fs/sysfs/group.c - linux-mtk - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * fs/sysfs/group.c - Operations for adding/removing multiple files at once.
  *
  * Copyright (c) 2003 Patrick Mochel
  * Copyright (c) 2003 Open Source Development Lab
  * Copyright (c) 2013 Greg Kroah-Hartman
  * Copyright (c) 2013 The Linux Foundation
  */

 #include <linux/kobject.h>
 #include <linux/module.h>
 #include <linux/dcache.h>
 #include <linux/namei.h>
 #include <linux/err.h>
 #include "sysfs.h"


 static void remove_files(struct kernfs_node *parent,
 			 const struct attribute_group *grp)
 {
 	struct attribute *const *attr;
 	struct bin_attribute *const *bin_attr;

 	if (grp->attrs)
 		for (attr = grp->attrs; *attr; attr++)
 			kernfs_remove_by_name(parent, (*attr)->name);
 	if (grp->bin_attrs)
 		for (bin_attr = grp->bin_attrs; *bin_attr; bin_attr++)
 			kernfs_remove_by_name(parent, (*bin_attr)->attr.name);
 }

 static int create_files(struct kernfs_node *parent, struct kobject *kobj,
 			kuid_t uid, kgid_t gid,
 			const struct attribute_group *grp, int update)
 {
 	struct attribute *const *attr;
 	struct bin_attribute *const *bin_attr;
 	int error = 0, i;

 	if (grp->attrs) {
 		for (i = 0, attr = grp->attrs; *attr && !error; i++, attr++) {
 			umode_t mode = (*attr)->mode;

 			/*
 			 * In update mode, we're changing the permissions or
 			 * visibility.  Do this by first removing then
 			 * re-adding (if required) the file.
 			 */
 			if (update)
 				kernfs_remove_by_name(parent, (*attr)->name);
 			if (grp->is_visible) {
 				mode = grp->is_visible(kobj, *attr, i);
 				if (!mode)
 					continue;
 			}

 			WARN(mode & ~(SYSFS_PREALLOC | 0664),
 			     "Attribute %s: Invalid permissions 0%o\n",
 			     (*attr)->name, mode);

 			mode &= SYSFS_PREALLOC | 0664;
 			error = sysfs_add_file_mode_ns(parent, *attr, false,
 						       mode, uid, gid, NULL);
 			if (unlikely(error))
 				break;
 		}
 		if (error) {
 			remove_files(parent, grp);
 			goto exit;
 		}
 	}

 	if (grp->bin_attrs) {
 		for (i = 0, bin_attr = grp->bin_attrs; *bin_attr; i++, bin_attr++) {
 			umode_t mode = (*bin_attr)->attr.mode;

 			if (update)
 				kernfs_remove_by_name(parent,
 						(*bin_attr)->attr.name);
 			if (grp->is_bin_visible) {
 				mode = grp->is_bin_visible(kobj, *bin_attr, i);
 				if (!mode)
 					continue;
 			}

 			WARN(mode & ~(SYSFS_PREALLOC | 0664),
 			     "Attribute %s: Invalid permissions 0%o\n",
 			     (*bin_attr)->attr.name, mode);

 			mode &= SYSFS_PREALLOC | 0664;
 			error = sysfs_add_file_mode_ns(parent,
 					&(*bin_attr)->attr, true,
 					mode,
 					uid, gid, NULL);
 			if (error)
 				break;
 		}
 		if (error)
 			remove_files(parent, grp);
 	}
 exit:
 	return error;
 }


 static int internal_create_group(struct kobject *kobj, int update,
 				 const struct attribute_group *grp)
 {
 	struct kernfs_node *kn;
 	kuid_t uid;
 	kgid_t gid;
 	int error;

 	BUG_ON(!kobj || (!update && !kobj->sd));

