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  * Copyright (c) 2006-2007 Greg Kroah-Hartman <greg@kroah.com>
   6  * Copyright (c) 2006-2007 Novell Inc.
   7  *
   8  * This file is released under the GPLv2.
   9  *
  10  *
  11  * Please see the file Documentation/kobject.txt for critical information
  12  * about using the kobject interface.
  13  */
  14
  15 #include <linux/kobject.h>
  16 #include <linux/string.h>
  17 #include <linux/module.h>
  18 #include <linux/stat.h>
  19 #include <linux/slab.h>
  20
  21 /*
  22  * populate_dir - populate directory with attributes.
  23  * @kobj: object we're working on.
  24  *
  25  * Most subsystems have a set of default attributes that are associated
  26  * with an object that registers with them.  This is a helper called during
  27  * object registration that loops through the default attributes of the
  28  * subsystem and creates attributes files for them in sysfs.
  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                         error = sysfs_create_file(kobj, attr);
  40                         if (error)
  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                         error = populate_dir(kobj);
  54                         if (error)
  55                                 sysfs_remove_dir(kobj);
  56                 }
  57         }
  58         return error;
  59 }
  60
  61 static int get_kobj_path_length(struct kobject *kobj)
  62 {
  63         int length = 1;
  64         struct kobject *parent = kobj;
  65
  66         /* walk up the ancestors until we hit the one pointing to the
  67          * root.
  68          * Add 1 to strlen for leading '/' of each level.
  69          */
  70         do {
  71                 if (kobject_name(parent) == NULL)
  72                         return 0;
  73                 length += strlen(kobject_name(parent)) + 1;
  74                 parent = parent->parent;
  75         } while (parent);
  76         return length;
  77 }
  78
  79 static void fill_kobj_path(struct kobject *kobj, char *path, int length)
  80 {
  81         struct kobject *parent;
  82
  83         --length;
  84         for (parent = kobj; parent; parent = parent->parent) {
  85                 int cur = strlen(kobject_name(parent));
  86                 /* back up enough to print this name with '/' */
  87                 length -= cur;
  88                 strncpy(path + length, kobject_name(parent), cur);
  89                 *(path + --length) = '/';
  90         }
  91
  92         pr_debug("kobject: '%s' (%p): %s: path = '%s'\n", kobject_name(kobj),
  93                  kobj, __func__, path);
  94 }
  95
  96 /**
  97  * kobject_get_path - generate and return the path associated with a given kobj and kset pair.
  98  *
  99  * @kobj:       kobject in question, with which to build the path
 100  * @gfp_mask:   the allocation type used to allocate the path
 101  *
 102  * The result must be freed by the caller with kfree().
 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         if (len == 0)
 111                 return NULL;
 112         path = kzalloc(len, gfp_mask);
 113         if (!path)
 114                 return NULL;
 115         fill_kobj_path(kobj, path, len);
 116
 117         return path;
 118 }
 119 EXPORT_SYMBOL_GPL(kobject_get_path);
 120
 121 /* add the kobject to its kset's list */
 122 static void kobj_kset_join(struct kobject *kobj)
 123 {
 124         if (!kobj->kset)
 125                 return;
 126
 127         kset_get(kobj->kset);
 128         spin_lock(&kobj->kset->list_lock);
 129         list_add_tail(&kobj->entry, &kobj->kset->list);
 130         spin_unlock(&kobj->kset->list_lock);
 131 }
 132
 133 /* remove the kobject from its kset's list */
 134 static void kobj_kset_leave(struct kobject *kobj)
 135 {
 136         if (!kobj->kset)
 137                 return;
 138
 139         spin_lock(&kobj->kset->list_lock);
 140         list_del_init(&kobj->entry);
 141         spin_unlock(&kobj->kset->list_lock);
 142         kset_put(kobj->kset);
 143 }
 144
 145 static void kobject_init_internal(struct kobject *kobj)
 146 {
 147         if (!kobj)
