/*
 * bus.c - bus driver management
 *
 * Copyright (c) 2002-3 Patrick Mochel
 * Copyright (c) 2002-3 Open Source Development Labs
 * Copyright (c) 2007 Greg Kroah-Hartman <gregkh@suse.de>
 * Copyright (c) 2007 Novell Inc.
 *
 * This file is released under the GPLv2
 *
 */

#include <linux/device.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/string.h>
#include "base.h"
#include "power/power.h"

#define to_bus_attr(_attr) container_of(_attr, struct bus_attribute, attr)
#define to_bus(obj) container_of(obj, struct bus_type_private, subsys.kobj)

/*
 * sysfs bindings for drivers
 */

#define to_drv_attr(_attr) container_of(_attr, struct driver_attribute, attr)


static int __must_check bus_rescan_devices_helper(struct device *dev,
                                                void *data);

static struct bus_type *bus_get(struct bus_type *bus)
{
        if (bus) {
                kset_get(&bus->p->subsys);
                return bus;
        }
        return NULL;
}

static void bus_put(struct bus_type *bus)
{
        if (bus)
                kset_put(&bus->p->subsys);
}

static ssize_t drv_attr_show(struct kobject *kobj, struct attribute *attr,
                             char *buf)
{
        struct driver_attribute *drv_attr = to_drv_attr(attr);
        struct driver_private *drv_priv = to_driver(kobj);
        ssize_t ret = -EIO;

        if (drv_attr->show)
                ret = drv_attr->show(drv_priv->driver, buf);
        return ret;
}

static ssize_t drv_attr_store(struct kobject *kobj, struct attribute *attr,
                              const char *buf, size_t count)
{
        struct driver_attribute *drv_attr = to_drv_attr(attr);
        struct driver_private *drv_priv = to_driver(kobj);
        ssize_t ret = -EIO;

        if (drv_attr->store)
                ret = drv_attr->store(drv_priv->driver, buf, count);
        return ret;
}

static struct sysfs_ops driver_sysfs_ops = {
        .show   = drv_attr_show,
        .store  = drv_attr_store,
};

static void driver_release(struct kobject *kobj)
{
        struct driver_private *drv_priv = to_driver(kobj);

        pr_debug("driver: '%s': %s\n", kobject_name(kobj), __func__);
        kfree(drv_priv);
}

static struct kobj_type driver_ktype = {
        .sysfs_ops      = &driver_sysfs_ops,
        .release        = driver_release,
};

/*
 * sysfs bindings for buses
 */
static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,
                             char *buf)
{
        struct bus_attribute *bus_attr = to_bus_attr(attr);
        struct bus_type_private *bus_priv = to_bus(kobj);
        ssize_t ret = 0;

        if (bus_attr->show)
                ret = bus_attr->show(bus_priv->bus, buf);
        return ret;
}

static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
                              const char *buf, size_t count)
{
        struct bus_attribute *bus_attr = to_bus_attr(attr);
        struct bus_type_private *bus_priv = to_bus(kobj);
        ssize_t ret = 0;

        if (bus_attr->store)
                ret = bus_attr->store(bus_priv->bus, buf, count);
        return ret;
}

static struct sysfs_ops bus_sysfs_ops = {
        .show   = bus_attr_show,
        .store  = bus_attr_store,
};

int bus_create_file(struct bus_type *bus, struct bus_attribute *attr)
{
        int error;
        if (bus_get(bus)) {
                error = sysfs_create_file(&bus->p->subsys.kobj, &attr->attr);
                bus_put(bus);
        } else
                error = -EINVAL;
        return error;
}
EXPORT_SYMBOL_GPL(bus_create_file);

void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)
{
        if (bus_get(bus)) {
                sysfs_remove_file(&bus->p->subsys.kobj, &attr->attr);
                bus_put(bus);
        }
}
EXPORT_SYMBOL_GPL(bus_remove_file);

static struct kobj_type bus_ktype = {
        .sysfs_ops      = &bus_sysfs_ops,
};

static int bus_uevent_filter(struct kset *kset, struct kobject *kobj)
{
        struct kobj_type *ktype = get_ktype(kobj);

        if (ktype == &bus_ktype)
                return 1;
        return 0;
}

static struct kset_uevent_ops bus_uevent_ops = {
        .filter = bus_uevent_filter,
};

static struct kset *bus_kset;


