/*
   * 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/async.h>

  #include <linux/device.h>
  #include <linux/module.h>
  #include <linux/errno.h>

  #include <linux/slab.h>

  #include <linux/init.h>
  #include <linux/string.h>

  #include <linux/mutex.h>

  #include <linux/sysfs.h>

  #include "base.h"
  #include "power/power.h"

  /* /sys/devices/system */

  static struct kset *system_kset;

  #define to_bus_attr(_attr) container_of(_attr, struct bus_attribute, attr)

  
  /*
   * sysfs bindings for drivers
   */
  
  #define to_drv_attr(_attr) container_of(_attr, struct driver_attribute, attr)

  #define DRIVER_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) \
  	struct driver_attribute driver_attr_##_name =		\
  		__ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store)

  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 const 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
  ", 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 subsys_private *subsys_priv = to_subsys_private(kobj);

  	ssize_t ret = 0;
  
  	if (bus_attr->show)

  		ret = bus_attr->show(subsys_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 subsys_private *subsys_priv = to_subsys_private(kobj);

  	ssize_t ret = 0;
  
  	if (bus_attr->store)

  		ret = bus_attr->store(subsys_priv->bus, buf, count);

  	return ret;
  }

  static const 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 void bus_release(struct kobject *kobj)
  {

  	struct subsys_private *priv = to_subsys_private(kobj);

  	struct bus_type *bus = priv->bus;
  
  	kfree(priv);
  	bus->p = NULL;
  }

  static struct kobj_type bus_ktype = {

  	.sysfs_ops	= &bus_sysfs_ops,

  	.release	= bus_release,

  };
  
  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 const struct kset_uevent_ops bus_uevent_ops = {

  	.filter = bus_uevent_filter,

  };

  static struct kset *bus_kset;

  /* Manually detach a device from its associated driver. */

  static ssize_t unbind_store(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 */

  			device_lock(dev->parent);

  		device_release_driver(dev);

  		if (dev->parent)

  			device_unlock(dev->parent);

  		err = count;
  	}

  	put_device(dev);

  	bus_put(bus);

  	return err;

  }

  static DRIVER_ATTR_IGNORE_LOCKDEP(unbind, S_IWUSR, NULL, unbind_store);

  /*
   * 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 bind_store(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 && driver_match_device(drv, dev)) {

  		if (dev->parent)	/* Needed for USB */

  			device_lock(dev->parent);
  		device_lock(dev);

  		err = driver_probe_device(drv, dev);

  		device_unlock(dev);

  		if (dev->parent)

  			device_unlock(dev->parent);

  		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_IGNORE_LOCKDEP(bind, S_IWUSR, NULL, bind_store);

  static ssize_t show_drivers_autoprobe(struct bus_type *bus, char *buf)
  {

  	return sprintf(buf, "%d
  ", 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;

  	int err = -EINVAL;

  	dev = bus_find_device_by_name(bus, NULL, buf);

  	if (!dev)
  		return -ENODEV;

  	if (bus_rescan_devices_helper(dev, NULL) == 0)
  		err = count;
  	put_device(dev);
  	return err;

  }

  static struct device *next_device(struct klist_iter *i)

  {

  	struct klist_node *n = klist_next(i);

  	struct device *dev = NULL;
  	struct device_private *dev_prv;
  
  	if (n) {
  		dev_prv = to_device_private_bus(n);
  		dev = dev_prv->device;
  	}
  	return dev;

  }

  /**

   * 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 so, 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 || !bus->p)

  		return -EINVAL;

  	klist_iter_init_node(&bus->p->klist_devices, &i,
  			     (start ? &start->p->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 || !bus->p)

  		return NULL;

  	klist_iter_init_node(&bus->p->klist_devices, &i,
  			     (start ? &start->p->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_name(dev));

  }
  
  /**
   * 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);

