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 #include <linux/slab.h>
  18
  19 /**
  20  *      populate_dir - populate directory with attributes.
  21  *      @kobj:  object we're working on.
  22  *
  23  *      Most subsystems have a set of default attributes that
  24  *      are associated with an object that registers with them.
  25  *      This is a helper called during object registration that
  26  *      loops through the default attributes of the subsystem
  27  *      and creates attributes files for them in sysfs.
  28  *
  29  */
  30
  31 static int populate_dir(struct kobject * kobj)
  32 {
  33         struct kobj_type * t = get_ktype(kobj);
  34         struct attribute * attr;
  35         int error = 0;
  36         int i;
  37
  38         if (t && t->default_attrs) {
  39                 for (i = 0; (attr = t->default_attrs[i]) != NULL; i++) {
  40                         if ((error = sysfs_create_file(kobj,attr)))
  41                                 break;
  42                 }
  43         }
  44         return error;
  45 }
  46
  47 static int create_dir(struct kobject * kobj)
  48 {
  49         int error = 0;
  50         if (kobject_name(kobj)) {
  51                 error = sysfs_create_dir(kobj);
  52                 if (!error) {
  53                         if ((error = populate_dir(kobj)))
  54                                 sysfs_remove_dir(kobj);
  55                 }
  56         }
  57         return error;
  58 }
  59
  60 static inline struct kobject * to_kobj(struct list_head * entry)
  61 {
  62         return container_of(entry,struct kobject,entry);
  63 }
  64
  65 static int get_kobj_path_length(struct kobject *kobj)
  66 {
  67         int length = 1;
  68         struct kobject * parent = kobj;
  69
  70         /* walk up the ancestors until we hit the one pointing to the
  71          * root.
  72          * Add 1 to strlen for leading '/' of each level.
  73          */
  74         do {
  75                 if (kobject_name(parent) == NULL)
  76                         return 0;
  77                 length += strlen(kobject_name(parent)) + 1;
  78                 parent = parent->parent;
  79         } while (parent);
  80         return length;
  81 }
  82
  83 static void fill_kobj_path(struct kobject *kobj, char *path, int length)
  84 {
  85         struct kobject * parent;
  86
  87         --length;
  88         for (parent = kobj; parent; parent = parent->parent) {
  89                 int cur = strlen(kobject_name(parent));
  90                 /* back up enough to print this name with '/' */
  91                 length -= cur;
  92                 strncpy (path + length, kobject_name(parent), cur);
  93                 *(path + --length) = '/';
  94         }
  95
  96         pr_debug("%s: path = '%s'\n",__FUNCTION__,path);
  97 }
  98
  99 /**
 100  * kobject_get_path - generate and return the path associated with a given kobj
 101  * and kset pair.  The result must be freed by the caller with kfree().
 102  *
 103  * @kobj:       kobject in question, with which to build the path
 104  * @gfp_mask:   the allocation type used to allocate the path
 105  */
 106 char *kobject_get_path(struct kobject *kobj, gfp_t gfp_mask)
 107 {
 108         char *path;
 109         int len;
 110
 111         len = get_kobj_path_length(kobj);
 112         if (len == 0)
 113                 return NULL;
 114         path = kmalloc(len, gfp_mask);
 115         if (!path)
 116                 return NULL;
 117         memset(path, 0x00, len);
 118         fill_kobj_path(kobj, path, len);
 119
 120         return path;
 121 }
 122
 123 /**
 124  *      kobject_init - initialize object.
 125  *      @kobj:  object in question.
 126  */
 127 void kobject_init(struct kobject * kobj)
 128 {
 129         kref_init(&kobj->kref);
 130         INIT_LIST_HEAD(&kobj->entry);
 131         kobj->kset = kset_get(kobj->kset);
 132 }
 133
 134
 135 /**
 136  *      unlink - remove kobject from kset list.
 137  *      @kobj:  kobject.
 138  *
 139  *      Remove the kobject from the kset list and decrement
 140  *      its parent's refcount.
 141  *      This is separated out, so we can use it in both
 142  *      kobject_del() and kobject_add() on error.
 143  */
 144
 145 static void unlink(struct kobject * kobj)
 146 {
 147         if (kobj->kset) {
 148                 spin_lock(&kobj->kset->list_lock);
 149                 list_del_init(&kobj->entry);
 150                 spin_unlock(&kobj->kset->list_lock);
 151         }
 152         kobject_put(kobj);
 153 }
 154
 155 /**
 156  *      kobject_add - add an object to the hierarchy.
 157  *      @kobj:  object.
