ehea: add kdump support

[linux-2.6.git] / drivers / base / core.c

/*
 * drivers/base/core.c - core driver model code (device registration, etc)
 *
 * Copyright (c) 2002-3 Patrick Mochel
 * Copyright (c) 2002-3 Open Source Development Labs
 * Copyright (c) 2006 Greg Kroah-Hartman <gregkh@suse.de>
 * Copyright (c) 2006 Novell, Inc.
 *
 * This file is released under the GPLv2
 *
 */

#include <linux/device.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/kdev_t.h>
#include <linux/notifier.h>
#include <linux/genhd.h>
#include <asm/semaphore.h>

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

int (*platform_notify)(struct device *dev) = NULL;
int (*platform_notify_remove)(struct device *dev) = NULL;

#ifdef CONFIG_BLOCK
static inline int device_is_not_partition(struct device *dev)
{
        return !(dev->type == &part_type);
}
#else
static inline int device_is_not_partition(struct device *dev)
{
        return 1;
}
#endif

/**
 * dev_driver_string - Return a device's driver name, if at all possible
 * @dev: struct device to get the name of
 *
 * Will return the device's driver's name if it is bound to a device.  If
 * the device is not bound to a device, it will return the name of the bus
 * it is attached to.  If it is not attached to a bus either, an empty
 * string will be returned.
 */
const char *dev_driver_string(struct device *dev)
{
        return dev->driver ? dev->driver->name :
                        (dev->bus ? dev->bus->name :
                        (dev->class ? dev->class->name : ""));
}
EXPORT_SYMBOL(dev_driver_string);

#define to_dev(obj) container_of(obj, struct device, kobj)
#define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)

static ssize_t dev_attr_show(struct kobject *kobj, struct attribute *attr,
                             char *buf)
{
        struct device_attribute *dev_attr = to_dev_attr(attr);
        struct device *dev = to_dev(kobj);
        ssize_t ret = -EIO;

        if (dev_attr->show)
                ret = dev_attr->show(dev, dev_attr, buf);
        return ret;
}

static ssize_t dev_attr_store(struct kobject *kobj, struct attribute *attr,
                              const char *buf, size_t count)
{
        struct device_attribute *dev_attr = to_dev_attr(attr);
        struct device *dev = to_dev(kobj);
        ssize_t ret = -EIO;

        if (dev_attr->store)
                ret = dev_attr->store(dev, dev_attr, buf, count);
        return ret;
}

static struct sysfs_ops dev_sysfs_ops = {
        .show   = dev_attr_show,
        .store  = dev_attr_store,
};


/**
 *      device_release - free device structure.
 *      @kobj:  device's kobject.
 *
 *      This is called once the reference count for the object
 *      reaches 0. We forward the call to the device's release
 *      method, which should handle actually freeing the structure.
 */
static void device_release(struct kobject *kobj)
{
        struct device *dev = to_dev(kobj);

        if (dev->release)
                dev->release(dev);
        else if (dev->type && dev->type->release)
                dev->type->release(dev);
        else if (dev->class && dev->class->dev_release)
                dev->class->dev_release(dev);
        else {
                printk(KERN_ERR "Device '%s' does not have a release() "
                        "function, it is broken and must be fixed.\n",
                        dev->bus_id);
                WARN_ON(1);
        }
}

static struct kobj_type device_ktype = {
        .release        = device_release,
        .sysfs_ops      = &dev_sysfs_ops,
};


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

        if (ktype == &device_ktype) {
                struct device *dev = to_dev(kobj);
                if (dev->uevent_suppress)
                        return 0;
                if (dev->bus)
                        return 1;
                if (dev->class)
                        return 1;
        }
        return 0;
}

static const char *dev_uevent_name(struct kset *kset, struct kobject *kobj)
{
        struct device *dev = to_dev(kobj);

        if (dev->bus)
                return dev->bus->name;
        if (dev->class)
                return dev->class->name;
        return NULL;
}

static int dev_uevent(struct kset *kset, struct kobject *kobj,
                      struct kobj_uevent_env *env)
{
        struct device *dev = to_dev(kobj);
        int retval = 0;

        /* add the major/minor if present */
        if (MAJOR(dev->devt)) {
                add_uevent_var(env, "MAJOR=%u", MAJOR(dev->devt));
                add_uevent_var(env, "MINOR=%u", MINOR(dev->devt));
        }

        if (dev->type && dev->type->name)
                add_uevent_var(env, "DEVTYPE=%s", dev->type->name);

        if (dev->driver)
                add_uevent_var(env, "DRIVER=%s", dev->driver->name);

#ifdef CONFIG_SYSFS_DEPRECATED
        if (dev->class) {
                struct device *parent = dev->parent;

                /* find first bus device in parent chain */
                while (parent && !parent->bus)
                        parent = parent->parent;
                if (parent && parent->bus) {
                        const char *path;

