Introduce struct bus_type for describing types of buses

Define bus_register for bus registration
Define get_bus and put_bus for bus refcounting

drivers/base/bus.c

+/*
+ * bus.c - bus driver management
+ * 
+ * Copyright (c) 2002 Patrick Mochel
+ *		 2002 Open Source Development Lab
+ * 
+ * 
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+
+
+static LIST_HEAD(bus_driver_list);
+
+static struct driver_dir_entry bus_dir = {
+	name:	"bus",
+	mode:	(S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO),
+};
+
+/**
+ * bus_add_device - add device to bus
+ * @dev:	device being added
+ *
+ * Add the device to its bus's list of devices.
+ * Create a symlink in the bus's 'devices' directory to the 
+ * device's physical location.
+ * Try and bind the device to a driver.
+ */
+int bus_add_device(struct device * dev)
+{
+	if (dev->bus) {
+		get_bus(dev->bus);
+		write_lock(&dev->bus->lock);
+		list_add_tail(&dev->bus_list,&dev->bus->devices);
+		write_unlock(&dev->bus->lock);
+	}
+	return 0;
+}
+
+/**
+ * bus_remove_device - remove device from bus
+ * @dev:	device to be removed
+ *
+ * Remove symlink from bus's directory.
+ * Delete device from bus's list.
+ */
+void bus_remove_device(struct device * dev)
+{
+	if (dev->bus) {
+		write_lock(&dev->bus->lock);
+		list_del_init(&dev->bus_list);
+		write_unlock(&dev->bus->lock);
+		put_bus(dev->bus);
+	}
+}
+
+static int bus_make_dir(struct bus_type * bus)
+{
+	int error;
+	bus->dir.name = bus->name;
+
+	error = device_create_dir(&bus->dir,&bus_dir);
+	if (!error) {
+		bus->device_dir.name = "devices";
+		device_create_dir(&bus->device_dir,&bus->dir);
+
+		bus->driver_dir.name = "drivers";
+		device_create_dir(&bus->driver_dir,&bus->dir);
+	}
+	return error;
+}
+
+
+int bus_register(struct bus_type * bus)
+{
+	spin_lock(&device_lock);
+	rwlock_init(&bus->lock);
+	INIT_LIST_HEAD(&bus->devices);
+	INIT_LIST_HEAD(&bus->drivers);
+	list_add_tail(&bus->node,&bus_driver_list);
+	atomic_set(&bus->refcount,2);
+	spin_unlock(&device_lock);
+
+	pr_debug("bus type '%s' registered\n",bus->name);
+
+	/* give it some driverfs entities */
+	bus_make_dir(bus);
+	put_bus(bus);
+
+	return 0;
+}
+
+void put_bus(struct bus_type * bus)
+{
+	if (!atomic_dec_and_lock(&bus->refcount,&device_lock))
+		return;
+	list_del_init(&bus->node);
+	spin_unlock(&device_lock);
+
+	/* remove driverfs entries */
+	driverfs_remove_dir(&bus->driver_dir);
+	driverfs_remove_dir(&bus->device_dir);
+	driverfs_remove_dir(&bus->dir);
+
+	/* tell the driver it can go away now */
+	if (bus->release)
+		bus->release();
+}
+
+static int __init bus_init(void)
+{
+	/* make 'bus' driverfs directory */
+	return driverfs_create_dir(&bus_dir,NULL);
+}
+
+subsys_initcall(bus_init);
+
+EXPORT_SYMBOL(bus_for_each_dev);
+EXPORT_SYMBOL(bus_add_device);
+EXPORT_SYMBOL(bus_remove_device);
+EXPORT_SYMBOL(bus_register);
+EXPORT_SYMBOL(put_bus);

include/linux/device.h

@@ -55,6 +55,29 @@ enum {
 
 struct device;
 
+
+struct bus_type {
+	char			* name;
+	rwlock_t		lock;
+	atomic_t		refcount;
+
+	list_t			node;
+	list_t			devices;
+};
+
+
+extern int bus_register(struct bus_type * bus);
+
+static inline struct bus_type * get_bus(struct bus_type * bus)
+{
+	BUG_ON(!atomic_read(&bus->refcount));
+	atomic_inc(&bus->refcount);
+	return bus;
+}
+
+extern void put_bus(struct bus_type * bus);
+
+
 struct device_driver {
 	int	(*probe)	(struct device * dev);
 	int 	(*remove)	(struct device * dev, u32 flags);
@@ -66,6 +89,7 @@ struct device_driver {
 struct device {
 	struct list_head g_list;        /* node in depth-first order list */
 	struct list_head node;		/* node in sibling list */
+	struct list_head bus_list;	/* node in bus's list */
 	struct list_head children;
 	struct device 	* parent;