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.h>
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/string.h>
15 #include <linux/kdev_t.h>
16 #include <linux/err.h>
17 #include <linux/slab.h>
18 #include <linux/genhd.h>
19 #include <linux/mutex.h>
22 #define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
24 static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
27 struct class_attribute *class_attr = to_class_attr(attr);
28 struct subsys_private *cp = to_subsys_private(kobj);
32 ret = class_attr->show(cp->class, class_attr, buf);
36 static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
37 const char *buf, size_t count)
39 struct class_attribute *class_attr = to_class_attr(attr);
40 struct subsys_private *cp = to_subsys_private(kobj);
43 if (class_attr->store)
44 ret = class_attr->store(cp->class, class_attr, buf, count);
48 static void class_release(struct kobject *kobj)
50 struct subsys_private *cp = to_subsys_private(kobj);
51 struct class *class = cp->class;
53 pr_debug("class '%s': release.\n", class->name);
55 if (class->class_release)
56 class->class_release(class);
58 pr_debug("class '%s' does not have a release() function, "
59 "be careful\n", class->name);
64 static const struct kobj_ns_type_operations *class_child_ns_type(struct kobject *kobj)
66 struct subsys_private *cp = to_subsys_private(kobj);
67 struct class *class = cp->class;
69 return class->ns_type;
72 static const struct sysfs_ops class_sysfs_ops = {
73 .show = class_attr_show,
74 .store = class_attr_store,
77 static struct kobj_type class_ktype = {
78 .sysfs_ops = &class_sysfs_ops,
79 .release = class_release,
80 .child_ns_type = class_child_ns_type,
83 /* Hotplug events for classes go to the class subsys */
84 static struct kset *class_kset;
87 int class_create_file_ns(struct class *cls, const struct class_attribute *attr,
93 error = sysfs_create_file_ns(&cls->p->subsys.kobj,
100 void class_remove_file_ns(struct class *cls, const struct class_attribute *attr,
104 sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns);
107 static struct class *class_get(struct class *cls)
110 kset_get(&cls->p->subsys);
114 static void class_put(struct class *cls)
117 kset_put(&cls->p->subsys);
120 static struct device *klist_class_to_dev(struct klist_node *n)
122 struct device_private *p = to_device_private_class(n);
126 static void klist_class_dev_get(struct klist_node *n)
128 struct device *dev = klist_class_to_dev(n);
133 static void klist_class_dev_put(struct klist_node *n)
135 struct device *dev = klist_class_to_dev(n);
140 static int class_add_groups(struct class *cls,
141 const struct attribute_group **groups)
143 return sysfs_create_groups(&cls->p->subsys.kobj, groups);
146 static void class_remove_groups(struct class *cls,
147 const struct attribute_group **groups)
149 return sysfs_remove_groups(&cls->p->subsys.kobj, groups);
152 int __class_register(struct class *cls, struct lock_class_key *key)
154 struct subsys_private *cp;
157 pr_debug("device class '%s': registering\n", cls->name);
159 cp = kzalloc(sizeof(*cp), GFP_KERNEL);
162 klist_init(&cp->klist_devices, klist_class_dev_get, klist_class_dev_put);
163 INIT_LIST_HEAD(&cp->interfaces);
164 kset_init(&cp->glue_dirs);
165 __mutex_init(&cp->mutex, "subsys mutex", key);
166 error = kobject_set_name(&cp->subsys.kobj, "%s", cls->name);
172 /* set the default /sys/dev directory for devices of this class */
174 cls->dev_kobj = sysfs_dev_char_kobj;
176 #if defined(CONFIG_BLOCK)
177 /* let the block class directory show up in the root of sysfs */
178 if (!sysfs_deprecated || cls != &block_class)
179 cp->subsys.kobj.kset = class_kset;
181 cp->subsys.kobj.kset = class_kset;
183 cp->subsys.kobj.ktype = &class_ktype;
187 error = kset_register(&cp->subsys);
192 error = class_add_groups(class_get(cls), cls->class_groups);
195 kobject_del(&cp->subsys.kobj);
196 kfree_const(cp->subsys.kobj.name);
201 EXPORT_SYMBOL_GPL(__class_register);
203 void class_unregister(struct class *cls)
205 pr_debug("device class '%s': unregistering\n", cls->name);
206 class_remove_groups(cls, cls->class_groups);
207 kset_unregister(&cls->p->subsys);
210 static void class_create_release(struct class *cls)
212 pr_debug("%s called for %s\n", __func__, cls->name);
217 * class_create - create a struct class structure
218 * @owner: pointer to the module that is to "own" this struct class
219 * @name: pointer to a string for the name of this class.