  /**
   * subsys_find_device_by_id - find a device with a specific enumeration number
   * @subsys: subsystem
   * @id: index 'id' in struct device
   * @hint: device to check first
   *
   * Check the hint's next object and if it is a match return it directly,
   * otherwise, fall back to a full list search. Either way a reference for
   * the returned object is taken.
   */
  struct device *subsys_find_device_by_id(struct bus_type *subsys, unsigned int id,
  					struct device *hint)
  {
  	struct klist_iter i;
  	struct device *dev;
  
  	if (!subsys)
  		return NULL;
  
  	if (hint) {

  		klist_iter_init_node(&subsys->p->klist_devices, &i, &hint->p->knode_bus);

  		dev = next_device(&i);
  		if (dev && dev->id == id && get_device(dev)) {
  			klist_iter_exit(&i);
  			return dev;
  		}
  		klist_iter_exit(&i);
  	}
  
  	klist_iter_init_node(&subsys->p->klist_devices, &i, NULL);
  	while ((dev = next_device(&i))) {
  		if (dev->id == id && get_device(dev)) {
  			klist_iter_exit(&i);
  			return dev;
  		}
  	}
  	klist_iter_exit(&i);
  	return NULL;
  }
  EXPORT_SYMBOL_GPL(subsys_find_device_by_id);

  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);

  /**

   * bus_add_device - add device to bus
   * @dev: device being added

   *

   * - Add device's bus attributes.
   * - Create links to device's bus.

   * - Add the device to its bus's list of devices.

   */

  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
  ", bus->name, dev_name(dev));

  		error = device_add_groups(dev, bus->dev_groups);
  		if (error)

  			goto out_put;

  		error = sysfs_create_link(&bus->p->devices_kset->kobj,

  						&dev->kobj, dev_name(dev));

  		if (error)

  			goto out_groups;

  		error = sysfs_create_link(&dev->kobj,

  				&dev->bus->p->subsys.kobj, "subsystem");

  		if (error)

  			goto out_subsys;

  		klist_add_tail(&dev->p->knode_bus, &bus->p->klist_devices);

  	}

  	return 0;

  out_subsys:

  	sysfs_remove_link(&bus->p->devices_kset->kobj, dev_name(dev));

  out_groups:
  	device_remove_groups(dev, bus->dev_groups);

  out_put:

  	bus_put(dev->bus);

  	return error;
  }
  
  /**

   * bus_probe_device - probe drivers for a new device
   * @dev: device to probe

   *

   * - Automatically probe for a driver if the bus allows it.

   */

  void bus_probe_device(struct device *dev)

  {

  	struct bus_type *bus = dev->bus;

  	struct subsys_interface *sif;

  	if (!bus)
  		return;

  	if (bus->p->drivers_autoprobe)
  		device_initial_probe(dev);

  
  	mutex_lock(&bus->p->mutex);
  	list_for_each_entry(sif, &bus->p->interfaces, node)
  		if (sif->add_dev)
  			sif->add_dev(dev, sif);
  	mutex_unlock(&bus->p->mutex);

  }
  
  /**

   * bus_remove_device - remove device from bus
   * @dev: device to be removed

   *

   * - Remove device from all interfaces.
   * - Remove symlink from bus' 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)

  {

  	struct bus_type *bus = dev->bus;
  	struct subsys_interface *sif;
  
  	if (!bus)
  		return;
  
  	mutex_lock(&bus->p->mutex);
  	list_for_each_entry(sif, &bus->p->interfaces, node)
  		if (sif->remove_dev)
  			sif->remove_dev(dev, sif);
  	mutex_unlock(&bus->p->mutex);
  
  	sysfs_remove_link(&dev->kobj, "subsystem");
  	sysfs_remove_link(&dev->bus->p->devices_kset->kobj,
  			  dev_name(dev));

  	device_remove_groups(dev, dev->bus->dev_groups);

  	if (klist_node_attached(&dev->p->knode_bus))
  		klist_del(&dev->p->knode_bus);
  
  	pr_debug("bus: '%s': remove device %s
  ",
  		 dev->bus->name, dev_name(dev));
  	device_release_driver(dev);
  	bus_put(dev->bus);

  }

  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);

  }

  static ssize_t uevent_store(struct device_driver *drv, const char *buf,
  			    size_t count)

  {

  	kobject_synth_uevent(&drv->p->kobj, buf, count);

  	return count;
  }

  static DRIVER_ATTR_WO(uevent);

  static void driver_attach_async(void *_drv, async_cookie_t cookie)
  {
  	struct device_driver *drv = _drv;
  	int ret;
  
  	ret = driver_attach(drv);
  
  	pr_debug("bus: '%s': driver %s async attach completed: %d
  ",
  		 drv->bus->name, drv->name, ret);
  }

