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
22 static 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 */
28 static void config_item_release(struct kref *kref);
29
30 /**
31 * config_item_init - initialize item.
32 * @item: item in question.
33 */
34 static 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 */
49 int 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 -EFAULT;
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 }
80 EXPORT_SYMBOL(config_item_set_name);
81
82 void 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 }
90 EXPORT_SYMBOL(config_item_init_type_name);
91
92 void 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 }
99 EXPORT_SYMBOL(config_group_init_type_name);
100
101 struct config_item *config_item_get(struct config_item *item)
102 {
103 if (item)
104 kref_get(&item->ci_kref);
105 return item;
106 }
107 EXPORT_SYMBOL(config_item_get);
108
109 struct 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 }
115 EXPORT_SYMBOL(config_item_get_unless_zero);
116
117 static 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
135 static 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 */
146 void config_item_put(struct config_item *item)
147 {
148 if (item)
149 kref_put(&item->ci_kref, config_item_release);
150 }
151 EXPORT_SYMBOL(config_item_put);
152
153 /**
154 * config_group_init - initialize a group for use
155 * @group: config_group
156 */
157 void 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 }
163 EXPORT_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 */
174 struct 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 }
190 EXPORT_SYMBOL(config_group_find_item);
191
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