 148                 return;
 149         kref_init(&kobj->kref);
 150         INIT_LIST_HEAD(&kobj->entry);
 151         kobj->state_in_sysfs = 0;
 152         kobj->state_add_uevent_sent = 0;
 153         kobj->state_remove_uevent_sent = 0;
 154         kobj->state_initialized = 1;
 155 }
 156
 157
 158 static int kobject_add_internal(struct kobject *kobj)
 159 {
 160         int error = 0;
 161         struct kobject *parent;
 162
 163         if (!kobj)
 164                 return -ENOENT;
 165
 166         if (!kobj->name || !kobj->name[0]) {
 167                 pr_debug("kobject: (%p): attempted to be registered with empty "
 168                          "name!\n", kobj);
 169                 WARN_ON(1);
 170                 return -EINVAL;
 171         }
 172
 173         parent = kobject_get(kobj->parent);
 174
 175         /* join kset if set, use it as parent if we do not already have one */
 176         if (kobj->kset) {
 177                 if (!parent)
 178                         parent = kobject_get(&kobj->kset->kobj);
 179                 kobj_kset_join(kobj);
 180                 kobj->parent = parent;
 181         }
 182
 183         pr_debug("kobject: '%s' (%p): %s: parent: '%s', set: '%s'\n",
 184                  kobject_name(kobj), kobj, __func__,
 185                  parent ? kobject_name(parent) : "<NULL>",
 186                  kobj->kset ? kobject_name(&kobj->kset->kobj) : "<NULL>");
 187
 188         error = create_dir(kobj);
 189         if (error) {
 190                 kobj_kset_leave(kobj);
 191                 kobject_put(parent);
 192                 kobj->parent = NULL;
 193
 194                 /* be noisy on error issues */
 195                 if (error == -EEXIST)
 196                         printk(KERN_ERR "%s failed for %s with "
 197                                "-EEXIST, don't try to register things with "
 198                                "the same name in the same directory.\n",
 199                                __func__, kobject_name(kobj));
 200                 else
 201                         printk(KERN_ERR "%s failed for %s (%d)\n",
 202                                __func__, kobject_name(kobj), error);
 203                 dump_stack();
 204         } else
 205                 kobj->state_in_sysfs = 1;
 206
 207         return error;
 208 }
 209
 210 /**
 211  * kobject_set_name_vargs - Set the name of an kobject
 212  * @kobj: struct kobject to set the name of
 213  * @fmt: format string used to build the name
 214  * @vargs: vargs to format the string.
 215  */
 216 static int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
 217                                   va_list vargs)
 218 {
 219         /* Free the old name, if necessary. */
 220         kfree(kobj->name);
 221
 222         kobj->name = kvasprintf(GFP_KERNEL, fmt, vargs);
 223         if (!kobj->name)
 224                 return -ENOMEM;
 225
 226         return 0;
 227 }
 228
 229 /**
 230  * kobject_set_name - Set the name of a kobject
 231  * @kobj: struct kobject to set the name of
 232  * @fmt: format string used to build the name
 233  *
 234  * This sets the name of the kobject.  If you have already added the
 235  * kobject to the system, you must call kobject_rename() in order to
 236  * change the name of the kobject.
 237  */
 238 int kobject_set_name(struct kobject *kobj, const char *fmt, ...)
 239 {
 240         va_list vargs;
 241         int retval;
 242
 243         va_start(vargs, fmt);
 244         retval = kobject_set_name_vargs(kobj, fmt, vargs);
 245         va_end(vargs);
 246
 247         return retval;
 248 }
 249 EXPORT_SYMBOL(kobject_set_name);
 250
 251 /**
 252  * kobject_init - initialize a kobject structure
 253  * @kobj: pointer to the kobject to initialize
 254  * @ktype: pointer to the ktype for this kobject.
 255  *
 256  * This function will properly initialize a kobject such that it can then
 257  * be passed to the kobject_add() call.
 258  *
 259  * After this function is called, the kobject MUST be cleaned up by a call
 260  * to kobject_put(), not by a call to kfree directly to ensure that all of
 261  * the memory is cleaned up properly.