 	/* Updates may happen before the object has been instantiated */
 	if (unlikely(update && !kobj->sd))
 		return -EINVAL;
 	if (!grp->attrs && !grp->bin_attrs) {
 		WARN(1, "sysfs: (bin_)attrs not set by subsystem for group: %s/%s\n",
 			kobj->name, grp->name ?: "");
 		return -EINVAL;
 	}
 	kobject_get_ownership(kobj, &uid, &gid);
 	if (grp->name) {
 		if (update) {
 			kn = kernfs_find_and_get(kobj->sd, grp->name);
 			if (!kn) {
 				pr_warn("Can't update unknown attr grp name: %s/%s\n",
 					kobj->name, grp->name);
 				return -EINVAL;
 			}
 		} else {
 			kn = kernfs_create_dir_ns(kobj->sd, grp->name,
 						  S_IRWXU | S_IRUGO | S_IXUGO,
 						  uid, gid, kobj, NULL);
 			if (IS_ERR(kn)) {
 				if (PTR_ERR(kn) == -EEXIST)
 					sysfs_warn_dup(kobj->sd, grp->name);
 				return PTR_ERR(kn);
 			}
 		}
 	} else
 		kn = kobj->sd;
 	kernfs_get(kn);
 	error = create_files(kn, kobj, uid, gid, grp, update);
 	if (error) {
 		if (grp->name)
 			kernfs_remove(kn);
 	}
 	kernfs_put(kn);

 	if (grp->name && update)
 		kernfs_put(kn);

 	return error;
 }

 /**
  * sysfs_create_group - given a directory kobject, create an attribute group
  * @kobj:	The kobject to create the group on
  * @grp:	The attribute group to create
  *
  * This function creates a group for the first time.  It will explicitly
  * warn and error if any of the attribute files being created already exist.
  *
  * Returns 0 on success or error code on failure.
  */
 int sysfs_create_group(struct kobject *kobj,
 		       const struct attribute_group *grp)
 {
 	return internal_create_group(kobj, 0, grp);
 }
 EXPORT_SYMBOL_GPL(sysfs_create_group);

 /**
  * sysfs_create_groups - given a directory kobject, create a bunch of attribute groups
  * @kobj:	The kobject to create the group on
  * @groups:	The attribute groups to create, NULL terminated
  *
  * This function creates a bunch of attribute groups.  If an error occurs when
  * creating a group, all previously created groups will be removed, unwinding
  * everything back to the original state when this function was called.
  * It will explicitly warn and error if any of the attribute files being
  * created already exist.
  *
  * Returns 0 on success or error code from sysfs_create_group on failure.
  */
 int sysfs_create_groups(struct kobject *kobj,
 			const struct attribute_group **groups)
 {
 	int error = 0;
 	int i;

 	if (!groups)
 		return 0;

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

 /**
  * sysfs_update_group - given a directory kobject, update an attribute group
  * @kobj:	The kobject to update the group on
  * @grp:	The attribute group to update
  *
  * This function updates an attribute group.  Unlike
  * sysfs_create_group(), it will explicitly not warn or error if any
  * of the attribute files being created already exist.  Furthermore,
  * if the visibility of the files has changed through the is_visible()
  * callback, it will update the permissions and add or remove the
  * relevant files. Changing a group's name (subdirectory name under
  * kobj's directory in sysfs) is not allowed.
  *
  * The primary use for this function is to call it after making a change
  * that affects group visibility.
  *
  * Returns 0 on success or error code on failure.
  */
 int sysfs_update_group(struct kobject *kobj,
 		       const struct attribute_group *grp)
 {
 	return internal_create_group(kobj, 1, grp);
 }
 EXPORT_SYMBOL_GPL(sysfs_update_group);

