xref: /openbmc/linux/lib/kobject.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
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 		length += strlen(kobject_name(parent)) + 1;
76 		parent = parent->parent;
77 	} while (parent);
78 	return length;
79 }
80 
81 static void fill_kobj_path(struct kobject *kobj, char *path, int length)
82 {
83 	struct kobject * parent;
84 
85 	--length;
86 	for (parent = kobj; parent; parent = parent->parent) {
87 		int cur = strlen(kobject_name(parent));
88 		/* back up enough to print this name with '/' */
89 		length -= cur;
90 		strncpy (path + length, kobject_name(parent), cur);
91 		*(path + --length) = '/';
92 	}
93 
94 	pr_debug("%s: path = '%s'\n",__FUNCTION__,path);
95 }
96 
97 /**
98  * kobject_get_path - generate and return the path associated with a given kobj
99  * and kset pair.  The result must be freed by the caller with kfree().
100  *
101  * @kobj:	kobject in question, with which to build the path
102  * @gfp_mask:	the allocation type used to allocate the path
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 	path = kmalloc(len, gfp_mask);
111 	if (!path)
112 		return NULL;
113 	memset(path, 0x00, len);
114 	fill_kobj_path(kobj, path, len);
115 
116 	return path;
117 }
118 
119 /**
120  *	kobject_init - initialize object.
121  *	@kobj:	object in question.
122  */
123 void kobject_init(struct kobject * kobj)
124 {
125 	kref_init(&kobj->kref);
126 	INIT_LIST_HEAD(&kobj->entry);
127 	kobj->kset = kset_get(kobj->kset);
128 }
129 
130 
131 /**
132  *	unlink - remove kobject from kset list.
133  *	@kobj:	kobject.
134  *
135  *	Remove the kobject from the kset list and decrement
136  *	its parent's refcount.
137  *	This is separated out, so we can use it in both
138  *	kobject_del() and kobject_add() on error.
139  */
140 
141 static void unlink(struct kobject * kobj)
142 {
143 	if (kobj->kset) {
144 		spin_lock(&kobj->kset->list_lock);
145 		list_del_init(&kobj->entry);
146 		spin_unlock(&kobj->kset->list_lock);
147 	}
148 	kobject_put(kobj);
149 }
150 
151 /**
152  *	kobject_add - add an object to the hierarchy.
153  *	@kobj:	object.
154  */
155 
156 int kobject_add(struct kobject * kobj)
157 {
158 	int error = 0;
159 	struct kobject * parent;
160 
161 	if (!(kobj = kobject_get(kobj)))
162 		return -ENOENT;
163 	if (!kobj->k_name)
164 		kobj->k_name = kobj->name;
165 	parent = kobject_get(kobj->parent);
166 
167 	pr_debug("kobject %s: registering. parent: %s, set: %s\n",
168 		 kobject_name(kobj), parent ? kobject_name(parent) : "<NULL>",
169 		 kobj->kset ? kobj->kset->kobj.name : "<NULL>" );
170 
171 	if (kobj->kset) {
172 		spin_lock(&kobj->kset->list_lock);
173 
174 		if (!parent)
175 			parent = kobject_get(&kobj->kset->kobj);
176 
177 		list_add_tail(&kobj->entry,&kobj->kset->list);
178 		spin_unlock(&kobj->kset->list_lock);
179 	}
180 	kobj->parent = parent;
181 
182 	error = create_dir(kobj);
183 	if (error) {
184 		/* unlink does the kobject_put() for us */
185 		unlink(kobj);
186 		if (parent)
187 			kobject_put(parent);
188 	}
189 
190 	return error;
191 }
192 
193 
194 /**
195  *	kobject_register - initialize and add an object.
196  *	@kobj:	object in question.
197  */
198 
199 int kobject_register(struct kobject * kobj)
200 {
201 	int error = 0;
202 	if (kobj) {
203 		kobject_init(kobj);
204 		error = kobject_add(kobj);
205 		if (error) {
206 			printk("kobject_register failed for %s (%d)\n",
207 			       kobject_name(kobj),error);
208 			dump_stack();
209 		} else
210 			kobject_hotplug(kobj, KOBJ_ADD);
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  *	@fmt:	format string used to build the 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 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, const 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);
544