 262  */
 263 void kobject_init(struct kobject *kobj, struct kobj_type *ktype)
 264 {
 265         char *err_str;
 266
 267         if (!kobj) {
 268                 err_str = "invalid kobject pointer!";
 269                 goto error;
 270         }
 271         if (!ktype) {
 272                 err_str = "must have a ktype to be initialized properly!\n";
 273                 goto error;
 274         }
 275         if (kobj->state_initialized) {
 276                 /* do not error out as sometimes we can recover */
 277                 printk(KERN_ERR "kobject (%p): tried to init an initialized "
 278                        "object, something is seriously wrong.\n", kobj);
 279                 dump_stack();
 280         }
 281
 282         kobject_init_internal(kobj);
 283         kobj->ktype = ktype;
 284         return;
 285
 286 error:
 287         printk(KERN_ERR "kobject (%p): %s\n", kobj, err_str);
 288         dump_stack();
 289 }
 290 EXPORT_SYMBOL(kobject_init);
 291
 292 static int kobject_add_varg(struct kobject *kobj, struct kobject *parent,
 293                             const char *fmt, va_list vargs)
 294 {
 295         int retval;
 296
 297         retval = kobject_set_name_vargs(kobj, fmt, vargs);
 298         if (retval) {
 299                 printk(KERN_ERR "kobject: can not set name properly!\n");
 300                 return retval;
 301         }
 302         kobj->parent = parent;
 303         return kobject_add_internal(kobj);
 304 }
 305
 306 /**
 307  * kobject_add - the main kobject add function
 308  * @kobj: the kobject to add
 309  * @parent: pointer to the parent of the kobject.
 310  * @fmt: format to name the kobject with.
 311  *
 312  * The kobject name is set and added to the kobject hierarchy in this
 313  * function.
 314  *
 315  * If @parent is set, then the parent of the @kobj will be set to it.
 316  * If @parent is NULL, then the parent of the @kobj will be set to the
 317  * kobject associted with the kset assigned to this kobject.  If no kset
 318  * is assigned to the kobject, then the kobject will be located in the
 319  * root of the sysfs tree.
 320  *
 321  * If this function returns an error, kobject_put() must be called to
 322  * properly clean up the memory associated with the object.
 323  * Under no instance should the kobject that is passed to this function
 324  * be directly freed with a call to kfree(), that can leak memory.
 325  *
 326  * Note, no "add" uevent will be created with this call, the caller should set
 327  * up all of the necessary sysfs files for the object and then call
 328  * kobject_uevent() with the UEVENT_ADD parameter to ensure that
 329  * userspace is properly notified of this kobject's creation.
 330  */
 331 int kobject_add(struct kobject *kobj, struct kobject *parent,
 332                 const char *fmt, ...)
 333 {
 334         va_list args;
 335         int retval;
 336
 337         if (!kobj)
 338                 return -EINVAL;
 339
 340         if (!kobj->state_initialized) {
 341                 printk(KERN_ERR "kobject '%s' (%p): tried to add an "
 342                        "uninitialized object, something is seriously wrong.\n",
 343                        kobject_name(kobj), kobj);
 344                 dump_stack();
 345                 return -EINVAL;
 346         }
 347         va_start(args, fmt);
 348         retval = kobject_add_varg(kobj, parent, fmt, args);
 349         va_end(args);
 350
 351         return retval;
 352 }
 353 EXPORT_SYMBOL(kobject_add);
 354
 355 /**
 356  * kobject_init_and_add - initialize a kobject structure and add it to the kobject hierarchy
 357  * @kobj: pointer to the kobject to initialize
 358  * @ktype: pointer to the ktype for this kobject.
 359  * @parent: pointer to the parent of this kobject.
 360  * @fmt: the name of the kobject.
 361  *
 362  * This function combines the call to kobject_init() and
 363  * kobject_add().  The same type of error handling after a call to
 364  * kobject_add() and kobject lifetime rules are the same here.
 365  */
 366 int kobject_init_and_add(struct kobject *kobj, struct kobj_type *ktype,
 367                          struct kobject *parent, const char *fmt, ...)