 /**
  * sysfs_remove_group: remove a group from a kobject
  * @kobj:	kobject to remove the group from
  * @grp:	group to remove
  *
  * This function removes a group of attributes from a kobject.  The attributes
  * previously have to have been created for this group, otherwise it will fail.
  */
 void sysfs_remove_group(struct kobject *kobj,
 			const struct attribute_group *grp)
 {
 	struct kernfs_node *parent = kobj->sd;
 	struct kernfs_node *kn;

 	if (grp->name) {
 		kn = kernfs_find_and_get(parent, grp->name);
 		if (!kn) {
 			WARN(!kn, KERN_WARNING
 			     "sysfs group '%s' not found for kobject '%s'\n",
 			     grp->name, kobject_name(kobj));
 			return;
 		}
 	} else {
 		kn = parent;
 		kernfs_get(kn);
 	}

 	remove_files(kn, grp);
 	if (grp->name)
 		kernfs_remove(kn);

 	kernfs_put(kn);
 }
 EXPORT_SYMBOL_GPL(sysfs_remove_group);

 /**
  * sysfs_remove_groups - remove a list of groups
  *
  * @kobj:	The kobject for the groups to be removed from
  * @groups:	NULL terminated list of groups to be removed
  *
  * If groups is not NULL, remove the specified groups from the kobject.
  */
 void sysfs_remove_groups(struct kobject *kobj,
 			 const struct attribute_group **groups)
 {
 	int i;

 	if (!groups)
 		return;
 	for (i = 0; groups[i]; i++)
 		sysfs_remove_group(kobj, groups[i]);
 }
 EXPORT_SYMBOL_GPL(sysfs_remove_groups);

 /**
  * sysfs_merge_group - merge files into a pre-existing attribute group.
  * @kobj:	The kobject containing the group.
  * @grp:	The files to create and the attribute group they belong to.
  *
  * This function returns an error if the group doesn't exist or any of the
  * files already exist in that group, in which case none of the new files
  * are created.
  */
 int sysfs_merge_group(struct kobject *kobj,
 		       const struct attribute_group *grp)
 {
 	struct kernfs_node *parent;
 	kuid_t uid;
 	kgid_t gid;
 	int error = 0;
 	struct attribute *const *attr;
 	int i;

 	parent = kernfs_find_and_get(kobj->sd, grp->name);
 	if (!parent)
 		return -ENOENT;

 	kobject_get_ownership(kobj, &uid, &gid);

 	for ((i = 0, attr = grp->attrs); *attr && !error; (++i, ++attr))
 		error = sysfs_add_file_mode_ns(parent, *attr, false,
 					       (*attr)->mode, uid, gid, NULL);
 	if (error) {
 		while (--i >= 0)
 			kernfs_remove_by_name(parent, (*--attr)->name);
 	}
 	kernfs_put(parent);

 	return error;
 }
 EXPORT_SYMBOL_GPL(sysfs_merge_group);

 /**
  * sysfs_unmerge_group - remove files from a pre-existing attribute group.
  * @kobj:	The kobject containing the group.
  * @grp:	The files to remove and the attribute group they belong to.
  */
 void sysfs_unmerge_group(struct kobject *kobj,
 		       const struct attribute_group *grp)
 {
 	struct kernfs_node *parent;
 	struct attribute *const *attr;

 	parent = kernfs_find_and_get(kobj->sd, grp->name);
 	if (parent) {
 		for (attr = grp->attrs; *attr; ++attr)
 			kernfs_remove_by_name(parent, (*attr)->name);
 		kernfs_put(parent);
 	}
 }
 EXPORT_SYMBOL_GPL(sysfs_unmerge_group);

 /**
  * sysfs_add_link_to_group - add a symlink to an attribute group.
  * @kobj:	The kobject containing the group.
  * @group_name:	The name of the group.
  * @target:	The target kobject of the symlink to create.
  * @link_name:	The name of the symlink to create.
  */
 int sysfs_add_link_to_group(struct kobject *kobj, const char *group_name,
 			    struct kobject *target, const char *link_name)
 {
 	struct kernfs_node *parent;
 	int error = 0;

 	parent = kernfs_find_and_get(kobj->sd, group_name);
 	if (!parent)
 		return -ENOENT;

 	error = sysfs_create_link_sd(parent, target, link_name);
 	kernfs_put(parent);

 	return error;
 }
 EXPORT_SYMBOL_GPL(sysfs_add_link_to_group);

