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
 199         return error;
 200 }
 201
 202
 203 /**
 204  *      kobject_register - initialize and add an object.
 205  *      @kobj:  object in question.
 206  */
 207
 208 int kobject_register(struct kobject * kobj)
 209 {
 210         int error = 0;
 211         if (kobj) {
 212                 kobject_init(kobj);
 213                 error = kobject_add(kobj);
 214                 if (error) {
 215                         printk("kobject_register failed for %s (%d)\n",
 216                                kobject_name(kobj),error);
 217                         dump_stack();
 218                 } else
 219                         kobject_uevent(kobj, KOBJ_ADD);
 220         } else
 221                 error = -EINVAL;
 222         return error;
 223 }
 224
 225
 226 /**
 227  *      kobject_set_name - Set the name of an object
 228  *      @kobj:  object.
 229  *      @fmt:   format string used to build the name
 230  *
 231  *      If strlen(name) >= KOBJ_NAME_LEN, then use a dynamically allocated
 232  *      string that @kobj->k_name points to. Otherwise, use the static
 233  *      @kobj->name array.
 234  */
 235 int kobject_set_name(struct kobject * kobj, const char * fmt, ...)
 236 {
 237         int error = 0;
 238         int limit = KOBJ_NAME_LEN;
 239         int need;
 240         va_list args;
 241         char * name;
 242
 243         /*
 244          * First, try the static array
 245          */
 246         va_start(args,fmt);
 247         need = vsnprintf(kobj->name,limit,fmt,args);
 248         va_end(args);
 249         if (need < limit)
 250                 name = kobj->name;
 251         else {
 252                 /*
 253                  * Need more space? Allocate it and try again
 254                  */
 255                 limit = need + 1;
 256                 name = kmalloc(limit,GFP_KERNEL);
 257                 if (!name) {
 258                         error = -ENOMEM;
 259                         goto Done;
 260                 }
 261                 va_start(args,fmt);
 262                 need = vsnprintf(name,limit,fmt,args);
 263                 va_end(args);
 264
 265                 /* Still? Give up. */
 266                 if (need >= limit) {
 267                         kfree(name);
 268                         error = -EFAULT;
 269                         goto Done;
 270                 }
 271         }
 272
 273         /* Free the old name, if necessary. */
 274         if (kobj->k_name && kobj->k_name != kobj->name)
 275                 kfree(kobj->k_name);
 276
 277         /* Now, set the new name */
 278         kobj->k_name = name;
 279  Done:
 280         return error;
 281 }
 282
 283 EXPORT_SYMBOL(kobject_set_name);
 284
 285
 286 /**
 287  *      kobject_rename - change the name of an object
 288  *      @kobj:  object in question.
 289  *      @new_name: object's new name
 290  */
 291
 292 int kobject_rename(struct kobject * kobj, const char *new_name)
 293 {
 294         int error = 0;
 295
 296         kobj = kobject_get(kobj);
 297         if (!kobj)
 298                 return -EINVAL;
 299         error = sysfs_rename_dir(kobj, new_name);
 300         kobject_put(kobj);
 301
 302         return error;
 303 }
 304
 305 /**
 306  *      kobject_del - unlink kobject from hierarchy.
 307  *      @kobj:  object.
 308  */
 309
 310 void kobject_del(struct kobject * kobj)
 311 {
 312         sysfs_remove_dir(kobj);
 313         unlink(kobj);
 314 }
 315
 316 /**
 317  *      kobject_unregister - remove object from hierarchy and decrement refcount.
 318  *      @kobj:  object going away.
 319  */
 320
 321 void kobject_unregister(struct kobject * kobj)
 322 {
 323         pr_debug("kobject %s: unregistering\n",kobject_name(kobj));
 324         kobject_uevent(kobj, KOBJ_REMOVE);
 325         kobject_del(kobj);
 326         kobject_put(kobj);
 327 }
 328
 329 /**
 330  *      kobject_get - increment refcount for object.
 331  *      @kobj:  object.
 332  */
 333
 334 struct kobject * kobject_get(struct kobject * kobj)
 335 {
 336         if (kobj)
 337                 kref_get(&kobj->kref);
 338         return kobj;
 339 }
 340
 341 /**
 342  *      kobject_cleanup - free kobject resources.
 343  *      @kobj:  object.
 344  */
 345
 346 void kobject_cleanup(struct kobject * kobj)
 347 {
 348         struct kobj_type * t = get_ktype(kobj);
 349         struct kset * s = kobj->kset;
 350         struct kobject * parent = kobj->parent;
 351
 352         pr_debug("kobject %s: cleaning up\n",kobject_name(kobj));
 353         if (kobj->k_name != kobj->name)
 354                 kfree(kobj->k_name);
 355         kobj->k_name = NULL;
 356         if (t && t->release)
 357                 t->release(kobj);
 358         if (s)
 359                 kset_put(s);
 360         if (parent)
 361                 kobject_put(parent);
 362 }
 363
 364 static void kobject_release(struct kref *kref)
 365 {
 366         kobject_cleanup(container_of(kref, struct kobject, kref));
 367 }
 368
 369 /**
 370  *      kobject_put - decrement refcount for object.
 371  *      @kobj:  object.
 372  *
 373  *      Decrement the refcount, and if 0, call kobject_cleanup().
