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(lock: &class_kset->list_lock);
51
52 if (list_empty(head: &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(lock: &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(key: &cp->lock_key);
107 kfree(objp: 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 void *ns)
131{
132 struct subsys_private *sp = class_to_subsys(class: cls);
133 int error;
134
135 if (!sp)
136 return -EINVAL;
137
138 error = sysfs_create_file_ns(kobj: &sp->subsys.kobj, attr: &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 void *ns)
147{
148 struct subsys_private *sp = class_to_subsys(class: cls);
149
150 if (!sp)
151 return;
152
153 sysfs_remove_file_ns(kobj: &sp->subsys.kobj, attr: &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 cp = kzalloc(size: sizeof(*cp), GFP_KERNEL);
187 if (!cp)
188 return -ENOMEM;
189 klist_init(k: &cp->klist_devices, get: klist_class_dev_get, put: klist_class_dev_put);
190 INIT_LIST_HEAD(list: &cp->interfaces);
191 kset_init(kset: &cp->glue_dirs);
192 key = &cp->lock_key;
193 lockdep_register_key(key);
194 __mutex_init(lock: &cp->mutex, name: "subsys mutex", key);
195 error = kobject_set_name(kobj: &cp->subsys.kobj, name: "%s", cls->name);
196 if (error)
197 goto err_out;
198
199 cp->subsys.kobj.kset = class_kset;
200 cp->subsys.kobj.ktype = &class_ktype;
201 cp->class = cls;
202
203 error = kset_register(kset: &cp->subsys);
204 if (error)
205 goto err_out;
206
207 error = sysfs_create_groups(kobj: &cp->subsys.kobj, groups: cls->class_groups);
208 if (error) {
209 kobject_del(kobj: &cp->subsys.kobj);
210 kfree_const(x: cp->subsys.kobj.name);
211 goto err_out;
212 }
213 return 0;
214
215err_out:
216 kfree(objp: cp);
217 return error;
218}
219EXPORT_SYMBOL_GPL(class_register);
220
221void class_unregister(const struct class *cls)
222{
223 struct subsys_private *sp = class_to_subsys(class: cls);
224
225 if (!sp)
226 return;
227
228 pr_debug("device class '%s': unregistering\n", cls->name);
229
230 sysfs_remove_groups(kobj: &sp->subsys.kobj, groups: cls->class_groups);
231 kset_unregister(kset: &sp->subsys);
232 subsys_put(sp);
233}
234EXPORT_SYMBOL_GPL(class_unregister);
235
236static void class_create_release(const struct class *cls)
237{
238 pr_debug("%s called for %s\n", __func__, cls->name);
239 kfree(objp: cls);
240}
241
242/**
243 * class_create - create a struct class structure
244 * @name: pointer to a string for the name of this class.
245 *
246 * This is used to create a struct class pointer that can then be used
247 * in calls to device_create().
248 *
249 * Returns &struct class pointer on success, or ERR_PTR() on error.
250 *
251 * Note, the pointer created here is to be destroyed when finished by
252 * making a call to class_destroy().
253 */
254struct class *class_create(const char *name)
255{
256 struct class *cls;
257 int retval;
258
259 cls = kzalloc(size: sizeof(*cls), GFP_KERNEL);
260 if (!cls) {
261 retval = -ENOMEM;
262 goto error;
263 }
264
265 cls->name = name;
266 cls->class_release = class_create_release;
267
268 retval = class_register(cls);
269 if (retval)
270 goto error;
271
272 return cls;
273
274error:
275 kfree(objp: cls);
276 return ERR_PTR(error: retval);
277}
278EXPORT_SYMBOL_GPL(class_create);
279
280/**
281 * class_destroy - destroys a struct class structure
282 * @cls: pointer to the struct class that is to be destroyed
283 *
284 * Note, the pointer to be destroyed must have been created with a call
285 * to class_create().