 158  */
 159
 160 int kobject_add(struct kobject * kobj)
 161 {
 162         int error = 0;
 163         struct kobject * parent;
 164
 165         if (!(kobj = kobject_get(kobj)))
 166                 return -ENOENT;
 167         if (!kobj->k_name)
 168                 kobj->k_name = kobj->name;
 169         if (!kobj->k_name) {
 170                 pr_debug("kobject attempted to be registered with no name!\n");
 171                 WARN_ON(1);
 172                 return -EINVAL;
 173         }
 174         parent = kobject_get(kobj->parent);
 175
 176         pr_debug("kobject %s: registering. parent: %s, set: %s\n",
 177                  kobject_name(kobj), parent ? kobject_name(parent) : "<NULL>",
 178                  kobj->kset ? kobj->kset->kobj.name : "<NULL>" );
 179
 180         if (kobj->kset) {
 181                 spin_lock(&kobj->kset->list_lock);
 182
 183                 if (!parent)
 184                         parent = kobject_get(&kobj->kset->kobj);
 185
 186                 list_add_tail(&kobj->entry,&kobj->kset->list);
 187                 spin_unlock(&kobj->kset->list_lock);
 188         }
 189         kobj->parent = parent;
 190
 191         error = create_dir(kobj);
 192         if (error) {
 193                 /* unlink does the kobject_put() for us */
 194                 unlink(kobj);
 195                 if (parent)
 196                         kobject_put(parent);
 197
 198                 /* be noisy on error issues */
 199                 if (error == -EEXIST)
 200                         printk("kobject_add failed for %s with -EEXIST, "
 201                                "don't try to register things with the "
 202                                "same name in the same directory.\n",
 203                                kobject_name(kobj));
 204                 else
 205                         printk("kobject_add failed for %s (%d)\n",
 206                                kobject_name(kobj), error);
 207                 dump_stack();
 208         }
 209
 210         return error;
 211 }
 212
 213
 214 /**
 215  *      kobject_register - initialize and add an object.
 216  *      @kobj:  object in question.
 217  */
 218
 219 int kobject_register(struct kobject * kobj)
 220 {
 221         int error = -EINVAL;
 222         if (kobj) {
 223                 kobject_init(kobj);
 224                 error = kobject_add(kobj);
 225                 if (!error)
 226                         kobject_uevent(kobj, KOBJ_ADD);
 227         }
 228         return error;
 229 }
 230
 231
 232 /**
 233  *      kobject_set_name - Set the name of an object
 234  *      @kobj:  object.
 235  *      @fmt:   format string used to build the name
 236  *
 237  *      If strlen(name) >= KOBJ_NAME_LEN, then use a dynamically allocated
 238  *      string that @kobj->k_name points to. Otherwise, use the static
 239  *      @kobj->name array.
 240  */
 241 int kobject_set_name(struct kobject * kobj, const char * fmt, ...)
 242 {
 243         int error = 0;
 244         int limit = KOBJ_NAME_LEN;
 245         int need;
 246         va_list args;
 247         char * name;
 248
 249         /*
 250          * First, try the static array
 251          */
 252         va_start(args,fmt);
 253         need = vsnprintf(kobj->name,limit,fmt,args);
 254         va_end(args);
 255         if (need < limit)
 256                 name = kobj->name;
 257         else {
 258                 /*
 259                  * Need more space? Allocate it and try again
 260                  */
 261                 limit = need + 1;
 262                 name = kmalloc(limit,GFP_KERNEL);
 263                 if (!name) {
 264                         error = -ENOMEM;
 265                         goto Done;
 266                 }
 267                 va_start(args,fmt);
 268                 need = vsnprintf(name,limit,fmt,args);
 269                 va_end(args);
 270
 271                 /* Still? Give up. */
 272                 if (need >= limit) {
 273                         kfree(name);
 274                         error = -EFAULT;
 275                         goto Done;
 276                 }
 277         }
 278
 279         /* Free the old name, if necessary. */
 280         if (kobj->k_name && kobj->k_name != kobj->name)
 281                 kfree(kobj->k_name);
 282
 283         /* Now, set the new name */
 284         kobj->k_name = name;
 285  Done:
 286         return error;
 287 }
 288
 289 EXPORT_SYMBOL(kobject_set_name);
 290
 291
 292 /**
 293  *      kobject_rename - change the name of an object
 294  *      @kobj:  object in question.
 295  *      @new_name: object's new name
 296  */
 297
 298 int kobject_rename(struct kobject * kobj, const char *new_name)
 299 {
 300         int error = 0;
 301
 302         kobj = kobject_get(kobj);
 303         if (!kobj)
 304                 return -EINVAL;
 305         error = sysfs_rename_dir(kobj, new_name);
 306         kobject_put(kobj);
 307
 308         return error;
 309 }
 310
 311 /**
 312  *      kobject_del - unlink kobject from hierarchy.