 368 {
 369         va_list args;
 370         int retval;
 371
 372         kobject_init(kobj, ktype);
 373
 374         va_start(args, fmt);
 375         retval = kobject_add_varg(kobj, parent, fmt, args);
 376         va_end(args);
 377
 378         return retval;
 379 }
 380 EXPORT_SYMBOL_GPL(kobject_init_and_add);
 381
 382 /**
 383  * kobject_rename - change the name of an object
 384  * @kobj: object in question.
 385  * @new_name: object's new name
 386  */
 387 int kobject_rename(struct kobject *kobj, const char *new_name)
 388 {
 389         int error = 0;
 390         const char *devpath = NULL;
 391         char *devpath_string = NULL;
 392         char *envp[2];
 393
 394         kobj = kobject_get(kobj);
 395         if (!kobj)
 396                 return -EINVAL;
 397         if (!kobj->parent)
 398                 return -EINVAL;
 399
 400         /* see if this name is already in use */
 401         if (kobj->kset) {
 402                 struct kobject *temp_kobj;
 403                 temp_kobj = kset_find_obj(kobj->kset, new_name);
 404                 if (temp_kobj) {
 405                         printk(KERN_WARNING "kobject '%s' cannot be renamed "
 406                                "to '%s' as '%s' is already in existence.\n",
 407                                kobject_name(kobj), new_name, new_name);
 408                         kobject_put(temp_kobj);
 409                         return -EINVAL;
 410                 }
 411         }
 412
 413         devpath = kobject_get_path(kobj, GFP_KERNEL);
 414         if (!devpath) {
 415                 error = -ENOMEM;
 416                 goto out;
 417         }
 418         devpath_string = kmalloc(strlen(devpath) + 15, GFP_KERNEL);
 419         if (!devpath_string) {
 420                 error = -ENOMEM;
 421                 goto out;
 422         }
 423         sprintf(devpath_string, "DEVPATH_OLD=%s", devpath);
 424         envp[0] = devpath_string;
 425         envp[1] = NULL;
 426
 427         error = sysfs_rename_dir(kobj, new_name);
 428
 429         /* This function is mostly/only used for network interface.
 430          * Some hotplug package track interfaces by their name and
 431          * therefore want to know when the name is changed by the user. */
 432         if (!error)
 433                 kobject_uevent_env(kobj, KOBJ_MOVE, envp);
 434
 435 out:
 436         kfree(devpath_string);
 437         kfree(devpath);
 438         kobject_put(kobj);
 439
 440         return error;
 441 }
 442
 443 /**
 444  * kobject_move - move object to another parent
 445  * @kobj: object in question.
 446  * @new_parent: object's new parent (can be NULL)
 447  */
 448 int kobject_move(struct kobject *kobj, struct kobject *new_parent)
 449 {
 450         int error;
 451         struct kobject *old_parent;
 452         const char *devpath = NULL;
 453         char *devpath_string = NULL;
 454         char *envp[2];
 455
 456         kobj = kobject_get(kobj);
 457         if (!kobj)
 458                 return -EINVAL;
 459         new_parent = kobject_get(new_parent);
 460         if (!new_parent) {
 461                 if (kobj->kset)
 462                         new_parent = kobject_get(&kobj->kset->kobj);
 463         }
 464         /* old object path */
 465         devpath = kobject_get_path(kobj, GFP_KERNEL);
 466         if (!devpath) {
 467                 error = -ENOMEM;
 468                 goto out;
 469         }
 470         devpath_string = kmalloc(strlen(devpath) + 15, GFP_KERNEL);
 471         if (!devpath_string) {
 472                 error = -ENOMEM;
 473                 goto out;
 474         }
 475         sprintf(devpath_string, "DEVPATH_OLD=%s", devpath);
 476         envp[0] = devpath_string;
 477         envp[1] = NULL;
 478         error = sysfs_move_dir(kobj, new_parent);
 479         if (error)
 480                 goto out;
 481         old_parent = kobj->parent;
 482         kobj->parent = new_parent;
 483         new_parent = NULL;
 484         kobject_put(old_parent);
 485         kobject_uevent_env(kobj, KOBJ_MOVE, envp);
 486 out:
 487         kobject_put(new_parent);
 488         kobject_put(kobj);
 489         kfree(devpath_string);
 490         kfree(devpath);
 491         return error;
 492 }
 493
 494 /**
 495  * kobject_del - unlink kobject from hierarchy.
