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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * class.c - basic device class management
4 *
5 * Copyright (c) 2002-3 Patrick Mochel
6 * Copyright (c) 2002-3 Open Source Development Labs
7 * Copyright (c) 2003-2004 Greg Kroah-Hartman
8 * Copyright (c) 2003-2004 IBM Corp.
9 */
10
11#include <linux/device/class.h>
12#include <linux/device.h>
13#include <linux/module.h>
14#include <linux/init.h>
15#include <linux/string.h>
16#include <linux/kdev_t.h>
17#include <linux/err.h>
18#include <linux/slab.h>
19#include <linux/blkdev.h>
20#include <linux/mutex.h>
21#include "base.h"
22
23/* /sys/class */
24static struct kset *class_kset;
25
26#define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
27
28/**
29 * class_to_subsys - Turn a struct class into a struct subsys_private
30 *
31 * @class: pointer to the struct bus_type to look up
32 *
33 * The driver core internals need to work on the subsys_private structure, not
34 * the external struct class pointer. This function walks the list of
35 * registered classes in the system and finds the matching one and returns the
36 * internal struct subsys_private that relates to that class.
37 *
38 * Note, the reference count of the return value is INCREMENTED if it is not
39 * NULL. A call to subsys_put() must be done when finished with the pointer in
40 * order for it to be properly freed.
41 */
42struct subsys_private *class_to_subsys(const struct class *class)
43{
44 struct subsys_private *sp = NULL;
45 struct kobject *kobj;
46
47 if (!class || !class_kset)
48 return NULL;
49
50 spin_lock(&class_kset->list_lock);
51
52 if (list_empty(&class_kset->list))
53 goto done;
54
55 list_for_each_entry(kobj, &class_kset->list, entry) {
56 struct kset *kset = container_of(kobj, struct kset, kobj);
57
58 sp = container_of_const(kset, struct subsys_private, subsys);
59 if (sp->class == class)
60 goto done;
61 }
62 sp = NULL;
63done:
64 sp = subsys_get(sp);
65 spin_unlock(&class_kset->list_lock);
66 return sp;
67}
68
69static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
70 char *buf)
71{
72 struct class_attribute *class_attr = to_class_attr(attr);
73 struct subsys_private *cp = to_subsys_private(kobj);
74 ssize_t ret = -EIO;
75
76 if (class_attr->show)
77 ret = class_attr->show(cp->class, class_attr, buf);
78 return ret;
79}
80
81static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
82 const char *buf, size_t count)
83{
84 struct class_attribute *class_attr = to_class_attr(attr);
85 struct subsys_private *cp = to_subsys_private(kobj);
86 ssize_t ret = -EIO;
87
88 if (class_attr->store)
89 ret = class_attr->store(cp->class, class_attr, buf, count);
90 return ret;
91}
92
93static void class_release(struct kobject *kobj)
94{
95 struct subsys_private *cp = to_subsys_private(kobj);
96 const struct class *class = cp->class;
97
98 pr_debug("class '%s': release.\n", class->name);
99
100 if (class->class_release)
101 class->class_release(class);
102 else
103 pr_debug("class '%s' does not have a release() function, "
104 "be careful\n", class->name);
105
106 lockdep_unregister_key(&cp->lock_key);
107 kfree(cp);
108}
109
110static const struct kobj_ns_type_operations *class_child_ns_type(const struct kobject *kobj)
111{
112 const struct subsys_private *cp = to_subsys_private(kobj);
113 const struct class *class = cp->class;
114
115 return class->ns_type;
116}
117
118static const struct sysfs_ops class_sysfs_ops = {
119 .show = class_attr_show,
120 .store = class_attr_store,
121};
122
123static const struct kobj_type class_ktype = {
