drivers/base/class.c - kernel/msm - Gitiles

 /*
  * class.c - basic device class management
  *
  * Copyright (c) 2002-3 Patrick Mochel
  * Copyright (c) 2002-3 Open Source Development Labs
  * Copyright (c) 2003-2004 Greg Kroah-Hartman
  * Copyright (c) 2003-2004 IBM Corp.
  *
  * This file is released under the GPLv2
  *
  */

 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/string.h>
 #include <linux/kdev_t.h>
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/genhd.h>
 #include <linux/mutex.h>
 #include "base.h"

 #define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)

 static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
 			       char *buf)
 {
 	struct class_attribute *class_attr = to_class_attr(attr);
 	struct class_private *cp = to_class(kobj);
 	ssize_t ret = -EIO;

 	if (class_attr->show)
 		ret = class_attr->show(cp->class, buf);
 	return ret;
 }

 static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
 				const char *buf, size_t count)
 {
 	struct class_attribute *class_attr = to_class_attr(attr);
 	struct class_private *cp = to_class(kobj);
 	ssize_t ret = -EIO;

 	if (class_attr->store)
 		ret = class_attr->store(cp->class, buf, count);
 	return ret;
 }

 static void class_release(struct kobject *kobj)
 {
 	struct class_private *cp = to_class(kobj);
 	struct class *class = cp->class;

 	pr_debug("class '%s': release.\n", class->name);

 	if (class->class_release)
 		class->class_release(class);
 	else
 		pr_debug("class '%s' does not have a release() function, "
 			 "be careful\n", class->name);
 }

 static struct sysfs_ops class_sysfs_ops = {
 	.show	= class_attr_show,
 	.store	= class_attr_store,
 };

 static struct kobj_type class_ktype = {
 	.sysfs_ops	= &class_sysfs_ops,
 	.release	= class_release,
 };

 /* Hotplug events for classes go to the class class_subsys */
 static struct kset *class_kset;


 int class_create_file(struct class *cls, const struct class_attribute *attr)
 {
 	int error;
 	if (cls)
 		error = sysfs_create_file(&cls->p->class_subsys.kobj,
 					  &attr->attr);
 	else
 		error = -EINVAL;
 	return error;
 }

 void class_remove_file(struct class *cls, const struct class_attribute *attr)
 {
 	if (cls)
 		sysfs_remove_file(&cls->p->class_subsys.kobj, &attr->attr);
 }

 static struct class *class_get(struct class *cls)
 {
 	if (cls)
 		kset_get(&cls->p->class_subsys);
 	return cls;
 }

 static void class_put(struct class *cls)
 {
 	if (cls)
 		kset_put(&cls->p->class_subsys);
 }

 static int add_class_attrs(struct class *cls)
 {
 	int i;
 	int error = 0;

 	if (cls->class_attrs) {
 		for (i = 0; attr_name(cls->class_attrs[i]); i++) {
 			error = class_create_file(cls, &cls->class_attrs[i]);
 			if (error)
 				goto error;
 		}
 	}
 done:
 	return error;
 error:
 	while (--i >= 0)
 		class_remove_file(cls, &cls->class_attrs[i]);
 	goto done;
 }

 static void remove_class_attrs(struct class *cls)
 {
 	int i;

 	if (cls->class_attrs) {
 		for (i = 0; attr_name(cls->class_attrs[i]); i++)
 			class_remove_file(cls, &cls->class_attrs[i]);
 	}
 }

 static void klist_class_dev_get(struct klist_node *n)
 {
 	struct device *dev = container_of(n, struct device, knode_class);

 	get_device(dev);
 }

 static void klist_class_dev_put(struct klist_node *n)
 {
 	struct device *dev = container_of(n, struct device, knode_class);

 	put_device(dev);
 }

 int __class_register(struct class *cls, struct lock_class_key *key)
 {
 	struct class_private *cp;
 	int error;

 	pr_debug("device class '%s': registering\n", cls->name);

 	cp = kzalloc(sizeof(*cp), GFP_KERNEL);
 	if (!cp)
 		return -ENOMEM;
 	klist_init(&cp->class_devices, klist_class_dev_get, klist_class_dev_put);
 	INIT_LIST_HEAD(&cp->class_interfaces);
 	kset_init(&cp->class_dirs);
 	__mutex_init(&cp->class_mutex, "struct class mutex", key);
 	error = kobject_set_name(&cp->class_subsys.kobj, "%s", cls->name);
 	if (error) {
 		kfree(cp);
 		return error;
 	}