 496  * @kobj: object.
 497  */
 498 void kobject_del(struct kobject *kobj)
 499 {
 500         if (!kobj)
 501                 return;
 502
 503         sysfs_remove_dir(kobj);
 504         kobj->state_in_sysfs = 0;
 505         kobj_kset_leave(kobj);
 506         kobject_put(kobj->parent);
 507         kobj->parent = NULL;
 508 }
 509
 510 /**
 511  * kobject_get - increment refcount for object.
 512  * @kobj: object.
 513  */
 514 struct kobject *kobject_get(struct kobject *kobj)
 515 {
 516         if (kobj)
 517                 kref_get(&kobj->kref);
 518         return kobj;
 519 }
 520
 521 /*
 522  * kobject_cleanup - free kobject resources.
 523  * @kobj: object to cleanup
 524  */
 525 static void kobject_cleanup(struct kobject *kobj)
 526 {
 527         struct kobj_type *t = get_ktype(kobj);
 528         const char *name = kobj->name;
 529
 530         pr_debug("kobject: '%s' (%p): %s\n",
 531                  kobject_name(kobj), kobj, __func__);
 532
 533         if (t && !t->release)
 534                 pr_debug("kobject: '%s' (%p): does not have a release() "
 535                          "function, it is broken and must be fixed.\n",
 536                          kobject_name(kobj), kobj);
 537
 538         /* send "remove" if the caller did not do it but sent "add" */
 539         if (kobj->state_add_uevent_sent && !kobj->state_remove_uevent_sent) {
 540                 pr_debug("kobject: '%s' (%p): auto cleanup 'remove' event\n",
 541                          kobject_name(kobj), kobj);
 542                 kobject_uevent(kobj, KOBJ_REMOVE);
 543         }
 544
 545         /* remove from sysfs if the caller did not do it */
 546         if (kobj->state_in_sysfs) {
 547                 pr_debug("kobject: '%s' (%p): auto cleanup kobject_del\n",
 548                          kobject_name(kobj), kobj);
 549                 kobject_del(kobj);
 550         }
 551
 552         if (t && t->release) {
 553                 pr_debug("kobject: '%s' (%p): calling ktype release\n",
 554                          kobject_name(kobj), kobj);
 555                 t->release(kobj);
 556         }
 557
 558         /* free name if we allocated it */
 559         if (name) {
 560                 pr_debug("kobject: '%s': free name\n", name);
 561                 kfree(name);
 562         }
 563 }
 564
 565 static void kobject_release(struct kref *kref)
 566 {
 567         kobject_cleanup(container_of(kref, struct kobject, kref));
 568 }
 569
 570 /**
 571  * kobject_put - decrement refcount for object.
 572  * @kobj: object.
 573  *
 574  * Decrement the refcount, and if 0, call kobject_cleanup().
 575  */
 576 void kobject_put(struct kobject *kobj)
 577 {
 578         if (kobj) {
 579                 if (!kobj->state_initialized) {
 580                         printk(KERN_WARNING "kobject: '%s' (%p): is not "
 581                                "initialized, yet kobject_put() is being "
 582                                "called.\n", kobject_name(kobj), kobj);
 583                         WARN_ON(1);
 584                 }
 585                 kref_put(&kobj->kref, kobject_release);
 586         }
 587 }
 588
 589 static void dynamic_kobj_release(struct kobject *kobj)
 590 {
 591         pr_debug("kobject: (%p): %s\n", kobj, __func__);
 592         kfree(kobj);
 593 }
 594
 595 static struct kobj_type dynamic_kobj_ktype = {
 596         .release        = dynamic_kobj_release,
 597         .sysfs_ops      = &kobj_sysfs_ops,
 598 };
 599
 600 /**
 601  * kobject_create - create a struct kobject dynamically
 602  *
 603  * This function creates a kobject structure dynamically and sets it up
 604  * to be a "dynamic" kobject with a default release function set up.
 605  *
 606  * If the kobject was not able to be created, NULL will be returned.