  /**

   * 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
  ", 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;

  	klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);

  	if (drv->bus->p->drivers_autoprobe) {

  		if (driver_allows_async_probing(drv)) {
  			pr_debug("bus: '%s': probing driver %s asynchronously
  ",
  				drv->bus->name, drv->name);
  			async_schedule(driver_attach_async, drv);
  		} else {
  			error = driver_attach(drv);
  			if (error)
  				goto out_unregister;
  		}

  	}

  	module_add_driver(drv->owner, drv);

  	error = driver_create_file(drv, &driver_attr_uevent);
  	if (error) {
  		printk(KERN_ERR "%s: uevent attr (%s) failed
  ",

  			__func__, drv->name);

  	}

  	error = driver_add_groups(drv, bus->drv_groups);

  	if (error) {
  		/* How the hell do we get out of this pickle? Give up */

  		printk(KERN_ERR "%s: driver_create_groups(%s) failed
  ",
  			__func__, drv->name);

  	}

  
  	if (!drv->suppress_bind_attrs) {
  		error = add_bind_files(drv);
  		if (error) {
  			/* Ditto */
  			printk(KERN_ERR "%s: add_bind_files(%s) failed
  ",
  				__func__, drv->name);
  		}

  	}

  	return 0;

  out_unregister:

  	kobject_put(&priv->kobj);

  	/* drv->p is freed in driver_release()  */

  	drv->p = NULL;

  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;

  	if (!drv->suppress_bind_attrs)
  		remove_bind_files(drv);

  	driver_remove_groups(drv, drv->bus->drv_groups);

  	driver_remove_file(drv, &driver_attr_uevent);

  	klist_remove(&drv->p->knode_bus);

  	pr_debug("bus: '%s': remove driver %s
  ", 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 */

  			device_lock(dev->parent);

  		ret = device_attach(dev);

  		if (dev->parent)

  			device_unlock(dev->parent);

  	}

  	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 */

  			device_lock(dev->parent);

  		device_release_driver(dev);
  		if (dev->parent)

  			device_unlock(dev->parent);

  	}

  	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  */

  static int bus_add_groups(struct bus_type *bus,
  			  const struct attribute_group **groups)
  {

  	return sysfs_create_groups(&bus->p->subsys.kobj, groups);

  }
  
  static void bus_remove_groups(struct bus_type *bus,
  			      const struct attribute_group **groups)
  {

  	sysfs_remove_groups(&bus->p->subsys.kobj, groups);

  }

  static void klist_devices_get(struct klist_node *n)
  {

  	struct device_private *dev_prv = to_device_private_bus(n);
  	struct device *dev = dev_prv->device;

  
  	get_device(dev);
  }
  
  static void klist_devices_put(struct klist_node *n)
  {

  	struct device_private *dev_prv = to_device_private_bus(n);
  	struct device *dev = dev_prv->device;

  
  	put_device(dev);
  }

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

  	kobject_synth_uevent(&bus->p->subsys.kobj, buf, count);

  	return count;
  }
  static BUS_ATTR(uevent, S_IWUSR, NULL, bus_uevent_store);

  /**

   * bus_register - register a driver-core subsystem

   * @bus: bus to register

   *

   * Once we have that, we register the bus with the kobject

   * infrastructure, then register the children subsystems it has:

   * the devices and drivers that belong to the subsystem.

   */

  int bus_register(struct bus_type *bus)

  {
  	int retval;

  	struct subsys_private *priv;

  	struct lock_class_key *key = &bus->lock_key;

  	priv = kzalloc(sizeof(struct subsys_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;

  	}

  	INIT_LIST_HEAD(&priv->interfaces);
  	__mutex_init(&priv->mutex, "subsys mutex", key);

  	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_groups(bus, bus->bus_groups);
  	if (retval)
  		goto bus_groups_fail;

  	pr_debug("bus: '%s': registered
  ", bus->name);

  	return 0;

  bus_groups_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);

  out:

  	kfree(bus->p);

  	bus->p = NULL;