 /**
  * sysfs_remove_link_from_group - remove a symlink from an attribute group.
  * @kobj:	The kobject containing the group.
  * @group_name:	The name of the group.
  * @link_name:	The name of the symlink to remove.
  */
 void sysfs_remove_link_from_group(struct kobject *kobj, const char *group_name,
 				  const char *link_name)
 {
 	struct kernfs_node *parent;

 	parent = kernfs_find_and_get(kobj->sd, group_name);
 	if (parent) {
 		kernfs_remove_by_name(parent, link_name);
 		kernfs_put(parent);
 	}
 }
 EXPORT_SYMBOL_GPL(sysfs_remove_link_from_group);

 /**
  * __compat_only_sysfs_link_entry_to_kobj - add a symlink to a kobject pointing
  * to a group or an attribute
  * @kobj:		The kobject containing the group.
  * @target_kobj:	The target kobject.
  * @target_name:	The name of the target group or attribute.
  */
 int __compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
 				      struct kobject *target_kobj,
 				      const char *target_name)
 {
 	struct kernfs_node *target;
 	struct kernfs_node *entry;
 	struct kernfs_node *link;

 	/*
 	 * We don't own @target_kobj and it may be removed at any time.
 	 * Synchronize using sysfs_symlink_target_lock. See sysfs_remove_dir()
 	 * for details.
 	 */
 	spin_lock(&sysfs_symlink_target_lock);
 	target = target_kobj->sd;
 	if (target)
 		kernfs_get(target);
 	spin_unlock(&sysfs_symlink_target_lock);
 	if (!target)
 		return -ENOENT;

 	entry = kernfs_find_and_get(target_kobj->sd, target_name);
 	if (!entry) {
 		kernfs_put(target);
 		return -ENOENT;
 	}

 	link = kernfs_create_link(kobj->sd, target_name, entry);
 	if (IS_ERR(link) && PTR_ERR(link) == -EEXIST)
 		sysfs_warn_dup(kobj->sd, target_name);

 	kernfs_put(entry);
 	kernfs_put(target);
 	return PTR_ERR_OR_ZERO(link);
 }
 EXPORT_SYMBOL_GPL(__compat_only_sysfs_link_entry_to_kobj);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* fs/sysfs/group.c - Operations for adding/removing multiple files at once.
	*
	* Copyright (c) 2003 Patrick Mochel
	* Copyright (c) 2003 Open Source Development Lab
	* Copyright (c) 2013 Greg Kroah-Hartman
	* Copyright (c) 2013 The Linux Foundation
	*/

	#include <linux/kobject.h>
	#include <linux/module.h>
	#include <linux/dcache.h>
	#include <linux/namei.h>
	#include <linux/err.h>
	#include "sysfs.h"


	static void remove_files(struct kernfs_node *parent,
	const struct attribute_group *grp)
	{
	struct attribute const attr;
	struct bin_attribute const bin_attr;

	if (grp->attrs)
	for (attr = grp->attrs; *attr; attr++)
	kernfs_remove_by_name(parent, (*attr)->name);
	if (grp->bin_attrs)
	for (bin_attr = grp->bin_attrs; *bin_attr; bin_attr++)
	kernfs_remove_by_name(parent, (*bin_attr)->attr.name);
	}

	static int create_files(struct kernfs_node parent, struct kobject kobj,
	kuid_t uid, kgid_t gid,
	const struct attribute_group *grp, int update)
	{
	struct attribute const attr;
	struct bin_attribute const bin_attr;
	int error = 0, i;

	if (grp->attrs) {
	for (i = 0, attr = grp->attrs; *attr && !error; i++, attr++) {
	umode_t mode = (*attr)->mode;

