text: /*
   * 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/fwnode.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/of.h>
  #include <linux/of_device.h>
  #include <linux/genhd.h>
  #include <linux/kallsyms.h>
  #include <linux/mutex.h>
  #include <linux/pm_runtime.h>
  #include <linux/netdevice.h>
  #include <linux/sysfs.h>
  
  #include "base.h"
  #include "power/power.h"
  
  #ifdef CONFIG_SYSFS_DEPRECATED
  #ifdef CONFIG_SYSFS_DEPRECATED_V2
  long sysfs_deprecated = 1;
  #else
  long sysfs_deprecated = 0;
  #endif
  static int __init sysfs_deprecated_setup(char *arg)
  {
  	return kstrtol(arg, 10, &sysfs_deprecated);
  }
  early_param("sysfs.deprecated", sysfs_deprecated_setup);
  #endif
  
  int (*platform_notify)(struct device *dev) = NULL;
  int (*platform_notify_remove)(struct device *dev) = NULL;
  static struct kobject *dev_kobj;
  struct kobject *sysfs_dev_char_kobj;
  struct kobject *sysfs_dev_block_kobj;
  
  static DEFINE_MUTEX(device_hotplug_lock);
  
  void lock_device_hotplug(void)
  {
  	mutex_lock(&device_hotplug_lock);
  }
  
  void unlock_device_hotplug(void)
  {
  	mutex_unlock(&device_hotplug_lock);
  }
  
  int lock_device_hotplug_sysfs(void)
  {
  	if (mutex_trylock(&device_hotplug_lock))
  		return 0;
  
  	/* Avoid busy looping (5 ms of sleep should do). */
  	msleep(5);
  	return restart_syscall();
  }
  
  #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 driver, 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(const struct device *dev)
  {
  	struct device_driver *drv;
  
  	/* dev->driver can change to NULL underneath us because of unbinding,
  	 * so be careful about accessing it.  dev->bus and dev->class should
  	 * never change once they are set, so they don't need special care.
  	 */
  	drv = ACCESS_ONCE(dev->driver);
  	return drv ? drv->name :
  			(dev->bus ? dev->bus->name :
  			(dev->class ? dev->class->name : ""));
  }
  EXPORT_SYMBOL(dev_driver_string);
  
  #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 = kobj_to_dev(kobj);
  	ssize_t ret = -EIO;
  
  	if (dev_attr->show)
  		ret = dev_attr->show(dev, dev_attr, buf);
  	if (ret >= (ssize_t)PAGE_SIZE) {
  		print_symbol("dev_attr_show: %s returned bad count\n",
  				(unsigned long)dev_attr->show);
  	}
  	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 = kobj_to_dev(kobj);
  	ssize_t ret = -EIO;
  
  	if (dev_attr->store)
  		ret = dev_attr->store(dev, dev_attr, buf, count);
  	return ret;
  }
  
  static const struct sysfs_ops dev_sysfs_ops = {
  	.show	= dev_attr_show,
  	.store	= dev_attr_store,
  };
  
  #define to_ext_attr(x) container_of(x, struct dev_ext_attribute, attr)
  
  ssize_t device_store_ulong(struct device *dev,
  			   struct device_attribute *attr,
  			   const char *buf, size_t size)
  {
  	struct dev_ext_attribute *ea = to_ext_attr(attr);
  	char *end;
  	unsigned long new = simple_strtoul(buf, &end, 0);
  	if (end == buf)
  		return -EINVAL;
  	*(unsigned long *)(ea->var) = new;
  	/* Always return full write size even if we didn't consume all */
  	return size;
  }
  EXPORT_SYMBOL_GPL(device_store_ulong);
  
  ssize_t device_show_ulong(struct device *dev,
  			  struct device_attribute *attr,
  			  char *buf)
  {
  	struct dev_ext_attribute *ea = to_ext_attr(attr);
  	return snprintf(buf, PAGE_SIZE, "%lx\n", *(unsigned long *)(ea->var));
  }
  EXPORT_SYMBOL_GPL(device_show_ulong);
  
  ssize_t device_store_int(struct device *dev,
  			 struct device_attribute *attr,
  			 const char *buf, size_t size)
  {
  	struct dev_ext_attribute *ea = to_ext_attr(attr);
  	char *end;
  	long new = simple_strtol(buf, &end, 0);
  	if (end == buf || new > INT_MAX || new < INT_MIN)
  		return -EINVAL;
  	*(int *)(ea->var) = new;
  	/* Always return full write size even if we didn't consume all */
  	return size;
  }
  EXPORT_SYMBOL_GPL(device_store_int);
  
  ssize_t device_show_int(struct device *dev,
  			struct device_attribute *attr,
  			char *buf)
  {
  	struct dev_ext_attribute *ea = to_ext_attr(attr);
  
  	return snprintf(buf, PAGE_SIZE, "%d\n", *(int *)(ea->var));
  }
  EXPORT_SYMBOL_GPL(device_show_int);
  
  ssize_t device_store_bool(struct device *dev, struct device_attribute *attr,
  			  const char *buf, size_t size)
  {
  	struct dev_ext_attribute *ea = to_ext_attr(attr);
  
  	if (strtobool(buf, ea->var) < 0)
  		return -EINVAL;
  
  	return size;
  }
  EXPORT_SYMBOL_GPL(device_store_bool);
  
  ssize_t device_show_bool(struct device *dev, struct device_attribute *attr,
  			 char *buf)
  {
  	struct dev_ext_attribute *ea = to_ext_attr(attr);
  
  	return snprintf(buf, PAGE_SIZE, "%d\n", *(bool *)(ea->var));
  }
  EXPORT_SYMBOL_GPL(device_show_bool);
  
  /**
   * 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 = kobj_to_dev(kobj);
  	struct device_private *p = dev->p;
  
  	/*
  	 * Some platform devices are driven without driver attached
  	 * and managed resources may have been acquired.  Make sure
  	 * all resources are released.
  	 *
  	 * Drivers still can add resources into device after device
  	 * is deleted but alive, so release devres here to avoid
  	 * possible memory leak.
  	 */
  	devres_release_all(dev);
  
  	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
  		WARN(1, KERN_ERR "Device '%s' does not have a release() "
  			"function, it is broken and must be fixed.\n",
  			dev_name(dev));
  	kfree(p);
  }
  
  static const void *device_namespace(struct kobject *kobj)
  {
  	struct device *dev = kobj_to_dev(kobj);
  	const void *ns = NULL;
  
  	if (dev->class && dev->class->ns_type)
  		ns = dev->class->namespace(dev);
  
  	return ns;
  }
  
  static struct kobj_type device_ktype = {
  	.release	= device_release,
  	.sysfs_ops	= &dev_sysfs_ops,
  	.namespace	= device_namespace,
  };
  
  
  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 = kobj_to_dev(kobj);
  		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 = kobj_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 = kobj_to_dev(kobj);
  	int retval = 0;
  