286 */
287void class_destroy(const struct class *cls)
288{
289 if (IS_ERR_OR_NULL(ptr: cls))
290 return;
291
292 class_unregister(cls);
293}
294EXPORT_SYMBOL_GPL(class_destroy);
295
296/**
297 * class_dev_iter_init - initialize class device iterator
298 * @iter: class iterator to initialize
299 * @class: the class we wanna iterate over
300 * @start: the device to start iterating from, if any
301 * @type: device_type of the devices to iterate over, NULL for all
302 *
303 * Initialize class iterator @iter such that it iterates over devices
304 * of @class. If @start is set, the list iteration will start there,
305 * otherwise if it is NULL, the iteration starts at the beginning of
306 * the list.
307 */
308void class_dev_iter_init(struct class_dev_iter *iter, const struct class *class,
309 const struct device *start, const struct device_type *type)
310{
311 struct subsys_private *sp = class_to_subsys(class);
312 struct klist_node *start_knode = NULL;
313
314 if (!sp)
315 return;
316
317 if (start)
318 start_knode = &start->p->knode_class;
319 klist_iter_init_node(k: &sp->klist_devices, i: &iter->ki, n: start_knode);
320 iter->type = type;
321 iter->sp = sp;
322}
323EXPORT_SYMBOL_GPL(class_dev_iter_init);
324
325/**
326 * class_dev_iter_next - iterate to the next device
327 * @iter: class iterator to proceed
328 *
329 * Proceed @iter to the next device and return it. Returns NULL if
330 * iteration is complete.
331 *
332 * The returned device is referenced and won't be released till
333 * iterator is proceed to the next device or exited. The caller is
334 * free to do whatever it wants to do with the device including
335 * calling back into class code.
336 */
337struct device *class_dev_iter_next(struct class_dev_iter *iter)
338{
339 struct klist_node *knode;
340 struct device *dev;
341
342 while (1) {
343 knode = klist_next(i: &iter->ki);
344 if (!knode)
345 return NULL;
346 dev = klist_class_to_dev(n: knode);
347 if (!iter->type || iter->type == dev->type)
348 return dev;
349 }
350}
351EXPORT_SYMBOL_GPL(class_dev_iter_next);
352
353/**
354 * class_dev_iter_exit - finish iteration
355 * @iter: class iterator to finish
356 *
357 * Finish an iteration. Always call this function after iteration is
358 * complete whether the iteration ran till the end or not.
359 */
360void class_dev_iter_exit(struct class_dev_iter *iter)
361{
362 klist_iter_exit(i: &iter->ki);
363 subsys_put(sp: iter->sp);
364}
365EXPORT_SYMBOL_GPL(class_dev_iter_exit);
366
367/**
368 * class_for_each_device - device iterator
369 * @class: the class we're iterating
370 * @start: the device to start with in the list, if any.
371 * @data: data for the callback
372 * @fn: function to be called for each device
373 *
374 * Iterate over @class's list of devices, and call @fn for each,
375 * passing it @data. If @start is set, the list iteration will start
376 * there, otherwise if it is NULL, the iteration starts at the
377 * beginning of the list.
378 *
379 * We check the return of @fn each time. If it returns anything
380 * other than 0, we break out and return that value.
381 *
382 * @fn is allowed to do anything including calling back into class
383 * code. There's no locking restriction.
384 */
385int class_for_each_device(const struct class *class, const struct device *start,
386 void *data, int (*fn)(struct device *, void *))
387{
388 struct subsys_private *sp = class_to_subsys(class);
389 struct class_dev_iter iter;
390 struct device *dev;
391 int error = 0;
392
393 if (!class)
394 return -EINVAL;
395 if (!sp) {
396 WARN(1, "%s called for class '%s' before it was initialized",
397 __func__, class->name);
398 return -EINVAL;
399 }
400
401 class_dev_iter_init(&iter, class, start, NULL);
402 while ((dev = class_dev_iter_next(&iter))) {
403 error = fn(dev, data);
404 if (error)
405 break;
406 }
407 class_dev_iter_exit(&iter);
408 subsys_put(sp);
409
410 return error;
411}
412EXPORT_SYMBOL_GPL(class_for_each_device);
413
414/**
415 * class_find_device - device iterator for locating a particular device
416 * @class: the class we're iterating
417 * @start: Device to begin with
418 * @data: data for the match function
419 * @match: function to check device
420 *
421 * This is similar to the class_for_each_dev() function above, but it
422 * returns a reference to a device that is 'found' for later use, as
423 * determined by the @match callback.
