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>
23 #define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
25 static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
28 struct class_attribute *class_attr = to_class_attr(attr);
29 struct subsys_private *cp = to_subsys_private(kobj);
33 ret = class_attr->show(cp->class, class_attr, buf);
37 static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
38 const char *buf, size_t count)
40 struct class_attribute *class_attr = to_class_attr(attr);
41 struct subsys_private *cp = to_subsys_private(kobj);
44 if (class_attr->store)
45 ret = class_attr->store(cp->class, class_attr, buf, count);
49 static void class_release(struct kobject *kobj)
51 struct subsys_private *cp = to_subsys_private(kobj);
52 struct class *class = cp->class;
54 pr_debug("class '%s': release.\n", class->name);
58 if (class->class_release)
59 class->class_release(class);
61 pr_debug("class '%s' does not have a release() function, "
62 "be careful\n", class->name);
67 static const struct kobj_ns_type_operations *class_child_ns_type(const struct kobject *kobj)
69 const struct subsys_private *cp = to_subsys_private(kobj);
70 struct class *class = cp->class;
72 return class->ns_type;
75 static const struct sysfs_ops class_sysfs_ops = {
76 .show = class_attr_show,
77 .store = class_attr_store,
80 static const struct kobj_type class_ktype = {
81 .sysfs_ops = &class_sysfs_ops,
82 .release = class_release,
83 .child_ns_type = class_child_ns_type,
86 /* Hotplug events for classes go to the class subsys */
87 static struct kset *class_kset;
90 int class_create_file_ns(const struct class *cls, const struct class_attribute *attr,
96 error = sysfs_create_file_ns(&cls->p->subsys.kobj,
102 EXPORT_SYMBOL_GPL(class_create_file_ns);
104 void class_remove_file_ns(const struct class *cls, const struct class_attribute *attr,
108 sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns);
110 EXPORT_SYMBOL_GPL(class_remove_file_ns);
112 static struct class *class_get(struct class *cls)
115 kset_get(&cls->p->subsys);
119 static void class_put(struct class *cls)
122 kset_put(&cls->p->subsys);
125 static struct device *klist_class_to_dev(struct klist_node *n)
127 struct device_private *p = to_device_private_class(n);
131 static void klist_class_dev_get(struct klist_node *n)
133 struct device *dev = klist_class_to_dev(n);
138 static void klist_class_dev_put(struct klist_node *n)
140 struct device *dev = klist_class_to_dev(n);
145 static int class_add_groups(struct class *cls,
146 const struct attribute_group **groups)
148 return sysfs_create_groups(&cls->p->subsys.kobj, groups);
151 static void class_remove_groups(struct class *cls,
152 const struct attribute_group **groups)
154 return sysfs_remove_groups(&cls->p->subsys.kobj, groups);
157 int class_register(struct class *cls)
159 struct subsys_private *cp;
160 struct lock_class_key *key;
163 pr_debug("device class '%s': registering\n", cls->name);
165 cp = kzalloc(sizeof(*cp), GFP_KERNEL);
168 klist_init(&cp->klist_devices, klist_class_dev_get, klist_class_dev_put);
169 INIT_LIST_HEAD(&cp->interfaces);
170 kset_init(&cp->glue_dirs);
172 lockdep_register_key(key);
173 __mutex_init(&cp->mutex, "subsys mutex", key);
174 error = kobject_set_name(&cp->subsys.kobj, "%s", cls->name);
180 /* set the default /sys/dev directory for devices of this class */
182 cls->dev_kobj = sysfs_dev_char_kobj;
184 cp->subsys.kobj.kset = class_kset;
185 cp->subsys.kobj.ktype = &class_ktype;
189 error = kset_register(&cp->subsys);
193 error = class_add_groups(class_get(cls), cls->class_groups);
196 kobject_del(&cp->subsys.kobj);
197 kfree_const(cp->subsys.kobj.name);
207 EXPORT_SYMBOL_GPL(class_register);
209 void class_unregister(struct class *cls)
211 pr_debug("device class '%s': unregistering\n", cls->name);
212 class_remove_groups(cls, cls->class_groups);
213 kset_unregister(&cls->p->subsys);
215 EXPORT_SYMBOL_GPL(class_unregister);
217 static void class_create_release(struct class *cls)
219 pr_debug("%s called for %s\n", __func__, cls->name);
224 * class_create - create a struct class structure
225 * @name: pointer to a string for the name of this class.
