drivers/base/attribute_container.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * attribute_container.c - implementation of a simple container for classes
  *
  * Copyright (c) 2005 - James Bottomley <James.Bottomley@steeleye.com>
  *
  * The basic idea here is to enable a device to be attached to an
  * aritrary numer of classes without having to allocate storage for them.
  * Instead, the contained classes select the devices they need to attach
  * to via a matching function.
  */

 #include <linux/attribute_container.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/mutex.h>

 #include "base.h"

 /* This is a private structure used to tie the classdev and the
  * container .. it should never be visible outside this file */
 struct internal_container {
 	struct klist_node node;
 	struct attribute_container *cont;
 	struct device classdev;
 };

 static void internal_container_klist_get(struct klist_node *n)
 {
 	struct internal_container *ic =
 		container_of(n, struct internal_container, node);
 	get_device(&ic->classdev);
 }

 static void internal_container_klist_put(struct klist_node *n)
 {
 	struct internal_container *ic =
 		container_of(n, struct internal_container, node);
 	put_device(&ic->classdev);
 }


 /**
  * attribute_container_classdev_to_container - given a classdev, return the container
  *
  * @classdev: the class device created by attribute_container_add_device.
  *
  * Returns the container associated with this classdev.
  */
 struct attribute_container *
 attribute_container_classdev_to_container(struct device *classdev)
 {
 	struct internal_container *ic =
 		container_of(classdev, struct internal_container, classdev);
 	return ic->cont;
 }
 EXPORT_SYMBOL_GPL(attribute_container_classdev_to_container);

 static LIST_HEAD(attribute_container_list);

 static DEFINE_MUTEX(attribute_container_mutex);

 /**
  * attribute_container_register - register an attribute container
  *
  * @cont: The container to register.  This must be allocated by the
  *        callee and should also be zeroed by it.
  */
 int
 attribute_container_register(struct attribute_container *cont)
 {
 	INIT_LIST_HEAD(&cont->node);
 	klist_init(&cont->containers, internal_container_klist_get,
 		   internal_container_klist_put);

 	mutex_lock(&attribute_container_mutex);
 	list_add_tail(&cont->node, &attribute_container_list);
 	mutex_unlock(&attribute_container_mutex);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(attribute_container_register);

 /**
  * attribute_container_unregister - remove a container registration
  *
  * @cont: previously registered container to remove
  */
 int
 attribute_container_unregister(struct attribute_container *cont)
 {
 	int retval = -EBUSY;

 	mutex_lock(&attribute_container_mutex);
 	spin_lock(&cont->containers.k_lock);
 	if (!list_empty(&cont->containers.k_list))
 		goto out;
 	retval = 0;
 	list_del(&cont->node);
  out:
 	spin_unlock(&cont->containers.k_lock);
 	mutex_unlock(&attribute_container_mutex);
 	return retval;

 }
 EXPORT_SYMBOL_GPL(attribute_container_unregister);

 /* private function used as class release */
 static void attribute_container_release(struct device *classdev)
 {
 	struct internal_container *ic
 		= container_of(classdev, struct internal_container, classdev);
 	struct device *dev = classdev->parent;

 	kfree(ic);
 	put_device(dev);
 }

 /**
  * attribute_container_add_device - see if any container is interested in dev
  *
  * @dev: device to add attributes to
  * @fn:	 function to trigger addition of class device.
  *
  * This function allocates storage for the class device(s) to be
  * attached to dev (one for each matching attribute_container).  If no
  * fn is provided, the code will simply register the class device via
  * device_add.  If a function is provided, it is expected to add
  * the class device at the appropriate time.  One of the things that
  * might be necessary is to allocate and initialise the classdev and
  * then add it a later time.  To do this, call this routine for
  * allocation and initialisation and then use
  * attribute_container_device_trigger() to call device_add() on
  * it.  Note: after this, the class device contains a reference to dev
  * which is not relinquished until the release of the classdev.
  */
 void
 attribute_container_add_device(struct device *dev,
 			       int (*fn)(struct attribute_container *,
 					 struct device *,
 					 struct device *))
 {
 	struct attribute_container *cont;