 607  * The kobject structure returned from here must be cleaned up with a
 608  * call to kobject_put() and not kfree(), as kobject_init() has
 609  * already been called on this structure.
 610  */
 611 struct kobject *kobject_create(void)
 612 {
 613         struct kobject *kobj;
 614
 615         kobj = kzalloc(sizeof(*kobj), GFP_KERNEL);
 616         if (!kobj)
 617                 return NULL;
 618
 619         kobject_init(kobj, &dynamic_kobj_ktype);
 620         return kobj;
 621 }
 622
 623 /**
 624  * kobject_create_and_add - create a struct kobject dynamically and register it with sysfs
 625  *
 626  * @name: the name for the kset
 627  * @parent: the parent kobject of this kobject, if any.
 628  *
 629  * This function creates a kobject structure dynamically and registers it
 630  * with sysfs.  When you are finished with this structure, call
 631  * kobject_put() and the structure will be dynamically freed when
 632  * it is no longer being used.
 633  *
 634  * If the kobject was not able to be created, NULL will be returned.
 635  */
 636 struct kobject *kobject_create_and_add(const char *name, struct kobject *parent)
 637 {
 638         struct kobject *kobj;
 639         int retval;
 640
 641         kobj = kobject_create();
 642         if (!kobj)
 643                 return NULL;
 644
 645         retval = kobject_add(kobj, parent, "%s", name);
 646         if (retval) {
 647                 printk(KERN_WARNING "%s: kobject_add error: %d\n",
 648                        __func__, retval);
 649                 kobject_put(kobj);
 650                 kobj = NULL;
 651         }
 652         return kobj;
 653 }
 654 EXPORT_SYMBOL_GPL(kobject_create_and_add);
 655
 656 /**
 657  * kset_init - initialize a kset for use
 658  * @k: kset
 659  */
 660 void kset_init(struct kset *k)
 661 {
 662         kobject_init_internal(&k->kobj);
 663         INIT_LIST_HEAD(&k->list);
 664         spin_lock_init(&k->list_lock);
 665 }
 666
 667 /* default kobject attribute operations */
 668 static ssize_t kobj_attr_show(struct kobject *kobj, struct attribute *attr,
 669                               char *buf)
 670 {
 671         struct kobj_attribute *kattr;
 672         ssize_t ret = -EIO;
 673
 674         kattr = container_of(attr, struct kobj_attribute, attr);
 675         if (kattr->show)
 676                 ret = kattr->show(kobj, kattr, buf);
 677         return ret;
 678 }
 679
 680 static ssize_t kobj_attr_store(struct kobject *kobj, struct attribute *attr,
 681                                const char *buf, size_t count)
 682 {
 683         struct kobj_attribute *kattr;
 684         ssize_t ret = -EIO;
 685
 686         kattr = container_of(attr, struct kobj_attribute, attr);
 687         if (kattr->store)
 688                 ret = kattr->store(kobj, kattr, buf, count);
 689         return ret;
 690 }
 691
 692 struct sysfs_ops kobj_sysfs_ops = {
 693         .show   = kobj_attr_show,
 694         .store  = kobj_attr_store,
 695 };
 696
 697 /**
 698  * kset_register - initialize and add a kset.
 699  * @k: kset.
 700  */
 701 int kset_register(struct kset *k)
 702 {
 703         int err;
 704
 705         if (!k)
 706                 return -EINVAL;
 707
 708         kset_init(k);
 709         err = kobject_add_internal(&k->kobj);
 710         if (err)
 711                 return err;
 712         kobject_uevent(&k->kobj, KOBJ_ADD);
 713         return 0;
 714 }
 715
 716 /**
 717  * kset_unregister - remove a kset.
 718  * @k: kset.
 719  */
 720 void kset_unregister(struct kset *k)
 721 {
 722         if (!k)
 723                 return;
 724         kobject_put(&k->kobj);
 725 }
 726
 727 /**
 728  * kset_find_obj - search for object in kset.
 729  * @kset: kset we're looking in.
 730  * @name: object's name.
