lib/kobject.c

   1 /*
   2  * kobject.c - library routines for handling generic kernel objects
   3  *
   4  * Copyright (c) 2002-2003 Patrick Mochel <mochel@osdl.org>
   5  *
   6  * This file is released under the GPLv2.
   7  *
   8  *
   9  * Please see the file Documentation/kobject.txt for critical information
  10  * about using the kobject interface.
  11  */
  12
  13 #include <linux/kobject.h>
  14 #include <linux/string.h>
  15 #include <linux/module.h>
  16 #include <linux/stat.h>
  17
  18 /**
  19  *      populate_dir - populate directory with attributes.
  20  *      @kobj:  object we're working on.
  21  *
  22  *      Most subsystems have a set of default attributes that
  23  *      are associated with an object that registers with them.
  24  *      This is a helper called during object registration that
  25  *      loops through the default attributes of the subsystem
  26  *      and creates attributes files for them in sysfs.
  27  *
  28  */
  29
  30 static int populate_dir(struct kobject * kobj)
  31 {
  32         struct kobj_type * t = get_ktype(kobj);
  33         struct attribute * attr;
  34         int error = 0;
  35         int i;
  36
  37         if (t && t->default_attrs) {
  38                 for (i = 0; (attr = t->default_attrs[i]) != NULL; i++) {
  39                         if ((error = sysfs_create_file(kobj,attr)))
  40                                 break;
  41                 }
  42         }
  43         return error;
  44 }
  45
  46 static int create_dir(struct kobject * kobj)
  47 {
  48         int error = 0;
  49         if (kobject_name(kobj)) {
  50                 error = sysfs_create_dir(kobj);
  51                 if (!error) {
  52                         if ((error = populate_dir(kobj)))
  53                                 sysfs_remove_dir(kobj);
  54                 }
  55         }
  56         return error;
  57 }
  58
  59 static inline struct kobject * to_kobj(struct list_head * entry)
  60 {
  61         return container_of(entry,struct kobject,entry);
  62 }
  63
  64 static int get_kobj_path_length(struct kobject *kobj)
  65 {
  66         int length = 1;
  67         struct kobject * parent = kobj;
  68
  69         /* walk up the ancestors until we hit the one pointing to the
  70          * root.
  71          * Add 1 to strlen for leading '/' of each level.
  72          */
  73         do {
  74                 length += strlen(kobject_name(parent)) + 1;
  75                 parent = parent->parent;
  76         } while (parent);
  77         return length;
  78 }
  79
  80 static void fill_kobj_path(struct kobject *kobj, char *path, int length)
  81 {
  82         struct kobject * parent;
  83
  84         --length;
  85         for (parent = kobj; parent; parent = parent->parent) {
  86                 int cur = strlen(kobject_name(parent));
  87                 /* back up enough to print this name with '/' */
  88                 length -= cur;
  89                 strncpy (path + length, kobject_name(parent), cur);
  90                 *(path + --length) = '/';
  91         }
  92
  93         pr_debug("%s: path = '%s'\n",__FUNCTION__,path);
  94 }
  95
  96 /**
  97  * kobject_get_path - generate and return the path associated with a given kobj
  98  * and kset pair.  The result must be freed by the caller with kfree().
  99  *
 100  * @kobj:       kobject in question, with which to build the path
 101  * @gfp_mask:   the allocation type used to allocate the path
 102  */
 103 char *kobject_get_path(struct kobject *kobj, int gfp_mask)
 104 {
 105         char *path;
 106         int len;
 107
 108         len = get_kobj_path_length(kobj);
 109         path = kmalloc(len, gfp_mask);
 110         if (!path)
 111                 return NULL;
 112         memset(path, 0x00, len);
 113         fill_kobj_path(kobj, path, len);
 114
 115         return path;
 116 }
 117
 118 /**
 119  *      kobject_init - initialize object.
 120  *      @kobj:  object in question.
 121  */
 122 void kobject_init(struct kobject * kobj)
 123 {
 124         kref_init(&kobj->kref);
 125         INIT_LIST_HEAD(&kobj->entry);
 126         kobj->kset = kset_get(kobj->kset);
 127 }
 128
 129
 130 /**
 131  *      unlink - remove kobject from kset list.
 132  *      @kobj:  kobject.
 133  *
 134  *      Remove the kobject from the kset list and decrement
 135  *      its parent's refcount.
