xref: /openbmc/linux/lib/kobject.c (revision 4800cd83)
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 		WARN(1, "kobject: (%p): attempted to be registered with empty "
168 			 "name!\n", kobj);
169 		return -EINVAL;
170 	}
171 
172 	parent = kobject_get(kobj->parent);
173 
174 	/* join kset if set, use it as parent if we do not already have one */
175 	if (kobj->kset) {
176 		if (!parent)
177 			parent = kobject_get(&kobj->kset->kobj);
178 		kobj_kset_join(kobj);
179 		kobj->parent = parent;
180 	}
181 
182 	pr_debug("kobject: '%s' (%p): %s: parent: '%s', set: '%s'\n",
183 		 kobject_name(kobj), kobj, __func__,
184 		 parent ? kobject_name(parent) : "<NULL>",
185 		 kobj->kset ? kobject_name(&kobj->kset->kobj) : "<NULL>");
186 
187 	error = create_dir(kobj);
188 	if (error) {
189 		kobj_kset_leave(kobj);
190 		kobject_put(parent);
191 		kobj->parent = NULL;
192 
193 		/* be noisy on error issues */
194 		if (error == -EEXIST)
195 			printk(KERN_ERR "%s failed for %s with "
196 			       "-EEXIST, don't try to register things with "
197 			       "the same name in the same directory.\n",
198 			       __func__, kobject_name(kobj));
199 		else
200 			printk(KERN_ERR "%s failed for %s (%d)\n",
201 			       __func__, kobject_name(kobj), error);
202 		dump_stack();
203 	} else
204 		kobj->state_in_sysfs = 1;
205 
206 	return error;
207 }
208 
209 /**
210  * kobject_set_name_vargs - Set the name of an kobject
211  * @kobj: struct kobject to set the name of
212  * @fmt: format string used to build the name
213  * @vargs: vargs to format the string.
214  */
215 int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
216 				  va_list vargs)
217 {
218 	const char *old_name = kobj->name;
219 	char *s;
220 
221 	if (kobj->name && !fmt)
222 		return 0;
223 
224 	kobj->name = kvasprintf(GFP_KERNEL, fmt, vargs);
225 	if (!kobj->name)
226 		return -ENOMEM;
227 
228 	/* ewww... some of these buggers have '/' in the name ... */
229 	while ((s = strchr(kobj->name, '/')))
230 		s[0] = '!';
231 
232 	kfree(old_name);
233 	return 0;
234 }
235 
236 /**
237  * kobject_set_name - Set the name of a kobject
238  * @kobj: struct kobject to set the name of
239  * @fmt: format string used to build the name
240  *
241  * This sets the name of the kobject.  If you have already added the
242  * kobject to the system, you must call kobject_rename() in order to
243  * change the name of the kobject.
244  */
245 int kobject_set_name(struct kobject *kobj, const char *fmt, ...)
246 {
247 	va_list vargs;
248 	int retval;
249 
250 	va_start(vargs, fmt);
251 	retval = kobject_set_name_vargs(kobj, fmt, vargs);
252 	va_end(vargs);
253 
254 	return retval;
255 }
256 EXPORT_SYMBOL(kobject_set_name);
257 
258 /**
259  * kobject_init - initialize a kobject structure
260  * @kobj: pointer to the kobject to initialize
261  * @ktype: pointer to the ktype for this kobject.
262  *
263  * This function will properly initialize a kobject such that it can then
264  * be passed to the kobject_add() call.
265  *
266  * After this function is called, the kobject MUST be cleaned up by a call
267  * to kobject_put(), not by a call to kfree directly to ensure that all of
268  * the memory is cleaned up properly.
