1 // SPDX-License-Identifier: GPL-2.0
3 * class.c - basic device class management
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.
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>
24 static struct kset *class_kset;
26 #define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
29 * class_to_subsys - Turn a struct class into a struct subsys_private
31 * @class: pointer to the struct bus_type to look up
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.
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.
42 struct subsys_private *class_to_subsys(const struct class *class)
44 struct subsys_private *sp = NULL;
47 if (!class || !class_kset)
50 spin_lock(&class_kset->list_lock);
52 if (list_empty(&class_kset->list))
55 list_for_each_entry(kobj, &class_kset->list, entry) {
56 struct kset *kset = container_of(kobj, struct kset, kobj);
58 sp = container_of_const(kset, struct subsys_private, subsys);
59 if (sp->class == class)
65 spin_unlock(&class_kset->list_lock);
69 static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
72 struct class_attribute *class_attr = to_class_attr(attr);
73 struct subsys_private *cp = to_subsys_private(kobj);
77 ret = class_attr->show(cp->class, class_attr, buf);
81 static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
82 const char *buf, size_t count)
84 struct class_attribute *class_attr = to_class_attr(attr);
85 struct subsys_private *cp = to_subsys_private(kobj);
88 if (class_attr->store)
89 ret = class_attr->store(cp->class, class_attr, buf, count);
93 static void class_release(struct kobject *kobj)
95 struct subsys_private *cp = to_subsys_private(kobj);
96 const struct class *class = cp->class;
98 pr_debug("class '%s': release.\n", class->name);
100 if (class->class_release)
101 class->class_release(class);
103 pr_debug("class '%s' does not have a release() function, "
104 "be careful\n", class->name);
106 lockdep_unregister_key(&cp->lock_key);
110 static const struct kobj_ns_type_operations *class_child_ns_type(const struct kobject *kobj)
112 const struct subsys_private *cp = to_subsys_private(kobj);
113 const struct class *class = cp->class;
115 return class->ns_type;
118 static const struct sysfs_ops class_sysfs_ops = {
119 .show = class_attr_show,
120 .store = class_attr_store,
123 static const struct kobj_type class_ktype = {
124 .sysfs_ops = &class_sysfs_ops,
125 .release = class_release,
126 .child_ns_type = class_child_ns_type,
129 int class_create_file_ns(const struct class *cls, const struct class_attribute *attr,
132 struct subsys_private *sp = class_to_subsys(cls);
138 error = sysfs_create_file_ns(&sp->subsys.kobj, &attr->attr, ns);
143 EXPORT_SYMBOL_GPL(class_create_file_ns);
145 void class_remove_file_ns(const struct class *cls, const struct class_attribute *attr,
148 struct subsys_private *sp = class_to_subsys(cls);
153 sysfs_remove_file_ns(&sp->subsys.kobj, &attr->attr, ns);
156 EXPORT_SYMBOL_GPL(class_remove_file_ns);
158 static struct device *klist_class_to_dev(struct klist_node *n)
160 struct device_private *p = to_device_private_class(n);
164 static void klist_class_dev_get(struct klist_node *n)
166 struct device *dev = klist_class_to_dev(n);
171 static void klist_class_dev_put(struct klist_node *n)
173 struct device *dev = klist_class_to_dev(n);
178 int class_register(const struct class *cls)
180 struct subsys_private *cp;
181 struct lock_class_key *key;
184 pr_debug("device class '%s': registering\n", cls->name);
186 cp = kzalloc(sizeof(*cp), GFP_KERNEL);
189 klist_init(&cp->klist_devices, klist_class_dev_get, klist_class_dev_put);
190 INIT_LIST_HEAD(&cp->interfaces);
191 kset_init(&cp->glue_dirs);
193 lockdep_register_key(key);
194 __mutex_init(&cp->mutex, "subsys mutex", key);
195 error = kobject_set_name(&cp->subsys.kobj, "%s", cls->name);
199 cp->subsys.kobj.kset = class_kset;
200 cp->subsys.kobj.ktype = &class_ktype;
203 error = kset_register(&cp->subsys);
207 error = sysfs_create_groups(&cp->subsys.kobj, cls->class_groups);
209 kobject_del(&cp->subsys.kobj);
210 kfree_const(cp->subsys.kobj.name);
216 lockdep_unregister_key(key);
220 EXPORT_SYMBOL_GPL(class_register);
222 void class_unregister(const struct class *cls)
224 struct subsys_private *sp = class_to_subsys(cls);
229 pr_debug("device class '%s': unregistering\n", cls->name);
231 sysfs_remove_groups(&sp->subsys.kobj, cls->class_groups);
232 kset_unregister(&sp->subsys);
235 EXPORT_SYMBOL_GPL(class_unregister);
237 static void class_create_release(const struct class *cls)
239 pr_debug("%s called for %s\n", __func__, cls->name);
244 * class_create - create a struct class structure
245 * @name: pointer to a string for the name of this class.
247 * This is used to create a struct class pointer that can then be used
248 * in calls to device_create().