                        path = kobject_get_path(&parent->kobj, GFP_KERNEL);
                        if (path) {
                                add_uevent_var(env, "PHYSDEVPATH=%s", path);
                                kfree(path);
                        }

                        add_uevent_var(env, "PHYSDEVBUS=%s", parent->bus->name);

                        if (parent->driver)
                                add_uevent_var(env, "PHYSDEVDRIVER=%s",
                                               parent->driver->name);
                }
        } else if (dev->bus) {
                add_uevent_var(env, "PHYSDEVBUS=%s", dev->bus->name);

                if (dev->driver)
                        add_uevent_var(env, "PHYSDEVDRIVER=%s",
                                       dev->driver->name);
        }
#endif

        /* have the bus specific function add its stuff */
        if (dev->bus && dev->bus->uevent) {
                retval = dev->bus->uevent(dev, env);
                if (retval)
                        pr_debug("device: '%s': %s: bus uevent() returned %d\n",
                                 dev->bus_id, __FUNCTION__, retval);
        }

        /* have the class specific function add its stuff */
        if (dev->class && dev->class->dev_uevent) {
                retval = dev->class->dev_uevent(dev, env);
                if (retval)
                        pr_debug("device: '%s': %s: class uevent() "
                                 "returned %d\n", dev->bus_id,
                                 __FUNCTION__, retval);
        }

        /* have the device type specific fuction add its stuff */
        if (dev->type && dev->type->uevent) {
                retval = dev->type->uevent(dev, env);
                if (retval)
                        pr_debug("device: '%s': %s: dev_type uevent() "
                                 "returned %d\n", dev->bus_id,
                                 __FUNCTION__, retval);
        }

        return retval;
}

static struct kset_uevent_ops device_uevent_ops = {
        .filter =       dev_uevent_filter,
        .name =         dev_uevent_name,
        .uevent =       dev_uevent,
};

static ssize_t show_uevent(struct device *dev, struct device_attribute *attr,
                           char *buf)
{
        struct kobject *top_kobj;
        struct kset *kset;
        struct kobj_uevent_env *env = NULL;
        int i;
        size_t count = 0;
        int retval;

        /* search the kset, the device belongs to */
        top_kobj = &dev->kobj;
        while (!top_kobj->kset && top_kobj->parent)
                top_kobj = top_kobj->parent;
        if (!top_kobj->kset)
                goto out;

        kset = top_kobj->kset;
        if (!kset->uevent_ops || !kset->uevent_ops->uevent)
                goto out;

        /* respect filter */
        if (kset->uevent_ops && kset->uevent_ops->filter)
                if (!kset->uevent_ops->filter(kset, &dev->kobj))
                        goto out;

        env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
        if (!env)
                return -ENOMEM;

        /* let the kset specific function add its keys */
        retval = kset->uevent_ops->uevent(kset, &dev->kobj, env);
        if (retval)
                goto out;

        /* copy keys to file */
        for (i = 0; i < env->envp_idx; i++)
                count += sprintf(&buf[count], "%s\n", env->envp[i]);
out:
        kfree(env);
        return count;
}

static ssize_t store_uevent(struct device *dev, struct device_attribute *attr,
                            const char *buf, size_t count)
{
        enum kobject_action action;

        if (kobject_action_type(buf, count, &action) == 0) {
                kobject_uevent(&dev->kobj, action);
                goto out;
        }

        dev_err(dev, "uevent: unsupported action-string; this will "
                     "be ignored in a future kernel version\n");
        kobject_uevent(&dev->kobj, KOBJ_ADD);
out:
        return count;
}

static struct device_attribute uevent_attr =
        __ATTR(uevent, S_IRUGO | S_IWUSR, show_uevent, store_uevent);

static int device_add_attributes(struct device *dev,
                                 struct device_attribute *attrs)
{
        int error = 0;
        int i;

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

static void device_remove_attributes(struct device *dev,
                                     struct device_attribute *attrs)
{
        int i;

        if (attrs)
                for (i = 0; attr_name(attrs[i]); i++)
                        device_remove_file(dev, &attrs[i]);
}

static int device_add_groups(struct device *dev,
                             struct attribute_group **groups)
{
        int error = 0;
        int i;

        if (groups) {
                for (i = 0; groups[i]; i++) {
                        error = sysfs_create_group(&dev->kobj, groups[i]);
                        if (error) {
                                while (--i >= 0)
                                        sysfs_remove_group(&dev->kobj,
                                                           groups[i]);
                                break;
                        }
                }
        }
        return error;
}

static void device_remove_groups(struct device *dev,
                                 struct attribute_group **groups)
{
        int i;

        if (groups)
                for (i = 0; groups[i]; i++)
                        sysfs_remove_group(&dev->kobj, groups[i]);
}

static int device_add_attrs(struct device *dev)
{
        struct class *class = dev->class;
        struct device_type *type = dev->type;
        int error;

        if (class) {
                error = device_add_attributes(dev, class->dev_attrs);
                if (error)
                        return error;
        }