 136  *      This is separated out, so we can use it in both
 137  *      kobject_del() and kobject_add() on error.
 138  */
 139
 140 static void unlink(struct kobject * kobj)
 141 {
 142         if (kobj->kset) {
 143                 spin_lock(&kobj->kset->list_lock);
 144                 list_del_init(&kobj->entry);
 145                 spin_unlock(&kobj->kset->list_lock);
 146         }
 147         kobject_put(kobj);
 148 }
 149
 150 /**
 151  *      kobject_add - add an object to the hierarchy.
 152  *      @kobj:  object.
 153  */
 154
 155 int kobject_add(struct kobject * kobj)
 156 {
 157         int error = 0;
 158         struct kobject * parent;
 159
 160         if (!(kobj = kobject_get(kobj)))
 161                 return -ENOENT;
 162         if (!kobj->k_name)
 163                 kobj->k_name = kobj->name;
 164         parent = kobject_get(kobj->parent);
 165
 166         pr_debug("kobject %s: registering. parent: %s, set: %s\n",
 167                  kobject_name(kobj), parent ? kobject_name(parent) : "<NULL>",
 168                  kobj->kset ? kobj->kset->kobj.name : "<NULL>" );
 169
 170         if (kobj->kset) {
 171                 spin_lock(&kobj->kset->list_lock);
 172
 173                 if (!parent)
 174                         parent = kobject_get(&kobj->kset->kobj);
 175
 176                 list_add_tail(&kobj->entry,&kobj->kset->list);
 177                 spin_unlock(&kobj->kset->list_lock);
 178         }
 179         kobj->parent = parent;
 180
 181         error = create_dir(kobj);
 182         if (error) {
 183                 /* unlink does the kobject_put() for us */
 184                 unlink(kobj);
 185                 if (parent)
 186                         kobject_put(parent);
 187         }
 188
 189         return error;
 190 }
 191
 192
 193 /**
 194  *      kobject_register - initialize and add an object.
 195  *      @kobj:  object in question.
 196  */
 197
 198 int kobject_register(struct kobject * kobj)
 199 {
 200         int error = 0;
 201         if (kobj) {
 202                 kobject_init(kobj);
 203                 error = kobject_add(kobj);
 204                 if (error) {
 205                         printk("kobject_register failed for %s (%d)\n",
 206                                kobject_name(kobj),error);
 207                         dump_stack();
 208                 } else
 209                         kobject_hotplug(kobj, KOBJ_ADD);
 210         } else
 211                 error = -EINVAL;
 212         return error;
 213 }
 214
 215
 216 /**
 217  *      kobject_set_name - Set the name of an object
 218  *      @kobj:  object.
 219  *      @fmt:   format string used to build the name
 220  *
 221  *      If strlen(name) >= KOBJ_NAME_LEN, then use a dynamically allocated
 222  *      string that @kobj->k_name points to. Otherwise, use the static
 223  *      @kobj->name array.
 224  */
 225 int kobject_set_name(struct kobject * kobj, const char * fmt, ...)
 226 {
 227         int error = 0;
 228         int limit = KOBJ_NAME_LEN;
 229         int need;
 230         va_list args;
 231         char * name;
 232
 233         /*
 234          * First, try the static array
 235          */
 236         va_start(args,fmt);
 237         need = vsnprintf(kobj->name,limit,fmt,args);
 238         va_end(args);
 239         if (need < limit)
 240                 name = kobj->name;
 241         else {
 242                 /*
 243                  * Need more space? Allocate it and try again
 244                  */
 245                 limit = need + 1;
 246                 name = kmalloc(limit,GFP_KERNEL);
 247                 if (!name) {
 248                         error = -ENOMEM;
 249                         goto Done;
 250                 }
 251                 va_start(args,fmt);
 252                 need = vsnprintf(name,limit,fmt,args);
 253                 va_end(args);
 254
 255                 /* Still? Give up. */
 256                 if (need >= limit) {
 257                         kfree(name);
 258                         error = -EFAULT;
 259                         goto Done;
 260                 }
 261         }
 262
 263         /* Free the old name, if necessary. */
 264         if (kobj->k_name && kobj->k_name != kobj->name)
 265                 kfree(kobj->k_name);
 266
 267         /* Now, set the new name */
 268         kobj->k_name = name;
 269  Done:
 270         return error;
 271 }
 272
 273 EXPORT_SYMBOL(kobject_set_name);
 274
 275
 276 /**
 277  *      kobject_rename - change the name of an object
 278  *      @kobj:  object in question.