	/*
	* In update mode, we're changing the permissions or
	* visibility. Do this by first removing then
	* re-adding (if required) the file.
	*/
	if (update)
	kernfs_remove_by_name(parent, (*attr)->name);
	if (grp->is_visible) {
	mode = grp->is_visible(kobj, *attr, i);
	if (!mode)
	continue;
	}

	WARN(mode & ~(SYSFS_PREALLOC \| 0664),
	"Attribute %s: Invalid permissions 0%o\n",
	(*attr)->name, mode);

	mode &= SYSFS_PREALLOC \| 0664;
	error = sysfs_add_file_mode_ns(parent, *attr, false,
	mode, uid, gid, NULL);
	if (unlikely(error))
	break;
	}
	if (error) {
	remove_files(parent, grp);
	goto exit;
	}
	}

	if (grp->bin_attrs) {
	for (i = 0, bin_attr = grp->bin_attrs; *bin_attr; i++, bin_attr++) {
	umode_t mode = (*bin_attr)->attr.mode;

	if (update)
	kernfs_remove_by_name(parent,
	(*bin_attr)->attr.name);
	if (grp->is_bin_visible) {
	mode = grp->is_bin_visible(kobj, *bin_attr, i);
	if (!mode)
	continue;
	}

	WARN(mode & ~(SYSFS_PREALLOC \| 0664),
	"Attribute %s: Invalid permissions 0%o\n",
	(*bin_attr)->attr.name, mode);

	mode &= SYSFS_PREALLOC \| 0664;
	error = sysfs_add_file_mode_ns(parent,
	&(*bin_attr)->attr, true,
	mode,
	uid, gid, NULL);
	if (error)
	break;
	}
	if (error)
	remove_files(parent, grp);
	}
	exit:
	return error;
	}


	static int internal_create_group(struct kobject *kobj, int update,
	const struct attribute_group *grp)
	{
	struct kernfs_node *kn;
	kuid_t uid;
	kgid_t gid;
	int error;

	BUG_ON(!kobj \|\| (!update && !kobj->sd));

	/* Updates may happen before the object has been instantiated */
	if (unlikely(update && !kobj->sd))
	return -EINVAL;
	if (!grp->attrs && !grp->bin_attrs) {
	WARN(1, "sysfs: (bin_)attrs not set by subsystem for group: %s/%s\n",
	kobj->name, grp->name ?: "");
	return -EINVAL;
	}
	kobject_get_ownership(kobj, &uid, &gid);
	if (grp->name) {
	if (update) {
	kn = kernfs_find_and_get(kobj->sd, grp->name);
	if (!kn) {
	pr_warn("Can't update unknown attr grp name: %s/%s\n",
	kobj->name, grp->name);
	return -EINVAL;
	}
	} else {
	kn = kernfs_create_dir_ns(kobj->sd, grp->name,
	S_IRWXU \| S_IRUGO \| S_IXUGO,
	uid, gid, kobj, NULL);
	if (IS_ERR(kn)) {
	if (PTR_ERR(kn) == -EEXIST)
	sysfs_warn_dup(kobj->sd, grp->name);
	return PTR_ERR(kn);
	}
	}
	} else
	kn = kobj->sd;
	kernfs_get(kn);
	error = create_files(kn, kobj, uid, gid, grp, update);
	if (error) {
	if (grp->name)
	kernfs_remove(kn);
	}
	kernfs_put(kn);

	if (grp->name && update)
	kernfs_put(kn);

	return error;
	}

	/**
	* sysfs_create_group - given a directory kobject, create an attribute group
	* @kobj: The kobject to create the group on
	* @grp: The attribute group to create
	*
	* This function creates a group for the first time. It will explicitly
	* warn and error if any of the attribute files being created already exist.
	*
	* Returns 0 on success or error code on failure.
	*/
	int sysfs_create_group(struct kobject *kobj,
	const struct attribute_group *grp)
	{
	return internal_create_group(kobj, 0, grp);
	}
	EXPORT_SYMBOL_GPL(sysfs_create_group);