269  */
270 void kobject_init(struct kobject *kobj, struct kobj_type *ktype)
271 {
272 	char *err_str;
273 
274 	if (!kobj) {
275 		err_str = "invalid kobject pointer!";
276 		goto error;
277 	}
278 	if (!ktype) {
279 		err_str = "must have a ktype to be initialized properly!\n";
280 		goto error;
281 	}
282 	if (kobj->state_initialized) {
283 		/* do not error out as sometimes we can recover */
284 		printk(KERN_ERR "kobject (%p): tried to init an initialized "
285 		       "object, something is seriously wrong.\n", kobj);
286 		dump_stack();
287 	}
288 
289 	kobject_init_internal(kobj);
290 	kobj->ktype = ktype;
291 	return;
292 
293 error:
294 	printk(KERN_ERR "kobject (%p): %s\n", kobj, err_str);
295 	dump_stack();
296 }
297 EXPORT_SYMBOL(kobject_init);
298 
299 static int kobject_add_varg(struct kobject *kobj, struct kobject *parent,
300 			    const char *fmt, va_list vargs)
301 {
302 	int retval;
303 
304 	retval = kobject_set_name_vargs(kobj, fmt, vargs);
305 	if (retval) {
306 		printk(KERN_ERR "kobject: can not set name properly!\n");
307 		return retval;
308 	}
309 	kobj->parent = parent;
310 	return kobject_add_internal(kobj);
311 }
312 
313 /**
314  * kobject_add - the main kobject add function
315  * @kobj: the kobject to add
316  * @parent: pointer to the parent of the kobject.
317  * @fmt: format to name the kobject with.
318  *
319  * The kobject name is set and added to the kobject hierarchy in this
320  * function.
321  *
322  * If @parent is set, then the parent of the @kobj will be set to it.
323  * If @parent is NULL, then the parent of the @kobj will be set to the
324  * kobject associted with the kset assigned to this kobject.  If no kset
325  * is assigned to the kobject, then the kobject will be located in the
326  * root of the sysfs tree.
327  *
328  * If this function returns an error, kobject_put() must be called to
329  * properly clean up the memory associated with the object.
330  * Under no instance should the kobject that is passed to this function
331  * be directly freed with a call to kfree(), that can leak memory.
332  *
333  * Note, no "add" uevent will be created with this call, the caller should set
334  * up all of the necessary sysfs files for the object and then call
335  * kobject_uevent() with the UEVENT_ADD parameter to ensure that
336  * userspace is properly notified of this kobject's creation.
337  */
338 int kobject_add(struct kobject *kobj, struct kobject *parent,
339 		const char *fmt, ...)
340 {
341 	va_list args;
342 	int retval;
343 
344 	if (!kobj)
345 		return -EINVAL;
346 
347 	if (!kobj->state_initialized) {
348 		printk(KERN_ERR "kobject '%s' (%p): tried to add an "
349 		       "uninitialized object, something is seriously wrong.\n",
350 		       kobject_name(kobj), kobj);
351 		dump_stack();
352 		return -EINVAL;
353 	}
354 	va_start(args, fmt);
355 	retval = kobject_add_varg(kobj, parent, fmt, args);
356 	va_end(args);
357 
358 	return retval;
359 }
360 EXPORT_SYMBOL(kobject_add);
361 
362 /**
363  * kobject_init_and_add - initialize a kobject structure and add it to the kobject hierarchy
364  * @kobj: pointer to the kobject to initialize
365  * @ktype: pointer to the ktype for this kobject.
366  * @parent: pointer to the parent of this kobject.
367  * @fmt: the name of the kobject.
368  *
369  * This function combines the call to kobject_init() and
370  * kobject_add().  The same type of error handling after a call to
371  * kobject_add() and kobject lifetime rules are the same here.
372  */
373 int kobject_init_and_add(struct kobject *kobj, struct kobj_type *ktype,
374 			 struct kobject *parent, const char *fmt, ...)
375 {
376 	va_list args;
377 	int retval;
378 
379 	kobject_init(kobj, ktype);
380 
381 	va_start(args, fmt);
382 	retval = kobject_add_varg(kobj, parent, fmt, args);
383 	va_end(args);
384 
385 	return retval;
386 }
387 EXPORT_SYMBOL_GPL(kobject_init_and_add);
388 
389 /**
390  * kobject_rename - change the name of an object
391  * @kobj: object in question.
392  * @new_name: object's new name
393  *
394  * It is the responsibility of the caller to provide mutual
395  * exclusion between two different calls of kobject_rename
396  * on the same kobject and to ensure that new_name is valid and
397  * won't conflict with other kobjects.