220 * @key: the lock_class_key for this class; used by mutex lock debugging
222 * This is used to create a struct class pointer that can then be used
223 * in calls to device_create().
225 * Returns &struct class pointer on success, or ERR_PTR() on error.
227 * Note, the pointer created here is to be destroyed when finished by
228 * making a call to class_destroy().
230 struct class *__class_create(struct module *owner, const char *name,
231 struct lock_class_key *key)
236 cls = kzalloc(sizeof(*cls), GFP_KERNEL);
244 cls->class_release = class_create_release;
246 retval = __class_register(cls, key);
254 return ERR_PTR(retval);
256 EXPORT_SYMBOL_GPL(__class_create);
259 * class_destroy - destroys a struct class structure
260 * @cls: pointer to the struct class that is to be destroyed
262 * Note, the pointer to be destroyed must have been created with a call
265 void class_destroy(struct class *cls)
267 if ((cls == NULL) || (IS_ERR(cls)))
270 class_unregister(cls);
274 * class_dev_iter_init - initialize class device iterator
275 * @iter: class iterator to initialize
276 * @class: the class we wanna iterate over
277 * @start: the device to start iterating from, if any
278 * @type: device_type of the devices to iterate over, NULL for all
280 * Initialize class iterator @iter such that it iterates over devices
281 * of @class. If @start is set, the list iteration will start there,
282 * otherwise if it is NULL, the iteration starts at the beginning of
285 void class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
286 struct device *start, const struct device_type *type)
288 struct klist_node *start_knode = NULL;
291 start_knode = &start->p->knode_class;
292 klist_iter_init_node(&class->p->klist_devices, &iter->ki, start_knode);
295 EXPORT_SYMBOL_GPL(class_dev_iter_init);
298 * class_dev_iter_next - iterate to the next device
299 * @iter: class iterator to proceed
301 * Proceed @iter to the next device and return it. Returns NULL if
302 * iteration is complete.
304 * The returned device is referenced and won't be released till
305 * iterator is proceed to the next device or exited. The caller is
306 * free to do whatever it wants to do with the device including
307 * calling back into class code.
309 struct device *class_dev_iter_next(struct class_dev_iter *iter)
311 struct klist_node *knode;
315 knode = klist_next(&iter->ki);
318 dev = klist_class_to_dev(knode);
319 if (!iter->type || iter->type == dev->type)
323 EXPORT_SYMBOL_GPL(class_dev_iter_next);
326 * class_dev_iter_exit - finish iteration
327 * @iter: class iterator to finish
329 * Finish an iteration. Always call this function after iteration is
330 * complete whether the iteration ran till the end or not.
332 void class_dev_iter_exit(struct class_dev_iter *iter)
334 klist_iter_exit(&iter->ki);
336 EXPORT_SYMBOL_GPL(class_dev_iter_exit);
339 * class_for_each_device - device iterator
340 * @class: the class we're iterating
341 * @start: the device to start with in the list, if any.
342 * @data: data for the callback
343 * @fn: function to be called for each device
345 * Iterate over @class's list of devices, and call @fn for each,
346 * passing it @data. If @start is set, the list iteration will start
347 * there, otherwise if it is NULL, the iteration starts at the
348 * beginning of the list.
350 * We check the return of @fn each time. If it returns anything
351 * other than 0, we break out and return that value.
353 * @fn is allowed to do anything including calling back into class
354 * code. There's no locking restriction.
356 int class_for_each_device(struct class *class, struct device *start,
357 void *data, int (*fn)(struct device *, void *))
359 struct class_dev_iter iter;
366 WARN(1, "%s called for class '%s' before it was initialized",
367 __func__, class->name);
371 class_dev_iter_init(&iter, class, start, NULL);
372 while ((dev = class_dev_iter_next(&iter))) {
373 error = fn(dev, data);
377 class_dev_iter_exit(&iter);
381 EXPORT_SYMBOL_GPL(class_for_each_device);
384 * class_find_device - device iterator for locating a particular device
385 * @class: the class we're iterating
386 * @start: Device to begin with
387 * @data: data for the match function
388 * @match: function to check device
390 * This is similar to the class_for_each_dev() function above, but it
391 * returns a reference to a device that is 'found' for later use, as
392 * determined by the @match callback.
394 * The callback should return 0 if the device doesn't match and non-zero
395 * if it does. If the callback returns non-zero, this function will
396 * return to the caller and not iterate over any more devices.
398 * Note, you will need to drop the reference with put_device() after use.
400 * @match is allowed to do anything including calling back into class
401 * code. There's no locking restriction.