	/**
	* sysfs_create_groups - given a directory kobject, create a bunch of attribute groups
	* @kobj: The kobject to create the group on
	* @groups: The attribute groups to create, NULL terminated
	*
	* This function creates a bunch of attribute groups. If an error occurs when
	* creating a group, all previously created groups will be removed, unwinding
	* everything back to the original state when this function was called.
	* It will explicitly warn and error if any of the attribute files being
	* created already exist.
	*
	* Returns 0 on success or error code from sysfs_create_group on failure.
	*/
	int sysfs_create_groups(struct kobject *kobj,
	const struct attribute_group **groups)
	{
	int error = 0;
	int i;

	if (!groups)
	return 0;

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

	/**
	* sysfs_update_group - given a directory kobject, update an attribute group
	* @kobj: The kobject to update the group on
	* @grp: The attribute group to update
	*
	* This function updates an attribute group. Unlike
	* sysfs_create_group(), it will explicitly not warn or error if any
	* of the attribute files being created already exist. Furthermore,
	* if the visibility of the files has changed through the is_visible()
	* callback, it will update the permissions and add or remove the
	* relevant files. Changing a group's name (subdirectory name under
	* kobj's directory in sysfs) is not allowed.
	*
	* The primary use for this function is to call it after making a change
	* that affects group visibility.
	*
	* Returns 0 on success or error code on failure.
	*/
	int sysfs_update_group(struct kobject *kobj,
	const struct attribute_group *grp)
	{
	return internal_create_group(kobj, 1, grp);
	}
	EXPORT_SYMBOL_GPL(sysfs_update_group);

	/**
	* sysfs_remove_group: remove a group from a kobject
	* @kobj: kobject to remove the group from
	* @grp: group to remove
	*
	* This function removes a group of attributes from a kobject. The attributes
	* previously have to have been created for this group, otherwise it will fail.
	*/
	void sysfs_remove_group(struct kobject *kobj,
	const struct attribute_group *grp)
	{
	struct kernfs_node *parent = kobj->sd;
	struct kernfs_node *kn;

	if (grp->name) {
	kn = kernfs_find_and_get(parent, grp->name);
	if (!kn) {
	WARN(!kn, KERN_WARNING
	"sysfs group '%s' not found for kobject '%s'\n",
	grp->name, kobject_name(kobj));
	return;
	}
	} else {
	kn = parent;
	kernfs_get(kn);
	}

	remove_files(kn, grp);
	if (grp->name)
	kernfs_remove(kn);

	kernfs_put(kn);
	}
	EXPORT_SYMBOL_GPL(sysfs_remove_group);

	/**
	* sysfs_remove_groups - remove a list of groups
	*
	* @kobj: The kobject for the groups to be removed from
	* @groups: NULL terminated list of groups to be removed
	*
	* If groups is not NULL, remove the specified groups from the kobject.
	*/
	void sysfs_remove_groups(struct kobject *kobj,
	const struct attribute_group **groups)
	{
	int i;

	if (!groups)
	return;
	for (i = 0; groups[i]; i++)
	sysfs_remove_group(kobj, groups[i]);
	}
	EXPORT_SYMBOL_GPL(sysfs_remove_groups);

	/**
	* sysfs_merge_group - merge files into a pre-existing attribute group.
	* @kobj: The kobject containing the group.
	* @grp: The files to create and the attribute group they belong to.
	*
	* This function returns an error if the group doesn't exist or any of the
	* files already exist in that group, in which case none of the new files
	* are created.
	*/
	int sysfs_merge_group(struct kobject *kobj,
	const struct attribute_group *grp)
	{
	struct kernfs_node *parent;
	kuid_t uid;
	kgid_t gid;
	int error = 0;
	struct attribute const attr;
	int i;

	parent = kernfs_find_and_get(kobj->sd, grp->name);
	if (!parent)
	return -ENOENT;

	kobject_get_ownership(kobj, &uid, &gid);

	for ((i = 0, attr = grp->attrs); *attr && !error; (++i, ++attr))
	error = sysfs_add_file_mode_ns(parent, *attr, false,
	(*attr)->mode, uid, gid, NULL);
	if (error) {
	while (--i >= 0)
	kernfs_remove_by_name(parent, (*--attr)->name);
	}
	kernfs_put(parent);

	return error;
	}
	EXPORT_SYMBOL_GPL(sysfs_merge_group);