  	/* add device node properties if present */
  	if (MAJOR(dev->devt)) {
  		const char *tmp;
  		const char *name;
  		umode_t mode = 0;
  		kuid_t uid = GLOBAL_ROOT_UID;
  		kgid_t gid = GLOBAL_ROOT_GID;
  
  		add_uevent_var(env, "MAJOR=%u", MAJOR(dev->devt));
  		add_uevent_var(env, "MINOR=%u", MINOR(dev->devt));
  		name = device_get_devnode(dev, &mode, &uid, &gid, &tmp);
  		if (name) {
  			add_uevent_var(env, "DEVNAME=%s", name);
  			if (mode)
  				add_uevent_var(env, "DEVMODE=%#o", mode & 0777);
  			if (!uid_eq(uid, GLOBAL_ROOT_UID))
  				add_uevent_var(env, "DEVUID=%u", from_kuid(&init_user_ns, uid));
  			if (!gid_eq(gid, GLOBAL_ROOT_GID))
  				add_uevent_var(env, "DEVGID=%u", from_kgid(&init_user_ns, gid));
  			kfree(tmp);
  		}
  	}
  
  	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);
  
  	/* Add common DT information about the device */
  	of_device_uevent(dev, env);
  
  	/* 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_name(dev), __func__, 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_name(dev),
  				 __func__, retval);
  	}
  
  	/* have the device type specific function 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_name(dev),
  				 __func__, retval);
  	}
  
  	return retval;
  }
  
  static const struct kset_uevent_ops device_uevent_ops = {
  	.filter =	dev_uevent_filter,
  	.name =		dev_uevent_name,
  	.uevent =	dev_uevent,
  };
  
  static ssize_t uevent_show(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 uevent_store(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);
  	else
  		dev_err(dev, "uevent: unknown action-string\n");
  	return count;
  }
  static DEVICE_ATTR_RW(uevent);
  
  static ssize_t online_show(struct device *dev, struct device_attribute *attr,
  			   char *buf)
  {
  	bool val;
  
  	device_lock(dev);
  	val = !dev->offline;
  	device_unlock(dev);
  	return sprintf(buf, "%u\n", val);
  }
  
  static ssize_t online_store(struct device *dev, struct device_attribute *attr,
  			    const char *buf, size_t count)
  {
  	bool val;
  	int ret;
  
  	ret = strtobool(buf, &val);
  	if (ret < 0)
  		return ret;
  
  	ret = lock_device_hotplug_sysfs();
  	if (ret)
  		return ret;
  
  	ret = val ? device_online(dev) : device_offline(dev);
  	unlock_device_hotplug();
  	return ret < 0 ? ret : count;
  }
  static DEVICE_ATTR_RW(online);
  
  int device_add_groups(struct device *dev, const struct attribute_group **groups)
  {
  	return sysfs_create_groups(&dev->kobj, groups);
  }
  
  void device_remove_groups(struct device *dev,
  			  const struct attribute_group **groups)
  {
  	sysfs_remove_groups(&dev->kobj, groups);
  }
  
  static int device_add_attrs(struct device *dev)
  {
  	struct class *class = dev->class;
  	const struct device_type *type = dev->type;
  	int error;
  
  	if (class) {
  		error = device_add_groups(dev, class->dev_groups);
  		if (error)
  			return error;
  	}
  
  	if (type) {
  		error = device_add_groups(dev, type->groups);
  		if (error)
  			goto err_remove_class_groups;
  	}
  
  	error = device_add_groups(dev, dev->groups);
  	if (error)
  		goto err_remove_type_groups;
  
  	if (device_supports_offline(dev) && !dev->offline_disabled) {
  		error = device_create_file(dev, &dev_attr_online);
  		if (error)
  			goto err_remove_dev_groups;
  	}
  
  	return 0;
  
   err_remove_dev_groups:
  	device_remove_groups(dev, dev->groups);
   err_remove_type_groups:
  	if (type)
  		device_remove_groups(dev, type->groups);
   err_remove_class_groups:
  	if (class)
  		device_remove_groups(dev, class->dev_groups);
  
  	return error;
  }
  
  static void device_remove_attrs(struct device *dev)
  {
  	struct class *class = dev->class;
  	const struct device_type *type = dev->type;
  
  	device_remove_file(dev, &dev_attr_online);
  	device_remove_groups(dev, dev->groups);
  
  	if (type)
  		device_remove_groups(dev, type->groups);
  
  	if (class)
  		device_remove_groups(dev, class->dev_groups);
  }
  
  static ssize_t dev_show(struct device *dev, struct device_attribute *attr,
  			char *buf)
  {
  	return print_dev_t(buf, dev->devt);
  }
  static DEVICE_ATTR_RO(dev);
  
  /* /sys/devices/ */
  struct kset *devices_kset;
  
  /**
   * devices_kset_move_before - Move device in the devices_kset's list.
   * @deva: Device to move.
   * @devb: Device @deva should come before.
   */
  static void devices_kset_move_before(struct device *deva, struct device *devb)
  {
  	if (!devices_kset)
  		return;
  	pr_debug("devices_kset: Moving %s before %s\n",
  		 dev_name(deva), dev_name(devb));
  	spin_lock(&devices_kset->list_lock);
  	list_move_tail(&deva->kobj.entry, &devb->kobj.entry);
  	spin_unlock(&devices_kset->list_lock);
  }
  
  /**
   * devices_kset_move_after - Move device in the devices_kset's list.
   * @deva: Device to move
   * @devb: Device @deva should come after.
   */
  static void devices_kset_move_after(struct device *deva, struct device *devb)
  {
  	if (!devices_kset)
  		return;
  	pr_debug("devices_kset: Moving %s after %s\n",
  		 dev_name(deva), dev_name(devb));
  	spin_lock(&devices_kset->list_lock);
  	list_move(&deva->kobj.entry, &devb->kobj.entry);
  	spin_unlock(&devices_kset->list_lock);
  }
  
  /**
   * devices_kset_move_last - move the device to the end of devices_kset's list.
   * @dev: device to move
   */
  void devices_kset_move_last(struct device *dev)
  {
  	if (!devices_kset)
  		return;
  	pr_debug("devices_kset: Moving %s to end of list\n", dev_name(dev));
  	spin_lock(&devices_kset->list_lock);
  	list_move_tail(&dev->kobj.entry, &devices_kset->list);
  	spin_unlock(&devices_kset->list_lock);
  }
  
  /**
   * device_create_file - create sysfs attribute file for device.
   * @dev: device.
   * @attr: device attribute descriptor.
   */
  int device_create_file(struct device *dev,
  		       const struct device_attribute *attr)
  {
  	int error = 0;
  
  	if (dev) {
  		WARN(((attr->attr.mode & S_IWUGO) && !attr->store),
  			"Attribute %s: write permission without 'store'\n",
  			attr->attr.name);
  		WARN(((attr->attr.mode & S_IRUGO) && !attr->show),
  			"Attribute %s: read permission without 'show'\n",
  			attr->attr.name);
  		error = sysfs_create_file(&dev->kobj, &attr->attr);
  	}
  
  	return error;
  }
  EXPORT_SYMBOL_GPL(device_create_file);
  
  /**
   * device_remove_file - remove sysfs attribute file.
   * @dev: device.
   * @attr: device attribute descriptor.
   */
  void device_remove_file(struct device *dev,
  			const struct device_attribute *attr)
  {
  	if (dev)
  		sysfs_remove_file(&dev->kobj, &attr->attr);
  }
  EXPORT_SYMBOL_GPL(device_remove_file);
  