 	mutex_lock(&attribute_container_mutex);
 	list_for_each_entry(cont, &attribute_container_list, node) {
 		struct internal_container *ic;

 		if (attribute_container_no_classdevs(cont))
 			continue;

 		if (!cont->match(cont, dev))
 			continue;

 		ic = kzalloc(sizeof(*ic), GFP_KERNEL);
 		if (!ic) {
 			dev_err(dev, "failed to allocate class container\n");
 			continue;
 		}

 		ic->cont = cont;
 		device_initialize(&ic->classdev);
 		ic->classdev.parent = get_device(dev);
 		ic->classdev.class = cont->class;
 		cont->class->dev_release = attribute_container_release;
 		dev_set_name(&ic->classdev, "%s", dev_name(dev));
 		if (fn)
 			fn(cont, dev, &ic->classdev);
 		else
 			attribute_container_add_class_device(&ic->classdev);
 		klist_add_tail(&ic->node, &cont->containers);
 	}
 	mutex_unlock(&attribute_container_mutex);
 }

 /* FIXME: can't break out of this unless klist_iter_exit is also
  * called before doing the break
  */
 #define klist_for_each_entry(pos, head, member, iter) \
 	for (klist_iter_init(head, iter); (pos = ({ \
 		struct klist_node *n = klist_next(iter); \
 		n ? container_of(n, typeof(*pos), member) : \
 			({ klist_iter_exit(iter) ; NULL; }); \
 	})) != NULL;)


 /**
  * attribute_container_remove_device - make device eligible for removal.
  *
  * @dev:  The generic device
  * @fn:	  A function to call to remove the device
  *
  * This routine triggers device removal.  If fn is NULL, then it is
  * simply done via device_unregister (note that if something
  * still has a reference to the classdev, then the memory occupied
  * will not be freed until the classdev is released).  If you want a
  * two phase release: remove from visibility and then delete the
  * device, then you should use this routine with a fn that calls
  * device_del() and then use attribute_container_device_trigger()
  * to do the final put on the classdev.
  */
 void
 attribute_container_remove_device(struct device *dev,
 				  void (*fn)(struct attribute_container *,
 					     struct device *,
 					     struct device *))
 {
 	struct attribute_container *cont;

 	mutex_lock(&attribute_container_mutex);
 	list_for_each_entry(cont, &attribute_container_list, node) {
 		struct internal_container *ic;
 		struct klist_iter iter;

 		if (attribute_container_no_classdevs(cont))
 			continue;

 		if (!cont->match(cont, dev))
 			continue;

 		klist_for_each_entry(ic, &cont->containers, node, &iter) {
 			if (dev != ic->classdev.parent)
 				continue;
 			klist_del(&ic->node);
 			if (fn)
 				fn(cont, dev, &ic->classdev);
 			else {
 				attribute_container_remove_attrs(&ic->classdev);
 				device_unregister(&ic->classdev);
 			}
 		}
 	}
 	mutex_unlock(&attribute_container_mutex);
 }

 static int
 do_attribute_container_device_trigger_safe(struct device *dev,
 					   struct attribute_container *cont,
 					   int (*fn)(struct attribute_container *,
 						     struct device *, struct device *),
 					   int (*undo)(struct attribute_container *,
 						       struct device *, struct device *))
 {
 	int ret;
 	struct internal_container *ic, *failed;
 	struct klist_iter iter;

 	if (attribute_container_no_classdevs(cont))
 		return fn(cont, dev, NULL);

 	klist_for_each_entry(ic, &cont->containers, node, &iter) {
 		if (dev == ic->classdev.parent) {
 			ret = fn(cont, dev, &ic->classdev);
 			if (ret) {
 				failed = ic;
 				klist_iter_exit(&iter);
 				goto fail;
 			}
 		}
 	}
 	return 0;

 fail:
 	if (!undo)
 		return ret;