 	/* set the default /sys/dev directory for devices of this class */
 	if (!cls->dev_kobj)
 		cls->dev_kobj = sysfs_dev_char_kobj;

 #if defined(CONFIG_SYSFS_DEPRECATED) && defined(CONFIG_BLOCK)
 	/* let the block class directory show up in the root of sysfs */
 	if (cls != &block_class)
 		cp->class_subsys.kobj.kset = class_kset;
 #else
 	cp->class_subsys.kobj.kset = class_kset;
 #endif
 	cp->class_subsys.kobj.ktype = &class_ktype;
 	cp->class = cls;
 	cls->p = cp;

 	error = kset_register(&cp->class_subsys);
 	if (error) {
 		kfree(cp);
 		return error;
 	}
 	error = add_class_attrs(class_get(cls));
 	class_put(cls);
 	return error;
 }
 EXPORT_SYMBOL_GPL(__class_register);

 void class_unregister(struct class *cls)
 {
 	pr_debug("device class '%s': unregistering\n", cls->name);
 	remove_class_attrs(cls);
 	kset_unregister(&cls->p->class_subsys);
 }

 static void class_create_release(struct class *cls)
 {
 	pr_debug("%s called for %s\n", __func__, cls->name);
 	kfree(cls);
 }

 /**
  * class_create - create a struct class structure
  * @owner: pointer to the module that is to "own" this struct class
  * @name: pointer to a string for the name of this class.
  * @key: the lock_class_key for this class; used by mutex lock debugging
  *
  * This is used to create a struct class pointer that can then be used
  * in calls to device_create().
  *
  * Note, the pointer created here is to be destroyed when finished by
  * making a call to class_destroy().
  */
 struct class *__class_create(struct module *owner, const char *name,
 			     struct lock_class_key *key)
 {
 	struct class *cls;
 	int retval;

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

 	cls->name = name;
 	cls->owner = owner;
 	cls->class_release = class_create_release;

 	retval = __class_register(cls, key);
 	if (retval)
 		goto error;

 	return cls;

 error:
 	kfree(cls);
 	return ERR_PTR(retval);
 }
 EXPORT_SYMBOL_GPL(__class_create);

 /**
  * class_destroy - destroys a struct class structure
  * @cls: pointer to the struct class that is to be destroyed
  *
  * Note, the pointer to be destroyed must have been created with a call
  * to class_create().
  */
 void class_destroy(struct class *cls)
 {
 	if ((cls == NULL) || (IS_ERR(cls)))
 		return;

 	class_unregister(cls);
 }

 #ifdef CONFIG_SYSFS_DEPRECATED
 char *make_class_name(const char *name, struct kobject *kobj)
 {
 	char *class_name;
 	int size;

 	size = strlen(name) + strlen(kobject_name(kobj)) + 2;

 	class_name = kmalloc(size, GFP_KERNEL);
 	if (!class_name)
 		return NULL;

 	strcpy(class_name, name);
 	strcat(class_name, ":");
 	strcat(class_name, kobject_name(kobj));
 	return class_name;
 }
 #endif

 /**
  * class_dev_iter_init - initialize class device iterator
  * @iter: class iterator to initialize
  * @class: the class we wanna iterate over
  * @start: the device to start iterating from, if any
  * @type: device_type of the devices to iterate over, NULL for all
  *
  * Initialize class iterator @iter such that it iterates over devices
  * of @class.  If @start is set, the list iteration will start there,
  * otherwise if it is NULL, the iteration starts at the beginning of
  * the list.
  */
 void class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
 			 struct device *start, const struct device_type *type)
 {
 	struct klist_node *start_knode = NULL;

 	if (start)
 		start_knode = &start->knode_class;
 	klist_iter_init_node(&class->p->class_devices, &iter->ki, start_knode);
 	iter->type = type;
 }
 EXPORT_SYMBOL_GPL(class_dev_iter_init);

