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