 	/* Attempt to undo the work partially done. */
 	klist_for_each_entry(ic, &cont->containers, node, &iter) {
 		if (ic == failed) {
 			klist_iter_exit(&iter);
 			break;
 		}
 		if (dev == ic->classdev.parent)
 			undo(cont, dev, &ic->classdev);
 	}
 	return ret;
 }

 /**
  * attribute_container_device_trigger_safe - execute a trigger for each
  * matching classdev or fail all of them.
  *
  * @dev:  The generic device to run the trigger for
  * @fn:   the function to execute for each classdev.
  * @undo: A function to undo the work previously done in case of error
  *
  * This function is a safe version of
  * attribute_container_device_trigger. It stops on the first error and
  * undo the partial work that has been done, on previous classdev.  It
  * is guaranteed that either they all succeeded, or none of them
  * succeeded.
  */
 int
 attribute_container_device_trigger_safe(struct device *dev,
 					int (*fn)(struct attribute_container *,
 						  struct device *,
 						  struct device *),
 					int (*undo)(struct attribute_container *,
 						    struct device *,
 						    struct device *))
 {
 	struct attribute_container *cont, *failed = NULL;
 	int ret = 0;

 	mutex_lock(&attribute_container_mutex);

 	list_for_each_entry(cont, &attribute_container_list, node) {

 		if (!cont->match(cont, dev))
 			continue;

 		ret = do_attribute_container_device_trigger_safe(dev, cont,
 								 fn, undo);
 		if (ret) {
 			failed = cont;
 			break;
 		}
 	}

 	if (ret && !WARN_ON(!undo)) {
 		list_for_each_entry(cont, &attribute_container_list, node) {

 			if (failed == cont)
 				break;

 			if (!cont->match(cont, dev))
 				continue;

 			do_attribute_container_device_trigger_safe(dev, cont,
 								   undo, NULL);
 		}
 	}

 	mutex_unlock(&attribute_container_mutex);
 	return ret;

 }

 /**
  * attribute_container_device_trigger - execute a trigger for each matching classdev
  *
  * @dev:  The generic device to run the trigger for
  * @fn:   the function to execute for each classdev.
  *
  * This function is for executing a trigger when you need to know both
  * the container and the classdev.
  */
 void
 attribute_container_device_trigger(struct device *dev,
 				   int (*fn)(struct attribute_container *,
 					     struct device *,
 					     struct device *))
 {
 	struct attribute_container *cont;

 	mutex_lock(&attribute_container_mutex);
 	list_for_each_entry(cont, &attribute_container_list, node) {
 		struct internal_container *ic;
 		struct klist_iter iter;

 		if (!cont->match(cont, dev))
 			continue;

 		if (attribute_container_no_classdevs(cont)) {
 			fn(cont, dev, NULL);
 			continue;
 		}

 		klist_for_each_entry(ic, &cont->containers, node, &iter) {
 			if (dev == ic->classdev.parent)
 				fn(cont, dev, &ic->classdev);
 		}
 	}
 	mutex_unlock(&attribute_container_mutex);
 }

 /**
  * attribute_container_add_attrs - add attributes
  *
  * @classdev: The class device
  *
  * This simply creates all the class device sysfs files from the
  * attributes listed in the container
  */
 int
 attribute_container_add_attrs(struct device *classdev)
 {
 	struct attribute_container *cont =
 		attribute_container_classdev_to_container(classdev);
 	struct device_attribute **attrs = cont->attrs;
 	int i, error;