  /**
   * device_remove_file_self - remove sysfs attribute file from its own method.
   * @dev: device.
   * @attr: device attribute descriptor.
   *
   * See kernfs_remove_self() for details.
   */
  bool device_remove_file_self(struct device *dev,
  			     const struct device_attribute *attr)
  {
  	if (dev)
  		return sysfs_remove_file_self(&dev->kobj, &attr->attr);
  	else
  		return false;
  }
  EXPORT_SYMBOL_GPL(device_remove_file_self);
  
  /**
   * 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,
  			   const 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,
  			    const struct bin_attribute *attr)
  {
  	if (dev)
  		sysfs_remove_bin_file(&dev->kobj, attr);
  }
  EXPORT_SYMBOL_GPL(device_remove_bin_file);
  
  static void klist_children_get(struct klist_node *n)
  {
  	struct device_private *p = to_device_private_parent(n);
  	struct device *dev = p->device;
  
  	get_device(dev);
  }
  
  static void klist_children_put(struct klist_node *n)
  {
  	struct device_private *p = to_device_private_parent(n);
  	struct device *dev = p->device;
  
  	put_device(dev);
  }
  
  /**
   * device_initialize - init device structure.
   * @dev: device.
   *
   * This prepares the device for use by other layers by initializing
   * its fields.
   * It is the first half of device_register(), if called by
   * that function, though it can also be called separately, so one
   * may use @dev's fields. In particular, get_device()/put_device()
   * may be used for reference counting of @dev after calling this
   * function.
   *
   * All fields in @dev must be initialized by the caller to 0, except
   * for those explicitly set to some other value.  The simplest
   * approach is to use kzalloc() to allocate the structure containing
   * @dev.
   *
   * NOTE: Use put_device() to give up your reference instead of freeing
   * @dev directly once you have called this function.
   */
  void device_initialize(struct device *dev)
  {
  	dev->kobj.kset = devices_kset;
  	kobject_init(&dev->kobj, &device_ktype);
  	INIT_LIST_HEAD(&dev->dma_pools);
  	mutex_init(&dev->mutex);
  	lockdep_set_novalidate_class(&dev->mutex);
  	spin_lock_init(&dev->devres_lock);
  	INIT_LIST_HEAD(&dev->devres_head);
  	device_pm_init(dev);
  	set_dev_node(dev, -1);
  #ifdef CONFIG_GENERIC_MSI_IRQ
  	INIT_LIST_HEAD(&dev->msi_list);
  #endif
  }
  EXPORT_SYMBOL_GPL(device_initialize);
  
  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;
  }
  
  struct class_dir {
  	struct kobject kobj;
  	struct class *class;
  };
  
  #define to_class_dir(obj) container_of(obj, struct class_dir, kobj)
  
  static void class_dir_release(struct kobject *kobj)
  {
  	struct class_dir *dir = to_class_dir(kobj);
  	kfree(dir);
  }
  
  static const
  struct kobj_ns_type_operations *class_dir_child_ns_type(struct kobject *kobj)
  {
  	struct class_dir *dir = to_class_dir(kobj);
  	return dir->class->ns_type;
  }
  
  static struct kobj_type class_dir_ktype = {
  	.release	= class_dir_release,
  	.sysfs_ops	= &kobj_sysfs_ops,
  	.child_ns_type	= class_dir_child_ns_type
  };
  
  static struct kobject *
  class_dir_create_and_add(struct class *class, struct kobject *parent_kobj)
  {
  	struct class_dir *dir;
  	int retval;
  
  	dir = kzalloc(sizeof(*dir), GFP_KERNEL);
  	if (!dir)
  		return NULL;
  
  	dir->class = class;
  	kobject_init(&dir->kobj, &class_dir_ktype);
  
  	dir->kobj.kset = &class->p->glue_dirs;
  
  	retval = kobject_add(&dir->kobj, parent_kobj, "%s", class->name);
  	if (retval < 0) {
  		kobject_put(&dir->kobj);
  		return NULL;
  	}
  	return &dir->kobj;
  }
  
  static DEFINE_MUTEX(gdp_mutex);
  
  static struct kobject *get_device_parent(struct device *dev,
  					 struct device *parent)
  {
  	if (dev->class) {
  		struct kobject *kobj = NULL;
  		struct kobject *parent_kobj;
  		struct kobject *k;
  
  #ifdef CONFIG_BLOCK
  		/* block disks show up in /sys/block */
  		if (sysfs_deprecated && dev->class == &block_class) {
  			if (parent && parent->class == &block_class)
  				return &parent->kobj;
  			return &block_class.p->subsys.kobj;
  		}
  #endif
  
  		/*
  		 * 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 && !dev->class->ns_type)
  			return &parent->kobj;
  		else
  			parent_kobj = &parent->kobj;
  
  		mutex_lock(&gdp_mutex);
  
  		/* find our class-directory at the parent and reference it */
  		spin_lock(&dev->class->p->glue_dirs.list_lock);
  		list_for_each_entry(k, &dev->class->p->glue_dirs.list, entry)
  			if (k->parent == parent_kobj) {
  				kobj = kobject_get(k);
  				break;
  			}
  		spin_unlock(&dev->class->p->glue_dirs.list_lock);
  		if (kobj) {
  			mutex_unlock(&gdp_mutex);
  			return kobj;
  		}
  
  		/* or create a new class-directory at the parent device */
  		k = class_dir_create_and_add(dev->class, parent_kobj);
  		/* do not emit an uevent for this simple "glue" directory */
  		mutex_unlock(&gdp_mutex);
  		return k;
  	}
  
  	/* subsystems can specify a default root directory for their devices */
  	if (!parent && dev->bus && dev->bus->dev_root)
  		return &dev->bus->dev_root->kobj;
  
  	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 (!glue_dir || !dev->class ||
  	    glue_dir->kset != &dev->class->p->glue_dirs)
  		return;
  
  	mutex_lock(&gdp_mutex);
  	kobject_put(glue_dir);
  	mutex_unlock(&gdp_mutex);
  }
  
  static void cleanup_device_parent(struct device *dev)
  {
  	cleanup_glue_dir(dev, dev->kobj.parent);
  }
  
  static int device_add_class_symlinks(struct device *dev)
  {
  	struct device_node *of_node = dev_of_node(dev);
  	int error;
  
  	if (of_node) {
  		error = sysfs_create_link(&dev->kobj, &of_node->kobj,"of_node");
  		if (error)
  			dev_warn(dev, "Error %d creating of_node link\n",error);
  		/* An error here doesn't warrant bringing down the device */
  	}
  
  	if (!dev->class)
  		return 0;
  
  	error = sysfs_create_link(&dev->kobj,
  				  &dev->class->p->subsys.kobj,
  				  "subsystem");
  	if (error)
  		goto out_devnode;
  
  	if (dev->parent && device_is_not_partition(dev)) {
  		error = sysfs_create_link(&dev->kobj, &dev->parent->kobj,
  					  "device");
  		if (error)
  			goto out_subsys;
  	}
  
  #ifdef CONFIG_BLOCK
  	/* /sys/block has directories and does not need symlinks */
  	if (sysfs_deprecated && dev->class == &block_class)
  		return 0;
  #endif
  
