item.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * item.c - library routines for handling generic config items
  4 *
  5 * Based on kobject:
  6 *	kobject is Copyright (c) 2002-2003 Patrick Mochel
  7 *
  8 * configfs Copyright (C) 2005 Oracle.  All rights reserved.
  9 *
 10 * Please see the file Documentation/filesystems/configfs.rst for
 11 * critical information about using the config_item interface.
 12 */
 13
 14#include <linux/string.h>
 15#include <linux/module.h>
 16#include <linux/stat.h>
 17#include <linux/slab.h>
 18
 19#include <linux/configfs.h>
 20
 21
 22static inline struct config_item *to_item(struct list_head *entry)
 23{
 24	return container_of(entry, struct config_item, ci_entry);
 25}
 26
 27/* Evil kernel */
 28static void config_item_release(struct kref *kref);
 29
 30/**
 31 *	config_item_init - initialize item.
 32 *	@item:	item in question.
 33 */
 34static void config_item_init(struct config_item *item)
 35{
 36	kref_init(&item->ci_kref);
 37	INIT_LIST_HEAD(&item->ci_entry);
 38}
 39
 40/**
 41 *	config_item_set_name - Set the name of an item
 42 *	@item:	item.
 43 *	@fmt:  The vsnprintf()'s format string.
 44 *
 45 *	If strlen(name) >= CONFIGFS_ITEM_NAME_LEN, then use a
 46 *	dynamically allocated string that @item->ci_name points to.
 47 *	Otherwise, use the static @item->ci_namebuf array.
 48 */
 49int config_item_set_name(struct config_item *item, const char *fmt, ...)
 50{
 51	int limit = CONFIGFS_ITEM_NAME_LEN;
 52	int need;
 53	va_list args;
 54	char *name;
 55
 56	/*
 57	 * First, try the static array
 58	 */
 59	va_start(args, fmt);
 60	need = vsnprintf(item->ci_namebuf, limit, fmt, args);
 61	va_end(args);
 62	if (need < limit)
 63		name = item->ci_namebuf;
 64	else {
 65		va_start(args, fmt);
 66		name = kvasprintf(GFP_KERNEL, fmt, args);
 67		va_end(args);
 68		if (!name)
 69			return -ENOMEM;
 70	}
 71
 72	/* Free the old name, if necessary. */
 73	if (item->ci_name && item->ci_name != item->ci_namebuf)
 74		kfree(item->ci_name);
 75
 76	/* Now, set the new name */
 77	item->ci_name = name;
 78	return 0;
 79}
 80EXPORT_SYMBOL(config_item_set_name);
 81
 82void config_item_init_type_name(struct config_item *item,
 83				const char *name,
 84				const struct config_item_type *type)
 85{
 86	config_item_set_name(item, "%s", name);
 87	item->ci_type = type;
 88	config_item_init(item);
 89}
 90EXPORT_SYMBOL(config_item_init_type_name);
 91
 92void config_group_init_type_name(struct config_group *group, const char *name,
 93			 const struct config_item_type *type)
 94{
 95	config_item_set_name(&group->cg_item, "%s", name);
 96	group->cg_item.ci_type = type;
 97	config_group_init(group);
 98}
 99EXPORT_SYMBOL(config_group_init_type_name);
100
101struct config_item *config_item_get(struct config_item *item)
102{
103	if (item)
104		kref_get(&item->ci_kref);
105	return item;
106}
107EXPORT_SYMBOL(config_item_get);
108
109struct config_item *config_item_get_unless_zero(struct config_item *item)
110{
111	if (item && kref_get_unless_zero(&item->ci_kref))
112		return item;
113	return NULL;
114}
115EXPORT_SYMBOL(config_item_get_unless_zero);
116
117static void config_item_cleanup(struct config_item *item)
118{
119	const struct config_item_type *t = item->ci_type;
120	struct config_group *s = item->ci_group;
121	struct config_item *parent = item->ci_parent;
122
123	pr_debug("config_item %s: cleaning up\n", config_item_name(item));
124	if (item->ci_name != item->ci_namebuf)
125		kfree(item->ci_name);
126	item->ci_name = NULL;
127	if (t && t->ct_item_ops && t->ct_item_ops->release)
128		t->ct_item_ops->release(item);
129	if (s)
130		config_group_put(s);
131	if (parent)
132		config_item_put(parent);
133}
134
135static void config_item_release(struct kref *kref)
136{
137	config_item_cleanup(container_of(kref, struct config_item, ci_kref));
138}
139
140/**
141 *	config_item_put - decrement refcount for item.
142 *	@item:	item.
143 *
144 *	Decrement the refcount, and if 0, call config_item_cleanup().
145 */
146void config_item_put(struct config_item *item)
147{
148	if (item)
149		kref_put(&item->ci_kref, config_item_release);
150}
151EXPORT_SYMBOL(config_item_put);
152
153/**
154 *	config_group_init - initialize a group for use
155 *	@group:	config_group
156 */
157void config_group_init(struct config_group *group)
158{
159	config_item_init(&group->cg_item);
160	INIT_LIST_HEAD(&group->cg_children);
161	INIT_LIST_HEAD(&group->default_groups);
162}
163EXPORT_SYMBOL(config_group_init);
164
165/**
166 *	config_group_find_item - search for item in group.
167 *	@group:	group we're looking in.
168 *	@name:	item's name.
169 *
170 *	Iterate over @group->cg_list, looking for a matching config_item.
171 *	If matching item is found take a reference and return the item.
172 *	Caller must have locked group via @group->cg_subsys->su_mtx.
173 */
174struct config_item *config_group_find_item(struct config_group *group,
175					   const char *name)
176{
177	struct list_head *entry;
178	struct config_item *ret = NULL;
179
180	list_for_each(entry, &group->cg_children) {
181		struct config_item *item = to_item(entry);
182		if (config_item_name(item) &&
183		    !strcmp(config_item_name(item), name)) {
184			ret = config_item_get(item);
185			break;
186		}
187	}
188	return ret;
189}
190EXPORT_SYMBOL(config_group_find_item);