 	BUG_ON(attrs && cont->grp);

 	if (!attrs && !cont->grp)
 		return 0;

 	if (cont->grp)
 		return sysfs_create_group(&classdev->kobj, cont->grp);

 	for (i = 0; attrs[i]; i++) {
 		sysfs_attr_init(&attrs[i]->attr);
 		error = device_create_file(classdev, attrs[i]);
 		if (error)
 			return error;
 	}

 	return 0;
 }

 /**
  * attribute_container_add_class_device - same function as device_add
  *
  * @classdev:	the class device to add
  *
  * This performs essentially the same function as device_add except for
  * attribute containers, namely add the classdev to the system and then
  * create the attribute files
  */
 int
 attribute_container_add_class_device(struct device *classdev)
 {
 	int error = device_add(classdev);

 	if (error)
 		return error;
 	return attribute_container_add_attrs(classdev);
 }

 /**
  * attribute_container_remove_attrs - remove any attribute files
  *
  * @classdev: The class device to remove the files from
  *
  */
 void
 attribute_container_remove_attrs(struct device *classdev)
 {
 	struct attribute_container *cont =
 		attribute_container_classdev_to_container(classdev);
 	struct device_attribute **attrs = cont->attrs;
 	int i;

 	if (!attrs && !cont->grp)
 		return;

 	if (cont->grp) {
 		sysfs_remove_group(&classdev->kobj, cont->grp);
 		return ;
 	}

 	for (i = 0; attrs[i]; i++)
 		device_remove_file(classdev, attrs[i]);
 }

 /**
  * attribute_container_class_device_del - equivalent of class_device_del
  *
  * @classdev: the class device
  *
  * This function simply removes all the attribute files and then calls
  * device_del.
  */
 void
 attribute_container_class_device_del(struct device *classdev)
 {
 	attribute_container_remove_attrs(classdev);
 	device_del(classdev);
 }

 /**
  * attribute_container_find_class_device - find the corresponding class_device
  *
  * @cont:	the container
  * @dev:	the generic device
  *
  * Looks up the device in the container's list of class devices and returns
  * the corresponding class_device.
  */
 struct device *
 attribute_container_find_class_device(struct attribute_container *cont,
 				      struct device *dev)
 {
 	struct device *cdev = NULL;
 	struct internal_container *ic;
 	struct klist_iter iter;

 	klist_for_each_entry(ic, &cont->containers, node, &iter) {
 		if (ic->classdev.parent == dev) {
 			cdev = &ic->classdev;
 			/* FIXME: must exit iterator then break */
 			klist_iter_exit(&iter);
 			break;
 		}
 	}

 	return cdev;
 }
 EXPORT_SYMBOL_GPL(attribute_container_find_class_device);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* attribute_container.c - implementation of a simple container for classes
	*
	* Copyright (c) 2005 - James Bottomley <James.Bottomley@steeleye.com>
	*
	* The basic idea here is to enable a device to be attached to an
	* aritrary numer of classes without having to allocate storage for them.
	* Instead, the contained classes select the devices they need to attach
	* to via a matching function.
	*/

	#include <linux/attribute_container.h>
	#include <linux/device.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/list.h>
	#include <linux/module.h>
	#include <linux/mutex.h>

	#include "base.h"

	/* This is a private structure used to tie the classdev and the
	* container .. it should never be visible outside this file */
	struct internal_container {
	struct klist_node node;
	struct attribute_container *cont;
	struct device classdev;
	};

	static void internal_container_klist_get(struct klist_node *n)
	{
	struct internal_container *ic =
	container_of(n, struct internal_container, node);
	get_device(&ic->classdev);
	}

	static void internal_container_klist_put(struct klist_node *n)
	{
	struct internal_container *ic =
	container_of(n, struct internal_container, node);
	put_device(&ic->classdev);
	}


	/**
	* attribute_container_classdev_to_container - given a classdev, return the container
	*
	* @classdev: the class device created by attribute_container_add_device.
	*
	* Returns the container associated with this classdev.
	*/
	struct attribute_container *
	attribute_container_classdev_to_container(struct device *classdev)
	{
	struct internal_container *ic =
	container_of(classdev, struct internal_container, classdev);
	return ic->cont;
	}
	EXPORT_SYMBOL_GPL(attribute_container_classdev_to_container);

	static LIST_HEAD(attribute_container_list);

	static DEFINE_MUTEX(attribute_container_mutex);

