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 static 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 struct class *class = cp->class;
98 pr_debug("class '%s': release.\n", class->name);
102 if (class->class_release)
103 class->class_release(class);
105 pr_debug("class '%s' does not have a release() function, "
106 "be careful\n", class->name);
111 static const struct kobj_ns_type_operations *class_child_ns_type(const struct kobject *kobj)
113 const struct subsys_private *cp = to_subsys_private(kobj);
114 struct class *class = cp->class;
116 return class->ns_type;
119 static const struct sysfs_ops class_sysfs_ops = {
120 .show = class_attr_show,
121 .store = class_attr_store,
124 static const struct kobj_type class_ktype = {
125 .sysfs_ops = &class_sysfs_ops,
126 .release = class_release,
127 .child_ns_type = class_child_ns_type,
130 int class_create_file_ns(const struct class *cls, const struct class_attribute *attr,
133 struct subsys_private *sp = class_to_subsys(cls);
139 error = sysfs_create_file_ns(&sp->subsys.kobj, &attr->attr, ns);
144 EXPORT_SYMBOL_GPL(class_create_file_ns);
146 void class_remove_file_ns(const struct class *cls, const struct class_attribute *attr,
149 struct subsys_private *sp = class_to_subsys(cls);
154 sysfs_remove_file_ns(&sp->subsys.kobj, &attr->attr, ns);
157 EXPORT_SYMBOL_GPL(class_remove_file_ns);
159 static struct device *klist_class_to_dev(struct klist_node *n)
161 struct device_private *p = to_device_private_class(n);
165 static void klist_class_dev_get(struct klist_node *n)
167 struct device *dev = klist_class_to_dev(n);
172 static void klist_class_dev_put(struct klist_node *n)
174 struct device *dev = klist_class_to_dev(n);
179 int class_register(struct class *cls)
181 struct subsys_private *cp;
182 struct lock_class_key *key;
185 pr_debug("device class '%s': registering\n", cls->name);
187 cp = kzalloc(sizeof(*cp), GFP_KERNEL);
190 klist_init(&cp->klist_devices, klist_class_dev_get, klist_class_dev_put);
191 INIT_LIST_HEAD(&cp->interfaces);
192 kset_init(&cp->glue_dirs);
194 lockdep_register_key(key);
195 __mutex_init(&cp->mutex, "subsys mutex", key);
196 error = kobject_set_name(&cp->subsys.kobj, "%s", cls->name);
202 /* set the default /sys/dev directory for devices of this class */
204 cls->dev_kobj = sysfs_dev_char_kobj;
206 cp->subsys.kobj.kset = class_kset;
207 cp->subsys.kobj.ktype = &class_ktype;
211 error = kset_register(&cp->subsys);
215 error = sysfs_create_groups(&cp->subsys.kobj, cls->class_groups);
217 kobject_del(&cp->subsys.kobj);
218 kfree_const(cp->subsys.kobj.name);
228 EXPORT_SYMBOL_GPL(class_register);
230 void class_unregister(const struct class *cls)
232 struct subsys_private *sp = class_to_subsys(cls);
237 pr_debug("device class '%s': unregistering\n", cls->name);
239 sysfs_remove_groups(&sp->subsys.kobj, cls->class_groups);
240 kset_unregister(&sp->subsys);
243 EXPORT_SYMBOL_GPL(class_unregister);
245 static void class_create_release(struct class *cls)
247 pr_debug("%s called for %s\n", __func__, cls->name);
252 * class_create - create a struct class structure
253 * @name: pointer to a string for the name of this class.
255 * This is used to create a struct class pointer that can then be used
256 * in calls to device_create().
258 * Returns &struct class pointer on success, or ERR_PTR() on error.
260 * Note, the pointer created here is to be destroyed when finished by
261 * making a call to class_destroy().