424 *
425 * The callback should return 0 if the device doesn't match and non-zero
426 * if it does. If the callback returns non-zero, this function will
427 * return to the caller and not iterate over any more devices.
428 *
429 * Note, you will need to drop the reference with put_device() after use.
430 *
431 * @match is allowed to do anything including calling back into class
432 * code. There's no locking restriction.
433 */
434struct device *class_find_device(const struct class *class, const struct device *start,
435 const void *data,
436 int (*match)(struct device *, const void *))
437{
438 struct subsys_private *sp = class_to_subsys(class);
439 struct class_dev_iter iter;
440 struct device *dev;
441
442 if (!class)
443 return NULL;
444 if (!sp) {
445 WARN(1, "%s called for class '%s' before it was initialized",
446 __func__, class->name);
447 return NULL;
448 }
449
450 class_dev_iter_init(&iter, class, start, NULL);
451 while ((dev = class_dev_iter_next(&iter))) {
452 if (match(dev, data)) {
453 get_device(dev);
454 break;
455 }
456 }
457 class_dev_iter_exit(&iter);
458 subsys_put(sp);
459
460 return dev;
461}
462EXPORT_SYMBOL_GPL(class_find_device);
463
464int class_interface_register(struct class_interface *class_intf)
465{
466 struct subsys_private *sp;
467 const struct class *parent;
468 struct class_dev_iter iter;
469 struct device *dev;
470
471 if (!class_intf || !class_intf->class)
472 return -ENODEV;
473
474 parent = class_intf->class;
475 sp = class_to_subsys(class: parent);
476 if (!sp)
477 return -EINVAL;
478
479 /*
480 * Reference in sp is now incremented and will be dropped when
481 * the interface is removed in the call to class_interface_unregister()
482 */
483
484 mutex_lock(&sp->mutex);
485 list_add_tail(new: &class_intf->node, head: &sp->interfaces);
486 if (class_intf->add_dev) {
487 class_dev_iter_init(&iter, parent, NULL, NULL);
488 while ((dev = class_dev_iter_next(&iter)))
489 class_intf->add_dev(dev);
490 class_dev_iter_exit(&iter);
491 }
492 mutex_unlock(lock: &sp->mutex);
493
494 return 0;
495}
496EXPORT_SYMBOL_GPL(class_interface_register);
497
498void class_interface_unregister(struct class_interface *class_intf)
499{
500 struct subsys_private *sp;
501 const struct class *parent = class_intf->class;
502 struct class_dev_iter iter;
503 struct device *dev;
504
505 if (!parent)
506 return;
507
508 sp = class_to_subsys(class: parent);
509 if (!sp)
510 return;
511
512 mutex_lock(&sp->mutex);
513 list_del_init(entry: &class_intf->node);
514 if (class_intf->remove_dev) {
515 class_dev_iter_init(&iter, parent, NULL, NULL);
516 while ((dev = class_dev_iter_next(&iter)))
517 class_intf->remove_dev(dev);
518 class_dev_iter_exit(&iter);
519 }
520 mutex_unlock(lock: &sp->mutex);
521
522 /*
523 * Decrement the reference count twice, once for the class_to_subsys()
524 * call in the start of this function, and the second one from the
525 * reference increment in class_interface_register()
526 */
527 subsys_put(sp);
528 subsys_put(sp);
529}
530EXPORT_SYMBOL_GPL(class_interface_unregister);
531
532ssize_t show_class_attr_string(const struct class *class,
533 const struct class_attribute *attr, char *buf)
534{
535 struct class_attribute_string *cs;
536
537 cs = container_of(attr, struct class_attribute_string, attr);
538 return sysfs_emit(buf, fmt: "%s\n", cs->str);
539}
540
541EXPORT_SYMBOL_GPL(show_class_attr_string);
542
543struct class_compat {
544 struct kobject *kobj;
545};
546
547/**
548 * class_compat_register - register a compatibility class
549 * @name: the name of the class
550 *
551 * Compatibility class are meant as a temporary user-space compatibility
552 * workaround when converting a family of class devices to a bus devices.