	/**
	* attribute_container_register - register an attribute container
	*
	* @cont: The container to register. This must be allocated by the
	* callee and should also be zeroed by it.
	*/
	int
	attribute_container_register(struct attribute_container *cont)
	{
	INIT_LIST_HEAD(&cont->node);
	klist_init(&cont->containers, internal_container_klist_get,
	internal_container_klist_put);

	mutex_lock(&attribute_container_mutex);
	list_add_tail(&cont->node, &attribute_container_list);
	mutex_unlock(&attribute_container_mutex);

	return 0;
	}
	EXPORT_SYMBOL_GPL(attribute_container_register);

	/**
	* attribute_container_unregister - remove a container registration
	*
	* @cont: previously registered container to remove
	*/
	int
	attribute_container_unregister(struct attribute_container *cont)
	{
	int retval = -EBUSY;

	mutex_lock(&attribute_container_mutex);
	spin_lock(&cont->containers.k_lock);
	if (!list_empty(&cont->containers.k_list))
	goto out;
	retval = 0;
	list_del(&cont->node);
	out:
	spin_unlock(&cont->containers.k_lock);
	mutex_unlock(&attribute_container_mutex);
	return retval;

	}
	EXPORT_SYMBOL_GPL(attribute_container_unregister);

	/* private function used as class release */
	static void attribute_container_release(struct device *classdev)
	{
	struct internal_container *ic
	= container_of(classdev, struct internal_container, classdev);
	struct device *dev = classdev->parent;

	kfree(ic);
	put_device(dev);
	}

	/**
	* attribute_container_add_device - see if any container is interested in dev
	*
	* @dev: device to add attributes to
	* @fn: function to trigger addition of class device.
	*
	* This function allocates storage for the class device(s) to be
	* attached to dev (one for each matching attribute_container). If no
	* fn is provided, the code will simply register the class device via
	* device_add. If a function is provided, it is expected to add
	* the class device at the appropriate time. One of the things that
	* might be necessary is to allocate and initialise the classdev and
	* then add it a later time. To do this, call this routine for
	* allocation and initialisation and then use
	* attribute_container_device_trigger() to call device_add() on
	* it. Note: after this, the class device contains a reference to dev
	* which is not relinquished until the release of the classdev.
	*/
	void
	attribute_container_add_device(struct device *dev,
	int (fn)(struct attribute_container ,
	struct device *,
	struct device *))
	{
	struct attribute_container *cont;

	mutex_lock(&attribute_container_mutex);
	list_for_each_entry(cont, &attribute_container_list, node) {
	struct internal_container *ic;

	if (attribute_container_no_classdevs(cont))
	continue;

	if (!cont->match(cont, dev))
	continue;

	ic = kzalloc(sizeof(*ic), GFP_KERNEL);
	if (!ic) {
	dev_err(dev, "failed to allocate class container\n");
	continue;
	}

	ic->cont = cont;
	device_initialize(&ic->classdev);
	ic->classdev.parent = get_device(dev);
	ic->classdev.class = cont->class;
	cont->class->dev_release = attribute_container_release;
	dev_set_name(&ic->classdev, "%s", dev_name(dev));
	if (fn)
	fn(cont, dev, &ic->classdev);
	else
	attribute_container_add_class_device(&ic->classdev);
	klist_add_tail(&ic->node, &cont->containers);
	}
	mutex_unlock(&attribute_container_mutex);
	}

	/* FIXME: can't break out of this unless klist_iter_exit is also
	* called before doing the break
	*/
	#define klist_for_each_entry(pos, head, member, iter) \
	for (klist_iter_init(head, iter); (pos = ({ \
	struct klist_node *n = klist_next(iter); \
	n ? container_of(n, typeof(*pos), member) : \
	({ klist_iter_exit(iter) ; NULL; }); \
	})) != NULL;)