398  */
399 int kobject_rename(struct kobject *kobj, const char *new_name)
400 {
401 	int error = 0;
402 	const char *devpath = NULL;
403 	const char *dup_name = NULL, *name;
404 	char *devpath_string = NULL;
405 	char *envp[2];
406 
407 	kobj = kobject_get(kobj);
408 	if (!kobj)
409 		return -EINVAL;
410 	if (!kobj->parent)
411 		return -EINVAL;
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 	name = dup_name = kstrdup(new_name, GFP_KERNEL);
428 	if (!name) {
429 		error = -ENOMEM;
430 		goto out;
431 	}
432 
433 	error = sysfs_rename_dir(kobj, new_name);
434 	if (error)
435 		goto out;
436 
437 	/* Install the new kobject name */
438 	dup_name = kobj->name;
439 	kobj->name = name;
440 
441 	/* This function is mostly/only used for network interface.
442 	 * Some hotplug package track interfaces by their name and
443 	 * therefore want to know when the name is changed by the user. */
444 	kobject_uevent_env(kobj, KOBJ_MOVE, envp);
445 
446 out:
447 	kfree(dup_name);
448 	kfree(devpath_string);
449 	kfree(devpath);
450 	kobject_put(kobj);
451 
452 	return error;
453 }
454 EXPORT_SYMBOL_GPL(kobject_rename);
455 
456 /**
457  * kobject_move - move object to another parent
458  * @kobj: object in question.
459  * @new_parent: object's new parent (can be NULL)
460  */
461 int kobject_move(struct kobject *kobj, struct kobject *new_parent)
462 {
463 	int error;
464 	struct kobject *old_parent;
465 	const char *devpath = NULL;
466 	char *devpath_string = NULL;
467 	char *envp[2];
468 
469 	kobj = kobject_get(kobj);
470 	if (!kobj)
471 		return -EINVAL;
472 	new_parent = kobject_get(new_parent);
473 	if (!new_parent) {
474 		if (kobj->kset)
475 			new_parent = kobject_get(&kobj->kset->kobj);
476 	}
477 	/* old object path */
478 	devpath = kobject_get_path(kobj, GFP_KERNEL);
479 	if (!devpath) {
480 		error = -ENOMEM;
481 		goto out;
482 	}
483 	devpath_string = kmalloc(strlen(devpath) + 15, GFP_KERNEL);
484 	if (!devpath_string) {
485 		error = -ENOMEM;
486 		goto out;
487 	}
488 	sprintf(devpath_string, "DEVPATH_OLD=%s", devpath);
489 	envp[0] = devpath_string;
490 	envp[1] = NULL;
491 	error = sysfs_move_dir(kobj, new_parent);
492 	if (error)
493 		goto out;
494 	old_parent = kobj->parent;
495 	kobj->parent = new_parent;
496 	new_parent = NULL;
497 	kobject_put(old_parent);
498 	kobject_uevent_env(kobj, KOBJ_MOVE, envp);
499 out:
500 	kobject_put(new_parent);
501 	kobject_put(kobj);
502 	kfree(devpath_string);
503 	kfree(devpath);
504 	return error;
505 }
506 
507 /**
508  * kobject_del - unlink kobject from hierarchy.
509  * @kobj: object.
510  */
511 void kobject_del(struct kobject *kobj)
512 {
513 	if (!kobj)
514 		return;
515 
516 	sysfs_remove_dir(kobj);
517 	kobj->state_in_sysfs = 0;
518 	kobj_kset_leave(kobj);
519 	kobject_put(kobj->parent);
520 	kobj->parent = NULL;
521 }
522 
523 /**
524  * kobject_get - increment refcount for object.
525  * @kobj: object.
526  */
527 struct kobject *kobject_get(struct kobject *kobj)
528 {
529 	if (kobj)
530 		kref_get(&kobj->kref);
531 	return kobj;
532 }
533 
534 /*
535  * kobject_cleanup - free kobject resources.