403 struct device *class_find_device(struct class *class, struct device *start,
405 int (*match)(struct device *, const void *))
407 struct class_dev_iter iter;
413 WARN(1, "%s called for class '%s' before it was initialized",
414 __func__, class->name);
418 class_dev_iter_init(&iter, class, start, NULL);
419 while ((dev = class_dev_iter_next(&iter))) {
420 if (match(dev, data)) {
425 class_dev_iter_exit(&iter);
429 EXPORT_SYMBOL_GPL(class_find_device);
431 int class_interface_register(struct class_interface *class_intf)
433 struct class *parent;
434 struct class_dev_iter iter;
437 if (!class_intf || !class_intf->class)
440 parent = class_get(class_intf->class);
444 mutex_lock(&parent->p->mutex);
445 list_add_tail(&class_intf->node, &parent->p->interfaces);
446 if (class_intf->add_dev) {
447 class_dev_iter_init(&iter, parent, NULL, NULL);
448 while ((dev = class_dev_iter_next(&iter)))
449 class_intf->add_dev(dev, class_intf);
450 class_dev_iter_exit(&iter);
452 mutex_unlock(&parent->p->mutex);
457 void class_interface_unregister(struct class_interface *class_intf)
459 struct class *parent = class_intf->class;
460 struct class_dev_iter iter;
466 mutex_lock(&parent->p->mutex);
467 list_del_init(&class_intf->node);
468 if (class_intf->remove_dev) {
469 class_dev_iter_init(&iter, parent, NULL, NULL);
470 while ((dev = class_dev_iter_next(&iter)))
471 class_intf->remove_dev(dev, class_intf);
472 class_dev_iter_exit(&iter);
474 mutex_unlock(&parent->p->mutex);
479 ssize_t show_class_attr_string(struct class *class,
480 struct class_attribute *attr, char *buf)
482 struct class_attribute_string *cs;
484 cs = container_of(attr, struct class_attribute_string, attr);
485 return snprintf(buf, PAGE_SIZE, "%s\n", cs->str);
488 EXPORT_SYMBOL_GPL(show_class_attr_string);
490 struct class_compat {
491 struct kobject *kobj;
495 * class_compat_register - register a compatibility class
496 * @name: the name of the class
498 * Compatibility class are meant as a temporary user-space compatibility
499 * workaround when converting a family of class devices to a bus devices.
501 struct class_compat *class_compat_register(const char *name)
503 struct class_compat *cls;
505 cls = kmalloc(sizeof(struct class_compat), GFP_KERNEL);
508 cls->kobj = kobject_create_and_add(name, &class_kset->kobj);
515 EXPORT_SYMBOL_GPL(class_compat_register);
518 * class_compat_unregister - unregister a compatibility class
519 * @cls: the class to unregister
521 void class_compat_unregister(struct class_compat *cls)
523 kobject_put(cls->kobj);
526 EXPORT_SYMBOL_GPL(class_compat_unregister);
529 * class_compat_create_link - create a compatibility class device link to
531 * @cls: the compatibility class
532 * @dev: the target bus device
533 * @device_link: an optional device to which a "device" link should be created
535 int class_compat_create_link(struct class_compat *cls, struct device *dev,
536 struct device *device_link)
540 error = sysfs_create_link(cls->kobj, &dev->kobj, dev_name(dev));
545 * Optionally add a "device" link (typically to the parent), as a
546 * class device would have one and we want to provide as much
547 * backwards compatibility as possible.
550 error = sysfs_create_link(&dev->kobj, &device_link->kobj,
553 sysfs_remove_link(cls->kobj, dev_name(dev));
558 EXPORT_SYMBOL_GPL(class_compat_create_link);
561 * class_compat_remove_link - remove a compatibility class device link to
563 * @cls: the compatibility class
564 * @dev: the target bus device
565 * @device_link: an optional device to which a "device" link was previously
568 void class_compat_remove_link(struct class_compat *cls, struct device *dev,
569 struct device *device_link)
572 sysfs_remove_link(&dev->kobj, "device");
573 sysfs_remove_link(cls->kobj, dev_name(dev));
575 EXPORT_SYMBOL_GPL(class_compat_remove_link);
577 int __init classes_init(void)
579 class_kset = kset_create_and_add("class", NULL, NULL);
585 EXPORT_SYMBOL_GPL(class_create_file_ns);
586 EXPORT_SYMBOL_GPL(class_remove_file_ns);
587 EXPORT_SYMBOL_GPL(class_unregister);
588 EXPORT_SYMBOL_GPL(class_destroy);
590 EXPORT_SYMBOL_GPL(class_interface_register);
591 EXPORT_SYMBOL_GPL(class_interface_unregister);