	/**
	* attribute_container_remove_device - make device eligible for removal.
	*
	* @dev: The generic device
	* @fn: A function to call to remove the device
	*
	* This routine triggers device removal. If fn is NULL, then it is
	* simply done via device_unregister (note that if something
	* still has a reference to the classdev, then the memory occupied
	* will not be freed until the classdev is released). If you want a
	* two phase release: remove from visibility and then delete the
	* device, then you should use this routine with a fn that calls
	* device_del() and then use attribute_container_device_trigger()
	* to do the final put on the classdev.
	*/
	void
	attribute_container_remove_device(struct device *dev,
	void (fn)(struct attribute_container ,
	struct device *,
	struct device *))
	{
	struct attribute_container *cont;

	mutex_lock(&attribute_container_mutex);
	list_for_each_entry(cont, &attribute_container_list, node) {
	struct internal_container *ic;
	struct klist_iter iter;

	if (attribute_container_no_classdevs(cont))
	continue;

	if (!cont->match(cont, dev))
	continue;

	klist_for_each_entry(ic, &cont->containers, node, &iter) {
	if (dev != ic->classdev.parent)
	continue;
	klist_del(&ic->node);
	if (fn)
	fn(cont, dev, &ic->classdev);
	else {
	attribute_container_remove_attrs(&ic->classdev);
	device_unregister(&ic->classdev);
	}
	}
	}
	mutex_unlock(&attribute_container_mutex);
	}

	static int
	do_attribute_container_device_trigger_safe(struct device *dev,
	struct attribute_container *cont,
	int (fn)(struct attribute_container ,
	struct device , struct device ),
	int (undo)(struct attribute_container ,
	struct device , struct device ))
	{
	int ret;
	struct internal_container ic, failed;
	struct klist_iter iter;

	if (attribute_container_no_classdevs(cont))
	return fn(cont, dev, NULL);

	klist_for_each_entry(ic, &cont->containers, node, &iter) {
	if (dev == ic->classdev.parent) {
	ret = fn(cont, dev, &ic->classdev);
	if (ret) {
	failed = ic;
	klist_iter_exit(&iter);
	goto fail;
	}
	}
	}
	return 0;

	fail:
	if (!undo)
	return ret;

	/* Attempt to undo the work partially done. */
	klist_for_each_entry(ic, &cont->containers, node, &iter) {
	if (ic == failed) {
	klist_iter_exit(&iter);
	break;
	}
	if (dev == ic->classdev.parent)
	undo(cont, dev, &ic->classdev);
	}
	return ret;
	}

	/**
	* attribute_container_device_trigger_safe - execute a trigger for each
	* matching classdev or fail all of them.
	*
	* @dev: The generic device to run the trigger for
	* @fn: the function to execute for each classdev.
	* @undo: A function to undo the work previously done in case of error
	*
	* This function is a safe version of
	* attribute_container_device_trigger. It stops on the first error and
	* undo the partial work that has been done, on previous classdev. It
	* is guaranteed that either they all succeeded, or none of them
	* succeeded.
	*/
	int
	attribute_container_device_trigger_safe(struct device *dev,
	int (fn)(struct attribute_container ,
	struct device *,
	struct device *),
	int (undo)(struct attribute_container ,
	struct device *,
	struct device *))
	{
	struct attribute_container cont, failed = NULL;
	int ret = 0;

	mutex_lock(&attribute_container_mutex);

	list_for_each_entry(cont, &attribute_container_list, node) {

	if (!cont->match(cont, dev))
	continue;

	ret = do_attribute_container_device_trigger_safe(dev, cont,
	fn, undo);
	if (ret) {
	failed = cont;
	break;
	}
	}

	if (ret && !WARN_ON(!undo)) {
	list_for_each_entry(cont, &attribute_container_list, node) {

	if (failed == cont)
	break;

	if (!cont->match(cont, dev))
	continue;

	do_attribute_container_device_trigger_safe(dev, cont,
	undo, NULL);
	}
	}

	mutex_unlock(&attribute_container_mutex);
	return ret;