536  * @kobj: object to cleanup
537  */
538 static void kobject_cleanup(struct kobject *kobj)
539 {
540 	struct kobj_type *t = get_ktype(kobj);
541 	const char *name = kobj->name;
542 
543 	pr_debug("kobject: '%s' (%p): %s\n",
544 		 kobject_name(kobj), kobj, __func__);
545 
546 	if (t && !t->release)
547 		pr_debug("kobject: '%s' (%p): does not have a release() "
548 			 "function, it is broken and must be fixed.\n",
549 			 kobject_name(kobj), kobj);
550 
551 	/* send "remove" if the caller did not do it but sent "add" */
552 	if (kobj->state_add_uevent_sent && !kobj->state_remove_uevent_sent) {
553 		pr_debug("kobject: '%s' (%p): auto cleanup 'remove' event\n",
554 			 kobject_name(kobj), kobj);
555 		kobject_uevent(kobj, KOBJ_REMOVE);
556 	}
557 
558 	/* remove from sysfs if the caller did not do it */
559 	if (kobj->state_in_sysfs) {
560 		pr_debug("kobject: '%s' (%p): auto cleanup kobject_del\n",
561 			 kobject_name(kobj), kobj);
562 		kobject_del(kobj);
563 	}
564 
565 	if (t && t->release) {
566 		pr_debug("kobject: '%s' (%p): calling ktype release\n",
567 			 kobject_name(kobj), kobj);
568 		t->release(kobj);
569 	}
570 
571 	/* free name if we allocated it */
572 	if (name) {
573 		pr_debug("kobject: '%s': free name\n", name);
574 		kfree(name);
575 	}
576 }
577 
578 static void kobject_release(struct kref *kref)
579 {
580 	kobject_cleanup(container_of(kref, struct kobject, kref));
581 }
582 
583 /**
584  * kobject_put - decrement refcount for object.
585  * @kobj: object.
586  *
587  * Decrement the refcount, and if 0, call kobject_cleanup().
588  */
589 void kobject_put(struct kobject *kobj)
590 {
591 	if (kobj) {
592 		if (!kobj->state_initialized)
593 			WARN(1, KERN_WARNING "kobject: '%s' (%p): is not "
594 			       "initialized, yet kobject_put() is being "
595 			       "called.\n", kobject_name(kobj), kobj);
596 		kref_put(&kobj->kref, kobject_release);
597 	}
598 }
599 
600 static void dynamic_kobj_release(struct kobject *kobj)
601 {
602 	pr_debug("kobject: (%p): %s\n", kobj, __func__);
603 	kfree(kobj);
604 }
605 
606 static struct kobj_type dynamic_kobj_ktype = {
607 	.release	= dynamic_kobj_release,
608 	.sysfs_ops	= &kobj_sysfs_ops,
609 };
610 
611 /**
612  * kobject_create - create a struct kobject dynamically
613  *
614  * This function creates a kobject structure dynamically and sets it up
615  * to be a "dynamic" kobject with a default release function set up.
616  *
617  * If the kobject was not able to be created, NULL will be returned.
618  * The kobject structure returned from here must be cleaned up with a
619  * call to kobject_put() and not kfree(), as kobject_init() has
620  * already been called on this structure.
621  */
622 struct kobject *kobject_create(void)
623 {
624 	struct kobject *kobj;
625 
626 	kobj = kzalloc(sizeof(*kobj), GFP_KERNEL);
627 	if (!kobj)
628 		return NULL;
629 
630 	kobject_init(kobj, &dynamic_kobj_ktype);
631 	return kobj;
632 }
633 
634 /**
635  * kobject_create_and_add - create a struct kobject dynamically and register it with sysfs
636  *
637  * @name: the name for the kset
638  * @parent: the parent kobject of this kobject, if any.
639  *
640  * This function creates a kobject structure dynamically and registers it
641  * with sysfs.  When you are finished with this structure, call
642  * kobject_put() and the structure will be dynamically freed when
643  * it is no longer being used.
644  *
645  * If the kobject was not able to be created, NULL will be returned.