124 .sysfs_ops = &class_sysfs_ops,
125 .release = class_release,
126 .child_ns_type = class_child_ns_type,
127};
128
129int class_create_file_ns(const struct class *cls, const struct class_attribute *attr,
130 const struct ns_common *ns)
131{
132 struct subsys_private *sp = class_to_subsys(cls);
133 int error;
134
135 if (!sp)
136 return -EINVAL;
137
138 error = sysfs_create_file_ns(&sp->subsys.kobj, &attr->attr, ns);
139 subsys_put(sp);
140
141 return error;
142}
143EXPORT_SYMBOL_GPL(class_create_file_ns);
144
145void class_remove_file_ns(const struct class *cls, const struct class_attribute *attr,
146 const struct ns_common *ns)
147{
148 struct subsys_private *sp = class_to_subsys(cls);
149
150 if (!sp)
151 return;
152
153 sysfs_remove_file_ns(&sp->subsys.kobj, &attr->attr, ns);
154 subsys_put(sp);
155}
156EXPORT_SYMBOL_GPL(class_remove_file_ns);
157
158static struct device *klist_class_to_dev(struct klist_node *n)
159{
160 struct device_private *p = to_device_private_class(n);
161 return p->device;
162}
163
164static void klist_class_dev_get(struct klist_node *n)
165{
166 struct device *dev = klist_class_to_dev(n);
167
168 get_device(dev);
169}
170
171static void klist_class_dev_put(struct klist_node *n)
172{
173 struct device *dev = klist_class_to_dev(n);
174
175 put_device(dev);
176}
177
178int class_register(const struct class *cls)
179{
180 struct subsys_private *cp;
181 struct lock_class_key *key;
182 int error;
183
184 pr_debug("device class '%s': registering\n", cls->name);
185
186 if (cls->ns_type && !cls->namespace) {
187 pr_err("%s: class '%s' does not have namespace\n",
188 __func__, cls->name);
189 return -EINVAL;
190 }
191 if (!cls->ns_type && cls->namespace) {
192 pr_err("%s: class '%s' does not have ns_type\n",
193 __func__, cls->name);
194 return -EINVAL;
195 }
196
197 cp = kzalloc_obj(*cp);
198 if (!cp)
199 return -ENOMEM;
200 klist_init(&cp->klist_devices, klist_class_dev_get, klist_class_dev_put);
201 INIT_LIST_HEAD(&cp->interfaces);
202 kset_init(&cp->glue_dirs);
203 key = &cp->lock_key;
204 lockdep_register_key(key);
205 __mutex_init(&cp->mutex, "subsys mutex", key);
206 error = kobject_set_name(&cp->subsys.kobj, "%s", cls->name);
207 if (error)
208 goto err_out;
209
210 cp->subsys.kobj.kset = class_kset;
211 cp->subsys.kobj.ktype = &class_ktype;
212 cp->class = cls;
213
214 error = kset_register(&cp->subsys);
215 if (error)
216 goto err_out;
217
218 error = sysfs_create_groups(&cp->subsys.kobj, cls->class_groups);
219 if (error) {
220 kobject_del(&cp->subsys.kobj);
221 kfree_const(cp->subsys.kobj.name);
222 goto err_out;
223 }
224 return 0;
225
226err_out:
227 lockdep_unregister_key(key);
228 kfree(cp);
229 return error;
230}
231EXPORT_SYMBOL_GPL(class_register);
232
233void class_unregister(const struct class *cls)
234{
235 struct subsys_private *sp = class_to_subsys(cls);
236
237 if (!sp)
238 return;
239
240 pr_debug("device class '%s': unregistering\n", cls->name);
241
242 sysfs_remove_groups(&sp->subsys.kobj, cls->class_groups);
243 kset_unregister(&sp->subsys);
244 subsys_put(sp);
245}
246EXPORT_SYMBOL_GPL(class_unregister);
247
248static void class_create_release(const struct class *cls)
249{
250 pr_debug("%s called for %s\n", __func__, cls->name);
251 kfree(cls);
252}
253
254/**
255 * class_create - create a struct class structure
256 * @name: pointer to a string for the name of this class.
257 *
258 * This is used to create a struct class pointer that can then be used
259 * in calls to device_create().
260 *
261 * Returns &struct class pointer on success, or ERR_PTR() on error.