  	/* link in the class directory pointing to the device */
  	error = sysfs_create_link(&dev->class->p->subsys.kobj,
  				  &dev->kobj, dev_name(dev));
  	if (error)
  		goto out_device;
  
  	return 0;
  
  out_device:
  	sysfs_remove_link(&dev->kobj, "device");
  
  out_subsys:
  	sysfs_remove_link(&dev->kobj, "subsystem");
  out_devnode:
  	sysfs_remove_link(&dev->kobj, "of_node");
  	return error;
  }
  
  static void device_remove_class_symlinks(struct device *dev)
  {
  	if (dev_of_node(dev))
  		sysfs_remove_link(&dev->kobj, "of_node");
  
  	if (!dev->class)
  		return;
  
  	if (dev->parent && device_is_not_partition(dev))
  		sysfs_remove_link(&dev->kobj, "device");
  	sysfs_remove_link(&dev->kobj, "subsystem");
  #ifdef CONFIG_BLOCK
  	if (sysfs_deprecated && dev->class == &block_class)
  		return;
  #endif
  	sysfs_delete_link(&dev->class->p->subsys.kobj, &dev->kobj, dev_name(dev));
  }
  
  /**
   * dev_set_name - set a device name
   * @dev: device
   * @fmt: format string for the device's name
   */
  int dev_set_name(struct device *dev, const char *fmt, ...)
  {
  	va_list vargs;
  	int err;
  
  	va_start(vargs, fmt);
  	err = kobject_set_name_vargs(&dev->kobj, fmt, vargs);
  	va_end(vargs);
  	return err;
  }
  EXPORT_SYMBOL_GPL(dev_set_name);
  
  /**
   * device_to_dev_kobj - select a /sys/dev/ directory for the device
   * @dev: device
   *
   * By default we select char/ for new entries.  Setting class->dev_obj
   * to NULL prevents an entry from being created.  class->dev_kobj must
   * be set (or cleared) before any devices are registered to the class
   * otherwise device_create_sys_dev_entry() and
   * device_remove_sys_dev_entry() will disagree about the presence of
   * the link.
   */
  static struct kobject *device_to_dev_kobj(struct device *dev)
  {
  	struct kobject *kobj;
  
  	if (dev->class)
  		kobj = dev->class->dev_kobj;
  	else
  		kobj = sysfs_dev_char_kobj;
  
  	return kobj;
  }
  
  static int device_create_sys_dev_entry(struct device *dev)
  {
  	struct kobject *kobj = device_to_dev_kobj(dev);
  	int error = 0;
  	char devt_str[15];
  
  	if (kobj) {
  		format_dev_t(devt_str, dev->devt);
  		error = sysfs_create_link(kobj, &dev->kobj, devt_str);
  	}
  
  	return error;
  }
  
  static void device_remove_sys_dev_entry(struct device *dev)
  {
  	struct kobject *kobj = device_to_dev_kobj(dev);
  	char devt_str[15];
  
  	if (kobj) {
  		format_dev_t(devt_str, dev->devt);
  		sysfs_remove_link(kobj, devt_str);
  	}
  }
  
  int device_private_init(struct device *dev)
  {
  	dev->p = kzalloc(sizeof(*dev->p), GFP_KERNEL);
  	if (!dev->p)
  		return -ENOMEM;
  	dev->p->device = dev;
  	klist_init(&dev->p->klist_children, klist_children_get,
  		   klist_children_put);
  	INIT_LIST_HEAD(&dev->p->deferred_probe);
  	return 0;
  }
  
  /**
   * 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 @dev 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.
   *
   * Do not call this routine or device_register() more than once for
   * any device structure.  The driver model core is not designed to work
   * with devices that get unregistered and then spring back to life.
   * (Among other things, it's very hard to guarantee that all references
   * to the previous incarnation of @dev have been dropped.)  Allocate
   * and register a fresh new struct device instead.
   *
   * NOTE: _Never_ directly free @dev after calling this function, even
   * if it returned an error! Always use put_device() to give up your
   * reference instead.
   */
  int device_add(struct device *dev)
  {
  	struct device *parent = NULL;
  	struct kobject *kobj;
  	struct class_interface *class_intf;
  	int error = -EINVAL;
  
  	dev = get_device(dev);
  	if (!dev)
  		goto done;
  
  	if (!dev->p) {
  		error = device_private_init(dev);
  		if (error)
  			goto done;
  	}
  
  	/*
  	 * for statically allocated devices, which should all be converted
  	 * some day, we need to initialize the name. We prevent reading back
  	 * the name, and force the use of dev_name()
  	 */
  	if (dev->init_name) {
  		dev_set_name(dev, "%s", dev->init_name);
  		dev->init_name = NULL;
  	}
  
  	/* subsystems can specify simple device enumeration */
  	if (!dev_name(dev) && dev->bus && dev->bus->dev_name)
  		dev_set_name(dev, "%s%u", dev->bus->dev_name, dev->id);
  
  	if (!dev_name(dev)) {
  		error = -EINVAL;
  		goto name_error;
  	}
  
  	pr_debug("device: '%s': %s\n", dev_name(dev), __func__);
  
  	parent = get_device(dev->parent);
  	kobj = get_device_parent(dev, parent);
  	if (kobj)
  		dev->kobj.parent = kobj;
  
  	/* use parent numa_node */
  	if (parent && (dev_to_node(dev) == NUMA_NO_NODE))
  		set_dev_node(dev, dev_to_node(parent));
  
  	/* first, register with generic layer. */
  	/* we require the name to be set before, and pass NULL */
  	error = kobject_add(&dev->kobj, dev->kobj.parent, NULL);
  	if (error)
  		goto Error;
  
  	/* notify platform of device entry */
  	if (platform_notify)
  		platform_notify(dev);
  
  	error = device_create_file(dev, &dev_attr_uevent);
  	if (error)
  		goto attrError;
  
  	error = device_add_class_symlinks(dev);
  	if (error)
  		goto SymlinkError;
  	error = device_add_attrs(dev);
  	if (error)
  		goto AttrsError;
  	error = bus_add_device(dev);
  	if (error)
  		goto BusError;
  	error = dpm_sysfs_add(dev);
  	if (error)
  		goto DPMError;
  	device_pm_add(dev);
  
  	if (MAJOR(dev->devt)) {
  		error = device_create_file(dev, &dev_attr_dev);
  		if (error)
  			goto DevAttrError;
  
  		error = device_create_sys_dev_entry(dev);
  		if (error)
  			goto SysEntryError;
  
  		devtmpfs_create_node(dev);
  	}
  
  	/* Notify clients of device addition.  This call must come
  	 * after dpm_sysfs_add() and before kobject_uevent().
  	 */
  	if (dev->bus)
  		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
  					     BUS_NOTIFY_ADD_DEVICE, dev);
  
  	kobject_uevent(&dev->kobj, KOBJ_ADD);
  	bus_probe_device(dev);
  	if (parent)
  		klist_add_tail(&dev->p->knode_parent,
  			       &parent->p->klist_children);
  
  	if (dev->class) {
  		mutex_lock(&dev->class->p->mutex);
  		/* tie the class to the device */
  		klist_add_tail(&dev->knode_class,
  			       &dev->class->p->klist_devices);
  