 /**
  * class_dev_iter_next - iterate to the next device
  * @iter: class iterator to proceed
  *
  * Proceed @iter to the next device and return it.  Returns NULL if
  * iteration is complete.
  *
  * The returned device is referenced and won't be released till
  * iterator is proceed to the next device or exited.  The caller is
  * free to do whatever it wants to do with the device including
  * calling back into class code.
  */
 struct device *class_dev_iter_next(struct class_dev_iter *iter)
 {
 	struct klist_node *knode;
 	struct device *dev;

 	while (1) {
 		knode = klist_next(&iter->ki);
 		if (!knode)
 			return NULL;
 		dev = container_of(knode, struct device, knode_class);
 		if (!iter->type || iter->type == dev->type)
 			return dev;
 	}
 }
 EXPORT_SYMBOL_GPL(class_dev_iter_next);

 /**
  * class_dev_iter_exit - finish iteration
  * @iter: class iterator to finish
  *
  * Finish an iteration.  Always call this function after iteration is
  * complete whether the iteration ran till the end or not.
  */
 void class_dev_iter_exit(struct class_dev_iter *iter)
 {
 	klist_iter_exit(&iter->ki);
 }
 EXPORT_SYMBOL_GPL(class_dev_iter_exit);

 /**
  * class_for_each_device - device iterator
  * @class: the class we're iterating
  * @start: the device to start with in the list, if any.
  * @data: data for the callback
  * @fn: function to be called for each device
  *
  * Iterate over @class's list of devices, and call @fn for each,
  * passing it @data.  If @start is set, the list iteration will start
  * there, otherwise if it is NULL, the iteration starts at the
  * beginning of the list.
  *
  * We check the return of @fn each time. If it returns anything
  * other than 0, we break out and return that value.
  *
  * @fn is allowed to do anything including calling back into class
  * code.  There's no locking restriction.
  */
 int class_for_each_device(struct class *class, struct device *start,
 			  void *data, int (*fn)(struct device *, void *))
 {
 	struct class_dev_iter iter;
 	struct device *dev;
 	int error = 0;

 	if (!class)
 		return -EINVAL;
 	if (!class->p) {
 		WARN(1, "%s called for class '%s' before it was initialized",
 		     __func__, class->name);
 		return -EINVAL;
 	}

 	class_dev_iter_init(&iter, class, start, NULL);
 	while ((dev = class_dev_iter_next(&iter))) {
 		error = fn(dev, data);
 		if (error)
 			break;
 	}
 	class_dev_iter_exit(&iter);

 	return error;
 }
 EXPORT_SYMBOL_GPL(class_for_each_device);

 /**
  * class_find_device - device iterator for locating a particular device
  * @class: the class we're iterating
  * @start: Device to begin with
  * @data: data for the match function
  * @match: function to check device
  *
  * This is similar to the class_for_each_dev() function above, but it
  * returns a reference to a device that is 'found' for later use, as
  * determined by the @match callback.
  *
  * The callback should return 0 if the device doesn't match and non-zero
  * if it does.  If the callback returns non-zero, this function will
  * return to the caller and not iterate over any more devices.
  *
  * Note, you will need to drop the reference with put_device() after use.
  *
  * @fn is allowed to do anything including calling back into class
  * code.  There's no locking restriction.
  */
 struct device *class_find_device(struct class *class, struct device *start,
 				 void *data,
 				 int (*match)(struct device *, void *))
 {
 	struct class_dev_iter iter;
 	struct device *dev;

 	if (!class)
 		return NULL;
 	if (!class->p) {
 		WARN(1, "%s called for class '%s' before it was initialized",
 		     __func__, class->name);
 		return NULL;
 	}

 	class_dev_iter_init(&iter, class, start, NULL);
 	while ((dev = class_dev_iter_next(&iter))) {
 		if (match(dev, data)) {
 			get_device(dev);
 			break;
 		}
 	}
 	class_dev_iter_exit(&iter);