#ifdef CONFIG_HOTPLUG
/* Manually detach a device from its associated driver. */
static ssize_t driver_unbind(struct device_driver *drv,
                             const char *buf, size_t count)
{
        struct bus_type *bus = bus_get(drv->bus);
        struct device *dev;
        int err = -ENODEV;

        dev = bus_find_device_by_name(bus, NULL, buf);
        if (dev && dev->driver == drv) {
                if (dev->parent)        /* Needed for USB */
                        down(&dev->parent->sem);
                device_release_driver(dev);
                if (dev->parent)
                        up(&dev->parent->sem);
                err = count;
        }
        put_device(dev);
        bus_put(bus);
        return err;
}
static DRIVER_ATTR(unbind, S_IWUSR, NULL, driver_unbind);

/*
 * Manually attach a device to a driver.
 * Note: the driver must want to bind to the device,
 * it is not possible to override the driver's id table.
 */
static ssize_t driver_bind(struct device_driver *drv,
                           const char *buf, size_t count)
{
        struct bus_type *bus = bus_get(drv->bus);
        struct device *dev;
        int err = -ENODEV;

        dev = bus_find_device_by_name(bus, NULL, buf);
        if (dev && dev->driver == NULL) {
                if (dev->parent)        /* Needed for USB */
                        down(&dev->parent->sem);
                down(&dev->sem);
                err = driver_probe_device(drv, dev);
                up(&dev->sem);
                if (dev->parent)
                        up(&dev->parent->sem);

                if (err > 0) {
                        /* success */
                        err = count;
                } else if (err == 0) {
                        /* driver didn't accept device */
                        err = -ENODEV;
                }
        }
        put_device(dev);
        bus_put(bus);
        return err;
}
static DRIVER_ATTR(bind, S_IWUSR, NULL, driver_bind);

static ssize_t show_drivers_autoprobe(struct bus_type *bus, char *buf)
{
        return sprintf(buf, "%d\n", bus->p->drivers_autoprobe);
}

static ssize_t store_drivers_autoprobe(struct bus_type *bus,
                                       const char *buf, size_t count)
{
        if (buf[0] == '0')
                bus->p->drivers_autoprobe = 0;
        else
                bus->p->drivers_autoprobe = 1;
        return count;
}

static ssize_t store_drivers_probe(struct bus_type *bus,
                                   const char *buf, size_t count)
{
        struct device *dev;

        dev = bus_find_device_by_name(bus, NULL, buf);
        if (!dev)
                return -ENODEV;
        if (bus_rescan_devices_helper(dev, NULL) != 0)
                return -EINVAL;
        return count;
}
#endif

static struct device *next_device(struct klist_iter *i)
{
        struct klist_node *n = klist_next(i);
        return n ? container_of(n, struct device, knode_bus) : NULL;
}

/**
 * bus_for_each_dev - device iterator.
 * @bus: bus type.
 * @start: device to start iterating from.
 * @data: data for the callback.
 * @fn: function to be called for each device.
 *
 * Iterate over @bus's list of devices, and call @fn for each,
 * passing it @data. If @start is not NULL, we use that device to
 * begin iterating from.
 *
 * We check the return of @fn each time. If it returns anything
 * other than 0, we break out and return that value.
 *
 * NOTE: The device that returns a non-zero value is not retained
 * in any way, nor is its refcount incremented. If the caller needs
 * to retain this data, it should do, and increment the reference
 * count in the supplied callback.
 */
int bus_for_each_dev(struct bus_type *bus, struct device *start,
                     void *data, int (*fn)(struct device *, void *))
{
        struct klist_iter i;
        struct device *dev;
        int error = 0;

        if (!bus)
                return -EINVAL;

        klist_iter_init_node(&bus->p->klist_devices, &i,
                             (start ? &start->knode_bus : NULL));
        while ((dev = next_device(&i)) && !error)
                error = fn(dev, data);
        klist_iter_exit(&i);
        return error;
}
EXPORT_SYMBOL_GPL(bus_for_each_dev);