        if (type) {
                error = device_add_groups(dev, type->groups);
                if (error)
                        goto err_remove_class_attrs;
        }

        error = device_add_groups(dev, dev->groups);
        if (error)
                goto err_remove_type_groups;

        return 0;

 err_remove_type_groups:
        if (type)
                device_remove_groups(dev, type->groups);
 err_remove_class_attrs:
        if (class)
                device_remove_attributes(dev, class->dev_attrs);

        return error;
}

static void device_remove_attrs(struct device *dev)
{
        struct class *class = dev->class;
        struct device_type *type = dev->type;

        device_remove_groups(dev, dev->groups);

        if (type)
                device_remove_groups(dev, type->groups);

        if (class)
                device_remove_attributes(dev, class->dev_attrs);
}


static ssize_t show_dev(struct device *dev, struct device_attribute *attr,
                        char *buf)
{
        return print_dev_t(buf, dev->devt);
}

static struct device_attribute devt_attr =
        __ATTR(dev, S_IRUGO, show_dev, NULL);

/* kset to create /sys/devices/  */
struct kset *devices_kset;

/**
 * device_create_file - create sysfs attribute file for device.
 * @dev: device.
 * @attr: device attribute descriptor.
 */
int device_create_file(struct device *dev, struct device_attribute *attr)
{
        int error = 0;
        if (dev)
                error = sysfs_create_file(&dev->kobj, &attr->attr);
        return error;
}

/**
 * device_remove_file - remove sysfs attribute file.
 * @dev: device.
 * @attr: device attribute descriptor.
 */
void device_remove_file(struct device *dev, struct device_attribute *attr)
{
        if (dev)
                sysfs_remove_file(&dev->kobj, &attr->attr);
}

/**
 * device_create_bin_file - create sysfs binary attribute file for device.
 * @dev: device.
 * @attr: device binary attribute descriptor.
 */
int device_create_bin_file(struct device *dev, struct bin_attribute *attr)
{
        int error = -EINVAL;
        if (dev)
                error = sysfs_create_bin_file(&dev->kobj, attr);
        return error;
}
EXPORT_SYMBOL_GPL(device_create_bin_file);

/**
 * device_remove_bin_file - remove sysfs binary attribute file
 * @dev: device.
 * @attr: device binary attribute descriptor.
 */
void device_remove_bin_file(struct device *dev, struct bin_attribute *attr)
{
        if (dev)
                sysfs_remove_bin_file(&dev->kobj, attr);
}
EXPORT_SYMBOL_GPL(device_remove_bin_file);

/**
 * device_schedule_callback_owner - helper to schedule a callback for a device
 * @dev: device.
 * @func: callback function to invoke later.
 * @owner: module owning the callback routine
 *
 * Attribute methods must not unregister themselves or their parent device
 * (which would amount to the same thing).  Attempts to do so will deadlock,
 * since unregistration is mutually exclusive with driver callbacks.
 *
 * Instead methods can call this routine, which will attempt to allocate
 * and schedule a workqueue request to call back @func with @dev as its
 * argument in the workqueue's process context.  @dev will be pinned until
 * @func returns.
 *
 * This routine is usually called via the inline device_schedule_callback(),
 * which automatically sets @owner to THIS_MODULE.
 *
 * Returns 0 if the request was submitted, -ENOMEM if storage could not
 * be allocated, -ENODEV if a reference to @owner isn't available.
 *
 * NOTE: This routine won't work if CONFIG_SYSFS isn't set!  It uses an
 * underlying sysfs routine (since it is intended for use by attribute
 * methods), and if sysfs isn't available you'll get nothing but -ENOSYS.
 */
int device_schedule_callback_owner(struct device *dev,
                void (*func)(struct device *), struct module *owner)
{
        return sysfs_schedule_callback(&dev->kobj,
                        (void (*)(void *)) func, dev, owner);
}
EXPORT_SYMBOL_GPL(device_schedule_callback_owner);

static void klist_children_get(struct klist_node *n)
{
        struct device *dev = container_of(n, struct device, knode_parent);

        get_device(dev);
}

static void klist_children_put(struct klist_node *n)
{
        struct device *dev = container_of(n, struct device, knode_parent);

        put_device(dev);
}

/**
 * device_initialize - init device structure.
 * @dev: device.
 *
 * This prepares the device for use by other layers,
 * including adding it to the device hierarchy.
 * It is the first half of device_register(), if called by
 * that, though it can also be called separately, so one
 * may use @dev's fields (e.g. the refcount).
 */
void device_initialize(struct device *dev)
{
        dev->kobj.kset = devices_kset;
        kobject_init(&dev->kobj, &device_ktype);
        klist_init(&dev->klist_children, klist_children_get,
                   klist_children_put);
        INIT_LIST_HEAD(&dev->dma_pools);
        INIT_LIST_HEAD(&dev->node);
        init_MUTEX(&dev->sem);
        spin_lock_init(&dev->devres_lock);
        INIT_LIST_HEAD(&dev->devres_head);
        device_init_wakeup(dev, 0);
        set_dev_node(dev, -1);
}