 	return dev;
 }
 EXPORT_SYMBOL_GPL(class_find_device);

 int class_interface_register(struct class_interface *class_intf)
 {
 	struct class *parent;
 	struct class_dev_iter iter;
 	struct device *dev;

 	if (!class_intf || !class_intf->class)
 		return -ENODEV;

 	parent = class_get(class_intf->class);
 	if (!parent)
 		return -EINVAL;

 	mutex_lock(&parent->p->class_mutex);
 	list_add_tail(&class_intf->node, &parent->p->class_interfaces);
 	if (class_intf->add_dev) {
 		class_dev_iter_init(&iter, parent, NULL, NULL);
 		while ((dev = class_dev_iter_next(&iter)))
 			class_intf->add_dev(dev, class_intf);
 		class_dev_iter_exit(&iter);
 	}
 	mutex_unlock(&parent->p->class_mutex);

 	return 0;
 }

 void class_interface_unregister(struct class_interface *class_intf)
 {
 	struct class *parent = class_intf->class;
 	struct class_dev_iter iter;
 	struct device *dev;

 	if (!parent)
 		return;

 	mutex_lock(&parent->p->class_mutex);
 	list_del_init(&class_intf->node);
 	if (class_intf->remove_dev) {
 		class_dev_iter_init(&iter, parent, NULL, NULL);
 		while ((dev = class_dev_iter_next(&iter)))
 			class_intf->remove_dev(dev, class_intf);
 		class_dev_iter_exit(&iter);
 	}
 	mutex_unlock(&parent->p->class_mutex);

 	class_put(parent);
 }

 int __init classes_init(void)
 {
 	class_kset = kset_create_and_add("class", NULL, NULL);
 	if (!class_kset)
 		return -ENOMEM;
 	return 0;
 }

 EXPORT_SYMBOL_GPL(class_create_file);
 EXPORT_SYMBOL_GPL(class_remove_file);
 EXPORT_SYMBOL_GPL(class_unregister);
 EXPORT_SYMBOL_GPL(class_destroy);

 EXPORT_SYMBOL_GPL(class_interface_register);
 EXPORT_SYMBOL_GPL(class_interface_unregister);
	/*
	* class.c - basic device class management
	*
	* Copyright (c) 2002-3 Patrick Mochel
	* Copyright (c) 2002-3 Open Source Development Labs
	* Copyright (c) 2003-2004 Greg Kroah-Hartman
	* Copyright (c) 2003-2004 IBM Corp.
	*
	* This file is released under the GPLv2
	*
	*/

	#include <linux/device.h>
	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/string.h>
	#include <linux/kdev_t.h>
	#include <linux/err.h>
	#include <linux/slab.h>
	#include <linux/genhd.h>
	#include <linux/mutex.h>
	#include "base.h"

	#define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)

	static ssize_t class_attr_show(struct kobject kobj, struct attribute attr,
	char *buf)
	{
	struct class_attribute *class_attr = to_class_attr(attr);
	struct class_private *cp = to_class(kobj);
	ssize_t ret = -EIO;

	if (class_attr->show)
	ret = class_attr->show(cp->class, buf);
	return ret;
	}

	static ssize_t class_attr_store(struct kobject kobj, struct attribute attr,
	const char *buf, size_t count)
	{
	struct class_attribute *class_attr = to_class_attr(attr);
	struct class_private *cp = to_class(kobj);
	ssize_t ret = -EIO;

	if (class_attr->store)
	ret = class_attr->store(cp->class, buf, count);
	return ret;
	}

	static void class_release(struct kobject *kobj)
	{
	struct class_private *cp = to_class(kobj);
	struct class *class = cp->class;

	pr_debug("class '%s': release.\n", class->name);

	if (class->class_release)
	class->class_release(class);
	else
	pr_debug("class '%s' does not have a release() function, "
	"be careful\n", class->name);
	}

	static struct sysfs_ops class_sysfs_ops = {
	.show = class_attr_show,
	.store = class_attr_store,
	};

	static struct kobj_type class_ktype = {
	.sysfs_ops = &class_sysfs_ops,
	.release = class_release,
	};

