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