/**
 * bus_find_device - device iterator for locating a particular device.
 * @bus: bus type
 * @start: Device to begin with
 * @data: Data to pass to match function
 * @match: Callback function to check device
 *
 * This is similar to the bus_for_each_dev() function above, but it
 * returns a reference to a device that is 'found' for later use, as
 * determined by the @match callback.
 *
 * The callback should return 0 if the device doesn't match and non-zero
 * if it does.  If the callback returns non-zero, this function will
 * return to the caller and not iterate over any more devices.
 */
struct device *bus_find_device(struct bus_type *bus,
                               struct device *start, void *data,
                               int (*match)(struct device *dev, void *data))
{
        struct klist_iter i;
        struct device *dev;

        if (!bus)
                return NULL;

        klist_iter_init_node(&bus->p->klist_devices, &i,
                             (start ? &start->knode_bus : NULL));
        while ((dev = next_device(&i)))
                if (match(dev, data) && get_device(dev))
                        break;
        klist_iter_exit(&i);
        return dev;
}
EXPORT_SYMBOL_GPL(bus_find_device);

static int match_name(struct device *dev, void *data)
{
        const char *name = data;

        return sysfs_streq(name, dev->bus_id);
}

/**
 * bus_find_device_by_name - device iterator for locating a particular device of a specific name
 * @bus: bus type
 * @start: Device to begin with
 * @name: name of the device to match
 *
 * This is similar to the bus_find_device() function above, but it handles
 * searching by a name automatically, no need to write another strcmp matching
 * function.
 */
struct device *bus_find_device_by_name(struct bus_type *bus,
                                       struct device *start, const char *name)
{
        return bus_find_device(bus, start, (void *)name, match_name);
}
EXPORT_SYMBOL_GPL(bus_find_device_by_name);

static struct device_driver *next_driver(struct klist_iter *i)
{
        struct klist_node *n = klist_next(i);
        struct driver_private *drv_priv;

        if (n) {
                drv_priv = container_of(n, struct driver_private, knode_bus);
                return drv_priv->driver;
        }
        return NULL;
}

/**
 * bus_for_each_drv - driver iterator
 * @bus: bus we're dealing with.
 * @start: driver to start iterating on.
 * @data: data to pass to the callback.
 * @fn: function to call for each driver.
 *
 * This is nearly identical to the device iterator above.
 * We iterate over each driver that belongs to @bus, and call
 * @fn for each. If @fn returns anything but 0, we break out
 * and return it. If @start is not NULL, we use it as the head
 * of the list.
 *
 * NOTE: we don't return the driver that returns a non-zero
 * value, nor do we leave the reference count incremented for that
 * driver. If the caller needs to know that info, it must set it
 * in the callback. It must also be sure to increment the refcount
 * so it doesn't disappear before returning to the caller.
 */
int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,
                     void *data, int (*fn)(struct device_driver *, void *))
{
        struct klist_iter i;
        struct device_driver *drv;
        int error = 0;

        if (!bus)
                return -EINVAL;

        klist_iter_init_node(&bus->p->klist_drivers, &i,
                             start ? &start->p->knode_bus : NULL);
        while ((drv = next_driver(&i)) && !error)
                error = fn(drv, data);
        klist_iter_exit(&i);
        return error;
}
EXPORT_SYMBOL_GPL(bus_for_each_drv);

static int device_add_attrs(struct bus_type *bus, struct device *dev)
{
        int error = 0;
        int i;

        if (!bus->dev_attrs)
                return 0;

        for (i = 0; attr_name(bus->dev_attrs[i]); i++) {
                error = device_create_file(dev, &bus->dev_attrs[i]);
                if (error) {
                        while (--i >= 0)
                                device_remove_file(dev, &bus->dev_attrs[i]);
                        break;
                }
        }
        return error;
}

static void device_remove_attrs(struct bus_type *bus, struct device *dev)
{
        int i;

        if (bus->dev_attrs) {
                for (i = 0; attr_name(bus->dev_attrs[i]); i++)
                        device_remove_file(dev, &bus->dev_attrs[i]);
        }
}

#ifdef CONFIG_SYSFS_DEPRECATED
static int make_deprecated_bus_links(struct device *dev)
{
        return sysfs_create_link(&dev->kobj,
                                 &dev->bus->p->subsys.kobj, "bus");
}

static void remove_deprecated_bus_links(struct device *dev)
{
        sysfs_remove_link(&dev->kobj, "bus");
}
#else
static inline int make_deprecated_bus_links(struct device *dev) { return 0; }
static inline void remove_deprecated_bus_links(struct device *dev) { }
#endif