 279  *      @new_name: object's new name
 280  */
 281
 282 int kobject_rename(struct kobject * kobj, char *new_name)
 283 {
 284         int error = 0;
 285
 286         kobj = kobject_get(kobj);
 287         if (!kobj)
 288                 return -EINVAL;
 289         error = sysfs_rename_dir(kobj, new_name);
 290         kobject_put(kobj);
 291
 292         return error;
 293 }
 294
 295 /**
 296  *      kobject_del - unlink kobject from hierarchy.
 297  *      @kobj:  object.
 298  */
 299
 300 void kobject_del(struct kobject * kobj)
 301 {
 302         sysfs_remove_dir(kobj);
 303         unlink(kobj);
 304 }
 305
 306 /**
 307  *      kobject_unregister - remove object from hierarchy and decrement refcount.
 308  *      @kobj:  object going away.
 309  */
 310
 311 void kobject_unregister(struct kobject * kobj)
 312 {
 313         pr_debug("kobject %s: unregistering\n",kobject_name(kobj));
 314         kobject_hotplug(kobj, KOBJ_REMOVE);
 315         kobject_del(kobj);
 316         kobject_put(kobj);
 317 }
 318
 319 /**
 320  *      kobject_get - increment refcount for object.
 321  *      @kobj:  object.
 322  */
 323
 324 struct kobject * kobject_get(struct kobject * kobj)
 325 {
 326         if (kobj)
 327                 kref_get(&kobj->kref);
 328         return kobj;
 329 }
 330
 331 /**
 332  *      kobject_cleanup - free kobject resources.
 333  *      @kobj:  object.
 334  */
 335
 336 void kobject_cleanup(struct kobject * kobj)
 337 {
 338         struct kobj_type * t = get_ktype(kobj);
 339         struct kset * s = kobj->kset;
 340         struct kobject * parent = kobj->parent;
 341
 342         pr_debug("kobject %s: cleaning up\n",kobject_name(kobj));
 343         if (kobj->k_name != kobj->name)
 344                 kfree(kobj->k_name);
 345         kobj->k_name = NULL;
 346         if (t && t->release)
 347                 t->release(kobj);
 348         if (s)
 349                 kset_put(s);
 350         if (parent)
 351                 kobject_put(parent);
 352 }
 353
 354 static void kobject_release(struct kref *kref)
 355 {
 356         kobject_cleanup(container_of(kref, struct kobject, kref));
 357 }
 358
 359 /**
 360  *      kobject_put - decrement refcount for object.
 361  *      @kobj:  object.
 362  *
 363  *      Decrement the refcount, and if 0, call kobject_cleanup().
 364  */
 365 void kobject_put(struct kobject * kobj)
 366 {
 367         if (kobj)
 368                 kref_put(&kobj->kref, kobject_release);
 369 }
 370
 371
 372 /**
 373  *      kset_init - initialize a kset for use
 374  *      @k:     kset
 375  */
 376
 377 void kset_init(struct kset * k)
 378 {
 379         kobject_init(&k->kobj);
 380         INIT_LIST_HEAD(&k->list);
 381         spin_lock_init(&k->list_lock);
 382 }
 383
 384
 385 /**
 386  *      kset_add - add a kset object to the hierarchy.
 387  *      @k:     kset.
 388  *
 389  *      Simply, this adds the kset's embedded kobject to the
 390  *      hierarchy.
 391  *      We also try to make sure that the kset's embedded kobject
 392  *      has a parent before it is added. We only care if the embedded
 393  *      kobject is not part of a kset itself, since kobject_add()
 394  *      assigns a parent in that case.
 395  *      If that is the case, and the kset has a controlling subsystem,
 396  *      then we set the kset's parent to be said subsystem.
 397  */
 398
 399 int kset_add(struct kset * k)
 400 {
 401         if (!k->kobj.parent && !k->kobj.kset && k->subsys)
 402                 k->kobj.parent = &k->subsys->kset.kobj;
 403
 404         return kobject_add(&k->kobj);
 405 }
 406
 407
 408 /**
 409  *      kset_register - initialize and add a kset.
 410  *      @k:     kset.