#ifdef CONFIG_SYSFS_DEPRECATED
static struct kobject *get_device_parent(struct device *dev,
                                         struct device *parent)
{
        /* class devices without a parent live in /sys/class/<classname>/ */
        if (dev->class && (!parent || parent->class != dev->class))
                return &dev->class->subsys.kobj;
        /* all other devices keep their parent */
        else if (parent)
                return &parent->kobj;

        return NULL;
}

static inline void cleanup_device_parent(struct device *dev) {}
static inline void cleanup_glue_dir(struct device *dev,
                                    struct kobject *glue_dir) {}
#else
static struct kobject *virtual_device_parent(struct device *dev)
{
        static struct kobject *virtual_dir = NULL;

        if (!virtual_dir)
                virtual_dir = kobject_create_and_add("virtual",
                                                     &devices_kset->kobj);

        return virtual_dir;
}

static struct kobject *get_device_parent(struct device *dev,
                                         struct device *parent)
{
        int retval;

        if (dev->class) {
                struct kobject *kobj = NULL;
                struct kobject *parent_kobj;
                struct kobject *k;

                /*
                 * If we have no parent, we live in "virtual".
                 * Class-devices with a non class-device as parent, live
                 * in a "glue" directory to prevent namespace collisions.
                 */
                if (parent == NULL)
                        parent_kobj = virtual_device_parent(dev);
                else if (parent->class)
                        return &parent->kobj;
                else
                        parent_kobj = &parent->kobj;

                /* find our class-directory at the parent and reference it */
                spin_lock(&dev->class->class_dirs.list_lock);
                list_for_each_entry(k, &dev->class->class_dirs.list, entry)
                        if (k->parent == parent_kobj) {
                                kobj = kobject_get(k);
                                break;
                        }
                spin_unlock(&dev->class->class_dirs.list_lock);
                if (kobj)
                        return kobj;

                /* or create a new class-directory at the parent device */
                k = kobject_create();
                if (!k)
                        return NULL;
                k->kset = &dev->class->class_dirs;
                retval = kobject_add(k, parent_kobj, "%s", dev->class->name);
                if (retval < 0) {
                        kobject_put(k);
                        return NULL;
                }
                /* do not emit an uevent for this simple "glue" directory */
                return k;
        }

        if (parent)
                return &parent->kobj;
        return NULL;
}

static void cleanup_glue_dir(struct device *dev, struct kobject *glue_dir)
{
        /* see if we live in a "glue" directory */
        if (!dev->class || glue_dir->kset != &dev->class->class_dirs)
                return;

        kobject_put(glue_dir);
}

static void cleanup_device_parent(struct device *dev)
{
        cleanup_glue_dir(dev, dev->kobj.parent);
}
#endif

static void setup_parent(struct device *dev, struct device *parent)
{
        struct kobject *kobj;
        kobj = get_device_parent(dev, parent);
        if (kobj)
                dev->kobj.parent = kobj;
}

static int device_add_class_symlinks(struct device *dev)
{
        int error;

        if (!dev->class)
                return 0;

        error = sysfs_create_link(&dev->kobj, &dev->class->subsys.kobj,
                                  "subsystem");
        if (error)
                goto out;

#ifdef CONFIG_SYSFS_DEPRECATED
        /* stacked class devices need a symlink in the class directory */
        if (dev->kobj.parent != &dev->class->subsys.kobj &&
            device_is_not_partition(dev)) {
                error = sysfs_create_link(&dev->class->subsys.kobj, &dev->kobj,
                                          dev->bus_id);
                if (error)
                        goto out_subsys;
        }

        if (dev->parent && device_is_not_partition(dev)) {
                struct device *parent = dev->parent;
                char *class_name;

                /*
                 * stacked class devices have the 'device' link
                 * pointing to the bus device instead of the parent
                 */
                while (parent->class && !parent->bus && parent->parent)
                        parent = parent->parent;

                error = sysfs_create_link(&dev->kobj,
                                          &parent->kobj,
                                          "device");
                if (error)
                        goto out_busid;

                class_name = make_class_name(dev->class->name,
                                                &dev->kobj);
                if (class_name)
                        error = sysfs_create_link(&dev->parent->kobj,
                                                &dev->kobj, class_name);
                kfree(class_name);
                if (error)
                        goto out_device;
        }
        return 0;

out_device:
        if (dev->parent && device_is_not_partition(dev))
                sysfs_remove_link(&dev->kobj, "device");
out_busid:
        if (dev->kobj.parent != &dev->class->subsys.kobj &&
            device_is_not_partition(dev))
                sysfs_remove_link(&dev->class->subsys.kobj, dev->bus_id);
#else
        /* link in the class directory pointing to the device */
        error = sysfs_create_link(&dev->class->subsys.kobj, &dev->kobj,
                                  dev->bus_id);
        if (error)
                goto out_subsys;

        if (dev->parent && device_is_not_partition(dev)) {
                error = sysfs_create_link(&dev->kobj, &dev->parent->kobj,
                                          "device");
                if (error)
                        goto out_busid;
        }
        return 0;

out_busid:
        sysfs_remove_link(&dev->class->subsys.kobj, dev->bus_id);
#endif

out_subsys:
        sysfs_remove_link(&dev->kobj, "subsystem");
out:
        return error;
}

static void device_remove_class_symlinks(struct device *dev)
{
        if (!dev->class)
                return;