263 struct class *class_create(const char *name)
268 cls = kzalloc(sizeof(*cls), GFP_KERNEL);
275 cls->class_release = class_create_release;
277 retval = class_register(cls);
285 return ERR_PTR(retval);
287 EXPORT_SYMBOL_GPL(class_create);
290 * class_destroy - destroys a struct class structure
291 * @cls: pointer to the struct class that is to be destroyed
293 * Note, the pointer to be destroyed must have been created with a call
296 void class_destroy(const struct class *cls)
298 if (IS_ERR_OR_NULL(cls))
301 class_unregister(cls);
303 EXPORT_SYMBOL_GPL(class_destroy);
306 * class_dev_iter_init - initialize class device iterator
307 * @iter: class iterator to initialize
308 * @class: the class we wanna iterate over
309 * @start: the device to start iterating from, if any
310 * @type: device_type of the devices to iterate over, NULL for all
312 * Initialize class iterator @iter such that it iterates over devices
313 * of @class. If @start is set, the list iteration will start there,
314 * otherwise if it is NULL, the iteration starts at the beginning of
317 void class_dev_iter_init(struct class_dev_iter *iter, const struct class *class,
318 const struct device *start, const struct device_type *type)
320 struct subsys_private *sp = class_to_subsys(class);
321 struct klist_node *start_knode = NULL;
327 start_knode = &start->p->knode_class;
328 klist_iter_init_node(&sp->klist_devices, &iter->ki, start_knode);
331 EXPORT_SYMBOL_GPL(class_dev_iter_init);
334 * class_dev_iter_next - iterate to the next device
335 * @iter: class iterator to proceed
337 * Proceed @iter to the next device and return it. Returns NULL if
338 * iteration is complete.
340 * The returned device is referenced and won't be released till
341 * iterator is proceed to the next device or exited. The caller is
342 * free to do whatever it wants to do with the device including
343 * calling back into class code.
345 struct device *class_dev_iter_next(struct class_dev_iter *iter)
347 struct klist_node *knode;
351 knode = klist_next(&iter->ki);
354 dev = klist_class_to_dev(knode);
355 if (!iter->type || iter->type == dev->type)
359 EXPORT_SYMBOL_GPL(class_dev_iter_next);
362 * class_dev_iter_exit - finish iteration
363 * @iter: class iterator to finish
365 * Finish an iteration. Always call this function after iteration is
366 * complete whether the iteration ran till the end or not.
368 void class_dev_iter_exit(struct class_dev_iter *iter)
370 klist_iter_exit(&iter->ki);
372 EXPORT_SYMBOL_GPL(class_dev_iter_exit);
375 * class_for_each_device - device iterator
376 * @class: the class we're iterating
377 * @start: the device to start with in the list, if any.
378 * @data: data for the callback
379 * @fn: function to be called for each device
381 * Iterate over @class's list of devices, and call @fn for each,
382 * passing it @data. If @start is set, the list iteration will start
383 * there, otherwise if it is NULL, the iteration starts at the
384 * beginning of the list.
386 * We check the return of @fn each time. If it returns anything
387 * other than 0, we break out and return that value.
389 * @fn is allowed to do anything including calling back into class
390 * code. There's no locking restriction.
392 int class_for_each_device(const struct class *class, const struct device *start,
393 void *data, int (*fn)(struct device *, void *))
395 struct subsys_private *sp = class_to_subsys(class);
396 struct class_dev_iter iter;
403 WARN(1, "%s called for class '%s' before it was initialized",
404 __func__, class->name);
408 class_dev_iter_init(&iter, class, start, NULL);
409 while ((dev = class_dev_iter_next(&iter))) {
410 error = fn(dev, data);
414 class_dev_iter_exit(&iter);
419 EXPORT_SYMBOL_GPL(class_for_each_device);
422 * class_find_device - device iterator for locating a particular device
423 * @class: the class we're iterating
424 * @start: Device to begin with
425 * @data: data for the match function
426 * @match: function to check device
428 * This is similar to the class_for_each_dev() function above, but it
429 * returns a reference to a device that is 'found' for later use, as
430 * determined by the @match callback.
432 * The callback should return 0 if the device doesn't match and non-zero
433 * if it does. If the callback returns non-zero, this function will
434 * return to the caller and not iterate over any more devices.
436 * Note, you will need to drop the reference with put_device() after use.
438 * @match is allowed to do anything including calling back into class
439 * code. There's no locking restriction.