	/* Hotplug events for classes go to the class class_subsys */
	static struct kset *class_kset;


	int class_create_file(struct class cls, const struct class_attribute attr)
	{
	int error;
	if (cls)
	error = sysfs_create_file(&cls->p->class_subsys.kobj,
	&attr->attr);
	else
	error = -EINVAL;
	return error;
	}

	void class_remove_file(struct class cls, const struct class_attribute attr)
	{
	if (cls)
	sysfs_remove_file(&cls->p->class_subsys.kobj, &attr->attr);
	}

	static struct class class_get(struct class cls)
	{
	if (cls)
	kset_get(&cls->p->class_subsys);
	return cls;
	}

	static void class_put(struct class *cls)
	{
	if (cls)
	kset_put(&cls->p->class_subsys);
	}

	static int add_class_attrs(struct class *cls)
	{
	int i;
	int error = 0;

	if (cls->class_attrs) {
	for (i = 0; attr_name(cls->class_attrs[i]); i++) {
	error = class_create_file(cls, &cls->class_attrs[i]);
	if (error)
	goto error;
	}
	}
	done:
	return error;
	error:
	while (--i >= 0)
	class_remove_file(cls, &cls->class_attrs[i]);
	goto done;
	}

	static void remove_class_attrs(struct class *cls)
	{
	int i;

	if (cls->class_attrs) {
	for (i = 0; attr_name(cls->class_attrs[i]); i++)
	class_remove_file(cls, &cls->class_attrs[i]);
	}
	}

	static void klist_class_dev_get(struct klist_node *n)
	{
	struct device *dev = container_of(n, struct device, knode_class);

	get_device(dev);
	}

	static void klist_class_dev_put(struct klist_node *n)
	{
	struct device *dev = container_of(n, struct device, knode_class);

	put_device(dev);
	}

	int __class_register(struct class cls, struct lock_class_key key)
	{
	struct class_private *cp;
	int error;

	pr_debug("device class '%s': registering\n", cls->name);

	cp = kzalloc(sizeof(*cp), GFP_KERNEL);
	if (!cp)
	return -ENOMEM;
	klist_init(&cp->class_devices, klist_class_dev_get, klist_class_dev_put);
	INIT_LIST_HEAD(&cp->class_interfaces);
	kset_init(&cp->class_dirs);
	__mutex_init(&cp->class_mutex, "struct class mutex", key);
	error = kobject_set_name(&cp->class_subsys.kobj, "%s", cls->name);
	if (error) {
	kfree(cp);
	return error;
	}

	/* set the default /sys/dev directory for devices of this class */
	if (!cls->dev_kobj)
	cls->dev_kobj = sysfs_dev_char_kobj;

	#if defined(CONFIG_SYSFS_DEPRECATED) && defined(CONFIG_BLOCK)
	/* let the block class directory show up in the root of sysfs */
	if (cls != &block_class)
	cp->class_subsys.kobj.kset = class_kset;
	#else
	cp->class_subsys.kobj.kset = class_kset;
	#endif
	cp->class_subsys.kobj.ktype = &class_ktype;
	cp->class = cls;
	cls->p = cp;

	error = kset_register(&cp->class_subsys);
	if (error) {
	kfree(cp);
	return error;
	}
	error = add_class_attrs(class_get(cls));
	class_put(cls);
	return error;
	}
	EXPORT_SYMBOL_GPL(__class_register);

	void class_unregister(struct class *cls)
	{
	pr_debug("device class '%s': unregistering\n", cls->name);
	remove_class_attrs(cls);
	kset_unregister(&cls->p->class_subsys);
	}

	static void class_create_release(struct class *cls)
	{
	pr_debug("%s called for %s\n", __func__, cls->name);
	kfree(cls);
	}