262 *
263 * Note, the pointer created here is to be destroyed when finished by
264 * making a call to class_destroy().
265 */
266struct class *class_create(const char *name)
267{
268 struct class *cls;
269 int retval;
270
271 cls = kzalloc_obj(*cls);
272 if (!cls) {
273 retval = -ENOMEM;
274 goto error;
275 }
276
277 cls->name = name;
278 cls->class_release = class_create_release;
279
280 retval = class_register(cls);
281 if (retval)
282 goto error;
283
284 return cls;
285
286error:
287 kfree(cls);
288 return ERR_PTR(retval);
289}
290EXPORT_SYMBOL_GPL(class_create);
291
292/**
293 * class_destroy - destroys a struct class structure
294 * @cls: pointer to the struct class that is to be destroyed
295 *
296 * Note, the pointer to be destroyed must have been created with a call
297 * to class_create().
298 */
299void class_destroy(const struct class *cls)
300{
301 if (IS_ERR_OR_NULL(cls))
302 return;
303
304 class_unregister(cls);
305}
306EXPORT_SYMBOL_GPL(class_destroy);
307
308/**
309 * class_dev_iter_init - initialize class device iterator
310 * @iter: class iterator to initialize
311 * @class: the class we wanna iterate over
312 * @start: the device to start iterating from, if any
313 * @type: device_type of the devices to iterate over, NULL for all
314 *
315 * Initialize class iterator @iter such that it iterates over devices
316 * of @class. If @start is set, the list iteration will start there,
317 * otherwise if it is NULL, the iteration starts at the beginning of
318 * the list.
319 */
320void class_dev_iter_init(struct class_dev_iter *iter, const struct class *class,
321 const struct device *start, const struct device_type *type)
322{
323 struct subsys_private *sp = class_to_subsys(class);
324 struct klist_node *start_knode = NULL;
325
326 memset(iter, 0, sizeof(*iter));
327 if (!sp) {
328 pr_crit("%s: class %p was not registered yet\n",
329 __func__, class);
330 return;
331 }
332
333 if (start)
334 start_knode = &start->p->knode_class;
335 klist_iter_init_node(&sp->klist_devices, &iter->ki, start_knode);
336 iter->type = type;
337 iter->sp = sp;
338}
339EXPORT_SYMBOL_GPL(class_dev_iter_init);
340
341/**
342 * class_dev_iter_next - iterate to the next device
343 * @iter: class iterator to proceed
344 *
345 * Proceed @iter to the next device and return it. Returns NULL if
346 * iteration is complete.
347 *
348 * The returned device is referenced and won't be released till
349 * iterator is proceed to the next device or exited. The caller is
350 * free to do whatever it wants to do with the device including
351 * calling back into class code.
352 */
353struct device *class_dev_iter_next(struct class_dev_iter *iter)
354{
355 struct klist_node *knode;
356 struct device *dev;
357
358 if (!iter->sp)
359 return NULL;
360
361 while (1) {
362 knode = klist_next(&iter->ki);
363 if (!knode)
364 return NULL;
365 dev = klist_class_to_dev(knode);
366 if (!iter->type || iter->type == dev->type)
367 return dev;
368 }
369}
370EXPORT_SYMBOL_GPL(class_dev_iter_next);
371
372/**
373 * class_dev_iter_exit - finish iteration
374 * @iter: class iterator to finish
375 *
376 * Finish an iteration. Always call this function after iteration is
377 * complete whether the iteration ran till the end or not.
378 */
379void class_dev_iter_exit(struct class_dev_iter *iter)
380{
381 klist_iter_exit(&iter->ki);
382 subsys_put(iter->sp);
383}
384EXPORT_SYMBOL_GPL(class_dev_iter_exit);
385
386/**
387 * class_for_each_device - device iterator
388 * @class: the class we're iterating
389 * @start: the device to start with in the list, if any.
390 * @data: data for the callback
391 * @fn: function to be called for each device
392 *
393 * Iterate over @class's list of devices, and call @fn for each,
394 * passing it @data. If @start is set, the list iteration will start
395 * there, otherwise if it is NULL, the iteration starts at the
396 * beginning of the list.