 374  */
 375 void kobject_put(struct kobject * kobj)
 376 {
 377         if (kobj)
 378                 kref_put(&kobj->kref, kobject_release);
 379 }
 380
 381
 382 /**
 383  *      kset_init - initialize a kset for use
 384  *      @k:     kset
 385  */
 386
 387 void kset_init(struct kset * k)
 388 {
 389         kobject_init(&k->kobj);
 390         INIT_LIST_HEAD(&k->list);
 391         spin_lock_init(&k->list_lock);
 392 }
 393
 394
 395 /**
 396  *      kset_add - add a kset object to the hierarchy.
 397  *      @k:     kset.
 398  *
 399  *      Simply, this adds the kset's embedded kobject to the
 400  *      hierarchy.
 401  *      We also try to make sure that the kset's embedded kobject
 402  *      has a parent before it is added. We only care if the embedded
 403  *      kobject is not part of a kset itself, since kobject_add()
 404  *      assigns a parent in that case.
 405  *      If that is the case, and the kset has a controlling subsystem,
 406  *      then we set the kset's parent to be said subsystem.
 407  */
 408
 409 int kset_add(struct kset * k)
 410 {
 411         if (!k->kobj.parent && !k->kobj.kset && k->subsys)
 412                 k->kobj.parent = &k->subsys->kset.kobj;
 413
 414         return kobject_add(&k->kobj);
 415 }
 416
 417
 418 /**
 419  *      kset_register - initialize and add a kset.
 420  *      @k:     kset.
 421  */
 422
 423 int kset_register(struct kset * k)
 424 {
 425         kset_init(k);
 426         return kset_add(k);
 427 }
 428
 429
 430 /**
 431  *      kset_unregister - remove a kset.
 432  *      @k:     kset.
 433  */
 434
 435 void kset_unregister(struct kset * k)
 436 {
 437         kobject_unregister(&k->kobj);
 438 }
 439
 440
 441 /**
 442  *      kset_find_obj - search for object in kset.
 443  *      @kset:  kset we're looking in.
 444  *      @name:  object's name.
 445  *
 446  *      Lock kset via @kset->subsys, and iterate over @kset->list,
 447  *      looking for a matching kobject. If matching object is found
 448  *      take a reference and return the object.
 449  */
 450
 451 struct kobject * kset_find_obj(struct kset * kset, const char * name)
 452 {
 453         struct list_head * entry;
 454         struct kobject * ret = NULL;
 455
 456         spin_lock(&kset->list_lock);
 457         list_for_each(entry,&kset->list) {
 458                 struct kobject * k = to_kobj(entry);
 459                 if (kobject_name(k) && !strcmp(kobject_name(k),name)) {
 460                         ret = kobject_get(k);
 461                         break;
 462                 }
 463         }
 464         spin_unlock(&kset->list_lock);
 465         return ret;
 466 }
 467
 468
 469 void subsystem_init(struct subsystem * s)
 470 {
 471         init_rwsem(&s->rwsem);
 472         kset_init(&s->kset);
 473 }
 474
 475 /**
 476  *      subsystem_register - register a subsystem.
 477  *      @s:     the subsystem we're registering.
 478  *
 479  *      Once we register the subsystem, we want to make sure that
 480  *      the kset points back to this subsystem for correct usage of
 481  *      the rwsem.
 482  */
 483
 484 int subsystem_register(struct subsystem * s)
 485 {
 486         int error;
 487
 488         subsystem_init(s);
 489         pr_debug("subsystem %s: registering\n",s->kset.kobj.name);
 490
 491         if (!(error = kset_add(&s->kset))) {
 492                 if (!s->kset.subsys)
 493                         s->kset.subsys = s;
 494         }
 495         return error;
 496 }
 497
 498 void subsystem_unregister(struct subsystem * s)
 499 {
 500         pr_debug("subsystem %s: unregistering\n",s->kset.kobj.name);
 501         kset_unregister(&s->kset);
 502 }
 503
 504
 505 /**
 506  *      subsystem_create_file - export sysfs attribute file.
 507  *      @s:     subsystem.
 508  *      @a:     subsystem attribute descriptor.
 509  */
 510
 511 int subsys_create_file(struct subsystem * s, struct subsys_attribute * a)
 512 {
 513         int error = 0;
 514         if (subsys_get(s)) {
 515                 error = sysfs_create_file(&s->kset.kobj,&a->attr);
 516                 subsys_put(s);
 517         }
 518         return error;
 519 }
 520
 521
 522 /**
 523  *      subsystem_remove_file - remove sysfs attribute file.
 524  *      @s:     subsystem.
 525  *      @a:     attribute desciptor.
 526  */
 527
 528 void subsys_remove_file(struct subsystem * s, struct subsys_attribute * a)
 529 {
 530         if (subsys_get(s)) {
 531                 sysfs_remove_file(&s->kset.kobj,&a->attr);
 532                 subsys_put(s);
 533         }
 534 }
 535
 536 EXPORT_SYMBOL(kobject_init);
 537 EXPORT_SYMBOL(kobject_register);
 538 EXPORT_SYMBOL(kobject_unregister);
 539 EXPORT_SYMBOL(kobject_get);
 540 EXPORT_SYMBOL(kobject_put);
 541 EXPORT_SYMBOL(kobject_add);
 542 EXPORT_SYMBOL(kobject_del);
 543
 544 EXPORT_SYMBOL(kset_register);
 545 EXPORT_SYMBOL(kset_unregister);
 546 EXPORT_SYMBOL(kset_find_obj);
 547
 548 EXPORT_SYMBOL(subsystem_init);
 549 EXPORT_SYMBOL(subsystem_register);
 550 EXPORT_SYMBOL(subsystem_unregister);
 551 EXPORT_SYMBOL(subsys_create_file);
 552 EXPORT_SYMBOL(subsys_remove_file);