bus.c

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/*
 * 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 <[email protected]>
 * 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/slab.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/mutex.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)


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\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 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 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 const 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 */
            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(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 && 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(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);
    struct device *dev = NULL;
    struct device_private *dev_prv;

    if (n) {
        dev_prv = to_device_private_bus(n);
        dev = dev_prv->device;
    }
    return dev;
}

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->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);

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->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));
}

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);

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;
}

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]);
    }
}

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_name(dev));
        error = device_add_attrs(bus, dev);
        if (error)
            goto out_put;
        error = sysfs_create_link(&bus->p->devices_kset->kobj,
                        &dev->kobj, dev_name(dev));
        if (error)
            goto out_id;
        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_id:
    device_remove_attrs(bus, dev);
out_put:
    bus_put(dev->bus);
    return error;
}

void bus_probe_device(struct device *dev)
{
    struct bus_type *bus = dev->bus;
    struct subsys_interface *sif;
    int ret;

    if (!bus)
        return;

    if (bus->p->drivers_autoprobe) {
        ret = device_attach(dev);
        WARN_ON(ret < 0);
    }

    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);
}

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_attrs(dev->bus, dev);
    if (klist_node_attached(&dev->p->knode_bus))
        klist_del(&dev->p->knode_bus);

    pr_debug("bus: '%s': remove device %s\n",
         dev->bus->name, dev_name(dev));
    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);

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);
    }

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

    return 0;

out_unregister:
    kobject_put(&priv->kobj);
    kfree(drv->p);
    drv->p = NULL;
out_put_bus:
    bus_put(bus);
    return error;
}

void bus_remove_driver(struct device_driver *drv)
{
    if (!drv->bus)
        return;

    if (!drv->suppress_bind_attrs)
        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 */
            device_lock(dev->parent);
        ret = device_attach(dev);
        if (dev->parent)
            device_unlock(dev->parent);
    }
    return ret < 0 ? ret : 0;
}

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);

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);

#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_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_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)
{
    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);

int __bus_register(struct bus_type *bus, struct lock_class_key *key)
{
    int retval;
    struct subsys_private *priv;

    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_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);
out:
    kfree(bus->p);
    bus->p = NULL;
    return retval;
}
EXPORT_SYMBOL_GPL(__bus_register);

void bus_unregister(struct bus_type *bus)
{
    pr_debug("bus: '%s': unregistering\n", bus->name);
    if (bus->dev_root)
        device_unregister(bus->dev_root);
    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);
    bus->p = NULL;
}
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 list_head *pos;
    struct klist_node *n;
    struct device_private *dev_prv;
    struct device *b;

    list_for_each(pos, list) {
        n = container_of(pos, struct klist_node, 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 list_head *pos, *tmp;
    struct klist_node *n;
    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_safe(pos, tmp, &device_klist->k_list) {
        n = container_of(pos, struct klist_node, 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);

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);

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 = container_of(knode, struct device_private, knode_bus)->device;
        if (!iter->type || iter->type == dev->type)
            return dev;
    }
}
EXPORT_SYMBOL_GPL(subsys_dev_iter_next);

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);
}
int subsys_system_register(struct bus_type *subsys,
               const struct attribute_group **groups)
{
    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 = &system_kset->kobj;
    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;
}
EXPORT_SYMBOL_GPL(subsys_system_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;
}