397 *
398 * We check the return of @fn each time. If it returns anything
399 * other than 0, we break out and return that value.
400 *
401 * @fn is allowed to do anything including calling back into class
402 * code. There's no locking restriction.
403 */
404int class_for_each_device(const struct class *class, const struct device *start,
405 void *data, device_iter_t fn)
406{
407 struct subsys_private *sp = class_to_subsys(class);
408 struct class_dev_iter iter;
409 struct device *dev;
410 int error = 0;
411
412 if (!class)
413 return -EINVAL;
414 if (!sp) {
415 WARN(1, "%s called for class '%s' before it was registered",
416 __func__, class->name);
417 return -EINVAL;
418 }
419
420 class_dev_iter_init(&iter, class, start, NULL);
421 while ((dev = class_dev_iter_next(&iter))) {
422 error = fn(dev, data);
423 if (error)
424 break;
425 }
426 class_dev_iter_exit(&iter);
427 subsys_put(sp);
428
429 return error;
430}
431EXPORT_SYMBOL_GPL(class_for_each_device);
432
433/**
434 * class_find_device - device iterator for locating a particular device
435 * @class: the class we're iterating
436 * @start: Device to begin with
437 * @data: data for the match function
438 * @match: function to check device
439 *
440 * This is similar to the class_for_each_dev() function above, but it
441 * returns a reference to a device that is 'found' for later use, as
442 * determined by the @match callback.
443 *
444 * The callback should return 0 if the device doesn't match and non-zero
445 * if it does. If the callback returns non-zero, this function will
446 * return to the caller and not iterate over any more devices.
447 *
448 * Note, you will need to drop the reference with put_device() after use.
449 *
450 * @match is allowed to do anything including calling back into class
451 * code. There's no locking restriction.
452 */
453struct device *class_find_device(const struct class *class, const struct device *start,
454 const void *data, device_match_t match)
455{
456 struct subsys_private *sp = class_to_subsys(class);
457 struct class_dev_iter iter;
458 struct device *dev;
459
460 if (!class)
461 return NULL;
462 if (!sp) {
463 WARN(1, "%s called for class '%s' before it was registered",
464 __func__, class->name);
465 return NULL;
466 }
467
468 class_dev_iter_init(&iter, class, start, NULL);
469 while ((dev = class_dev_iter_next(&iter))) {
470 if (match(dev, data)) {
471 get_device(dev);
472 break;
473 }
474 }
475 class_dev_iter_exit(&iter);
476 subsys_put(sp);
477
478 return dev;
479}
480EXPORT_SYMBOL_GPL(class_find_device);
481
482int class_interface_register(struct class_interface *class_intf)
483{
484 struct subsys_private *sp;
485 const struct class *parent;
486 struct class_dev_iter iter;
487 struct device *dev;
488
489 if (!class_intf || !class_intf->class)
490 return -ENODEV;
491
492 parent = class_intf->class;
493 sp = class_to_subsys(parent);
494 if (!sp)
495 return -EINVAL;
496
497 /*
498 * Reference in sp is now incremented and will be dropped when
499 * the interface is removed in the call to class_interface_unregister()
500 */
501
502 mutex_lock(&sp->mutex);
503 list_add_tail(&class_intf->node, &sp->interfaces);
504 if (class_intf->add_dev) {
505 class_dev_iter_init(&iter, parent, NULL, NULL);
506 while ((dev = class_dev_iter_next(&iter)))
507 class_intf->add_dev(dev);
508 class_dev_iter_exit(&iter);
509 }
510 mutex_unlock(&sp->mutex);
511
512 return 0;
513}
514EXPORT_SYMBOL_GPL(class_interface_register);
515
516void class_interface_unregister(struct class_interface *class_intf)
517{
518 struct subsys_private *sp;
519 const struct class *parent = class_intf->class;
520 struct class_dev_iter iter;
521 struct device *dev;
522
523 if (!parent)
524 return;
525
