
+	idr_for_each_entry(&i3c_bus_idr, bus, id)
+		fn(bus, data);
+	mutex_unlock(&i3c_core_lock);
+}
+EXPORT_SYMBOL_GPL(i3c_for_each_bus_locked);
+
+int i3c_register_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&i3c_bus_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(i3c_register_notifier);
+
+int i3c_unregister_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&i3c_bus_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(i3c_unregister_notifier);
+
+static void i3c_bus_notify(struct i3c_bus *bus, unsigned int action)
+{
+	blocking_notifier_call_chain(&i3c_bus_notifier, action, bus);
+}
+
 static const char * const i3c_bus_mode_strings[] = {
 	[I3C_BUS_MODE_PURE] = "pure",
 	[I3C_BUS_MODE_MIXED_FAST] = "mixed-fast",
@@ -2682,6 +2713,8 @@ int i3c_master_register(struct i3c_master_controller *master,
 	if (ret)
 		goto err_del_dev;
 
+	i3c_bus_notify(i3cbus, I3C_NOTIFY_BUS_ADD);
+
 	/*
 	 * We're done initializing the bus and the controller, we can now
 	 * register I3C devices discovered during the initial DAA.
@@ -2714,6 +2747,8 @@ EXPORT_SYMBOL_GPL(i3c_master_register);
  */
 void i3c_master_unregister(struct i3c_master_controller *master)
 {
+	i3c_bus_notify(&master->bus, I3C_NOTIFY_BUS_REMOVE);
+
 	i3c_master_i2c_adapter_cleanup(master);
 	i3c_master_unregister_i3c_devs(master);
 	i3c_master_bus_cleanup(master);

include/linux/i3c/master.h

@@ -24,6 +24,12 @@
 
 struct i2c_client;
 
+/* notifier actions. notifier call data is the struct i3c_bus */
+enum {
+	I3C_NOTIFY_BUS_ADD,
+	I3C_NOTIFY_BUS_REMOVE,
+};
+
 struct i3c_master_controller;
 struct i3c_bus;
 struct i3c_device;
@@ -652,4 +658,9 @@ void i3c_master_queue_ibi(struct i3c_dev_desc *dev, struct i3c_ibi_slot *slot);
 
 struct i3c_ibi_slot *i3c_master_get_free_ibi_slot(struct i3c_dev_desc *dev);
 
+void i3c_for_each_bus_locked(int (*fn)(struct i3c_bus *bus, void *data),
+			     void *data);
+int i3c_register_notifier(struct notifier_block *nb);
+int i3c_unregister_notifier(struct notifier_block *nb);
+
 #endif /* I3C_MASTER_H */