	/**
	* sysfs_unmerge_group - remove files from a pre-existing attribute group.
	* @kobj: The kobject containing the group.
	* @grp: The files to remove and the attribute group they belong to.
	*/
	void sysfs_unmerge_group(struct kobject *kobj,
	const struct attribute_group *grp)
	{
	struct kernfs_node *parent;
	struct attribute const attr;

	parent = kernfs_find_and_get(kobj->sd, grp->name);
	if (parent) {
	for (attr = grp->attrs; *attr; ++attr)
	kernfs_remove_by_name(parent, (*attr)->name);
	kernfs_put(parent);
	}
	}
	EXPORT_SYMBOL_GPL(sysfs_unmerge_group);

	/**
	* sysfs_add_link_to_group - add a symlink to an attribute group.
	* @kobj: The kobject containing the group.
	* @group_name: The name of the group.
	* @target: The target kobject of the symlink to create.
	* @link_name: The name of the symlink to create.
	*/
	int sysfs_add_link_to_group(struct kobject kobj, const char group_name,
	struct kobject target, const char link_name)
	{
	struct kernfs_node *parent;
	int error = 0;

	parent = kernfs_find_and_get(kobj->sd, group_name);
	if (!parent)
	return -ENOENT;

	error = sysfs_create_link_sd(parent, target, link_name);
	kernfs_put(parent);

	return error;
	}
	EXPORT_SYMBOL_GPL(sysfs_add_link_to_group);

	/**
	* sysfs_remove_link_from_group - remove a symlink from an attribute group.
	* @kobj: The kobject containing the group.
	* @group_name: The name of the group.
	* @link_name: The name of the symlink to remove.
	*/
	void sysfs_remove_link_from_group(struct kobject kobj, const char group_name,
	const char *link_name)
	{
	struct kernfs_node *parent;

	parent = kernfs_find_and_get(kobj->sd, group_name);
	if (parent) {
	kernfs_remove_by_name(parent, link_name);
	kernfs_put(parent);
	}
	}
	EXPORT_SYMBOL_GPL(sysfs_remove_link_from_group);

	/**
	* __compat_only_sysfs_link_entry_to_kobj - add a symlink to a kobject pointing
	* to a group or an attribute
	* @kobj: The kobject containing the group.
	* @target_kobj: The target kobject.
	* @target_name: The name of the target group or attribute.
	*/
	int __compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
	struct kobject *target_kobj,
	const char *target_name)
	{
	struct kernfs_node *target;
	struct kernfs_node *entry;
	struct kernfs_node *link;

	/*
	* We don't own @target_kobj and it may be removed at any time.
	* Synchronize using sysfs_symlink_target_lock. See sysfs_remove_dir()
	* for details.
	*/
	spin_lock(&sysfs_symlink_target_lock);
	target = target_kobj->sd;
	if (target)
	kernfs_get(target);
	spin_unlock(&sysfs_symlink_target_lock);
	if (!target)
	return -ENOENT;

	entry = kernfs_find_and_get(target_kobj->sd, target_name);
	if (!entry) {
	kernfs_put(target);
	return -ENOENT;
	}

	link = kernfs_create_link(kobj->sd, target_name, entry);
	if (IS_ERR(link) && PTR_ERR(link) == -EEXIST)
	sysfs_warn_dup(kobj->sd, target_name);

	kernfs_put(entry);
	kernfs_put(target);
	return PTR_ERR_OR_ZERO(link);
	}
	EXPORT_SYMBOL_GPL(__compat_only_sysfs_link_entry_to_kobj);