#ifdef CONFIG_SYSFS_DEPRECATED
        if (dev->parent && device_is_not_partition(dev)) {
                char *class_name;

                class_name = make_class_name(dev->class->name, &dev->kobj);
                if (class_name) {
                        sysfs_remove_link(&dev->parent->kobj, class_name);
                        kfree(class_name);
                }
                sysfs_remove_link(&dev->kobj, "device");
        }

        if (dev->kobj.parent != &dev->class->subsys.kobj &&
            device_is_not_partition(dev))
                sysfs_remove_link(&dev->class->subsys.kobj, dev->bus_id);
#else
        if (dev->parent && device_is_not_partition(dev))
                sysfs_remove_link(&dev->kobj, "device");

        sysfs_remove_link(&dev->class->subsys.kobj, dev->bus_id);
#endif

        sysfs_remove_link(&dev->kobj, "subsystem");
}

/**
 * device_add - add device to device hierarchy.
 * @dev: device.
 *
 * This is part 2 of device_register(), though may be called
 * separately _iff_ device_initialize() has been called separately.
 *
 * This adds it to the kobject hierarchy via kobject_add(), adds it
 * to the global and sibling lists for the device, then
 * adds it to the other relevant subsystems of the driver model.
 */
int device_add(struct device *dev)
{
        struct device *parent = NULL;
        struct class_interface *class_intf;
        int error;

        error = pm_sleep_lock();
        if (error) {
                dev_warn(dev, "Suspicious %s during suspend\n", __FUNCTION__);
                dump_stack();
                return error;
        }

        dev = get_device(dev);
        if (!dev || !strlen(dev->bus_id)) {
                error = -EINVAL;
                goto Error;
        }

        pr_debug("device: '%s': %s\n", dev->bus_id, __FUNCTION__);

        parent = get_device(dev->parent);
        setup_parent(dev, parent);

        /* first, register with generic layer. */
        error = kobject_add(&dev->kobj, dev->kobj.parent, "%s", dev->bus_id);
        if (error)
                goto Error;

        /* notify platform of device entry */
        if (platform_notify)
                platform_notify(dev);

        /* notify clients of device entry (new way) */
        if (dev->bus)
                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
                                             BUS_NOTIFY_ADD_DEVICE, dev);

        error = device_create_file(dev, &uevent_attr);
        if (error)
                goto attrError;

        if (MAJOR(dev->devt)) {
                error = device_create_file(dev, &devt_attr);
                if (error)
                        goto ueventattrError;
        }

        error = device_add_class_symlinks(dev);
        if (error)
                goto SymlinkError;
        error = device_add_attrs(dev);
        if (error)
                goto AttrsError;
        error = dpm_sysfs_add(dev);
        if (error)
                goto PMError;
        device_pm_add(dev);
        error = bus_add_device(dev);
        if (error)
                goto BusError;
        kobject_uevent(&dev->kobj, KOBJ_ADD);
        bus_attach_device(dev);
        if (parent)
                klist_add_tail(&dev->knode_parent, &parent->klist_children);

        if (dev->class) {
                down(&dev->class->sem);
                /* tie the class to the device */
                list_add_tail(&dev->node, &dev->class->devices);

                /* notify any interfaces that the device is here */
                list_for_each_entry(class_intf, &dev->class->interfaces, node)
                        if (class_intf->add_dev)
                                class_intf->add_dev(dev, class_intf);
                up(&dev->class->sem);
        }
 Done:
        put_device(dev);
        pm_sleep_unlock();
        return error;
 BusError:
        device_pm_remove(dev);
        dpm_sysfs_remove(dev);
 PMError:
        if (dev->bus)
                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
                                             BUS_NOTIFY_DEL_DEVICE, dev);
        device_remove_attrs(dev);
 AttrsError:
        device_remove_class_symlinks(dev);
 SymlinkError:
        if (MAJOR(dev->devt))
                device_remove_file(dev, &devt_attr);
 ueventattrError:
        device_remove_file(dev, &uevent_attr);
 attrError:
        kobject_uevent(&dev->kobj, KOBJ_REMOVE);
        kobject_del(&dev->kobj);
 Error:
        cleanup_device_parent(dev);
        if (parent)
                put_device(parent);
        goto Done;
}