250 * Returns &struct class pointer on success, or ERR_PTR() on error.
252 * Note, the pointer created here is to be destroyed when finished by
253 * making a call to class_destroy().
255 struct class *class_create(const char *name)
260 cls = kzalloc(sizeof(*cls), GFP_KERNEL);
267 cls->class_release = class_create_release;
269 retval = class_register(cls);
277 return ERR_PTR(retval);
279 EXPORT_SYMBOL_GPL(class_create);
282 * class_destroy - destroys a struct class structure
283 * @cls: pointer to the struct class that is to be destroyed
285 * Note, the pointer to be destroyed must have been created with a call
288 void class_destroy(const struct class *cls)
290 if (IS_ERR_OR_NULL(cls))
293 class_unregister(cls);
295 EXPORT_SYMBOL_GPL(class_destroy);
298 * class_dev_iter_init - initialize class device iterator
299 * @iter: class iterator to initialize
300 * @class: the class we wanna iterate over
301 * @start: the device to start iterating from, if any
302 * @type: device_type of the devices to iterate over, NULL for all
304 * Initialize class iterator @iter such that it iterates over devices
305 * of @class. If @start is set, the list iteration will start there,
306 * otherwise if it is NULL, the iteration starts at the beginning of
309 void class_dev_iter_init(struct class_dev_iter *iter, const struct class *class,
310 const struct device *start, const struct device_type *type)
312 struct subsys_private *sp = class_to_subsys(class);
313 struct klist_node *start_knode = NULL;
319 start_knode = &start->p->knode_class;
320 klist_iter_init_node(&sp->klist_devices, &iter->ki, start_knode);
324 EXPORT_SYMBOL_GPL(class_dev_iter_init);
327 * class_dev_iter_next - iterate to the next device
328 * @iter: class iterator to proceed
330 * Proceed @iter to the next device and return it. Returns NULL if
331 * iteration is complete.
333 * The returned device is referenced and won't be released till
334 * iterator is proceed to the next device or exited. The caller is
335 * free to do whatever it wants to do with the device including
336 * calling back into class code.
338 struct device *class_dev_iter_next(struct class_dev_iter *iter)
340 struct klist_node *knode;
344 knode = klist_next(&iter->ki);
347 dev = klist_class_to_dev(knode);
348 if (!iter->type || iter->type == dev->type)
352 EXPORT_SYMBOL_GPL(class_dev_iter_next);
355 * class_dev_iter_exit - finish iteration
356 * @iter: class iterator to finish
358 * Finish an iteration. Always call this function after iteration is
359 * complete whether the iteration ran till the end or not.
361 void class_dev_iter_exit(struct class_dev_iter *iter)
363 klist_iter_exit(&iter->ki);
364 subsys_put(iter->sp);
366 EXPORT_SYMBOL_GPL(class_dev_iter_exit);
369 * class_for_each_device - device iterator
370 * @class: the class we're iterating
371 * @start: the device to start with in the list, if any.
372 * @data: data for the callback
373 * @fn: function to be called for each device
375 * Iterate over @class's list of devices, and call @fn for each,
376 * passing it @data. If @start is set, the list iteration will start
377 * there, otherwise if it is NULL, the iteration starts at the
378 * beginning of the list.
380 * We check the return of @fn each time. If it returns anything
381 * other than 0, we break out and return that value.
383 * @fn is allowed to do anything including calling back into class
384 * code. There's no locking restriction.
386 int class_for_each_device(const struct class *class, const struct device *start,
387 void *data, int (*fn)(struct device *, void *))
389 struct subsys_private *sp = class_to_subsys(class);
390 struct class_dev_iter iter;
397 WARN(1, "%s called for class '%s' before it was initialized",
398 __func__, class->name);
402 class_dev_iter_init(&iter, class, start, NULL);
403 while ((dev = class_dev_iter_next(&iter))) {
404 error = fn(dev, data);
408 class_dev_iter_exit(&iter);
413 EXPORT_SYMBOL_GPL(class_for_each_device);
416 * class_find_device - device iterator for locating a particular device
417 * @class: the class we're iterating
418 * @start: Device to begin with
419 * @data: data for the match function
420 * @match: function to check device
422 * This is similar to the class_for_each_dev() function above, but it
423 * returns a reference to a device that is 'found' for later use, as
424 * determined by the @match callback.
426 * The callback should return 0 if the device doesn't match and non-zero
427 * if it does. If the callback returns non-zero, this function will
428 * return to the caller and not iterate over any more devices.
430 * Note, you will need to drop the reference with put_device() after use.
432 * @match is allowed to do anything including calling back into class
433 * code. There's no locking restriction.