 313  *      @kobj:  object.
 314  */
 315
 316 void kobject_del(struct kobject * kobj)
 317 {
 318         sysfs_remove_dir(kobj);
 319         unlink(kobj);
 320 }
 321
 322 /**
 323  *      kobject_unregister - remove object from hierarchy and decrement refcount.
 324  *      @kobj:  object going away.
 325  */
 326
 327 void kobject_unregister(struct kobject * kobj)
 328 {
 329         pr_debug("kobject %s: unregistering\n",kobject_name(kobj));
 330         kobject_uevent(kobj, KOBJ_REMOVE);
 331         kobject_del(kobj);
 332         kobject_put(kobj);
 333 }
 334
 335 /**
 336  *      kobject_get - increment refcount for object.
 337  *      @kobj:  object.
 338  */
 339
 340 struct kobject * kobject_get(struct kobject * kobj)
 341 {
 342         if (kobj)
 343                 kref_get(&kobj->kref);
 344         return kobj;
 345 }
 346
 347 /**
 348  *      kobject_cleanup - free kobject resources.
 349  *      @kobj:  object.
 350  */
 351
 352 void kobject_cleanup(struct kobject * kobj)
 353 {
 354         struct kobj_type * t = get_ktype(kobj);
 355         struct kset * s = kobj->kset;
 356         struct kobject * parent = kobj->parent;
 357
 358         pr_debug("kobject %s: cleaning up\n",kobject_name(kobj));
 359         if (kobj->k_name != kobj->name)
 360                 kfree(kobj->k_name);
 361         kobj->k_name = NULL;
 362         if (t && t->release)
 363                 t->release(kobj);
 364         if (s)
 365                 kset_put(s);
 366         if (parent)
 367                 kobject_put(parent);
 368 }
 369
 370 static void kobject_release(struct kref *kref)
 371 {
 372         kobject_cleanup(container_of(kref, struct kobject, kref));
 373 }
 374
 375 /**
 376  *      kobject_put - decrement refcount for object.
 377  *      @kobj:  object.
 378  *
 379  *      Decrement the refcount, and if 0, call kobject_cleanup().
 380  */
 381 void kobject_put(struct kobject * kobj)
 382 {
 383         if (kobj)
 384                 kref_put(&kobj->kref, kobject_release);
 385 }
 386
 387
 388 static void dir_release(struct kobject *kobj)
 389 {
 390         kfree(kobj);
 391 }
 392
 393 static struct kobj_type dir_ktype = {
 394         .release        = dir_release,
 395         .sysfs_ops      = NULL,
 396         .default_attrs  = NULL,
 397 };
 398
 399 /**
 400  *      kobject_add_dir - add sub directory of object.
 401  *      @parent:        object in which a directory is created.
 402  *      @name:  directory name.
 403  *
 404  *      Add a plain directory object as child of given object.
 405  */
 406 struct kobject *kobject_add_dir(struct kobject *parent, const char *name)
 407 {
 408         struct kobject *k;
 409
 410         if (!parent)
 411                 return NULL;
 412
 413         k = kzalloc(sizeof(*k), GFP_KERNEL);
 414         if (!k)
 415                 return NULL;
 416
 417         k->parent = parent;
 418         k->ktype = &dir_ktype;
 419         kobject_set_name(k, name);
 420         kobject_register(k);
 421
 422         return k;
 423 }
 424 EXPORT_SYMBOL_GPL(kobject_add_dir);
 425
 426 /**
 427  *      kset_init - initialize a kset for use
 428  *      @k:     kset
 429  */
 430
 431 void kset_init(struct kset * k)
 432 {
 433         kobject_init(&k->kobj);
 434         INIT_LIST_HEAD(&k->list);
 435         spin_lock_init(&k->list_lock);
 436 }
 437
 438
 439 /**
 440  *      kset_add - add a kset object to the hierarchy.
 441  *      @k:     kset.
 442  *
 443  *      Simply, this adds the kset's embedded kobject to the
 444  *      hierarchy.
 445  *      We also try to make sure that the kset's embedded kobject
 446  *      has a parent before it is added. We only care if the embedded
 447  *      kobject is not part of a kset itself, since kobject_add()
 448  *      assigns a parent in that case.
 449  *      If that is the case, and the kset has a controlling subsystem,
 450  *      then we set the kset's parent to be said subsystem.