	}

	/**
	* attribute_container_device_trigger - execute a trigger for each matching classdev
	*
	* @dev: The generic device to run the trigger for
	* @fn: the function to execute for each classdev.
	*
	* This function is for executing a trigger when you need to know both
	* the container and the classdev.
	*/
	void
	attribute_container_device_trigger(struct device *dev,
	int (fn)(struct attribute_container ,
	struct device *,
	struct device *))
	{
	struct attribute_container *cont;

	mutex_lock(&attribute_container_mutex);
	list_for_each_entry(cont, &attribute_container_list, node) {
	struct internal_container *ic;
	struct klist_iter iter;

	if (!cont->match(cont, dev))
	continue;

	if (attribute_container_no_classdevs(cont)) {
	fn(cont, dev, NULL);
	continue;
	}

	klist_for_each_entry(ic, &cont->containers, node, &iter) {
	if (dev == ic->classdev.parent)
	fn(cont, dev, &ic->classdev);
	}
	}
	mutex_unlock(&attribute_container_mutex);
	}

	/**
	* attribute_container_add_attrs - add attributes
	*
	* @classdev: The class device
	*
	* This simply creates all the class device sysfs files from the
	* attributes listed in the container
	*/
	int
	attribute_container_add_attrs(struct device *classdev)
	{
	struct attribute_container *cont =
	attribute_container_classdev_to_container(classdev);
	struct device_attribute **attrs = cont->attrs;
	int i, error;

	BUG_ON(attrs && cont->grp);

	if (!attrs && !cont->grp)
	return 0;

	if (cont->grp)
	return sysfs_create_group(&classdev->kobj, cont->grp);

	for (i = 0; attrs[i]; i++) {
	sysfs_attr_init(&attrs[i]->attr);
	error = device_create_file(classdev, attrs[i]);
	if (error)
	return error;
	}

	return 0;
	}

	/**
	* attribute_container_add_class_device - same function as device_add
	*
	* @classdev: the class device to add
	*
	* This performs essentially the same function as device_add except for
	* attribute containers, namely add the classdev to the system and then
	* create the attribute files
	*/
	int
	attribute_container_add_class_device(struct device *classdev)
	{
	int error = device_add(classdev);

	if (error)
	return error;
	return attribute_container_add_attrs(classdev);
	}

	/**
	* attribute_container_remove_attrs - remove any attribute files
	*
	* @classdev: The class device to remove the files from
	*
	*/
	void
	attribute_container_remove_attrs(struct device *classdev)
	{
	struct attribute_container *cont =
	attribute_container_classdev_to_container(classdev);
	struct device_attribute **attrs = cont->attrs;
	int i;

	if (!attrs && !cont->grp)
	return;

	if (cont->grp) {
	sysfs_remove_group(&classdev->kobj, cont->grp);
	return ;
	}

	for (i = 0; attrs[i]; i++)
	device_remove_file(classdev, attrs[i]);
	}

	/**
	* attribute_container_class_device_del - equivalent of class_device_del
	*
	* @classdev: the class device
	*
	* This function simply removes all the attribute files and then calls
	* device_del.
	*/
	void
	attribute_container_class_device_del(struct device *classdev)
	{
	attribute_container_remove_attrs(classdev);
	device_del(classdev);
	}

	/**
	* attribute_container_find_class_device - find the corresponding class_device
	*
	* @cont: the container
	* @dev: the generic device
	*
	* Looks up the device in the container's list of class devices and returns
	* the corresponding class_device.
	*/
	struct device *
	attribute_container_find_class_device(struct attribute_container *cont,
	struct device *dev)
	{
	struct device *cdev = NULL;
	struct internal_container *ic;
	struct klist_iter iter;

	klist_for_each_entry(ic, &cont->containers, node, &iter) {
	if (ic->classdev.parent == dev) {
	cdev = &ic->classdev;
	/* FIXME: must exit iterator then break */
	klist_iter_exit(&iter);
	break;
	}
	}

	return cdev;
	}
	EXPORT_SYMBOL_GPL(attribute_container_find_class_device);