  		/* notify any interfaces that the device is here */
  		list_for_each_entry(class_intf,
  				    &dev->class->p->interfaces, node)
  			if (class_intf->add_dev)
  				class_intf->add_dev(dev, class_intf);
  		mutex_unlock(&dev->class->p->mutex);
  	}
  done:
  	put_device(dev);
  	return error;
   SysEntryError:
  	if (MAJOR(dev->devt))
  		device_remove_file(dev, &dev_attr_dev);
   DevAttrError:
  	device_pm_remove(dev);
  	dpm_sysfs_remove(dev);
   DPMError:
  	bus_remove_device(dev);
   BusError:
  	device_remove_attrs(dev);
   AttrsError:
  	device_remove_class_symlinks(dev);
   SymlinkError:
  	device_remove_file(dev, &dev_attr_uevent);
   attrError:
  	kobject_uevent(&dev->kobj, KOBJ_REMOVE);
  	kobject_del(&dev->kobj);
   Error:
  	cleanup_device_parent(dev);
  	put_device(parent);
  name_error:
  	kfree(dev->p);
  	dev->p = NULL;
  	goto done;
  }
  EXPORT_SYMBOL_GPL(device_add);
  
  /**
   * 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.
   *
   * For more information, see the kerneldoc for device_initialize()
   * and device_add().
   *
   * NOTE: _Never_ directly free @dev after calling this function, even
   * if it returned an error! Always use put_device() to give up the
   * reference initialized in this function instead.
   */
  int device_register(struct device *dev)
  {
  	device_initialize(dev);
  	return device_add(dev);
  }
  EXPORT_SYMBOL_GPL(device_register);
  
  /**
   * 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 ? kobj_to_dev(kobject_get(&dev->kobj)) : NULL;
  }
  EXPORT_SYMBOL_GPL(get_device);
  
  /**
   * put_device - decrement reference count.
   * @dev: device in question.
   */
  void put_device(struct device *dev)
  {
  	/* might_sleep(); */
  	if (dev)
  		kobject_put(&dev->kobj);
  }
  EXPORT_SYMBOL_GPL(put_device);
  
  /**
   * 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;
  
  	/* Notify clients of device removal.  This call must come
  	 * before dpm_sysfs_remove().
  	 */
  	if (dev->bus)
  		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
  					     BUS_NOTIFY_DEL_DEVICE, dev);
  	dpm_sysfs_remove(dev);
  	if (parent)
  		klist_del(&dev->p->knode_parent);
  	if (MAJOR(dev->devt)) {
  		devtmpfs_delete_node(dev);
  		device_remove_sys_dev_entry(dev);
  		device_remove_file(dev, &dev_attr_dev);
  	}
  	if (dev->class) {
  		device_remove_class_symlinks(dev);
  
  		mutex_lock(&dev->class->p->mutex);
  		/* notify any interfaces that the device is now gone */
  		list_for_each_entry(class_intf,
  				    &dev->class->p->interfaces, node)
  			if (class_intf->remove_dev)
  				class_intf->remove_dev(dev, class_intf);
  		/* remove the device from the class list */
  		klist_del(&dev->knode_class);
  		mutex_unlock(&dev->class->p->mutex);
  	}
  	device_remove_file(dev, &dev_attr_uevent);
  	device_remove_attrs(dev);
  	bus_remove_device(dev);
  	device_pm_remove(dev);
  	driver_deferred_probe_del(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_REMOVED_DEVICE, dev);
  	kobject_uevent(&dev->kobj, KOBJ_REMOVE);
  	cleanup_device_parent(dev);
  	kobject_del(&dev->kobj);
  	put_device(parent);
  }
  EXPORT_SYMBOL_GPL(device_del);
  
  /**
   * 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_name(dev), __func__);
  	device_del(dev);
  	put_device(dev);
  }
  EXPORT_SYMBOL_GPL(device_unregister);
  
  static struct device *prev_device(struct klist_iter *i)
  {
  	struct klist_node *n = klist_prev(i);
  	struct device *dev = NULL;
  	struct device_private *p;
  
  	if (n) {
  		p = to_device_private_parent(n);
  		dev = p->device;
  	}
  	return dev;
  }
  
  static struct device *next_device(struct klist_iter *i)
  {
  	struct klist_node *n = klist_next(i);
  	struct device *dev = NULL;
  	struct device_private *p;
  
  	if (n) {
  		p = to_device_private_parent(n);
  		dev = p->device;
  	}
  	return dev;
  }
  
  /**
   * device_get_devnode - path of device node file
   * @dev: device
   * @mode: returned file access mode
   * @uid: returned file owner
   * @gid: returned file group
   * @tmp: possibly allocated string
   *
   * Return the relative path of a possible device node.
   * Non-default names may need to allocate a memory to compose
   * a name. This memory is returned in tmp and needs to be
   * freed by the caller.
   */
  const char *device_get_devnode(struct device *dev,
  			       umode_t *mode, kuid_t *uid, kgid_t *gid,
  			       const char **tmp)
  {
  	char *s;
  
  	*tmp = NULL;
  
  	/* the device type may provide a specific name */
  	if (dev->type && dev->type->devnode)
  		*tmp = dev->type->devnode(dev, mode, uid, gid);
  	if (*tmp)
  		return *tmp;
  
  	/* the class may provide a specific name */
  	if (dev->class && dev->class->devnode)
  		*tmp = dev->class->devnode(dev, mode);
  	if (*tmp)
  		return *tmp;
  
  	/* return name without allocation, tmp == NULL */
  	if (strchr(dev_name(dev), '!') == NULL)
  		return dev_name(dev);
  
  	/* replace '!' in the name with '/' */
  	s = kstrdup(dev_name(dev), GFP_KERNEL);
  	if (!s)
  		return NULL;
  	strreplace(s, '!', '/');
  	return *tmp = s;
  }
  
  /**
   * device_for_each_child - device child iterator.
   * @parent: parent struct device.
   * @fn: function to be called for each device.
   * @data: data for the callback.
   *
   * 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;
  
  	if (!parent->p)
  		return 0;
  
  	klist_iter_init(&parent->p->klist_children, &i);
  	while ((child = next_device(&i)) && !error)
  		error = fn(child, data);
  	klist_iter_exit(&i);
  	return error;
  }
  EXPORT_SYMBOL_GPL(device_for_each_child);
  
  /**
   * device_for_each_child_reverse - device child iterator in reversed order.
   * @parent: parent struct device.
   * @fn: function to be called for each device.
   * @data: data for the callback.
   *
   * 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_reverse(struct device *parent, void *data,
  				  int (*fn)(struct device *dev, void *data))
  {
  	struct klist_iter i;
  	struct device *child;
  	int error = 0;
  
  	if (!parent->p)
  		return 0;
  
  	klist_iter_init(&parent->p->klist_children, &i);
  	while ((child = prev_device(&i)) && !error)
  		error = fn(child, data);
  	klist_iter_exit(&i);
  	return error;
  }
  EXPORT_SYMBOL_GPL(device_for_each_child_reverse);
  