435 struct device *class_find_device(const struct class *class, const struct device *start,
437 int (*match)(struct device *, const void *))
439 struct subsys_private *sp = class_to_subsys(class);
440 struct class_dev_iter iter;
446 WARN(1, "%s called for class '%s' before it was initialized",
447 __func__, class->name);
451 class_dev_iter_init(&iter, class, start, NULL);
452 while ((dev = class_dev_iter_next(&iter))) {
453 if (match(dev, data)) {
458 class_dev_iter_exit(&iter);
463 EXPORT_SYMBOL_GPL(class_find_device);
465 int class_interface_register(struct class_interface *class_intf)
467 struct subsys_private *sp;
468 const struct class *parent;
469 struct class_dev_iter iter;
472 if (!class_intf || !class_intf->class)
475 parent = class_intf->class;
476 sp = class_to_subsys(parent);
481 * Reference in sp is now incremented and will be dropped when
482 * the interface is removed in the call to class_interface_unregister()
485 mutex_lock(&sp->mutex);
486 list_add_tail(&class_intf->node, &sp->interfaces);
487 if (class_intf->add_dev) {
488 class_dev_iter_init(&iter, parent, NULL, NULL);
489 while ((dev = class_dev_iter_next(&iter)))
490 class_intf->add_dev(dev);
491 class_dev_iter_exit(&iter);
493 mutex_unlock(&sp->mutex);
497 EXPORT_SYMBOL_GPL(class_interface_register);
499 void class_interface_unregister(struct class_interface *class_intf)
501 struct subsys_private *sp;
502 const struct class *parent = class_intf->class;
503 struct class_dev_iter iter;
509 sp = class_to_subsys(parent);
513 mutex_lock(&sp->mutex);
514 list_del_init(&class_intf->node);
515 if (class_intf->remove_dev) {
516 class_dev_iter_init(&iter, parent, NULL, NULL);
517 while ((dev = class_dev_iter_next(&iter)))
518 class_intf->remove_dev(dev);
519 class_dev_iter_exit(&iter);
521 mutex_unlock(&sp->mutex);
524 * Decrement the reference count twice, once for the class_to_subsys()
525 * call in the start of this function, and the second one from the
526 * reference increment in class_interface_register()
531 EXPORT_SYMBOL_GPL(class_interface_unregister);
533 ssize_t show_class_attr_string(const struct class *class,
534 const struct class_attribute *attr, char *buf)
536 struct class_attribute_string *cs;
538 cs = container_of(attr, struct class_attribute_string, attr);
539 return sysfs_emit(buf, "%s\n", cs->str);
542 EXPORT_SYMBOL_GPL(show_class_attr_string);
544 struct class_compat {
545 struct kobject *kobj;
549 * class_compat_register - register a compatibility class
550 * @name: the name of the class
552 * Compatibility class are meant as a temporary user-space compatibility
553 * workaround when converting a family of class devices to a bus devices.
555 struct class_compat *class_compat_register(const char *name)
557 struct class_compat *cls;
559 cls = kmalloc(sizeof(struct class_compat), GFP_KERNEL);
562 cls->kobj = kobject_create_and_add(name, &class_kset->kobj);
569 EXPORT_SYMBOL_GPL(class_compat_register);
572 * class_compat_unregister - unregister a compatibility class
573 * @cls: the class to unregister
575 void class_compat_unregister(struct class_compat *cls)
577 kobject_put(cls->kobj);
580 EXPORT_SYMBOL_GPL(class_compat_unregister);
583 * class_compat_create_link - create a compatibility class device link to
585 * @cls: the compatibility class
586 * @dev: the target bus device
587 * @device_link: an optional device to which a "device" link should be created
589 int class_compat_create_link(struct class_compat *cls, struct device *dev,
590 struct device *device_link)
594 error = sysfs_create_link(cls->kobj, &dev->kobj, dev_name(dev));
599 * Optionally add a "device" link (typically to the parent), as a
600 * class device would have one and we want to provide as much
601 * backwards compatibility as possible.
604 error = sysfs_create_link(&dev->kobj, &device_link->kobj,
607 sysfs_remove_link(cls->kobj, dev_name(dev));
612 EXPORT_SYMBOL_GPL(class_compat_create_link);
615 * class_compat_remove_link - remove a compatibility class device link to
617 * @cls: the compatibility class
618 * @dev: the target bus device
619 * @device_link: an optional device to which a "device" link was previously
622 void class_compat_remove_link(struct class_compat *cls, struct device *dev,
623 struct device *device_link)
626 sysfs_remove_link(&dev->kobj, "device");
627 sysfs_remove_link(cls->kobj, dev_name(dev));
629 EXPORT_SYMBOL_GPL(class_compat_remove_link);
632 * class_is_registered - determine if at this moment in time, a class is
633 * registered in the driver core or not.
634 * @class: the class to check
636 * Returns a boolean to state if the class is registered in the driver core
637 * or not. Note that the value could switch right after this call is made,
638 * so only use this in places where you "know" it is safe to do so (usually
639 * to determine if the specific class has been registered yet or not).
641 * Be careful in using this.
643 bool class_is_registered(const struct class *class)
645 struct subsys_private *sp = class_to_subsys(class);
646 bool is_initialized = false;
649 is_initialized = true;
652 return is_initialized;
654 EXPORT_SYMBOL_GPL(class_is_registered);
656 int __init classes_init(void)
658 class_kset = kset_create_and_add("class", NULL, NULL);