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