 451  */
 452
 453 int kset_add(struct kset * k)
 454 {
 455         if (!k->kobj.parent && !k->kobj.kset && k->subsys)
 456                 k->kobj.parent = &k->subsys->kset.kobj;
 457
 458         return kobject_add(&k->kobj);
 459 }
 460
 461
 462 /**
 463  *      kset_register - initialize and add a kset.
 464  *      @k:     kset.
 465  */
 466
 467 int kset_register(struct kset * k)
 468 {
 469         kset_init(k);
 470         return kset_add(k);
 471 }
 472
 473
 474 /**
 475  *      kset_unregister - remove a kset.
 476  *      @k:     kset.
 477  */
 478
 479 void kset_unregister(struct kset * k)
 480 {
 481         kobject_unregister(&k->kobj);
 482 }
 483
 484
 485 /**
 486  *      kset_find_obj - search for object in kset.
 487  *      @kset:  kset we're looking in.
 488  *      @name:  object's name.
 489  *
 490  *      Lock kset via @kset->subsys, and iterate over @kset->list,
 491  *      looking for a matching kobject. If matching object is found
 492  *      take a reference and return the object.
 493  */
 494
 495 struct kobject * kset_find_obj(struct kset * kset, const char * name)
 496 {
 497         struct list_head * entry;
 498         struct kobject * ret = NULL;
 499
 500         spin_lock(&kset->list_lock);
 501         list_for_each(entry,&kset->list) {
 502                 struct kobject * k = to_kobj(entry);
 503                 if (kobject_name(k) && !strcmp(kobject_name(k),name)) {
 504                         ret = kobject_get(k);
 505                         break;
 506                 }
 507         }
 508         spin_unlock(&kset->list_lock);
 509         return ret;
 510 }
 511
 512
 513 void subsystem_init(struct subsystem * s)
 514 {
 515         init_rwsem(&s->rwsem);
 516         kset_init(&s->kset);
 517 }
 518
 519 /**
 520  *      subsystem_register - register a subsystem.
 521  *      @s:     the subsystem we're registering.
 522  *
 523  *      Once we register the subsystem, we want to make sure that
 524  *      the kset points back to this subsystem for correct usage of
 525  *      the rwsem.
 526  */
 527
 528 int subsystem_register(struct subsystem * s)
 529 {
 530         int error;
 531
 532         subsystem_init(s);
 533         pr_debug("subsystem %s: registering\n",s->kset.kobj.name);
 534
 535         if (!(error = kset_add(&s->kset))) {
 536                 if (!s->kset.subsys)
 537                         s->kset.subsys = s;
 538         }
 539         return error;
 540 }
 541
 542 void subsystem_unregister(struct subsystem * s)
 543 {
 544         pr_debug("subsystem %s: unregistering\n",s->kset.kobj.name);
 545         kset_unregister(&s->kset);
 546 }
 547
 548
 549 /**
 550  *      subsystem_create_file - export sysfs attribute file.
 551  *      @s:     subsystem.
 552  *      @a:     subsystem attribute descriptor.
 553  */
 554
 555 int subsys_create_file(struct subsystem * s, struct subsys_attribute * a)
 556 {
 557         int error = 0;
 558         if (subsys_get(s)) {
 559                 error = sysfs_create_file(&s->kset.kobj,&a->attr);
 560                 subsys_put(s);
 561         }
 562         return error;
 563 }
 564
 565
 566 /**
 567  *      subsystem_remove_file - remove sysfs attribute file.
 568  *      @s:     subsystem.
 569  *      @a:     attribute desciptor.
 570  */
 571
 572 void subsys_remove_file(struct subsystem * s, struct subsys_attribute * a)
 573 {
 574         if (subsys_get(s)) {
 575                 sysfs_remove_file(&s->kset.kobj,&a->attr);
 576                 subsys_put(s);
 577         }
 578 }
 579
 580 EXPORT_SYMBOL(kobject_init);
 581 EXPORT_SYMBOL(kobject_register);
 582 EXPORT_SYMBOL(kobject_unregister);
 583 EXPORT_SYMBOL(kobject_get);
 584 EXPORT_SYMBOL(kobject_put);
 585 EXPORT_SYMBOL(kobject_add);
 586 EXPORT_SYMBOL(kobject_del);
 587
 588 EXPORT_SYMBOL(kset_register);
 589 EXPORT_SYMBOL(kset_unregister);
 590 EXPORT_SYMBOL(kset_find_obj);
 591
 592 EXPORT_SYMBOL(subsystem_init);
 593 EXPORT_SYMBOL(subsystem_register);
 594 EXPORT_SYMBOL(subsystem_unregister);
 595 EXPORT_SYMBOL(subsys_create_file);
 596 EXPORT_SYMBOL(subsys_remove_file);