	/**
	* class_create - create a struct class structure
	* @owner: pointer to the module that is to "own" this struct class
	* @name: pointer to a string for the name of this class.
	* @key: the lock_class_key for this class; used by mutex lock debugging
	*
	* This is used to create a struct class pointer that can then be used
	* in calls to device_create().
	*
	* Note, the pointer created here is to be destroyed when finished by
	* making a call to class_destroy().
	*/
	struct class __class_create(struct module owner, const char *name,
	struct lock_class_key *key)
	{
	struct class *cls;
	int retval;

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

	cls->name = name;
	cls->owner = owner;
	cls->class_release = class_create_release;

	retval = __class_register(cls, key);
	if (retval)
	goto error;

	return cls;

	error:
	kfree(cls);
	return ERR_PTR(retval);
	}
	EXPORT_SYMBOL_GPL(__class_create);

	/**
	* class_destroy - destroys a struct class structure
	* @cls: pointer to the struct class that is to be destroyed
	*
	* Note, the pointer to be destroyed must have been created with a call
	* to class_create().
	*/
	void class_destroy(struct class *cls)
	{
	if ((cls == NULL) \|\| (IS_ERR(cls)))
	return;

	class_unregister(cls);
	}

	#ifdef CONFIG_SYSFS_DEPRECATED
	char make_class_name(const char name, struct kobject *kobj)
	{
	char *class_name;
	int size;

	size = strlen(name) + strlen(kobject_name(kobj)) + 2;

	class_name = kmalloc(size, GFP_KERNEL);
	if (!class_name)
	return NULL;

	strcpy(class_name, name);
	strcat(class_name, ":");
	strcat(class_name, kobject_name(kobj));
	return class_name;
	}
	#endif

	/**
	* class_dev_iter_init - initialize class device iterator
	* @iter: class iterator to initialize
	* @class: the class we wanna iterate over
	* @start: the device to start iterating from, if any
	* @type: device_type of the devices to iterate over, NULL for all
	*
	* Initialize class iterator @iter such that it iterates over devices
	* of @class. If @start is set, the list iteration will start there,
	* otherwise if it is NULL, the iteration starts at the beginning of
	* the list.
	*/
	void class_dev_iter_init(struct class_dev_iter iter, struct class class,
	struct device start, const struct device_type type)
	{
	struct klist_node *start_knode = NULL;

	if (start)
	start_knode = &start->knode_class;
	klist_iter_init_node(&class->p->class_devices, &iter->ki, start_knode);
	iter->type = type;
	}
	EXPORT_SYMBOL_GPL(class_dev_iter_init);

	/**
	* class_dev_iter_next - iterate to the next device
	* @iter: class iterator to proceed
	*
	* Proceed @iter to the next device and return it. Returns NULL if
	* iteration is complete.
	*
	* The returned device is referenced and won't be released till
	* iterator is proceed to the next device or exited. The caller is
	* free to do whatever it wants to do with the device including
	* calling back into class code.
	*/
	struct device class_dev_iter_next(struct class_dev_iter iter)
	{
	struct klist_node *knode;
	struct device *dev;

	while (1) {
	knode = klist_next(&iter->ki);
	if (!knode)
	return NULL;
	dev = container_of(knode, struct device, knode_class);
	if (!iter->type \|\| iter->type == dev->type)
	return dev;
	}
	}
	EXPORT_SYMBOL_GPL(class_dev_iter_next);

	/**
	* class_dev_iter_exit - finish iteration
	* @iter: class iterator to finish
	*
	* Finish an iteration. Always call this function after iteration is
	* complete whether the iteration ran till the end or not.
	*/
	void class_dev_iter_exit(struct class_dev_iter *iter)
	{
	klist_iter_exit(&iter->ki);
	}
	EXPORT_SYMBOL_GPL(class_dev_iter_exit);