/**
 * bus_add_device - add device to bus
 * @dev: device being added
 *
 * - Add the device to its bus's list of devices.
 * - Create link to device's bus.
 */
int bus_add_device(struct device *dev)
{
        struct bus_type *bus = bus_get(dev->bus);
        int error = 0;

        if (bus) {
                pr_debug("bus: '%s': add device %s\n", bus->name, dev->bus_id);
                error = device_add_attrs(bus, dev);
                if (error)
                        goto out_put;
                error = sysfs_create_link(&bus->p->devices_kset->kobj,
                                                &dev->kobj, dev->bus_id);
                if (error)
                        goto out_id;
                error = sysfs_create_link(&dev->kobj,
                                &dev->bus->p->subsys.kobj, "subsystem");
                if (error)
                        goto out_subsys;
                error = make_deprecated_bus_links(dev);
                if (error)
                        goto out_deprecated;
        }
        return 0;

out_deprecated:
        sysfs_remove_link(&dev->kobj, "subsystem");
out_subsys:
        sysfs_remove_link(&bus->p->devices_kset->kobj, dev->bus_id);
out_id:
        device_remove_attrs(bus, dev);
out_put:
        bus_put(dev->bus);
        return error;
}

/**
 * bus_attach_device - add device to bus
 * @dev: device tried to attach to a driver
 *
 * - Add device to bus's list of devices.
 * - Try to attach to driver.
 */
void bus_attach_device(struct device *dev)
{
        struct bus_type *bus = dev->bus;
        int ret = 0;

        if (bus) {
                if (bus->p->drivers_autoprobe)
                        ret = device_attach(dev);
                WARN_ON(ret < 0);
                if (ret >= 0)
                        klist_add_tail(&dev->knode_bus, &bus->p->klist_devices);
        }
}

/**
 * bus_remove_device - remove device from bus
 * @dev: device to be removed
 *
 * - Remove symlink from bus's directory.
 * - Delete device from bus's list.
 * - Detach from its driver.
 * - Drop reference taken in bus_add_device().
 */
void bus_remove_device(struct device *dev)
{
        if (dev->bus) {
                sysfs_remove_link(&dev->kobj, "subsystem");
                remove_deprecated_bus_links(dev);
                sysfs_remove_link(&dev->bus->p->devices_kset->kobj,
                                  dev->bus_id);
                device_remove_attrs(dev->bus, dev);
                if (klist_node_attached(&dev->knode_bus))
                        klist_del(&dev->knode_bus);

                pr_debug("bus: '%s': remove device %s\n",
                         dev->bus->name, dev->bus_id);
                device_release_driver(dev);
                bus_put(dev->bus);
        }
}

static int driver_add_attrs(struct bus_type *bus, struct device_driver *drv)
{
        int error = 0;
        int i;

        if (bus->drv_attrs) {
                for (i = 0; attr_name(bus->drv_attrs[i]); i++) {
                        error = driver_create_file(drv, &bus->drv_attrs[i]);
                        if (error)
                                goto err;
                }
        }
done:
        return error;
err:
        while (--i >= 0)
                driver_remove_file(drv, &bus->drv_attrs[i]);
        goto done;
}

static void driver_remove_attrs(struct bus_type *bus,
                                struct device_driver *drv)
{
        int i;

        if (bus->drv_attrs) {
                for (i = 0; attr_name(bus->drv_attrs[i]); i++)
                        driver_remove_file(drv, &bus->drv_attrs[i]);
        }
}

#ifdef CONFIG_HOTPLUG
/*
 * Thanks to drivers making their tables __devinit, we can't allow manual
 * bind and unbind from userspace unless CONFIG_HOTPLUG is enabled.
 */
static int __must_check add_bind_files(struct device_driver *drv)
{
        int ret;

        ret = driver_create_file(drv, &driver_attr_unbind);
        if (ret == 0) {
                ret = driver_create_file(drv, &driver_attr_bind);
                if (ret)
                        driver_remove_file(drv, &driver_attr_unbind);
        }
        return ret;
}

static void remove_bind_files(struct device_driver *drv)
{
        driver_remove_file(drv, &driver_attr_bind);
        driver_remove_file(drv, &driver_attr_unbind);
}

static BUS_ATTR(drivers_probe, S_IWUSR, NULL, store_drivers_probe);
static BUS_ATTR(drivers_autoprobe, S_IWUSR | S_IRUGO,
                show_drivers_autoprobe, store_drivers_autoprobe);