227 * This is used to create a struct class pointer that can then be used
228 * in calls to device_create().
230 * Returns &struct class pointer on success, or ERR_PTR() on error.
232 * Note, the pointer created here is to be destroyed when finished by
233 * making a call to class_destroy().
235 struct class *class_create(const char *name)
240 cls = kzalloc(sizeof(*cls), GFP_KERNEL);
247 cls->class_release = class_create_release;
249 retval = class_register(cls);
257 return ERR_PTR(retval);
259 EXPORT_SYMBOL_GPL(class_create);
262 * class_destroy - destroys a struct class structure
263 * @cls: pointer to the struct class that is to be destroyed
265 * Note, the pointer to be destroyed must have been created with a call
268 void class_destroy(struct class *cls)
270 if (IS_ERR_OR_NULL(cls))
273 class_unregister(cls);
275 EXPORT_SYMBOL_GPL(class_destroy);
278 * class_dev_iter_init - initialize class device iterator
279 * @iter: class iterator to initialize
280 * @class: the class we wanna iterate over
281 * @start: the device to start iterating from, if any
282 * @type: device_type of the devices to iterate over, NULL for all
284 * Initialize class iterator @iter such that it iterates over devices
285 * of @class. If @start is set, the list iteration will start there,
286 * otherwise if it is NULL, the iteration starts at the beginning of
289 void class_dev_iter_init(struct class_dev_iter *iter, const struct class *class,
290 const struct device *start, const struct device_type *type)
292 struct klist_node *start_knode = NULL;
295 start_knode = &start->p->knode_class;
296 klist_iter_init_node(&class->p->klist_devices, &iter->ki, start_knode);
299 EXPORT_SYMBOL_GPL(class_dev_iter_init);
302 * class_dev_iter_next - iterate to the next device
303 * @iter: class iterator to proceed
305 * Proceed @iter to the next device and return it. Returns NULL if
306 * iteration is complete.
308 * The returned device is referenced and won't be released till
309 * iterator is proceed to the next device or exited. The caller is
310 * free to do whatever it wants to do with the device including
311 * calling back into class code.
313 struct device *class_dev_iter_next(struct class_dev_iter *iter)
315 struct klist_node *knode;
319 knode = klist_next(&iter->ki);
322 dev = klist_class_to_dev(knode);
323 if (!iter->type || iter->type == dev->type)
327 EXPORT_SYMBOL_GPL(class_dev_iter_next);
330 * class_dev_iter_exit - finish iteration
331 * @iter: class iterator to finish
333 * Finish an iteration. Always call this function after iteration is
334 * complete whether the iteration ran till the end or not.
336 void class_dev_iter_exit(struct class_dev_iter *iter)
338 klist_iter_exit(&iter->ki);
340 EXPORT_SYMBOL_GPL(class_dev_iter_exit);
343 * class_for_each_device - device iterator
344 * @class: the class we're iterating
345 * @start: the device to start with in the list, if any.
346 * @data: data for the callback
347 * @fn: function to be called for each device
349 * Iterate over @class's list of devices, and call @fn for each,
350 * passing it @data. If @start is set, the list iteration will start
351 * there, otherwise if it is NULL, the iteration starts at the
352 * beginning of the list.
354 * We check the return of @fn each time. If it returns anything
355 * other than 0, we break out and return that value.
357 * @fn is allowed to do anything including calling back into class
358 * code. There's no locking restriction.
360 int class_for_each_device(const struct class *class, const struct device *start,
361 void *data, int (*fn)(struct device *, void *))
363 struct class_dev_iter iter;
370 WARN(1, "%s called for class '%s' before it was initialized",
371 __func__, class->name);
375 class_dev_iter_init(&iter, class, start, NULL);
376 while ((dev = class_dev_iter_next(&iter))) {
377 error = fn(dev, data);
381 class_dev_iter_exit(&iter);
385 EXPORT_SYMBOL_GPL(class_for_each_device);
388 * class_find_device - device iterator for locating a particular device
389 * @class: the class we're iterating
390 * @start: Device to begin with
391 * @data: data for the match function
392 * @match: function to check device
394 * This is similar to the class_for_each_dev() function above, but it
395 * returns a reference to a device that is 'found' for later use, as
396 * determined by the @match callback.
398 * The callback should return 0 if the device doesn't match and non-zero
399 * if it does. If the callback returns non-zero, this function will
400 * return to the caller and not iterate over any more devices.
402 * Note, you will need to drop the reference with put_device() after use.