/**
 * device_register - register a device with the system.
 * @dev: pointer to the device structure
 *
 * This happens in two clean steps - initialize the device
 * and add it to the system. The two steps can be called
 * separately, but this is the easiest and most common.
 * I.e. you should only call the two helpers separately if
 * have a clearly defined need to use and refcount the device
 * before it is added to the hierarchy.
 */
int device_register(struct device *dev)
{
        device_initialize(dev);
        return device_add(dev);
}

/**
 * get_device - increment reference count for device.
 * @dev: device.
 *
 * This simply forwards the call to kobject_get(), though
 * we do take care to provide for the case that we get a NULL
 * pointer passed in.
 */
struct device *get_device(struct device *dev)
{
        return dev ? to_dev(kobject_get(&dev->kobj)) : NULL;
}

/**
 * put_device - decrement reference count.
 * @dev: device in question.
 */
void put_device(struct device *dev)
{
        /* might_sleep(); */
        if (dev)
                kobject_put(&dev->kobj);
}

/**
 * device_del - delete device from system.
 * @dev: device.
 *
 * This is the first part of the device unregistration
 * sequence. This removes the device from the lists we control
 * from here, has it removed from the other driver model
 * subsystems it was added to in device_add(), and removes it
 * from the kobject hierarchy.
 *
 * NOTE: this should be called manually _iff_ device_add() was
 * also called manually.
 */
void device_del(struct device *dev)
{
        struct device *parent = dev->parent;
        struct class_interface *class_intf;

        device_pm_remove(dev);
        if (parent)
                klist_del(&dev->knode_parent);
        if (MAJOR(dev->devt))
                device_remove_file(dev, &devt_attr);
        if (dev->class) {
                device_remove_class_symlinks(dev);

                down(&dev->class->sem);
                /* notify any interfaces that the device is now gone */
                list_for_each_entry(class_intf, &dev->class->interfaces, node)
                        if (class_intf->remove_dev)
                                class_intf->remove_dev(dev, class_intf);
                /* remove the device from the class list */
                list_del_init(&dev->node);
                up(&dev->class->sem);
        }
        device_remove_file(dev, &uevent_attr);
        device_remove_attrs(dev);
        bus_remove_device(dev);

        /*
         * Some platform devices are driven without driver attached
         * and managed resources may have been acquired.  Make sure
         * all resources are released.
         */
        devres_release_all(dev);

        /* Notify the platform of the removal, in case they
         * need to do anything...
         */
        if (platform_notify_remove)
                platform_notify_remove(dev);
        if (dev->bus)
                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
                                             BUS_NOTIFY_DEL_DEVICE, dev);
        kobject_uevent(&dev->kobj, KOBJ_REMOVE);
        cleanup_device_parent(dev);
        kobject_del(&dev->kobj);
        put_device(parent);
}

/**
 * device_unregister - unregister device from system.
 * @dev: device going away.
 *
 * We do this in two parts, like we do device_register(). First,
 * we remove it from all the subsystems with device_del(), then
 * we decrement the reference count via put_device(). If that
 * is the final reference count, the device will be cleaned up
 * via device_release() above. Otherwise, the structure will
 * stick around until the final reference to the device is dropped.
 */
void device_unregister(struct device *dev)
{
        pr_debug("device: '%s': %s\n", dev->bus_id, __FUNCTION__);
        device_del(dev);
        put_device(dev);
}

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

/**
 * device_for_each_child - device child iterator.
 * @parent: parent struct device.
 * @data: data for the callback.
 * @fn: function to be called for each device.
 *
 * Iterate over @parent's child devices, and call @fn for each,
 * passing it @data.
 *
 * We check the return of @fn each time. If it returns anything
 * other than 0, we break out and return that value.
 */
int device_for_each_child(struct device *parent, void *data,
                          int (*fn)(struct device *dev, void *data))
{
        struct klist_iter i;
        struct device *child;
        int error = 0;

        klist_iter_init(&parent->klist_children, &i);
        while ((child = next_device(&i)) && !error)
                error = fn(child, data);
        klist_iter_exit(&i);
        return error;
}

/**
 * device_find_child - device iterator for locating a particular device.
 * @parent: parent struct device
 * @data: Data to pass to match function
 * @match: Callback function to check device
 *
 * This is similar to the device_for_each_child() 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 and a reference to the
 * current device can be obtained, this function will return to the caller
 * and not iterate over any more devices.
 */
struct device *device_find_child(struct device *parent, void *data,
                                 int (*match)(struct device *dev, void *data))
{
        struct klist_iter i;
        struct device *child;

        if (!parent)
                return NULL;

        klist_iter_init(&parent->klist_children, &i);
        while ((child = next_device(&i)))
                if (match(child, data) && get_device(child))
                        break;
        klist_iter_exit(&i);
        return child;
}

int __init devices_init(void)
{
        devices_kset = kset_create_and_add("devices", &device_uevent_ops, NULL);
        if (!devices_kset)
                return -ENOMEM;
        return 0;
}

EXPORT_SYMBOL_GPL(device_for_each_child);
EXPORT_SYMBOL_GPL(device_find_child);