646  */
647 struct kobject *kobject_create_and_add(const char *name, struct kobject *parent)
648 {
649 	struct kobject *kobj;
650 	int retval;
651 
652 	kobj = kobject_create();
653 	if (!kobj)
654 		return NULL;
655 
656 	retval = kobject_add(kobj, parent, "%s", name);
657 	if (retval) {
658 		printk(KERN_WARNING "%s: kobject_add error: %d\n",
659 		       __func__, retval);
660 		kobject_put(kobj);
661 		kobj = NULL;
662 	}
663 	return kobj;
664 }
665 EXPORT_SYMBOL_GPL(kobject_create_and_add);
666 
667 /**
668  * kset_init - initialize a kset for use
669  * @k: kset
670  */
671 void kset_init(struct kset *k)
672 {
673 	kobject_init_internal(&k->kobj);
674 	INIT_LIST_HEAD(&k->list);
675 	spin_lock_init(&k->list_lock);
676 }
677 
678 /* default kobject attribute operations */
679 static ssize_t kobj_attr_show(struct kobject *kobj, struct attribute *attr,
680 			      char *buf)
681 {
682 	struct kobj_attribute *kattr;
683 	ssize_t ret = -EIO;
684 
685 	kattr = container_of(attr, struct kobj_attribute, attr);
686 	if (kattr->show)
687 		ret = kattr->show(kobj, kattr, buf);
688 	return ret;
689 }
690 
691 static ssize_t kobj_attr_store(struct kobject *kobj, struct attribute *attr,
692 			       const char *buf, size_t count)
693 {
694 	struct kobj_attribute *kattr;
695 	ssize_t ret = -EIO;
696 
697 	kattr = container_of(attr, struct kobj_attribute, attr);
698 	if (kattr->store)
699 		ret = kattr->store(kobj, kattr, buf, count);
700 	return ret;
701 }
702 
703 const struct sysfs_ops kobj_sysfs_ops = {
704 	.show	= kobj_attr_show,
705 	.store	= kobj_attr_store,
706 };
707 
708 /**
709  * kset_register - initialize and add a kset.
710  * @k: kset.
711  */
712 int kset_register(struct kset *k)
713 {
714 	int err;
715 
716 	if (!k)
717 		return -EINVAL;
718 
719 	kset_init(k);
720 	err = kobject_add_internal(&k->kobj);
721 	if (err)
722 		return err;
723 	kobject_uevent(&k->kobj, KOBJ_ADD);
724 	return 0;
725 }
726 
727 /**
728  * kset_unregister - remove a kset.
729  * @k: kset.
730  */
731 void kset_unregister(struct kset *k)
732 {
733 	if (!k)
734 		return;
735 	kobject_put(&k->kobj);
736 }
737 
738 /**
739  * kset_find_obj - search for object in kset.
740  * @kset: kset we're looking in.
741  * @name: object's name.
742  *
743  * Lock kset via @kset->subsys, and iterate over @kset->list,
744  * looking for a matching kobject. If matching object is found
745  * take a reference and return the object.
746  */
747 struct kobject *kset_find_obj(struct kset *kset, const char *name)
748 {
749 	return kset_find_obj_hinted(kset, name, NULL);
750 }
751 
752 /**
753  * kset_find_obj_hinted - search for object in kset given a predecessor hint.
754  * @kset: kset we're looking in.
755  * @name: object's name.
756  * @hint: hint to possible object's predecessor.
757  *
758  * Check the hint's next object and if it is a match return it directly,
759  * otherwise, fall back to the behavior of kset_find_obj().  Either way
760  * a reference for the returned object is held and the reference on the
761  * hinted object is released.