404 * @match is allowed to do anything including calling back into class
405 * code. There's no locking restriction.
407 struct device *class_find_device(const struct class *class, const struct device *start,
409 int (*match)(struct device *, const void *))
411 struct class_dev_iter iter;
417 WARN(1, "%s called for class '%s' before it was initialized",
418 __func__, class->name);
422 class_dev_iter_init(&iter, class, start, NULL);
423 while ((dev = class_dev_iter_next(&iter))) {
424 if (match(dev, data)) {
429 class_dev_iter_exit(&iter);
433 EXPORT_SYMBOL_GPL(class_find_device);
435 int class_interface_register(struct class_interface *class_intf)
437 struct class *parent;
438 struct class_dev_iter iter;
441 if (!class_intf || !class_intf->class)
444 parent = class_get(class_intf->class);
448 mutex_lock(&parent->p->mutex);
449 list_add_tail(&class_intf->node, &parent->p->interfaces);
450 if (class_intf->add_dev) {
451 class_dev_iter_init(&iter, parent, NULL, NULL);
452 while ((dev = class_dev_iter_next(&iter)))
453 class_intf->add_dev(dev, class_intf);
454 class_dev_iter_exit(&iter);
456 mutex_unlock(&parent->p->mutex);
460 EXPORT_SYMBOL_GPL(class_interface_register);
462 void class_interface_unregister(struct class_interface *class_intf)
464 struct class *parent = class_intf->class;
465 struct class_dev_iter iter;
471 mutex_lock(&parent->p->mutex);
472 list_del_init(&class_intf->node);
473 if (class_intf->remove_dev) {
474 class_dev_iter_init(&iter, parent, NULL, NULL);
475 while ((dev = class_dev_iter_next(&iter)))
476 class_intf->remove_dev(dev, class_intf);
477 class_dev_iter_exit(&iter);
479 mutex_unlock(&parent->p->mutex);
483 EXPORT_SYMBOL_GPL(class_interface_unregister);
485 ssize_t show_class_attr_string(struct class *class,
486 struct class_attribute *attr, char *buf)
488 struct class_attribute_string *cs;
490 cs = container_of(attr, struct class_attribute_string, attr);
491 return sysfs_emit(buf, "%s\n", cs->str);
494 EXPORT_SYMBOL_GPL(show_class_attr_string);
496 struct class_compat {
497 struct kobject *kobj;
501 * class_compat_register - register a compatibility class
502 * @name: the name of the class
504 * Compatibility class are meant as a temporary user-space compatibility
505 * workaround when converting a family of class devices to a bus devices.
507 struct class_compat *class_compat_register(const char *name)
509 struct class_compat *cls;
511 cls = kmalloc(sizeof(struct class_compat), GFP_KERNEL);
514 cls->kobj = kobject_create_and_add(name, &class_kset->kobj);
521 EXPORT_SYMBOL_GPL(class_compat_register);
524 * class_compat_unregister - unregister a compatibility class
525 * @cls: the class to unregister
527 void class_compat_unregister(struct class_compat *cls)
529 kobject_put(cls->kobj);
532 EXPORT_SYMBOL_GPL(class_compat_unregister);
535 * class_compat_create_link - create a compatibility class device link to
537 * @cls: the compatibility class
538 * @dev: the target bus device
539 * @device_link: an optional device to which a "device" link should be created
541 int class_compat_create_link(struct class_compat *cls, struct device *dev,
542 struct device *device_link)
546 error = sysfs_create_link(cls->kobj, &dev->kobj, dev_name(dev));
551 * Optionally add a "device" link (typically to the parent), as a
552 * class device would have one and we want to provide as much
553 * backwards compatibility as possible.
556 error = sysfs_create_link(&dev->kobj, &device_link->kobj,
559 sysfs_remove_link(cls->kobj, dev_name(dev));
564 EXPORT_SYMBOL_GPL(class_compat_create_link);
567 * class_compat_remove_link - remove a compatibility class device link to
569 * @cls: the compatibility class
570 * @dev: the target bus device
571 * @device_link: an optional device to which a "device" link was previously
574 void class_compat_remove_link(struct class_compat *cls, struct device *dev,
575 struct device *device_link)
578 sysfs_remove_link(&dev->kobj, "device");
579 sysfs_remove_link(cls->kobj, dev_name(dev));
581 EXPORT_SYMBOL_GPL(class_compat_remove_link);
583 int __init classes_init(void)
585 class_kset = kset_create_and_add("class", NULL, NULL);