  /**
   * device_find_child - device iterator for locating a particular device.
   * @parent: parent struct device
   * @match: Callback function to check device
   * @data: Data to pass to match function
   *
   * 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.
   *
   * NOTE: you will need to drop the reference with put_device() after use.
   */
  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->p->klist_children, &i);
  	while ((child = next_device(&i)))
  		if (match(child, data) && get_device(child))
  			break;
  	klist_iter_exit(&i);
  	return child;
  }
  EXPORT_SYMBOL_GPL(device_find_child);
  
  int __init devices_init(void)
  {
  	devices_kset = kset_create_and_add("devices", &device_uevent_ops, NULL);
  	if (!devices_kset)
  		return -ENOMEM;
  	dev_kobj = kobject_create_and_add("dev", NULL);
  	if (!dev_kobj)
  		goto dev_kobj_err;
  	sysfs_dev_block_kobj = kobject_create_and_add("block", dev_kobj);
  	if (!sysfs_dev_block_kobj)
  		goto block_kobj_err;
  	sysfs_dev_char_kobj = kobject_create_and_add("char", dev_kobj);
  	if (!sysfs_dev_char_kobj)
  		goto char_kobj_err;
  
  	return 0;
  
   char_kobj_err:
  	kobject_put(sysfs_dev_block_kobj);
   block_kobj_err:
  	kobject_put(dev_kobj);
   dev_kobj_err:
  	kset_unregister(devices_kset);
  	return -ENOMEM;
  }
  
  static int device_check_offline(struct device *dev, void *not_used)
  {
  	int ret;
  
  	ret = device_for_each_child(dev, NULL, device_check_offline);
  	if (ret)
  		return ret;
  
  	return device_supports_offline(dev) && !dev->offline ? -EBUSY : 0;
  }
  
  /**
   * device_offline - Prepare the device for hot-removal.
   * @dev: Device to be put offline.
   *
   * Execute the device bus type's .offline() callback, if present, to prepare
   * the device for a subsequent hot-removal.  If that succeeds, the device must
   * not be used until either it is removed or its bus type's .online() callback
   * is executed.
   *
   * Call under device_hotplug_lock.
   */
  int device_offline(struct device *dev)
  {
  	int ret;
  
  	if (dev->offline_disabled)
  		return -EPERM;
  
  	ret = device_for_each_child(dev, NULL, device_check_offline);
  	if (ret)
  		return ret;
  
  	device_lock(dev);
  	if (device_supports_offline(dev)) {
  		if (dev->offline) {
  			ret = 1;
  		} else {
  			ret = dev->bus->offline(dev);
  			if (!ret) {
  				kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
  				dev->offline = true;
  			}
  		}
  	}
  	device_unlock(dev);
  
  	return ret;
  }
  
  /**
   * device_online - Put the device back online after successful device_offline().
   * @dev: Device to be put back online.
   *
   * If device_offline() has been successfully executed for @dev, but the device
   * has not been removed subsequently, execute its bus type's .online() callback
   * to indicate that the device can be used again.
   *
   * Call under device_hotplug_lock.
   */
  int device_online(struct device *dev)
  {
  	int ret = 0;
  
  	device_lock(dev);
  	if (device_supports_offline(dev)) {
  		if (dev->offline) {
  			ret = dev->bus->online(dev);
  			if (!ret) {
  				kobject_uevent(&dev->kobj, KOBJ_ONLINE);
  				dev->offline = false;
  			}
  		} else {
  			ret = 1;
  		}
  	}
  	device_unlock(dev);
  
  	return ret;
  }
  
  struct root_device {
  	struct device dev;
  	struct module *owner;
  };
  
  static inline struct root_device *to_root_device(struct device *d)
  {
  	return container_of(d, struct root_device, dev);
  }
  
  static void root_device_release(struct device *dev)
  {
  	kfree(to_root_device(dev));
  }
  
  /**
   * __root_device_register - allocate and register a root device
   * @name: root device name
   * @owner: owner module of the root device, usually THIS_MODULE
   *
   * This function allocates a root device and registers it
   * using device_register(). In order to free the returned
   * device, use root_device_unregister().
   *
   * Root devices are dummy devices which allow other devices
   * to be grouped under /sys/devices. Use this function to
   * allocate a root device and then use it as the parent of
   * any device which should appear under /sys/devices/{name}
   *
   * The /sys/devices/{name} directory will also contain a
   * 'module' symlink which points to the @owner directory
   * in sysfs.
   *
   * Returns &struct device pointer on success, or ERR_PTR() on error.
   *
   * Note: You probably want to use root_device_register().
   */
  struct device *__root_device_register(const char *name, struct module *owner)
  {
  	struct root_device *root;
  	int err = -ENOMEM;
  
  	root = kzalloc(sizeof(struct root_device), GFP_KERNEL);
  	if (!root)
  		return ERR_PTR(err);
  
  	err = dev_set_name(&root->dev, "%s", name);
  	if (err) {
  		kfree(root);
  		return ERR_PTR(err);
  	}
  
  	root->dev.release = root_device_release;
  
  	err = device_register(&root->dev);
  	if (err) {
  		put_device(&root->dev);
  		return ERR_PTR(err);
  	}
  
  #ifdef CONFIG_MODULES	/* gotta find a "cleaner" way to do this */
  	if (owner) {
  		struct module_kobject *mk = &owner->mkobj;
  
  		err = sysfs_create_link(&root->dev.kobj, &mk->kobj, "module");
  		if (err) {
  			device_unregister(&root->dev);
  			return ERR_PTR(err);
  		}
  		root->owner = owner;
  	}
  #endif
  
  	return &root->dev;
  }
  EXPORT_SYMBOL_GPL(__root_device_register);
  
  /**
   * root_device_unregister - unregister and free a root device
   * @dev: device going away
   *
   * This function unregisters and cleans up a device that was created by
   * root_device_register().
   */
  void root_device_unregister(struct device *dev)
  {
  	struct root_device *root = to_root_device(dev);
  
  	if (root->owner)
  		sysfs_remove_link(&root->dev.kobj, "module");
  
  	device_unregister(dev);
  }
  EXPORT_SYMBOL_GPL(root_device_unregister);
  
  
  static void device_create_release(struct device *dev)
  {
  	pr_debug("device: '%s': %s\n", dev_name(dev), __func__);
  	kfree(dev);
  }
  
  static struct device *
  device_create_groups_vargs(struct class *class, struct device *parent,
  			   dev_t devt, void *drvdata,
  			   const struct attribute_group **groups,
  			   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;
  	}
  
  	device_initialize(dev);
  	dev->devt = devt;
  	dev->class = class;
  	dev->parent = parent;
  	dev->groups = groups;
  	dev->release = device_create_release;
  	dev_set_drvdata(dev, drvdata);
  
  	retval = kobject_set_name_vargs(&dev->kobj, fmt, args);
  	if (retval)
  		goto error;
  
  	retval = device_add(dev);
  	if (retval)
  		goto error;
  
  	return dev;
  
  error:
  	put_device(dev);
  	return ERR_PTR(retval);
  }
  
  /**
   * device_create_vargs - 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
   * @drvdata: the data to be added to the device for callbacks
   * @fmt: string for the device's name
   * @args: va_list 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.
   *
   * Returns &struct device pointer on success, or ERR_PTR() on error.
   *
   * Note: the struct class passed to this function must have previously
   * been created with a call to class_create().
   */
  struct device *device_create_vargs(struct class *class, struct device *parent,
  				   dev_t devt, void *drvdata, const char *fmt,
  				   va_list args)
  {
  	return device_create_groups_vargs(class, parent, devt, drvdata, NULL,
  					  fmt, args);
  }
  EXPORT_SYMBOL_GPL(device_create_vargs);
  