 411  */
 412
 413 int kset_register(struct kset * k)
 414 {
 415         kset_init(k);
 416         return kset_add(k);
 417 }
 418
 419
 420 /**
 421  *      kset_unregister - remove a kset.
 422  *      @k:     kset.
 423  */
 424
 425 void kset_unregister(struct kset * k)
 426 {
 427         kobject_unregister(&k->kobj);
 428 }
 429
 430
 431 /**
 432  *      kset_find_obj - search for object in kset.
 433  *      @kset:  kset we're looking in.
 434  *      @name:  object's name.
 435  *
 436  *      Lock kset via @kset->subsys, and iterate over @kset->list,
 437  *      looking for a matching kobject. If matching object is found
 438  *      take a reference and return the object.
 439  */
 440
 441 struct kobject * kset_find_obj(struct kset * kset, const char * name)
 442 {
 443         struct list_head * entry;
 444         struct kobject * ret = NULL;
 445
 446         spin_lock(&kset->list_lock);
 447         list_for_each(entry,&kset->list) {
 448                 struct kobject * k = to_kobj(entry);
 449                 if (kobject_name(k) && !strcmp(kobject_name(k),name)) {
 450                         ret = kobject_get(k);
 451                         break;
 452                 }
 453         }
 454         spin_unlock(&kset->list_lock);
 455         return ret;
 456 }
 457
 458
 459 void subsystem_init(struct subsystem * s)
 460 {
 461         init_rwsem(&s->rwsem);
 462         kset_init(&s->kset);
 463 }
 464
 465 /**
 466  *      subsystem_register - register a subsystem.
 467  *      @s:     the subsystem we're registering.
 468  *
 469  *      Once we register the subsystem, we want to make sure that
 470  *      the kset points back to this subsystem for correct usage of
 471  *      the rwsem.
 472  */
 473
 474 int subsystem_register(struct subsystem * s)
 475 {
 476         int error;
 477
 478         subsystem_init(s);
 479         pr_debug("subsystem %s: registering\n",s->kset.kobj.name);
 480
 481         if (!(error = kset_add(&s->kset))) {
 482                 if (!s->kset.subsys)
 483                         s->kset.subsys = s;
 484         }
 485         return error;
 486 }
 487
 488 void subsystem_unregister(struct subsystem * s)
 489 {
 490         pr_debug("subsystem %s: unregistering\n",s->kset.kobj.name);
 491         kset_unregister(&s->kset);
 492 }
 493
 494
 495 /**
 496  *      subsystem_create_file - export sysfs attribute file.
 497  *      @s:     subsystem.
 498  *      @a:     subsystem attribute descriptor.
 499  */
 500
 501 int subsys_create_file(struct subsystem * s, struct subsys_attribute * a)
 502 {
 503         int error = 0;
 504         if (subsys_get(s)) {
 505                 error = sysfs_create_file(&s->kset.kobj,&a->attr);
 506                 subsys_put(s);
 507         }
 508         return error;
 509 }
 510
 511
 512 /**
 513  *      subsystem_remove_file - remove sysfs attribute file.
 514  *      @s:     subsystem.
 515  *      @a:     attribute desciptor.
 516  */
 517
 518 void subsys_remove_file(struct subsystem * s, struct subsys_attribute * a)
 519 {
 520         if (subsys_get(s)) {
 521                 sysfs_remove_file(&s->kset.kobj,&a->attr);
 522                 subsys_put(s);
 523         }
 524 }
 525
 526 EXPORT_SYMBOL(kobject_init);
 527 EXPORT_SYMBOL(kobject_register);
 528 EXPORT_SYMBOL(kobject_unregister);
 529 EXPORT_SYMBOL(kobject_get);
 530 EXPORT_SYMBOL(kobject_put);
 531 EXPORT_SYMBOL(kobject_add);
 532 EXPORT_SYMBOL(kobject_del);
 533
 534 EXPORT_SYMBOL(kset_register);
 535 EXPORT_SYMBOL(kset_unregister);
 536 EXPORT_SYMBOL(kset_find_obj);
 537
 538 EXPORT_SYMBOL(subsystem_init);
 539 EXPORT_SYMBOL(subsystem_register);
 540 EXPORT_SYMBOL(subsystem_unregister);
 541 EXPORT_SYMBOL(subsys_create_file);
 542 EXPORT_SYMBOL(subsys_remove_file);