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         } else {
 188                 kobject_hotplug(kobj, KOBJ_ADD);
 189         }
 190
 191         return error;
 192 }
 193
 194
 195 /**
 196  *      kobject_register - initialize and add an object.
 197  *      @kobj:  object in question.
 198  */
 199
 200 int kobject_register(struct kobject * kobj)
 201 {
 202         int error = 0;
 203         if (kobj) {
 204                 kobject_init(kobj);
 205                 error = kobject_add(kobj);
 206                 if (error) {
 207                         printk("kobject_register failed for %s (%d)\n",
 208                                kobject_name(kobj),error);
 209                         dump_stack();
 210                 }
 211         } else
 212                 error = -EINVAL;
 213         return error;
 214 }
 215
 216
 217 /**
 218  *      kobject_set_name - Set the name of an object
 219  *      @kobj:  object.
 220  *      @name:  name.
 221  *
 222  *      If strlen(name) >= KOBJ_NAME_LEN, then use a dynamically allocated
 223  *      string that @kobj->k_name points to. Otherwise, use the static
 224  *      @kobj->name array.
 225  */
 226
 227 int kobject_set_name(struct kobject * kobj, const char * fmt, ...)
 228 {
 229         int error = 0;
 230         int limit = KOBJ_NAME_LEN;
 231         int need;
 232         va_list args;
 233         char * name;
 234
 235         /*
 236          * First, try the static array
 237          */
 238         va_start(args,fmt);
 239         need = vsnprintf(kobj->name,limit,fmt,args);
 240         va_end(args);
 241         if (need < limit)
 242                 name = kobj->name;
 243         else {
 244                 /*
 245                  * Need more space? Allocate it and try again
 246                  */
 247                 limit = need + 1;
 248                 name = kmalloc(limit,GFP_KERNEL);
 249                 if (!name) {
 250                         error = -ENOMEM;
 251                         goto Done;
 252                 }
 253                 va_start(args,fmt);
 254                 need = vsnprintf(name,limit,fmt,args);
 255                 va_end(args);
 256
 257                 /* Still? Give up. */
 258                 if (need >= limit) {
 259                         kfree(name);
 260                         error = -EFAULT;
 261                         goto Done;
 262                 }
 263         }
 264
 265         /* Free the old name, if necessary. */
 266         if (kobj->k_name && kobj->k_name != kobj->name)
 267                 kfree(kobj->k_name);
 268
 269         /* Now, set the new name */
 270         kobj->k_name = name;
 271  Done:
 272         return error;
 273 }
 274
 275 EXPORT_SYMBOL(kobject_set_name);
 276
 277
 278 /**
 279  *      kobject_rename - change the name of an object
 280  *      @kobj:  object in question.
 281  *      @new_name: object's new name
 282  */
 283
 284 int kobject_rename(struct kobject * kobj, char *new_name)
 285 {
 286         int error = 0;
 287
 288         kobj = kobject_get(kobj);
 289         if (!kobj)
 290                 return -EINVAL;
 291         error = sysfs_rename_dir(kobj, new_name);
 292         kobject_put(kobj);
 293
 294         return error;
 295 }
 296
 297 /**
 298  *      kobject_del - unlink kobject from hierarchy.
 299  *      @kobj:  object.
 300  */
 301
 302 void kobject_del(struct kobject * kobj)
 303 {
 304         kobject_hotplug(kobj, KOBJ_REMOVE);
 305         sysfs_remove_dir(kobj);
 306         unlink(kobj);
 307 }
 308
 309 /**
 310  *      kobject_unregister - remove object from hierarchy and decrement refcount.
 311  *      @kobj:  object going away.
 312  */
 313
 314 void kobject_unregister(struct kobject * kobj)
 315 {
 316         pr_debug("kobject %s: unregistering\n",kobject_name(kobj));
 317         kobject_del(kobj);
 318         kobject_put(kobj);
 319 }
 320
 321 /**
 322  *      kobject_get - increment refcount for object.
 323  *      @kobj:  object.
 324  */
 325
 326 struct kobject * kobject_get(struct kobject * kobj)
 327 {
 328         if (kobj)
 329                 kref_get(&kobj->kref);
 330         return kobj;
 331 }
 332
 333 /**
 334  *      kobject_cleanup - free kobject resources.
 335  *      @kobj:  object.
 336  */
 337
 338 void kobject_cleanup(struct kobject * kobj)
 339 {
 340         struct kobj_type * t = get_ktype(kobj);
 341         struct kset * s = kobj->kset;
 342         struct kobject * parent = kobj->parent;
 343
 344         pr_debug("kobject %s: cleaning up\n",kobject_name(kobj));
 345         if (kobj->k_name != kobj->name)
 346                 kfree(kobj->k_name);
 347         kobj->k_name = NULL;
 348         if (t && t->release)
 349                 t->release(kobj);
 350         if (s)
 351                 kset_put(s);
 352         if (parent)
 353                 kobject_put(parent);
 354 }
 355
 356 static void kobject_release(struct kref *kref)
 357 {
 358         kobject_cleanup(container_of(kref, struct kobject, kref));
 359 }
 360
 361 /**
 362  *      kobject_put - decrement refcount for object.
 363  *      @kobj:  object.
 364  *
 365  *      Decrement the refcount, and if 0, call kobject_cleanup().