static int add_probe_files(struct bus_type *bus)
{
        int retval;

        retval = bus_create_file(bus, &bus_attr_drivers_probe);
        if (retval)
                goto out;

        retval = bus_create_file(bus, &bus_attr_drivers_autoprobe);
        if (retval)
                bus_remove_file(bus, &bus_attr_drivers_probe);
out:
        return retval;
}

static void remove_probe_files(struct bus_type *bus)
{
        bus_remove_file(bus, &bus_attr_drivers_autoprobe);
        bus_remove_file(bus, &bus_attr_drivers_probe);
}
#else
static inline int add_bind_files(struct device_driver *drv) { return 0; }
static inline void remove_bind_files(struct device_driver *drv) {}
static inline int add_probe_files(struct bus_type *bus) { return 0; }
static inline void remove_probe_files(struct bus_type *bus) {}
#endif

static ssize_t driver_uevent_store(struct device_driver *drv,
                                   const char *buf, size_t count)
{
        enum kobject_action action;

        if (kobject_action_type(buf, count, &action) == 0)
                kobject_uevent(&drv->p->kobj, action);
        return count;
}
static DRIVER_ATTR(uevent, S_IWUSR, NULL, driver_uevent_store);

/**
 * bus_add_driver - Add a driver to the bus.
 * @drv: driver.
 */
int bus_add_driver(struct device_driver *drv)
{
        struct bus_type *bus;
        struct driver_private *priv;
        int error = 0;

        bus = bus_get(drv->bus);
        if (!bus)
                return -EINVAL;

        pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);

        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
        if (!priv) {
                error = -ENOMEM;
                goto out_put_bus;
        }
        klist_init(&priv->klist_devices, NULL, NULL);
        priv->driver = drv;
        drv->p = priv;
        priv->kobj.kset = bus->p->drivers_kset;
        error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
                                     "%s", drv->name);
        if (error)
                goto out_unregister;

        if (drv->bus->p->drivers_autoprobe) {
                error = driver_attach(drv);
                if (error)
                        goto out_unregister;
        }
        klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
        module_add_driver(drv->owner, drv);

        error = driver_create_file(drv, &driver_attr_uevent);
        if (error) {
                printk(KERN_ERR "%s: uevent attr (%s) failed\n",
                        __func__, drv->name);
        }
        error = driver_add_attrs(bus, drv);
        if (error) {
                /* How the hell do we get out of this pickle? Give up */
                printk(KERN_ERR "%s: driver_add_attrs(%s) failed\n",
                        __func__, drv->name);
        }
        error = add_bind_files(drv);
        if (error) {
                /* Ditto */
                printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
                        __func__, drv->name);
        }

        kobject_uevent(&priv->kobj, KOBJ_ADD);
        return error;
out_unregister:
        kobject_put(&priv->kobj);
out_put_bus:
        bus_put(bus);
        return error;
}

/**
 * bus_remove_driver - delete driver from bus's knowledge.
 * @drv: driver.
 *
 * Detach the driver from the devices it controls, and remove
 * it from its bus's list of drivers. Finally, we drop the reference
 * to the bus we took in bus_add_driver().
 */
void bus_remove_driver(struct device_driver *drv)
{
        if (!drv->bus)
                return;

        remove_bind_files(drv);
        driver_remove_attrs(drv->bus, drv);
        driver_remove_file(drv, &driver_attr_uevent);
        klist_remove(&drv->p->knode_bus);
        pr_debug("bus: '%s': remove driver %s\n", drv->bus->name, drv->name);
        driver_detach(drv);
        module_remove_driver(drv);
        kobject_put(&drv->p->kobj);
        bus_put(drv->bus);
}

/* Helper for bus_rescan_devices's iter */
static int __must_check bus_rescan_devices_helper(struct device *dev,
                                                  void *data)
{
        int ret = 0;

        if (!dev->driver) {
                if (dev->parent)        /* Needed for USB */
                        down(&dev->parent->sem);
                ret = device_attach(dev);
                if (dev->parent)
                        up(&dev->parent->sem);
        }
        return ret < 0 ? ret : 0;
}