762  */
763 struct kobject *kset_find_obj_hinted(struct kset *kset, const char *name,
764 				     struct kobject *hint)
765 {
766 	struct kobject *k;
767 	struct kobject *ret = NULL;
768 
769 	spin_lock(&kset->list_lock);
770 
771 	if (!hint)
772 		goto slow_search;
773 
774 	/* end of list detection */
775 	if (hint->entry.next == kset->list.next)
776 		goto slow_search;
777 
778 	k = container_of(hint->entry.next, struct kobject, entry);
779 	if (!kobject_name(k) || strcmp(kobject_name(k), name))
780 		goto slow_search;
781 
782 	ret = kobject_get(k);
783 	goto unlock_exit;
784 
785 slow_search:
786 	list_for_each_entry(k, &kset->list, entry) {
787 		if (kobject_name(k) && !strcmp(kobject_name(k), name)) {
788 			ret = kobject_get(k);
789 			break;
790 		}
791 	}
792 
793 unlock_exit:
794 	spin_unlock(&kset->list_lock);
795 
796 	if (hint)
797 		kobject_put(hint);
798 
799 	return ret;
800 }
801 
802 static void kset_release(struct kobject *kobj)
803 {
804 	struct kset *kset = container_of(kobj, struct kset, kobj);
805 	pr_debug("kobject: '%s' (%p): %s\n",
806 		 kobject_name(kobj), kobj, __func__);
807 	kfree(kset);
808 }
809 
810 static struct kobj_type kset_ktype = {
811 	.sysfs_ops	= &kobj_sysfs_ops,
812 	.release = kset_release,
813 };
814 
815 /**
816  * kset_create - create a struct kset dynamically
817  *
818  * @name: the name for the kset
819  * @uevent_ops: a struct kset_uevent_ops for the kset
820  * @parent_kobj: the parent kobject of this kset, if any.
821  *
822  * This function creates a kset structure dynamically.  This structure can
823  * then be registered with the system and show up in sysfs with a call to
824  * kset_register().  When you are finished with this structure, if
825  * kset_register() has been called, call kset_unregister() and the
826  * structure will be dynamically freed when it is no longer being used.
827  *
828  * If the kset was not able to be created, NULL will be returned.
829  */
830 static struct kset *kset_create(const char *name,
831 				const struct kset_uevent_ops *uevent_ops,
832 				struct kobject *parent_kobj)
833 {
834 	struct kset *kset;
835 	int retval;
836 
837 	kset = kzalloc(sizeof(*kset), GFP_KERNEL);
838 	if (!kset)
839 		return NULL;
840 	retval = kobject_set_name(&kset->kobj, name);
841 	if (retval) {
842 		kfree(kset);
843 		return NULL;
844 	}
845 	kset->uevent_ops = uevent_ops;
846 	kset->kobj.parent = parent_kobj;
847 
848 	/*
849 	 * The kobject of this kset will have a type of kset_ktype and belong to
850 	 * no kset itself.  That way we can properly free it when it is
851 	 * finished being used.
852 	 */
853 	kset->kobj.ktype = &kset_ktype;
854 	kset->kobj.kset = NULL;
855 
856 	return kset;
857 }
858 
859 /**
860  * kset_create_and_add - create a struct kset dynamically and add it to sysfs
861  *
862  * @name: the name for the kset
863  * @uevent_ops: a struct kset_uevent_ops for the kset
864  * @parent_kobj: the parent kobject of this kset, if any.
865  *
866  * This function creates a kset structure dynamically and registers it
867  * with sysfs.  When you are finished with this structure, call
868  * kset_unregister() and the structure will be dynamically freed when it
869  * is no longer being used.
870  *
871  * If the kset was not able to be created, NULL will be returned.
