include/linux/configfs.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * configfs.h - definitions for the device driver filesystem
   4  *
   5  * Based on sysfs:
   6  *      sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
   7  *
   8  * Based on kobject.h:
   9  *      Copyright (c) 2002-2003 Patrick Mochel
  10  *      Copyright (c) 2002-2003 Open Source Development Labs
  11  *
  12  * configfs Copyright (C) 2005 Oracle.  All rights reserved.
  13  *
  14  * Please read Documentation/filesystems/configfs.rst before using
  15  * the configfs interface, ESPECIALLY the parts about reference counts and
  16  * item destructors.
  17  */
  18
  19 #ifndef _CONFIGFS_H_
  20 #define _CONFIGFS_H_
  21
  22 #include <linux/stat.h>   /* S_IRUGO */
  23 #include <linux/types.h>  /* ssize_t */
  24 #include <linux/list.h>   /* struct list_head */
  25 #include <linux/kref.h>   /* struct kref */
  26 #include <linux/mutex.h>  /* struct mutex */
  27
  28 #define CONFIGFS_ITEM_NAME_LEN  20
  29
  30 struct module;
  31
  32 struct configfs_item_operations;
  33 struct configfs_group_operations;
  34 struct configfs_attribute;
  35 struct configfs_bin_attribute;
  36 struct configfs_subsystem;
  37
  38 struct config_item {
  39         char                    *ci_name;
  40         char                    ci_namebuf[CONFIGFS_ITEM_NAME_LEN];
  41         struct kref             ci_kref;
  42         struct list_head        ci_entry;
  43         struct config_item      *ci_parent;
  44         struct config_group     *ci_group;
  45         const struct config_item_type   *ci_type;
  46         struct dentry           *ci_dentry;
  47 };
  48
  49 extern __printf(2, 3)
  50 int config_item_set_name(struct config_item *, const char *, ...);
  51
  52 static inline char *config_item_name(struct config_item * item)
  53 {
  54         return item->ci_name;
  55 }
  56
  57 extern void config_item_init_type_name(struct config_item *item,
  58                                        const char *name,
  59                                        const struct config_item_type *type);
  60
  61 extern struct config_item *config_item_get(struct config_item *);
  62 extern struct config_item *config_item_get_unless_zero(struct config_item *);
  63 extern void config_item_put(struct config_item *);
  64
  65 struct config_item_type {
  66         struct module                           *ct_owner;
  67         struct configfs_item_operations         *ct_item_ops;
  68         struct configfs_group_operations        *ct_group_ops;
  69         struct configfs_attribute               **ct_attrs;
  70         struct configfs_bin_attribute           **ct_bin_attrs;
  71 };
  72
  73 /**
  74  *      group - a group of config_items of a specific type, belonging
  75  *      to a specific subsystem.
  76  */
  77 struct config_group {
  78         struct config_item              cg_item;
  79         struct list_head                cg_children;
  80         struct configfs_subsystem       *cg_subsys;
  81         struct list_head                default_groups;
  82         struct list_head                group_entry;
  83 };
  84
  85 extern void config_group_init(struct config_group *group);
  86 extern void config_group_init_type_name(struct config_group *group,
  87                                         const char *name,
  88                                         const struct config_item_type *type);
  89
  90 static inline struct config_group *to_config_group(struct config_item *item)
  91 {
  92         return item ? container_of(item,struct config_group,cg_item) : NULL;
  93 }
  94
  95 static inline struct config_group *config_group_get(struct config_group *group)
  96 {
  97         return group ? to_config_group(config_item_get(&group->cg_item)) : NULL;
  98 }
  99
 100 static inline void config_group_put(struct config_group *group)
 101 {
 102         config_item_put(&group->cg_item);
 103 }
 104
 105 extern struct config_item *config_group_find_item(struct config_group *,
 106                                                   const char *);
 107
 108
 109 static inline void configfs_add_default_group(struct config_group *new_group,
 110                 struct config_group *group)
 111 {
 112         list_add_tail(&new_group->group_entry, &group->default_groups);
 113 }
 114
 115 struct configfs_attribute {
 116         const char              *ca_name;
 117         struct module           *ca_owner;
 118         umode_t                 ca_mode;
 119         ssize_t (*show)(struct config_item *, char *);
 120         ssize_t (*store)(struct config_item *, const char *, size_t);
 121 };
 122
 123 #define CONFIGFS_ATTR(_pfx, _name)                      \
 124 static struct configfs_attribute _pfx##attr_##_name = { \
 125         .ca_name        = __stringify(_name),           \
 126         .ca_mode        = S_IRUGO | S_IWUSR,            \
 127         .ca_owner       = THIS_MODULE,                  \
 128         .show           = _pfx##_name##_show,           \
 129         .store          = _pfx##_name##_store,          \
 130 }
 131
 132 #define CONFIGFS_ATTR_RO(_pfx, _name)                   \
 133 static struct configfs_attribute _pfx##attr_##_name = { \
 134         .ca_name        = __stringify(_name),           \
 135         .ca_mode        = S_IRUGO,                      \
 136         .ca_owner       = THIS_MODULE,                  \
 137         .show           = _pfx##_name##_show,           \
 138 }
 139
 140 #define CONFIGFS_ATTR_WO(_pfx, _name)                   \
 141 static struct configfs_attribute _pfx##attr_##_name = { \
 142         .ca_name        = __stringify(_name),           \
 143         .ca_mode        = S_IWUSR,                      \
 144         .ca_owner       = THIS_MODULE,                  \
 145         .store          = _pfx##_name##_store,          \
 146 }
 147
 148 struct file;
 149 struct vm_area_struct;
 150
 151 struct configfs_bin_attribute {
 152         struct configfs_attribute cb_attr;      /* std. attribute */
 153         void *cb_private;                       /* for user       */
 154         size_t cb_max_size;                     /* max core size  */