EXPORT_SYMBOL_GPL(device_initialize);
EXPORT_SYMBOL_GPL(device_add);
EXPORT_SYMBOL_GPL(device_register);

EXPORT_SYMBOL_GPL(device_del);
EXPORT_SYMBOL_GPL(device_unregister);
EXPORT_SYMBOL_GPL(get_device);
EXPORT_SYMBOL_GPL(put_device);

EXPORT_SYMBOL_GPL(device_create_file);
EXPORT_SYMBOL_GPL(device_remove_file);


static void device_create_release(struct device *dev)
{
        pr_debug("device: '%s': %s\n", dev->bus_id, __FUNCTION__);
        kfree(dev);
}

/**
 * device_create - creates a device and registers it with sysfs
 * @class: pointer to the struct class that this device should be registered to
 * @parent: pointer to the parent struct device of this new device, if any
 * @devt: the dev_t for the char device to be added
 * @fmt: string for the device's name
 *
 * This function can be used by char device classes.  A struct device
 * will be created in sysfs, registered to the specified class.
 *
 * A "dev" file will be created, showing the dev_t for the device, if
 * the dev_t is not 0,0.
 * If a pointer to a parent struct device is passed in, the newly created
 * struct device will be a child of that device in sysfs.
 * The pointer to the struct device will be returned from the call.
 * Any further sysfs files that might be required can be created using this
 * pointer.
 *
 * Note: the struct class passed to this function must have previously
 * been created with a call to class_create().
 */
struct device *device_create(struct class *class, struct device *parent,
                             dev_t devt, const char *fmt, ...)
{
        va_list args;
        struct device *dev = NULL;
        int retval = -ENODEV;

        if (class == NULL || IS_ERR(class))
                goto error;

        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
        if (!dev) {
                retval = -ENOMEM;
                goto error;
        }

        dev->devt = devt;
        dev->class = class;
        dev->parent = parent;
        dev->release = device_create_release;

        va_start(args, fmt);
        vsnprintf(dev->bus_id, BUS_ID_SIZE, fmt, args);
        va_end(args);
        retval = device_register(dev);
        if (retval)
                goto error;

        return dev;

error:
        kfree(dev);
        return ERR_PTR(retval);
}
EXPORT_SYMBOL_GPL(device_create);

static int __match_devt(struct device *dev, void *data)
{
        dev_t *devt = data;

        return dev->devt == *devt;
}

/**
 * device_destroy - removes a device that was created with device_create()
 * @class: pointer to the struct class that this device was registered with
 * @devt: the dev_t of the device that was previously registered
 *
 * This call unregisters and cleans up a device that was created with a
 * call to device_create().
 */
void device_destroy(struct class *class, dev_t devt)
{
        struct device *dev;

        dev = class_find_device(class, &devt, __match_devt);
        if (dev) {
                put_device(dev);
                device_unregister(dev);
        }
}
EXPORT_SYMBOL_GPL(device_destroy);

#ifdef CONFIG_PM_SLEEP
/**
 * destroy_suspended_device - asks the PM core to remove a suspended device
 * @class: pointer to the struct class that this device was registered with
 * @devt: the dev_t of the device that was previously registered
 *
 * This call notifies the PM core of the necessity to unregister a suspended
 * device created with a call to device_create() (devices cannot be
 * unregistered directly while suspended, since the PM core holds their
 * semaphores at that time).
 *
 * It can only be called within the scope of a system sleep transition.  In
 * practice this means it has to be directly or indirectly invoked either by
 * a suspend or resume method, or by the PM core (e.g. via
 * disable_nonboot_cpus() or enable_nonboot_cpus()).
 */
void destroy_suspended_device(struct class *class, dev_t devt)
{
        struct device *dev;

        dev = class_find_device(class, &devt, __match_devt);
        if (dev) {
                device_pm_schedule_removal(dev);
                put_device(dev);
        }
}
EXPORT_SYMBOL_GPL(destroy_suspended_device);
#endif /* CONFIG_PM_SLEEP */

/**
 * device_rename - renames a device
 * @dev: the pointer to the struct device to be renamed
 * @new_name: the new name of the device
 */
int device_rename(struct device *dev, char *new_name)
{
        char *old_class_name = NULL;
        char *new_class_name = NULL;
        char *old_device_name = NULL;
        int error;

        dev = get_device(dev);
        if (!dev)
                return -EINVAL;

        pr_debug("device: '%s': %s: renaming to '%s'\n", dev->bus_id,
                 __FUNCTION__, new_name);

#ifdef CONFIG_SYSFS_DEPRECATED
        if ((dev->class) && (dev->parent))
                old_class_name = make_class_name(dev->class->name, &dev->kobj);
#endif

        old_device_name = kmalloc(BUS_ID_SIZE, GFP_KERNEL);
        if (!old_device_name) {
                error = -ENOMEM;
                goto out;
        }
        strlcpy(old_device_name, dev->bus_id, BUS_ID_SIZE);
        strlcpy(dev->bus_id, new_name, BUS_ID_SIZE);

        error = kobject_rename(&dev->kobj, new_name);
        if (error) {
                strlcpy(dev->bus_id, old_device_name, BUS_ID_SIZE);
                goto out;
        }

