class.c

  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 void *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 void *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(sizeof(*cp), GFP_KERNEL);
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(sizeof(*cls), GFP_KERNEL);
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(sizeof(struct class_compat), GFP_KERNEL);
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}