	/**
	* class_for_each_device - device iterator
	* @class: the class we're iterating
	* @start: the device to start with in the list, if any.
	* @data: data for the callback
	* @fn: function to be called for each device
	*
	* Iterate over @class's list of devices, and call @fn for each,
	* passing it @data. If @start is set, the list iteration will start
	* there, otherwise if it is NULL, the iteration starts at the
	* beginning of the list.
	*
	* We check the return of @fn each time. If it returns anything
	* other than 0, we break out and return that value.
	*
	* @fn is allowed to do anything including calling back into class
	* code. There's no locking restriction.
	*/
	int class_for_each_device(struct class class, struct device start,
	void data, int (fn)(struct device , void ))
	{
	struct class_dev_iter iter;
	struct device *dev;
	int error = 0;

	if (!class)
	return -EINVAL;
	if (!class->p) {
	WARN(1, "%s called for class '%s' before it was initialized",
	__func__, class->name);
	return -EINVAL;
	}

	class_dev_iter_init(&iter, class, start, NULL);
	while ((dev = class_dev_iter_next(&iter))) {
	error = fn(dev, data);
	if (error)
	break;
	}
	class_dev_iter_exit(&iter);

	return error;
	}
	EXPORT_SYMBOL_GPL(class_for_each_device);

	/**
	* class_find_device - device iterator for locating a particular device
	* @class: the class we're iterating
	* @start: Device to begin with
	* @data: data for the match function
	* @match: function to check device
	*
	* This is similar to the class_for_each_dev() function above, but it
	* returns a reference to a device that is 'found' for later use, as
	* determined by the @match callback.
	*
	* The callback should return 0 if the device doesn't match and non-zero
	* if it does. If the callback returns non-zero, this function will
	* return to the caller and not iterate over any more devices.
	*
	* Note, you will need to drop the reference with put_device() after use.
	*
	* @fn is allowed to do anything including calling back into class
	* code. There's no locking restriction.
	*/
	struct device class_find_device(struct class class, struct device *start,
	void *data,
	int (match)(struct device , void *))
	{
	struct class_dev_iter iter;
	struct device *dev;

	if (!class)
	return NULL;
	if (!class->p) {
	WARN(1, "%s called for class '%s' before it was initialized",
	__func__, class->name);
	return NULL;
	}

	class_dev_iter_init(&iter, class, start, NULL);
	while ((dev = class_dev_iter_next(&iter))) {
	if (match(dev, data)) {
	get_device(dev);
	break;
	}
	}
	class_dev_iter_exit(&iter);

	return dev;
	}
	EXPORT_SYMBOL_GPL(class_find_device);

	int class_interface_register(struct class_interface *class_intf)
	{
	struct class *parent;
	struct class_dev_iter iter;
	struct device *dev;

	if (!class_intf \|\| !class_intf->class)
	return -ENODEV;

	parent = class_get(class_intf->class);
	if (!parent)
	return -EINVAL;

	mutex_lock(&parent->p->class_mutex);
	list_add_tail(&class_intf->node, &parent->p->class_interfaces);
	if (class_intf->add_dev) {
	class_dev_iter_init(&iter, parent, NULL, NULL);
	while ((dev = class_dev_iter_next(&iter)))
	class_intf->add_dev(dev, class_intf);
	class_dev_iter_exit(&iter);
	}
	mutex_unlock(&parent->p->class_mutex);

	return 0;
	}

	void class_interface_unregister(struct class_interface *class_intf)
	{
	struct class *parent = class_intf->class;
	struct class_dev_iter iter;
	struct device *dev;

	if (!parent)
	return;

	mutex_lock(&parent->p->class_mutex);
	list_del_init(&class_intf->node);
	if (class_intf->remove_dev) {
	class_dev_iter_init(&iter, parent, NULL, NULL);
	while ((dev = class_dev_iter_next(&iter)))
	class_intf->remove_dev(dev, class_intf);
	class_dev_iter_exit(&iter);
	}
	mutex_unlock(&parent->p->class_mutex);

	class_put(parent);
	}

	int __init classes_init(void)
	{
	class_kset = kset_create_and_add("class", NULL, NULL);
	if (!class_kset)
	return -ENOMEM;
	return 0;
	}

	EXPORT_SYMBOL_GPL(class_create_file);
	EXPORT_SYMBOL_GPL(class_remove_file);
	EXPORT_SYMBOL_GPL(class_unregister);
	EXPORT_SYMBOL_GPL(class_destroy);

	EXPORT_SYMBOL_GPL(class_interface_register);
	EXPORT_SYMBOL_GPL(class_interface_unregister);