 366  */
 367 void kobject_put(struct kobject * kobj)
 368 {
 369         if (kobj)
 370                 kref_put(&kobj->kref, kobject_release);
 371 }
 372
 373
 374 /**
 375  *      kset_init - initialize a kset for use
 376  *      @k:     kset
 377  */
 378
 379 void kset_init(struct kset * k)
 380 {
 381         kobject_init(&k->kobj);
 382         INIT_LIST_HEAD(&k->list);
 383         spin_lock_init(&k->list_lock);
 384 }
 385
 386
 387 /**
 388  *      kset_add - add a kset object to the hierarchy.
 389  *      @k:     kset.
 390  *
 391  *      Simply, this adds the kset's embedded kobject to the
 392  *      hierarchy.
 393  *      We also try to make sure that the kset's embedded kobject
 394  *      has a parent before it is added. We only care if the embedded
 395  *      kobject is not part of a kset itself, since kobject_add()
 396  *      assigns a parent in that case.
 397  *      If that is the case, and the kset has a controlling subsystem,
 398  *      then we set the kset's parent to be said subsystem.
 399  */
 400
 401 int kset_add(struct kset * k)
 402 {
 403         if (!k->kobj.parent && !k->kobj.kset && k->subsys)
 404                 k->kobj.parent = &k->subsys->kset.kobj;
 405
 406         return kobject_add(&k->kobj);
 407 }
 408
 409
 410 /**
 411  *      kset_register - initialize and add a kset.
 412  *      @k:     kset.
 413  */
 414
 415 int kset_register(struct kset * k)
 416 {
 417         kset_init(k);
 418         return kset_add(k);
 419 }
 420
 421
 422 /**
 423  *      kset_unregister - remove a kset.
 424  *      @k:     kset.
 425  */
 426
 427 void kset_unregister(struct kset * k)
 428 {
 429         kobject_unregister(&k->kobj);
 430 }
 431
 432
 433 /**
 434  *      kset_find_obj - search for object in kset.
 435  *      @kset:  kset we're looking in.
 436  *      @name:  object's name.
 437  *
 438  *      Lock kset via @kset->subsys, and iterate over @kset->list,
 439  *      looking for a matching kobject. If matching object is found
 440  *      take a reference and return the object.
 441  */
 442
 443 struct kobject * kset_find_obj(struct kset * kset, const char * name)
 444 {
 445         struct list_head * entry;
 446         struct kobject * ret = NULL;
 447
 448         spin_lock(&kset->list_lock);
 449         list_for_each(entry,&kset->list) {
 450                 struct kobject * k = to_kobj(entry);
 451                 if (kobject_name(k) && !strcmp(kobject_name(k),name)) {
 452                         ret = kobject_get(k);
 453                         break;
 454                 }
 455         }
 456         spin_unlock(&kset->list_lock);
 457         return ret;
 458 }
 459
 460
 461 void subsystem_init(struct subsystem * s)
 462 {
 463         init_rwsem(&s->rwsem);
 464         kset_init(&s->kset);
 465 }
 466
 467 /**
 468  *      subsystem_register - register a subsystem.
 469  *      @s:     the subsystem we're registering.
 470  *
 471  *      Once we register the subsystem, we want to make sure that
 472  *      the kset points back to this subsystem for correct usage of
 473  *      the rwsem.
 474  */
 475
 476 int subsystem_register(struct subsystem * s)
 477 {
 478         int error;
 479
 480         subsystem_init(s);
 481         pr_debug("subsystem %s: registering\n",s->kset.kobj.name);
 482
 483         if (!(error = kset_add(&s->kset))) {
 484                 if (!s->kset.subsys)
 485                         s->kset.subsys = s;
 486         }
 487         return error;
 488 }
 489
 490 void subsystem_unregister(struct subsystem * s)
 491 {
 492         pr_debug("subsystem %s: unregistering\n",s->kset.kobj.name);
 493         kset_unregister(&s->kset);
 494 }
 495
 496
 497 /**
 498  *      subsystem_create_file - export sysfs attribute file.
 499  *      @s:     subsystem.
 500  *      @a:     subsystem attribute descriptor.
 501  */
 502
 503 int subsys_create_file(struct subsystem * s, struct subsys_attribute * a)
 504 {
 505         int error = 0;
 506         if (subsys_get(s)) {
 507                 error = sysfs_create_file(&s->kset.kobj,&a->attr);
 508                 subsys_put(s);
 509         }
 510         return error;
 511 }
 512
 513
 514 /**
 515  *      subsystem_remove_file - remove sysfs attribute file.
 516  *      @s:     subsystem.
 517  *      @a:     attribute desciptor.
 518  */
 519
 520 void subsys_remove_file(struct subsystem * s, struct subsys_attribute * a)
 521 {
 522         if (subsys_get(s)) {
 523                 sysfs_remove_file(&s->kset.kobj,&a->attr);
 524                 subsys_put(s);
 525         }
 526 }
 527
 528 EXPORT_SYMBOL(kobject_init);
 529 EXPORT_SYMBOL(kobject_register);
 530 EXPORT_SYMBOL(kobject_unregister);
 531 EXPORT_SYMBOL(kobject_get);
 532 EXPORT_SYMBOL(kobject_put);
 533 EXPORT_SYMBOL(kobject_add);
 534 EXPORT_SYMBOL(kobject_del);
 535
 536 EXPORT_SYMBOL(kset_register);
 537 EXPORT_SYMBOL(kset_unregister);
 538 EXPORT_SYMBOL(kset_find_obj);
 539
 540 EXPORT_SYMBOL(subsystem_init);
 541 EXPORT_SYMBOL(subsystem_register);
 542 EXPORT_SYMBOL(subsystem_unregister);
 543 EXPORT_SYMBOL(subsys_create_file);
 544 EXPORT_SYMBOL(subsys_remove_file);