  	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
  ", bus->name);

  	if (bus->dev_root)
  		device_unregister(bus->dev_root);

  	bus_remove_groups(bus, bus->bus_groups);

  	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);

  }

  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 forcibly 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 klist_node *n;

  	struct device_private *dev_prv;

  	struct device *b;

  	list_for_each_entry(n, list, n_node) {

  		dev_prv = to_device_private_bus(n);
  		b = dev_prv->device;

  		if (compare(a, b) <= 0) {

  			list_move_tail(&a->p->knode_bus.n_node,
  				       &b->p->knode_bus.n_node);

  			return;
  		}
  	}

  	list_move_tail(&a->p->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 klist_node *n, *tmp;

  	struct device_private *dev_prv;

  	struct device *dev;
  	struct klist *device_klist;
  
  	device_klist = bus_get_device_klist(bus);
  
  	spin_lock(&device_klist->k_lock);

  	list_for_each_entry_safe(n, tmp, &device_klist->k_list, n_node) {

  		dev_prv = to_device_private_bus(n);
  		dev = dev_prv->device;

  		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);

  /**
   * subsys_dev_iter_init - initialize subsys device iterator
   * @iter: subsys iterator to initialize
   * @subsys: the subsys we wanna iterate over
   * @start: the device to start iterating from, if any
   * @type: device_type of the devices to iterate over, NULL for all
   *
   * Initialize subsys iterator @iter such that it iterates over devices
   * of @subsys.  If @start is set, the list iteration will start there,
   * otherwise if it is NULL, the iteration starts at the beginning of
   * the list.
   */

  void subsys_dev_iter_init(struct subsys_dev_iter *iter, struct bus_type *subsys,
  			  struct device *start, const struct device_type *type)

  {
  	struct klist_node *start_knode = NULL;
  
  	if (start)
  		start_knode = &start->p->knode_bus;

  	klist_iter_init_node(&subsys->p->klist_devices, &iter->ki, start_knode);
  	iter->type = type;

  }
  EXPORT_SYMBOL_GPL(subsys_dev_iter_init);
  
  /**
   * subsys_dev_iter_next - iterate to the next device
   * @iter: subsys iterator to proceed
   *
   * Proceed @iter to the next device and return it.  Returns NULL if
   * iteration is complete.
   *
   * The returned device is referenced and won't be released till
   * iterator is proceed to the next device or exited.  The caller is
   * free to do whatever it wants to do with the device including
   * calling back into subsys code.
   */
  struct device *subsys_dev_iter_next(struct subsys_dev_iter *iter)
  {
  	struct klist_node *knode;
  	struct device *dev;
  
  	for (;;) {
  		knode = klist_next(&iter->ki);
  		if (!knode)
  			return NULL;

  		dev = to_device_private_bus(knode)->device;

  		if (!iter->type || iter->type == dev->type)
  			return dev;
  	}
  }
  EXPORT_SYMBOL_GPL(subsys_dev_iter_next);
  
  /**
   * subsys_dev_iter_exit - finish iteration
   * @iter: subsys iterator to finish
   *
   * Finish an iteration.  Always call this function after iteration is
   * complete whether the iteration ran till the end or not.
   */
  void subsys_dev_iter_exit(struct subsys_dev_iter *iter)
  {
  	klist_iter_exit(&iter->ki);
  }
  EXPORT_SYMBOL_GPL(subsys_dev_iter_exit);
  
  int subsys_interface_register(struct subsys_interface *sif)
  {
  	struct bus_type *subsys;
  	struct subsys_dev_iter iter;
  	struct device *dev;
  
  	if (!sif || !sif->subsys)
  		return -ENODEV;
  
  	subsys = bus_get(sif->subsys);
  	if (!subsys)
  		return -EINVAL;
  
  	mutex_lock(&subsys->p->mutex);
  	list_add_tail(&sif->node, &subsys->p->interfaces);
  	if (sif->add_dev) {
  		subsys_dev_iter_init(&iter, subsys, NULL, NULL);
  		while ((dev = subsys_dev_iter_next(&iter)))
  			sif->add_dev(dev, sif);
  		subsys_dev_iter_exit(&iter);
  	}
  	mutex_unlock(&subsys->p->mutex);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(subsys_interface_register);
  