/**
 * bus_rescan_devices - rescan devices on the bus for possible drivers
 * @bus: the bus to scan.
 *
 * This function will look for devices on the bus with no driver
 * attached and rescan it against existing drivers to see if it matches
 * any by calling device_attach() for the unbound devices.
 */
int bus_rescan_devices(struct bus_type *bus)
{
        return bus_for_each_dev(bus, NULL, NULL, bus_rescan_devices_helper);
}
EXPORT_SYMBOL_GPL(bus_rescan_devices);

/**
 * device_reprobe - remove driver for a device and probe for a new driver
 * @dev: the device to reprobe
 *
 * This function detaches the attached driver (if any) for the given
 * device and restarts the driver probing process.  It is intended
 * to use if probing criteria changed during a devices lifetime and
 * driver attachment should change accordingly.
 */
int device_reprobe(struct device *dev)
{
        if (dev->driver) {
                if (dev->parent)        /* Needed for USB */
                        down(&dev->parent->sem);
                device_release_driver(dev);
                if (dev->parent)
                        up(&dev->parent->sem);
        }
        return bus_rescan_devices_helper(dev, NULL);
}
EXPORT_SYMBOL_GPL(device_reprobe);

/**
 * find_bus - locate bus by name.
 * @name: name of bus.
 *
 * Call kset_find_obj() to iterate over list of buses to
 * find a bus by name. Return bus if found.
 *
 * Note that kset_find_obj increments bus' reference count.
 */
#if 0
struct bus_type *find_bus(char *name)
{
        struct kobject *k = kset_find_obj(bus_kset, name);
        return k ? to_bus(k) : NULL;
}
#endif  /*  0  */


/**
 * bus_add_attrs - Add default attributes for this bus.
 * @bus: Bus that has just been registered.
 */

static int bus_add_attrs(struct bus_type *bus)
{
        int error = 0;
        int i;

        if (bus->bus_attrs) {
                for (i = 0; attr_name(bus->bus_attrs[i]); i++) {
                        error = bus_create_file(bus, &bus->bus_attrs[i]);
                        if (error)
                                goto err;
                }
        }
done:
        return error;
err:
        while (--i >= 0)
                bus_remove_file(bus, &bus->bus_attrs[i]);
        goto done;
}

static void bus_remove_attrs(struct bus_type *bus)
{
        int i;

        if (bus->bus_attrs) {
                for (i = 0; attr_name(bus->bus_attrs[i]); i++)
                        bus_remove_file(bus, &bus->bus_attrs[i]);
        }
}

static void klist_devices_get(struct klist_node *n)
{
        struct device *dev = container_of(n, struct device, knode_bus);

        get_device(dev);
}

static void klist_devices_put(struct klist_node *n)
{
        struct device *dev = container_of(n, struct device, knode_bus);

        put_device(dev);
}

static ssize_t bus_uevent_store(struct bus_type *bus,
                                const char *buf, size_t count)
{
        enum kobject_action action;

        if (kobject_action_type(buf, count, &action) == 0)
                kobject_uevent(&bus->p->subsys.kobj, action);
        return count;
}
static BUS_ATTR(uevent, S_IWUSR, NULL, bus_uevent_store);

/**
 * bus_register - register a bus with the system.
 * @bus: bus.
 *
 * Once we have that, we registered the bus with the kobject
 * infrastructure, then register the children subsystems it has:
 * the devices and drivers that belong to the bus.
 */
int bus_register(struct bus_type *bus)
{
        int retval;
        struct bus_type_private *priv;

        priv = kzalloc(sizeof(struct bus_type_private), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        priv->bus = bus;
        bus->p = priv;

        BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);

        retval = kobject_set_name(&priv->subsys.kobj, "%s", bus->name);
        if (retval)
                goto out;

        priv->subsys.kobj.kset = bus_kset;
        priv->subsys.kobj.ktype = &bus_ktype;
        priv->drivers_autoprobe = 1;

        retval = kset_register(&priv->subsys);
        if (retval)
                goto out;

        retval = bus_create_file(bus, &bus_attr_uevent);
        if (retval)
                goto bus_uevent_fail;

        priv->devices_kset = kset_create_and_add("devices", NULL,
                                                 &priv->subsys.kobj);
        if (!priv->devices_kset) {
                retval = -ENOMEM;
                goto bus_devices_fail;
        }

        priv->drivers_kset = kset_create_and_add("drivers", NULL,
                                                 &priv->subsys.kobj);
        if (!priv->drivers_kset) {
                retval = -ENOMEM;
                goto bus_drivers_fail;
        }

        klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);
        klist_init(&priv->klist_drivers, NULL, NULL);

        retval = add_probe_files(bus);
        if (retval)
                goto bus_probe_files_fail;

        retval = bus_add_attrs(bus);
        if (retval)
                goto bus_attrs_fail;

        pr_debug("bus: '%s': registered\n", bus->name);
        return 0;

bus_attrs_fail:
        remove_probe_files(bus);
bus_probe_files_fail:
        kset_unregister(bus->p->drivers_kset);
bus_drivers_fail:
        kset_unregister(bus->p->devices_kset);
bus_devices_fail:
        bus_remove_file(bus, &bus_attr_uevent);
bus_uevent_fail:
        kset_unregister(&bus->p->subsys);
        kfree(bus->p);
out:
        return retval;
}
EXPORT_SYMBOL_GPL(bus_register);

/**
 * bus_unregister - remove a bus from the system
 * @bus: bus.
 *
 * Unregister the child subsystems and the bus itself.
 * Finally, we call bus_put() to release the refcount
 */
void bus_unregister(struct bus_type *bus)
{
        pr_debug("bus: '%s': unregistering\n", bus->name);
        bus_remove_attrs(bus);
        remove_probe_files(bus);
        kset_unregister(bus->p->drivers_kset);
        kset_unregister(bus->p->devices_kset);
        bus_remove_file(bus, &bus_attr_uevent);
        kset_unregister(&bus->p->subsys);
        kfree(bus->p);
}
EXPORT_SYMBOL_GPL(bus_unregister);

int bus_register_notifier(struct bus_type *bus, struct notifier_block *nb)
{
        return blocking_notifier_chain_register(&bus->p->bus_notifier, nb);
}
EXPORT_SYMBOL_GPL(bus_register_notifier);

int bus_unregister_notifier(struct bus_type *bus, struct notifier_block *nb)
{
        return blocking_notifier_chain_unregister(&bus->p->bus_notifier, nb);
}
EXPORT_SYMBOL_GPL(bus_unregister_notifier);

struct kset *bus_get_kset(struct bus_type *bus)
{
        return &bus->p->subsys;
}
EXPORT_SYMBOL_GPL(bus_get_kset);

struct klist *bus_get_device_klist(struct bus_type *bus)
{
        return &bus->p->klist_devices;
}
EXPORT_SYMBOL_GPL(bus_get_device_klist);

/*
 * Yes, this forcably breaks the klist abstraction temporarily.  It
 * just wants to sort the klist, not change reference counts and
 * take/drop locks rapidly in the process.  It does all this while
 * holding the lock for the list, so objects can't otherwise be
 * added/removed while we're swizzling.
 */
static void device_insertion_sort_klist(struct device *a, struct list_head *list,
                                        int (*compare)(const struct device *a,
                                                        const struct device *b))
{
        struct list_head *pos;
        struct klist_node *n;
        struct device *b;

        list_for_each(pos, list) {
                n = container_of(pos, struct klist_node, n_node);
                b = container_of(n, struct device, knode_bus);

                if (compare(a, b) <= 0) {
                        list_move_tail(&a->knode_bus.n_node,
                                       &b->knode_bus.n_node);
                        return;
                }
        }
        list_move_tail(&a->knode_bus.n_node, list);
}

void bus_sort_breadthfirst(struct bus_type *bus,
                           int (*compare)(const struct device *a,
                                          const struct device *b))
{
        LIST_HEAD(sorted_devices);
        struct list_head *pos, *tmp;
        struct klist_node *n;
        struct device *dev;
        struct klist *device_klist;

        device_klist = bus_get_device_klist(bus);

        spin_lock(&device_klist->k_lock);
        list_for_each_safe(pos, tmp, &device_klist->k_list) {
                n = container_of(pos, struct klist_node, n_node);
                dev = container_of(n, struct device, knode_bus);
                device_insertion_sort_klist(dev, &sorted_devices, compare);
        }
        list_splice(&sorted_devices, &device_klist->k_list);
        spin_unlock(&device_klist->k_lock);
}
EXPORT_SYMBOL_GPL(bus_sort_breadthfirst);

int __init buses_init(void)
{
        bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);
        if (!bus_kset)
                return -ENOMEM;
        return 0;
}