  /**
   * 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
   * @drvdata: the data to be added to the device for callbacks
   * @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.
   *
   * Returns &struct device pointer on success, or ERR_PTR() on error.
   *
   * 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, void *drvdata, const char *fmt, ...)
  {
  	va_list vargs;
  	struct device *dev;
  
  	va_start(vargs, fmt);
  	dev = device_create_vargs(class, parent, devt, drvdata, fmt, vargs);
  	va_end(vargs);
  	return dev;
  }
  EXPORT_SYMBOL_GPL(device_create);
  
  /**
   * device_create_with_groups - 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
   * @drvdata: the data to be added to the device for callbacks
   * @groups: NULL-terminated list of attribute groups to be created
   * @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.
   * Additional attributes specified in the groups parameter will also
   * be created automatically.
   *
   * 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.
   *
   * Returns &struct device pointer on success, or ERR_PTR() on error.
   *
   * Note: the struct class passed to this function must have previously
   * been created with a call to class_create().
   */
  struct device *device_create_with_groups(struct class *class,
  					 struct device *parent, dev_t devt,
  					 void *drvdata,
  					 const struct attribute_group **groups,
  					 const char *fmt, ...)
  {
  	va_list vargs;
  	struct device *dev;
  
  	va_start(vargs, fmt);
  	dev = device_create_groups_vargs(class, parent, devt, drvdata, groups,
  					 fmt, vargs);
  	va_end(vargs);
  	return dev;
  }
  EXPORT_SYMBOL_GPL(device_create_with_groups);
  
  static int __match_devt(struct device *dev, const void *data)
  {
  	const 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, NULL, &devt, __match_devt);
  	if (dev) {
  		put_device(dev);
  		device_unregister(dev);
  	}
  }
  EXPORT_SYMBOL_GPL(device_destroy);
  
  /**
   * device_rename - renames a device
   * @dev: the pointer to the struct device to be renamed
   * @new_name: the new name of the device
   *
   * It is the responsibility of the caller to provide mutual
   * exclusion between two different calls of device_rename
   * on the same device to ensure that new_name is valid and
   * won't conflict with other devices.
   *
   * Note: Don't call this function.  Currently, the networking layer calls this
   * function, but that will change.  The following text from Kay Sievers offers
   * some insight:
   *
   * Renaming devices is racy at many levels, symlinks and other stuff are not
   * replaced atomically, and you get a "move" uevent, but it's not easy to
   * connect the event to the old and new device. Device nodes are not renamed at
   * all, there isn't even support for that in the kernel now.
   *
   * In the meantime, during renaming, your target name might be taken by another
   * driver, creating conflicts. Or the old name is taken directly after you
   * renamed it -- then you get events for the same DEVPATH, before you even see
   * the "move" event. It's just a mess, and nothing new should ever rely on
   * kernel device renaming. Besides that, it's not even implemented now for
   * other things than (driver-core wise very simple) network devices.
   *
   * We are currently about to change network renaming in udev to completely
   * disallow renaming of devices in the same namespace as the kernel uses,
   * because we can't solve the problems properly, that arise with swapping names
   * of multiple interfaces without races. Means, renaming of eth[0-9]* will only
   * be allowed to some other name than eth[0-9]*, for the aforementioned
   * reasons.
   *
   * Make up a "real" name in the driver before you register anything, or add
   * some other attributes for userspace to find the device, or use udev to add
   * symlinks -- but never rename kernel devices later, it's a complete mess. We
   * don't even want to get into that and try to implement the missing pieces in
   * the core. We really have other pieces to fix in the driver core mess. :)
   */
  int device_rename(struct device *dev, const char *new_name)
  {
  	struct kobject *kobj = &dev->kobj;
  	char *old_device_name = NULL;
  	int error;
  
  	dev = get_device(dev);
  	if (!dev)
  		return -EINVAL;
  
  	dev_dbg(dev, "renaming to %s\n", new_name);
  
  	old_device_name = kstrdup(dev_name(dev), GFP_KERNEL);
  	if (!old_device_name) {
  		error = -ENOMEM;
  		goto out;
  	}
  
  	if (dev->class) {
  		error = sysfs_rename_link_ns(&dev->class->p->subsys.kobj,
  					     kobj, old_device_name,
  					     new_name, kobject_namespace(kobj));
  		if (error)
  			goto out;
  	}
  
  	error = kobject_rename(kobj, new_name);
  	if (error)
  		goto out;
  
  out:
  	put_device(dev);
  
  	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;
  
  	if (old_parent)
  		sysfs_remove_link(&dev->kobj, "device");
  	if (new_parent)
  		error = sysfs_create_link(&dev->kobj, &new_parent->kobj,
  					  "device");
  	return error;
  }
  
  /**
   * 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)
   * @dpm_order: how to reorder the dpm_list
   */
  int device_move(struct device *dev, struct device *new_parent,
  		enum dpm_order dpm_order)
  {
  	int error;
  	struct device *old_parent;
  	struct kobject *new_parent_kobj;
  
  	dev = get_device(dev);
  	if (!dev)
  		return -EINVAL;
  
  	device_pm_lock();
  	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_name(dev),
  		 __func__, new_parent ? dev_name(new_parent) : "<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->p->knode_parent);
  	if (new_parent) {
  		klist_add_tail(&dev->p->knode_parent,
  			       &new_parent->p->klist_children);
  		set_dev_node(dev, dev_to_node(new_parent));
  	}
  
  	if (dev->class) {
  		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->p->knode_parent);
  				dev->parent = old_parent;
  				if (old_parent) {
  					klist_add_tail(&dev->p->knode_parent,
  						       &old_parent->p->klist_children);
  					set_dev_node(dev, dev_to_node(old_parent));
  				}
  			}
  			cleanup_glue_dir(dev, new_parent_kobj);
  			put_device(new_parent);
  			goto out;
  		}
  	}
  	switch (dpm_order) {
  	case DPM_ORDER_NONE:
  		break;
  	case DPM_ORDER_DEV_AFTER_PARENT:
  		device_pm_move_after(dev, new_parent);
  		devices_kset_move_after(dev, new_parent);
  		break;
  	case DPM_ORDER_PARENT_BEFORE_DEV:
  		device_pm_move_before(new_parent, dev);
  		devices_kset_move_before(new_parent, dev);
  		break;
  	case DPM_ORDER_DEV_LAST:
  		device_pm_move_last(dev);
  		devices_kset_move_last(dev);
  		break;
  	}
  
  	put_device(old_parent);
  out:
  	device_pm_unlock();
  	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, *parent;
  
  	spin_lock(&devices_kset->list_lock);
  	/*
  	 * Walk the devices list backward, shutting down each in turn.
  	 * Beware that device unplug events may also start pulling
  	 * devices offline, even as the system is shutting down.
  	 */
  	while (!list_empty(&devices_kset->list)) {
  		dev = list_entry(devices_kset->list.prev, struct device,
  				kobj.entry);
  