  void subsys_interface_unregister(struct subsys_interface *sif)
  {

  	struct bus_type *subsys;

  	struct subsys_dev_iter iter;
  	struct device *dev;

  	if (!sif || !sif->subsys)

  		return;

  	subsys = sif->subsys;

  	mutex_lock(&subsys->p->mutex);
  	list_del_init(&sif->node);
  	if (sif->remove_dev) {
  		subsys_dev_iter_init(&iter, subsys, NULL, NULL);
  		while ((dev = subsys_dev_iter_next(&iter)))
  			sif->remove_dev(dev, sif);
  		subsys_dev_iter_exit(&iter);
  	}
  	mutex_unlock(&subsys->p->mutex);
  
  	bus_put(subsys);
  }
  EXPORT_SYMBOL_GPL(subsys_interface_unregister);
  
  static void system_root_device_release(struct device *dev)
  {
  	kfree(dev);
  }

  
  static int subsys_register(struct bus_type *subsys,
  			   const struct attribute_group **groups,
  			   struct kobject *parent_of_root)

  {
  	struct device *dev;
  	int err;
  
  	err = bus_register(subsys);
  	if (err < 0)
  		return err;
  
  	dev = kzalloc(sizeof(struct device), GFP_KERNEL);
  	if (!dev) {
  		err = -ENOMEM;
  		goto err_dev;
  	}
  
  	err = dev_set_name(dev, "%s", subsys->name);
  	if (err < 0)
  		goto err_name;

  	dev->kobj.parent = parent_of_root;

  	dev->groups = groups;
  	dev->release = system_root_device_release;
  
  	err = device_register(dev);
  	if (err < 0)
  		goto err_dev_reg;
  
  	subsys->dev_root = dev;
  	return 0;
  
  err_dev_reg:
  	put_device(dev);
  	dev = NULL;
  err_name:
  	kfree(dev);
  err_dev:
  	bus_unregister(subsys);
  	return err;
  }

  
  /**
   * subsys_system_register - register a subsystem at /sys/devices/system/
   * @subsys: system subsystem
   * @groups: default attributes for the root device
   *
   * All 'system' subsystems have a /sys/devices/system/<name> root device
   * with the name of the subsystem. The root device can carry subsystem-
   * wide attributes. All registered devices are below this single root
   * device and are named after the subsystem with a simple enumeration

   * number appended. The registered devices are not explicitly named;

   * only 'id' in the device needs to be set.
   *
   * Do not use this interface for anything new, it exists for compatibility
   * with bad ideas only. New subsystems should use plain subsystems; and
   * add the subsystem-wide attributes should be added to the subsystem
   * directory itself and not some create fake root-device placed in
   * /sys/devices/system/<name>.
   */
  int subsys_system_register(struct bus_type *subsys,
  			   const struct attribute_group **groups)
  {
  	return subsys_register(subsys, groups, &system_kset->kobj);
  }

  EXPORT_SYMBOL_GPL(subsys_system_register);

  /**
   * subsys_virtual_register - register a subsystem at /sys/devices/virtual/
   * @subsys: virtual subsystem
   * @groups: default attributes for the root device
   *
   * All 'virtual' subsystems have a /sys/devices/system/<name> root device
   * with the name of the subystem.  The root device can carry subsystem-wide
   * attributes.  All registered devices are below this single root device.
   * There's no restriction on device naming.  This is for kernel software
   * constructs which need sysfs interface.
   */
  int subsys_virtual_register(struct bus_type *subsys,
  			    const struct attribute_group **groups)
  {
  	struct kobject *virtual_dir;
  
  	virtual_dir = virtual_device_parent(NULL);
  	if (!virtual_dir)
  		return -ENOMEM;
  
  	return subsys_register(subsys, groups, virtual_dir);
  }

  EXPORT_SYMBOL_GPL(subsys_virtual_register);

  int __init buses_init(void)
  {

  	bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);
  	if (!bus_kset)
  		return -ENOMEM;

  
  	system_kset = kset_create_and_add("system", NULL, &devices_kset->kobj);
  	if (!system_kset)
  		return -ENOMEM;

  	return 0;

  }