 155         ssize_t (*read)(struct config_item *, void *, size_t);
 156         ssize_t (*write)(struct config_item *, const void *, size_t);
 157 };
 158
 159 #define CONFIGFS_BIN_ATTR(_pfx, _name, _priv, _maxsz)           \
 160 static struct configfs_bin_attribute _pfx##attr_##_name = {     \
 161         .cb_attr = {                                            \
 162                 .ca_name        = __stringify(_name),           \
 163                 .ca_mode        = S_IRUGO | S_IWUSR,            \
 164                 .ca_owner       = THIS_MODULE,                  \
 165         },                                                      \
 166         .cb_private     = _priv,                                \
 167         .cb_max_size    = _maxsz,                               \
 168         .read           = _pfx##_name##_read,                   \
 169         .write          = _pfx##_name##_write,                  \
 170 }
 171
 172 #define CONFIGFS_BIN_ATTR_RO(_pfx, _name, _priv, _maxsz)        \
 173 static struct configfs_bin_attribute _pfx##attr_##_name = {     \
 174         .cb_attr = {                                            \
 175                 .ca_name        = __stringify(_name),           \
 176                 .ca_mode        = S_IRUGO,                      \
 177                 .ca_owner       = THIS_MODULE,                  \
 178         },                                                      \
 179         .cb_private     = _priv,                                \
 180         .cb_max_size    = _maxsz,                               \
 181         .read           = _pfx##_name##_read,                   \
 182 }
 183
 184 #define CONFIGFS_BIN_ATTR_WO(_pfx, _name, _priv, _maxsz)        \
 185 static struct configfs_bin_attribute _pfx##attr_##_name = {     \
 186         .cb_attr = {                                            \
 187                 .ca_name        = __stringify(_name),           \
 188                 .ca_mode        = S_IWUSR,                      \
 189                 .ca_owner       = THIS_MODULE,                  \
 190         },                                                      \
 191         .cb_private     = _priv,                                \
 192         .cb_max_size    = _maxsz,                               \
 193         .write          = _pfx##_name##_write,                  \
 194 }
 195
 196 /*
 197  * If allow_link() exists, the item can symlink(2) out to other
 198  * items.  If the item is a group, it may support mkdir(2).
 199  * Groups supply one of make_group() and make_item().  If the
 200  * group supports make_group(), one can create group children.  If it
 201  * supports make_item(), one can create config_item children.  make_group()
 202  * and make_item() return ERR_PTR() on errors.  If it has
 203  * default_groups on group->default_groups, it has automatically created
 204  * group children.  default_groups may coexist alongsize make_group() or
 205  * make_item(), but if the group wishes to have only default_groups
 206  * children (disallowing mkdir(2)), it need not provide either function.
 207  */
 208 struct configfs_item_operations {
 209         void (*release)(struct config_item *);
 210         int (*allow_link)(struct config_item *src, struct config_item *target);
 211         void (*drop_link)(struct config_item *src, struct config_item *target);
 212 };
 213
 214 struct configfs_group_operations {
 215         struct config_item *(*make_item)(struct config_group *group, const char *name);
 216         struct config_group *(*make_group)(struct config_group *group, const char *name);
 217         void (*disconnect_notify)(struct config_group *group, struct config_item *item);
 218         void (*drop_item)(struct config_group *group, struct config_item *item);
 219         bool (*is_visible)(struct config_item *item, struct configfs_attribute *attr, int n);
 220         bool (*is_bin_visible)(struct config_item *item, struct configfs_bin_attribute *attr,
 221                                int n);
 222 };
 223
 224 struct configfs_subsystem {
 225         struct config_group     su_group;
 226         struct mutex            su_mutex;
 227 };
 228
 229 static inline struct configfs_subsystem *to_configfs_subsystem(struct config_group *group)
 230 {
 231         return group ?
 232                 container_of(group, struct configfs_subsystem, su_group) :
 233                 NULL;
 234 }
 235
 236 int configfs_register_subsystem(struct configfs_subsystem *subsys);
 237 void configfs_unregister_subsystem(struct configfs_subsystem *subsys);
 238
 239 int configfs_register_group(struct config_group *parent_group,
 240                             struct config_group *group);
 241 void configfs_unregister_group(struct config_group *group);
 242
 243 void configfs_remove_default_groups(struct config_group *group);
 244
 245 struct config_group *
 246 configfs_register_default_group(struct config_group *parent_group,
 247                                 const char *name,
 248                                 const struct config_item_type *item_type);
 249 void configfs_unregister_default_group(struct config_group *group);
 250
 251 /* These functions can sleep and can alloc with GFP_KERNEL */
 252 /* WARNING: These cannot be called underneath configfs callbacks!! */
 253 int configfs_depend_item(struct configfs_subsystem *subsys,
 254                          struct config_item *target);
 255 void configfs_undepend_item(struct config_item *target);
 256
 257 /*
 258  * These functions can sleep and can alloc with GFP_KERNEL
 259  * NOTE: These should be called only underneath configfs callbacks.
 260  * NOTE: First parameter is a caller's subsystem, not target's.
 261  * WARNING: These cannot be called on newly created item
 262  *        (in make_group()/make_item() callback)
 263  */
 264 int configfs_depend_item_unlocked(struct configfs_subsystem *caller_subsys,
 265                                   struct config_item *target);
 266
 267
 268 static inline void configfs_undepend_item_unlocked(struct config_item *target)
 269 {
 270         configfs_undepend_item(target);
 271 }
 272
 273 #endif /* _CONFIGFS_H_ */