553 */
554struct class_compat *class_compat_register(const char *name)
555{
556 struct class_compat *cls;
557
558 cls = kmalloc(size: sizeof(struct class_compat), GFP_KERNEL);
559 if (!cls)
560 return NULL;
561 cls->kobj = kobject_create_and_add(name, parent: &class_kset->kobj);
562 if (!cls->kobj) {
563 kfree(objp: cls);
564 return NULL;
565 }
566 return cls;
567}
568EXPORT_SYMBOL_GPL(class_compat_register);
569
570/**
571 * class_compat_unregister - unregister a compatibility class
572 * @cls: the class to unregister
573 */
574void class_compat_unregister(struct class_compat *cls)
575{
576 kobject_put(kobj: cls->kobj);
577 kfree(objp: cls);
578}
579EXPORT_SYMBOL_GPL(class_compat_unregister);
580
581/**
582 * class_compat_create_link - create a compatibility class device link to
583 * a bus device
584 * @cls: the compatibility class
585 * @dev: the target bus device
586 * @device_link: an optional device to which a "device" link should be created
587 */
588int class_compat_create_link(struct class_compat *cls, struct device *dev,
589 struct device *device_link)
590{
591 int error;
592
593 error = sysfs_create_link(kobj: cls->kobj, target: &dev->kobj, name: dev_name(dev));
594 if (error)
595 return error;
596
597 /*
598 * Optionally add a "device" link (typically to the parent), as a
599 * class device would have one and we want to provide as much
600 * backwards compatibility as possible.
601 */
602 if (device_link) {
603 error = sysfs_create_link(kobj: &dev->kobj, target: &device_link->kobj,
604 name: "device");
605 if (error)
606 sysfs_remove_link(kobj: cls->kobj, name: dev_name(dev));
607 }
608
609 return error;
610}
611EXPORT_SYMBOL_GPL(class_compat_create_link);
612
613/**
614 * class_compat_remove_link - remove a compatibility class device link to
615 * a bus device
616 * @cls: the compatibility class
617 * @dev: the target bus device
618 * @device_link: an optional device to which a "device" link was previously
619 * created
620 */
621void class_compat_remove_link(struct class_compat *cls, struct device *dev,
622 struct device *device_link)
623{
624 if (device_link)
625 sysfs_remove_link(kobj: &dev->kobj, name: "device");
626 sysfs_remove_link(kobj: cls->kobj, name: dev_name(dev));
627}
628EXPORT_SYMBOL_GPL(class_compat_remove_link);
629
630/**
631 * class_is_registered - determine if at this moment in time, a class is
632 * registered in the driver core or not.
633 * @class: the class to check
634 *
635 * Returns a boolean to state if the class is registered in the driver core
636 * or not. Note that the value could switch right after this call is made,
637 * so only use this in places where you "know" it is safe to do so (usually
638 * to determine if the specific class has been registered yet or not).
639 *
640 * Be careful in using this.
641 */
642bool class_is_registered(const struct class *class)
643{
644 struct subsys_private *sp = class_to_subsys(class);
645 bool is_initialized = false;
646
647 if (sp) {
648 is_initialized = true;
649 subsys_put(sp);
650 }
651 return is_initialized;
652}
653EXPORT_SYMBOL_GPL(class_is_registered);
654
655int __init classes_init(void)
656{
657 class_kset = kset_create_and_add(name: "class", NULL, NULL);
658 if (!class_kset)
659 return -ENOMEM;
660 return 0;
661}
662

source code of linux/drivers/base/class.c