872  */
873 struct kset *kset_create_and_add(const char *name,
874 				 const struct kset_uevent_ops *uevent_ops,
875 				 struct kobject *parent_kobj)
876 {
877 	struct kset *kset;
878 	int error;
879 
880 	kset = kset_create(name, uevent_ops, parent_kobj);
881 	if (!kset)
882 		return NULL;
883 	error = kset_register(kset);
884 	if (error) {
885 		kfree(kset);
886 		return NULL;
887 	}
888 	return kset;
889 }
890 EXPORT_SYMBOL_GPL(kset_create_and_add);
891 
892 
893 static DEFINE_SPINLOCK(kobj_ns_type_lock);
894 static const struct kobj_ns_type_operations *kobj_ns_ops_tbl[KOBJ_NS_TYPES];
895 
896 int kobj_ns_type_register(const struct kobj_ns_type_operations *ops)
897 {
898 	enum kobj_ns_type type = ops->type;
899 	int error;
900 
901 	spin_lock(&kobj_ns_type_lock);
902 
903 	error = -EINVAL;
904 	if (type >= KOBJ_NS_TYPES)
905 		goto out;
906 
907 	error = -EINVAL;
908 	if (type <= KOBJ_NS_TYPE_NONE)
909 		goto out;
910 
911 	error = -EBUSY;
912 	if (kobj_ns_ops_tbl[type])
913 		goto out;
914 
915 	error = 0;
916 	kobj_ns_ops_tbl[type] = ops;
917 
918 out:
919 	spin_unlock(&kobj_ns_type_lock);
920 	return error;
921 }
922 
923 int kobj_ns_type_registered(enum kobj_ns_type type)
924 {
925 	int registered = 0;
926 
927 	spin_lock(&kobj_ns_type_lock);
928 	if ((type > KOBJ_NS_TYPE_NONE) && (type < KOBJ_NS_TYPES))
929 		registered = kobj_ns_ops_tbl[type] != NULL;
930 	spin_unlock(&kobj_ns_type_lock);
931 
932 	return registered;
933 }
934 
935 const struct kobj_ns_type_operations *kobj_child_ns_ops(struct kobject *parent)
936 {
937 	const struct kobj_ns_type_operations *ops = NULL;
938 
939 	if (parent && parent->ktype->child_ns_type)
940 		ops = parent->ktype->child_ns_type(parent);
941 
942 	return ops;
943 }
944 
945 const struct kobj_ns_type_operations *kobj_ns_ops(struct kobject *kobj)
946 {
947 	return kobj_child_ns_ops(kobj->parent);
948 }
949 
950 
951 const void *kobj_ns_current(enum kobj_ns_type type)
952 {
953 	const void *ns = NULL;
954 
955 	spin_lock(&kobj_ns_type_lock);
956 	if ((type > KOBJ_NS_TYPE_NONE) && (type < KOBJ_NS_TYPES) &&
957 	    kobj_ns_ops_tbl[type])
958 		ns = kobj_ns_ops_tbl[type]->current_ns();
959 	spin_unlock(&kobj_ns_type_lock);
960 
961 	return ns;
962 }
963 
964 const void *kobj_ns_netlink(enum kobj_ns_type type, struct sock *sk)
965 {
966 	const void *ns = NULL;
967 
968 	spin_lock(&kobj_ns_type_lock);
969 	if ((type > KOBJ_NS_TYPE_NONE) && (type < KOBJ_NS_TYPES) &&
970 	    kobj_ns_ops_tbl[type])
971 		ns = kobj_ns_ops_tbl[type]->netlink_ns(sk);
972 	spin_unlock(&kobj_ns_type_lock);
973 
974 	return ns;
975 }
976 
977 const void *kobj_ns_initial(enum kobj_ns_type type)
978 {
979 	const void *ns = NULL;
980 
981 	spin_lock(&kobj_ns_type_lock);
982 	if ((type > KOBJ_NS_TYPE_NONE) && (type < KOBJ_NS_TYPES) &&
983 	    kobj_ns_ops_tbl[type])
984 		ns = kobj_ns_ops_tbl[type]->initial_ns();
985 	spin_unlock(&kobj_ns_type_lock);
986 
987 	return ns;
988 }
989 
990 /*
991  * kobj_ns_exit - invalidate a namespace tag
992  *
993  * @type: the namespace type (i.e. KOBJ_NS_TYPE_NET)
994  * @ns: the actual namespace being invalidated
995  *
996  * This is called when a tag is no longer valid.  For instance,
997  * when a network namespace exits, it uses this helper to
998  * make sure no sb's sysfs_info points to the now-invalidated
999  * netns.
1000  */
1001 void kobj_ns_exit(enum kobj_ns_type type, const void *ns)
1002 {
1003 	sysfs_exit_ns(type, ns);
1004 }
1005 
1006 
1007 EXPORT_SYMBOL(kobject_get);
1008 EXPORT_SYMBOL(kobject_put);
1009 EXPORT_SYMBOL(kobject_del);
1010 
1011 EXPORT_SYMBOL(kset_register);
1012 EXPORT_SYMBOL(kset_unregister);
1013