526 sp = class_to_subsys(parent);
527 if (!sp)
528 return;
529
530 mutex_lock(&sp->mutex);
531 list_del_init(&class_intf->node);
532 if (class_intf->remove_dev) {
533 class_dev_iter_init(&iter, parent, NULL, NULL);
534 while ((dev = class_dev_iter_next(&iter)))
535 class_intf->remove_dev(dev);
536 class_dev_iter_exit(&iter);
537 }
538 mutex_unlock(&sp->mutex);
539
540 /*
541 * Decrement the reference count twice, once for the class_to_subsys()
542 * call in the start of this function, and the second one from the
543 * reference increment in class_interface_register()
544 */
545 subsys_put(sp);
546 subsys_put(sp);
547}
548EXPORT_SYMBOL_GPL(class_interface_unregister);
549
550ssize_t show_class_attr_string(const struct class *class,
551 const struct class_attribute *attr, char *buf)
552{
553 struct class_attribute_string *cs;
554
555 cs = container_of(attr, struct class_attribute_string, attr);
556 return sysfs_emit(buf, "%s\n", cs->str);
557}
558
559EXPORT_SYMBOL_GPL(show_class_attr_string);
560
561struct class_compat {
562 struct kobject *kobj;
563};
564
565/**
566 * class_compat_register - register a compatibility class
567 * @name: the name of the class
568 *
569 * Compatibility class are meant as a temporary user-space compatibility
570 * workaround when converting a family of class devices to a bus devices.
571 */
572struct class_compat *class_compat_register(const char *name)
573{
574 struct class_compat *cls;
575
576 cls = kmalloc_obj(struct class_compat);
577 if (!cls)
578 return NULL;
579 cls->kobj = kobject_create_and_add(name, &class_kset->kobj);
580 if (!cls->kobj) {
581 kfree(cls);
582 return NULL;
583 }
584 return cls;
585}
586EXPORT_SYMBOL_GPL(class_compat_register);
587
588/**
589 * class_compat_unregister - unregister a compatibility class
590 * @cls: the class to unregister
591 */
592void class_compat_unregister(struct class_compat *cls)
593{
594 kobject_put(cls->kobj);
595 kfree(cls);
596}
597EXPORT_SYMBOL_GPL(class_compat_unregister);
598
599/**
600 * class_compat_create_link - create a compatibility class device link to
601 * a bus device
602 * @cls: the compatibility class
603 * @dev: the target bus device
604 */
605int class_compat_create_link(struct class_compat *cls, struct device *dev)
606{
607 return sysfs_create_link(cls->kobj, &dev->kobj, dev_name(dev));
608}
609EXPORT_SYMBOL_GPL(class_compat_create_link);
610
611/**
612 * class_compat_remove_link - remove a compatibility class device link to
613 * a bus device
614 * @cls: the compatibility class
615 * @dev: the target bus device
616 */
617void class_compat_remove_link(struct class_compat *cls, struct device *dev)
618{
619 sysfs_remove_link(cls->kobj, dev_name(dev));
620}
621EXPORT_SYMBOL_GPL(class_compat_remove_link);
622
623/**
624 * class_is_registered - determine if at this moment in time, a class is
625 * registered in the driver core or not.
626 * @class: the class to check
627 *
628 * Returns a boolean to state if the class is registered in the driver core
629 * or not. Note that the value could switch right after this call is made,
630 * so only use this in places where you "know" it is safe to do so (usually
631 * to determine if the specific class has been registered yet or not).
632 *
633 * Be careful in using this.
634 */
635bool class_is_registered(const struct class *class)
636{
637 struct subsys_private *sp = class_to_subsys(class);
638 bool is_initialized = false;
639
640 if (sp) {
641 is_initialized = true;
642 subsys_put(sp);
643 }
644 return is_initialized;
645}
646EXPORT_SYMBOL_GPL(class_is_registered);
647
648int __init classes_init(void)
649{
650 class_kset = kset_create_and_add("class", NULL, NULL);
651 if (!class_kset)
652 return -ENOMEM;
653 return 0;
654}