441 struct device *class_find_device(const struct class *class, const struct device *start,
443 int (*match)(struct device *, const void *))
445 struct subsys_private *sp = class_to_subsys(class);
446 struct class_dev_iter iter;
452 WARN(1, "%s called for class '%s' before it was initialized",
453 __func__, class->name);
457 class_dev_iter_init(&iter, class, start, NULL);
458 while ((dev = class_dev_iter_next(&iter))) {
459 if (match(dev, data)) {
464 class_dev_iter_exit(&iter);
469 EXPORT_SYMBOL_GPL(class_find_device);
471 int class_interface_register(struct class_interface *class_intf)
473 struct subsys_private *sp;
474 const struct class *parent;
475 struct class_dev_iter iter;
478 if (!class_intf || !class_intf->class)
481 parent = class_intf->class;
482 sp = class_to_subsys(parent);
487 * Reference in sp is now incremented and will be dropped when
488 * the interface is removed in the call to class_interface_unregister()
491 mutex_lock(&sp->mutex);
492 list_add_tail(&class_intf->node, &sp->interfaces);
493 if (class_intf->add_dev) {
494 class_dev_iter_init(&iter, parent, NULL, NULL);
495 while ((dev = class_dev_iter_next(&iter)))
496 class_intf->add_dev(dev, class_intf);
497 class_dev_iter_exit(&iter);
499 mutex_unlock(&sp->mutex);
503 EXPORT_SYMBOL_GPL(class_interface_register);
505 void class_interface_unregister(struct class_interface *class_intf)
507 struct subsys_private *sp;
508 struct class *parent = class_intf->class;
509 struct class_dev_iter iter;
515 sp = class_to_subsys(parent);
519 mutex_lock(&sp->mutex);
520 list_del_init(&class_intf->node);
521 if (class_intf->remove_dev) {
522 class_dev_iter_init(&iter, parent, NULL, NULL);
523 while ((dev = class_dev_iter_next(&iter)))
524 class_intf->remove_dev(dev, class_intf);
525 class_dev_iter_exit(&iter);
527 mutex_unlock(&sp->mutex);
530 * Decrement the reference count twice, once for the class_to_subsys()
531 * call in the start of this function, and the second one from the
532 * reference increment in class_interface_register()
537 EXPORT_SYMBOL_GPL(class_interface_unregister);
539 ssize_t show_class_attr_string(const struct class *class,
540 const struct class_attribute *attr, char *buf)
542 struct class_attribute_string *cs;
544 cs = container_of(attr, struct class_attribute_string, attr);
545 return sysfs_emit(buf, "%s\n", cs->str);
548 EXPORT_SYMBOL_GPL(show_class_attr_string);
550 struct class_compat {
551 struct kobject *kobj;
555 * class_compat_register - register a compatibility class
556 * @name: the name of the class
558 * Compatibility class are meant as a temporary user-space compatibility
559 * workaround when converting a family of class devices to a bus devices.
561 struct class_compat *class_compat_register(const char *name)
563 struct class_compat *cls;
565 cls = kmalloc(sizeof(struct class_compat), GFP_KERNEL);
568 cls->kobj = kobject_create_and_add(name, &class_kset->kobj);
575 EXPORT_SYMBOL_GPL(class_compat_register);
578 * class_compat_unregister - unregister a compatibility class
579 * @cls: the class to unregister
581 void class_compat_unregister(struct class_compat *cls)
583 kobject_put(cls->kobj);
586 EXPORT_SYMBOL_GPL(class_compat_unregister);
589 * class_compat_create_link - create a compatibility class device link to
591 * @cls: the compatibility class
592 * @dev: the target bus device
593 * @device_link: an optional device to which a "device" link should be created
595 int class_compat_create_link(struct class_compat *cls, struct device *dev,
596 struct device *device_link)
600 error = sysfs_create_link(cls->kobj, &dev->kobj, dev_name(dev));
605 * Optionally add a "device" link (typically to the parent), as a
606 * class device would have one and we want to provide as much
607 * backwards compatibility as possible.
610 error = sysfs_create_link(&dev->kobj, &device_link->kobj,
613 sysfs_remove_link(cls->kobj, dev_name(dev));
618 EXPORT_SYMBOL_GPL(class_compat_create_link);
621 * class_compat_remove_link - remove a compatibility class device link to
623 * @cls: the compatibility class
624 * @dev: the target bus device
625 * @device_link: an optional device to which a "device" link was previously
628 void class_compat_remove_link(struct class_compat *cls, struct device *dev,
629 struct device *device_link)
632 sysfs_remove_link(&dev->kobj, "device");
633 sysfs_remove_link(cls->kobj, dev_name(dev));
635 EXPORT_SYMBOL_GPL(class_compat_remove_link);
637 int __init classes_init(void)
639 class_kset = kset_create_and_add("class", NULL, NULL);