  		/*
  		 * hold reference count of device's parent to
  		 * prevent it from being freed because parent's
  		 * lock is to be held
  		 */
  		parent = get_device(dev->parent);
  		get_device(dev);
  		/*
  		 * Make sure the device is off the kset list, in the
  		 * event that dev->*->shutdown() doesn't remove it.
  		 */
  		list_del_init(&dev->kobj.entry);
  		spin_unlock(&devices_kset->list_lock);
  
  		/* hold lock to avoid race with probe/release */
  		if (parent)
  			device_lock(parent);
  		device_lock(dev);
  
  		/* Don't allow any more runtime suspends */
  		pm_runtime_get_noresume(dev);
  		pm_runtime_barrier(dev);
  
  		if (dev->bus && dev->bus->shutdown) {
  			if (initcall_debug)
  				dev_info(dev, "shutdown\n");
  			dev->bus->shutdown(dev);
  		} else if (dev->driver && dev->driver->shutdown) {
  			if (initcall_debug)
  				dev_info(dev, "shutdown\n");
  			dev->driver->shutdown(dev);
  		}
  
  		device_unlock(dev);
  		if (parent)
  			device_unlock(parent);
  
  		put_device(dev);
  		put_device(parent);
  
  		spin_lock(&devices_kset->list_lock);
  	}
  	spin_unlock(&devices_kset->list_lock);
  }
  
  /*
   * Device logging functions
   */
  
  #ifdef CONFIG_PRINTK
  static int
  create_syslog_header(const struct device *dev, char *hdr, size_t hdrlen)
  {
  	const char *subsys;
  	size_t pos = 0;
  
  	if (dev->class)
  		subsys = dev->class->name;
  	else if (dev->bus)
  		subsys = dev->bus->name;
  	else
  		return 0;
  
  	pos += snprintf(hdr + pos, hdrlen - pos, "SUBSYSTEM=%s", subsys);
  	if (pos >= hdrlen)
  		goto overflow;
  
  	/*
  	 * Add device identifier DEVICE=:
  	 *   b12:8         block dev_t
  	 *   c127:3        char dev_t
  	 *   n8            netdev ifindex
  	 *   +sound:card0  subsystem:devname
  	 */
  	if (MAJOR(dev->devt)) {
  		char c;
  
  		if (strcmp(subsys, "block") == 0)
  			c = 'b';
  		else
  			c = 'c';
  		pos++;
  		pos += snprintf(hdr + pos, hdrlen - pos,
  				"DEVICE=%c%u:%u",
  				c, MAJOR(dev->devt), MINOR(dev->devt));
  	} else if (strcmp(subsys, "net") == 0) {
  		struct net_device *net = to_net_dev(dev);
  
  		pos++;
  		pos += snprintf(hdr + pos, hdrlen - pos,
  				"DEVICE=n%u", net->ifindex);
  	} else {
  		pos++;
  		pos += snprintf(hdr + pos, hdrlen - pos,
  				"DEVICE=+%s:%s", subsys, dev_name(dev));
  	}
  
  	if (pos >= hdrlen)
  		goto overflow;
  
  	return pos;
  
  overflow:
  	dev_WARN(dev, "device/subsystem name too long");
  	return 0;
  }
  
  int dev_vprintk_emit(int level, const struct device *dev,
  		     const char *fmt, va_list args)
  {
  	char hdr[128];
  	size_t hdrlen;
  
  	hdrlen = create_syslog_header(dev, hdr, sizeof(hdr));
  
  	return vprintk_emit(0, level, hdrlen ? hdr : NULL, hdrlen, fmt, args);
  }
  EXPORT_SYMBOL(dev_vprintk_emit);
  
  int dev_printk_emit(int level, const struct device *dev, const char *fmt, ...)
  {
  	va_list args;
  	int r;
  
  	va_start(args, fmt);
  
  	r = dev_vprintk_emit(level, dev, fmt, args);
  
  	va_end(args);
  
  	return r;
  }
  EXPORT_SYMBOL(dev_printk_emit);
  
  static void __dev_printk(const char *level, const struct device *dev,
  			struct va_format *vaf)
  {
  	if (dev)
  		dev_printk_emit(level[1] - '0', dev, "%s %s: %pV",
  				dev_driver_string(dev), dev_name(dev), vaf);
  	else
  		printk("%s(NULL device *): %pV", level, vaf);
  }
  
  void dev_printk(const char *level, const struct device *dev,
  		const char *fmt, ...)
  {
  	struct va_format vaf;
  	va_list args;
  
  	va_start(args, fmt);
  
  	vaf.fmt = fmt;
  	vaf.va = &args;
  
  	__dev_printk(level, dev, &vaf);
  
  	va_end(args);
  }
  EXPORT_SYMBOL(dev_printk);
  
  #define define_dev_printk_level(func, kern_level)		\
  void func(const struct device *dev, const char *fmt, ...)	\
  {								\
  	struct va_format vaf;					\
  	va_list args;						\
  								\
  	va_start(args, fmt);					\
  								\
  	vaf.fmt = fmt;						\
  	vaf.va = &args;						\
  								\
  	__dev_printk(kern_level, dev, &vaf);			\
  								\
  	va_end(args);						\
  }								\
  EXPORT_SYMBOL(func);
  
  define_dev_printk_level(dev_emerg, KERN_EMERG);
  define_dev_printk_level(dev_alert, KERN_ALERT);
  define_dev_printk_level(dev_crit, KERN_CRIT);
  define_dev_printk_level(dev_err, KERN_ERR);
  define_dev_printk_level(dev_warn, KERN_WARNING);
  define_dev_printk_level(dev_notice, KERN_NOTICE);
  define_dev_printk_level(_dev_info, KERN_INFO);
  
  #endif
  
  static inline bool fwnode_is_primary(struct fwnode_handle *fwnode)
  {
  	return fwnode && !IS_ERR(fwnode->secondary);
  }
  
  /**
   * set_primary_fwnode - Change the primary firmware node of a given device.
   * @dev: Device to handle.
   * @fwnode: New primary firmware node of the device.
   *
   * Set the device's firmware node pointer to @fwnode, but if a secondary
   * firmware node of the device is present, preserve it.
   */
  void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
  {
  	if (fwnode) {
  		struct fwnode_handle *fn = dev->fwnode;
  
  		if (fwnode_is_primary(fn))
  			fn = fn->secondary;
  
  		if (fn) {
  			WARN_ON(fwnode->secondary);
  			fwnode->secondary = fn;
  		}
  		dev->fwnode = fwnode;
  	} else {
  		dev->fwnode = fwnode_is_primary(dev->fwnode) ?
  			dev->fwnode->secondary : NULL;
  	}
  }
  EXPORT_SYMBOL_GPL(set_primary_fwnode);
  
  /**
   * set_secondary_fwnode - Change the secondary firmware node of a given device.
   * @dev: Device to handle.
   * @fwnode: New secondary firmware node of the device.
   *
   * If a primary firmware node of the device is present, set its secondary
   * pointer to @fwnode.  Otherwise, set the device's firmware node pointer to
   * @fwnode.
   */
  void set_secondary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
  {
  	if (fwnode)
  		fwnode->secondary = ERR_PTR(-ENODEV);
  
  	if (fwnode_is_primary(dev->fwnode))
  		dev->fwnode->secondary = fwnode;
  	else
  		dev->fwnode = fwnode;
  }
  