#ifdef CONFIG_SYSFS_DEPRECATED
        if (old_class_name) {
                new_class_name = make_class_name(dev->class->name, &dev->kobj);
                if (new_class_name) {
                        error = sysfs_create_link(&dev->parent->kobj,
                                                  &dev->kobj, new_class_name);
                        if (error)
                                goto out;
                        sysfs_remove_link(&dev->parent->kobj, old_class_name);
                }
        }
#else
        if (dev->class) {
                sysfs_remove_link(&dev->class->subsys.kobj, old_device_name);
                error = sysfs_create_link(&dev->class->subsys.kobj, &dev->kobj,
                                          dev->bus_id);
                if (error) {
                        dev_err(dev, "%s: sysfs_create_symlink failed (%d)\n",
                                __FUNCTION__, error);
                }
        }
#endif

out:
        put_device(dev);

        kfree(new_class_name);
        kfree(old_class_name);
        kfree(old_device_name);

        return error;
}
EXPORT_SYMBOL_GPL(device_rename);

static int device_move_class_links(struct device *dev,
                                   struct device *old_parent,
                                   struct device *new_parent)
{
        int error = 0;
#ifdef CONFIG_SYSFS_DEPRECATED
        char *class_name;

        class_name = make_class_name(dev->class->name, &dev->kobj);
        if (!class_name) {
                error = -ENOMEM;
                goto out;
        }
        if (old_parent) {
                sysfs_remove_link(&dev->kobj, "device");
                sysfs_remove_link(&old_parent->kobj, class_name);
        }
        if (new_parent) {
                error = sysfs_create_link(&dev->kobj, &new_parent->kobj,
                                          "device");
                if (error)
                        goto out;
                error = sysfs_create_link(&new_parent->kobj, &dev->kobj,
                                          class_name);
                if (error)
                        sysfs_remove_link(&dev->kobj, "device");
        } else
                error = 0;
out:
        kfree(class_name);
        return error;
#else
        if (old_parent)
                sysfs_remove_link(&dev->kobj, "device");
        if (new_parent)
                error = sysfs_create_link(&dev->kobj, &new_parent->kobj,
                                          "device");
        return error;
#endif
}

/**
 * device_move - moves a device to a new parent
 * @dev: the pointer to the struct device to be moved
 * @new_parent: the new parent of the device (can by NULL)
 */
int device_move(struct device *dev, struct device *new_parent)
{
        int error;
        struct device *old_parent;
        struct kobject *new_parent_kobj;

        dev = get_device(dev);
        if (!dev)
                return -EINVAL;

        new_parent = get_device(new_parent);
        new_parent_kobj = get_device_parent(dev, new_parent);

        pr_debug("device: '%s': %s: moving to '%s'\n", dev->bus_id,
                 __FUNCTION__, new_parent ? new_parent->bus_id : "<NULL>");
        error = kobject_move(&dev->kobj, new_parent_kobj);
        if (error) {
                cleanup_glue_dir(dev, new_parent_kobj);
                put_device(new_parent);
                goto out;
        }
        old_parent = dev->parent;
        dev->parent = new_parent;
        if (old_parent)
                klist_remove(&dev->knode_parent);
        if (new_parent)
                klist_add_tail(&dev->knode_parent, &new_parent->klist_children);
        if (!dev->class)
                goto out_put;
        error = device_move_class_links(dev, old_parent, new_parent);
        if (error) {
                /* We ignore errors on cleanup since we're hosed anyway... */
                device_move_class_links(dev, new_parent, old_parent);
                if (!kobject_move(&dev->kobj, &old_parent->kobj)) {
                        if (new_parent)
                                klist_remove(&dev->knode_parent);
                        if (old_parent)
                                klist_add_tail(&dev->knode_parent,
                                               &old_parent->klist_children);
                }
                cleanup_glue_dir(dev, new_parent_kobj);
                put_device(new_parent);
                goto out;
        }
out_put:
        put_device(old_parent);
out:
        put_device(dev);
        return error;
}
EXPORT_SYMBOL_GPL(device_move);

/**
 * device_shutdown - call ->shutdown() on each device to shutdown.
 */
void device_shutdown(void)
{
        struct device *dev, *devn;

        list_for_each_entry_safe_reverse(dev, devn, &devices_kset->list,
                                kobj.entry) {
                if (dev->bus && dev->bus->shutdown) {
                        dev_dbg(dev, "shutdown\n");
                        dev->bus->shutdown(dev);
                } else if (dev->driver && dev->driver->shutdown) {
                        dev_dbg(dev, "shutdown\n");
                        dev->driver->shutdown(dev);
                }
        }
}