 731  *
 732  * Lock kset via @kset->subsys, and iterate over @kset->list,
 733  * looking for a matching kobject. If matching object is found
 734  * take a reference and return the object.
 735  */
 736 struct kobject *kset_find_obj(struct kset *kset, const char *name)
 737 {
 738         struct kobject *k;
 739         struct kobject *ret = NULL;
 740
 741         spin_lock(&kset->list_lock);
 742         list_for_each_entry(k, &kset->list, entry) {
 743                 if (kobject_name(k) && !strcmp(kobject_name(k), name)) {
 744                         ret = kobject_get(k);
 745                         break;
 746                 }
 747         }
 748         spin_unlock(&kset->list_lock);
 749         return ret;
 750 }
 751
 752 static void kset_release(struct kobject *kobj)
 753 {
 754         struct kset *kset = container_of(kobj, struct kset, kobj);
 755         pr_debug("kobject: '%s' (%p): %s\n",
 756                  kobject_name(kobj), kobj, __func__);
 757         kfree(kset);
 758 }
 759
 760 static struct kobj_type kset_ktype = {
 761         .sysfs_ops      = &kobj_sysfs_ops,
 762         .release = kset_release,
 763 };
 764
 765 /**
 766  * kset_create - create a struct kset dynamically
 767  *
 768  * @name: the name for the kset
 769  * @uevent_ops: a struct kset_uevent_ops for the kset
 770  * @parent_kobj: the parent kobject of this kset, if any.
 771  *
 772  * This function creates a kset structure dynamically.  This structure can
 773  * then be registered with the system and show up in sysfs with a call to
 774  * kset_register().  When you are finished with this structure, if
 775  * kset_register() has been called, call kset_unregister() and the
 776  * structure will be dynamically freed when it is no longer being used.
 777  *
 778  * If the kset was not able to be created, NULL will be returned.
 779  */
 780 static struct kset *kset_create(const char *name,
 781                                 struct kset_uevent_ops *uevent_ops,
 782                                 struct kobject *parent_kobj)
 783 {
 784         struct kset *kset;
 785
 786         kset = kzalloc(sizeof(*kset), GFP_KERNEL);
 787         if (!kset)
 788                 return NULL;
 789         kobject_set_name(&kset->kobj, name);
 790         kset->uevent_ops = uevent_ops;
 791         kset->kobj.parent = parent_kobj;
 792
 793         /*
 794          * The kobject of this kset will have a type of kset_ktype and belong to
 795          * no kset itself.  That way we can properly free it when it is
 796          * finished being used.
 797          */
 798         kset->kobj.ktype = &kset_ktype;
 799         kset->kobj.kset = NULL;
 800
 801         return kset;
 802 }
 803
 804 /**
 805  * kset_create_and_add - create a struct kset dynamically and add it to sysfs
 806  *
 807  * @name: the name for the kset
 808  * @uevent_ops: a struct kset_uevent_ops for the kset
 809  * @parent_kobj: the parent kobject of this kset, if any.
 810  *
 811  * This function creates a kset structure dynamically and registers it
 812  * with sysfs.  When you are finished with this structure, call
 813  * kset_unregister() and the structure will be dynamically freed when it
 814  * is no longer being used.
 815  *
 816  * If the kset was not able to be created, NULL will be returned.
 817  */
 818 struct kset *kset_create_and_add(const char *name,
 819                                  struct kset_uevent_ops *uevent_ops,
 820                                  struct kobject *parent_kobj)
 821 {
 822         struct kset *kset;
 823         int error;
 824
 825         kset = kset_create(name, uevent_ops, parent_kobj);
 826         if (!kset)
 827                 return NULL;
 828         error = kset_register(kset);
 829         if (error) {
 830                 kfree(kset);
 831                 return NULL;
 832         }
 833         return kset;
 834 }
 835 EXPORT_SYMBOL_GPL(kset_create_and_add);
 836
 837 EXPORT_SYMBOL(kobject_get);
 838 EXPORT_SYMBOL(kobject_put);
 839 EXPORT_SYMBOL(kobject_del);
 840
 841 EXPORT_SYMBOL(kset_register);
 842 EXPORT_SYMBOL(kset_unregister);