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.
10 * This file is released under the GPLv2
14 #include <linux/device.h>
15 #include <linux/module.h>
16 #include <linux/init.h>
17 #include <linux/string.h>
18 #include <linux/kdev_t.h>
19 #include <linux/err.h>
20 #include <linux/slab.h>
21 #include <linux/genhd.h>
22 #include <linux/mutex.h>
25 #define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
27 static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
30 struct class_attribute *class_attr = to_class_attr(attr);
31 struct subsys_private *cp = to_subsys_private(kobj);
35 ret = class_attr->show(cp->class, class_attr, buf);
39 static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
40 const char *buf, size_t count)
42 struct class_attribute *class_attr = to_class_attr(attr);
43 struct subsys_private *cp = to_subsys_private(kobj);
46 if (class_attr->store)
47 ret = class_attr->store(cp->class, class_attr, buf, count);
51 static void class_release(struct kobject *kobj)
53 struct subsys_private *cp = to_subsys_private(kobj);
54 struct class *class = cp->class;
56 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(struct kobject *kobj)
69 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 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(struct class *cls, const struct class_attribute *attr,
96 error = sysfs_create_file_ns(&cls->p->subsys.kobj,
103 void class_remove_file_ns(struct class *cls, const struct class_attribute *attr,
107 sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns);
110 static struct class *class_get(struct class *cls)
113 kset_get(&cls->p->subsys);
117 static void class_put(struct class *cls)
120 kset_put(&cls->p->subsys);
123 static void klist_class_dev_get(struct klist_node *n)
125 struct device *dev = container_of(n, struct device, knode_class);
130 static void klist_class_dev_put(struct klist_node *n)
132 struct device *dev = container_of(n, struct device, knode_class);
137 static int class_add_groups(struct class *cls,
138 const struct attribute_group **groups)
140 return sysfs_create_groups(&cls->p->subsys.kobj, groups);
143 static void class_remove_groups(struct class *cls,
144 const struct attribute_group **groups)
146 return sysfs_remove_groups(&cls->p->subsys.kobj, groups);
149 int __class_register(struct class *cls, struct lock_class_key *key)
151 struct subsys_private *cp;
154 pr_debug("device class '%s': registering\n", cls->name);
156 cp = kzalloc(sizeof(*cp), GFP_KERNEL);
159 klist_init(&cp->klist_devices, klist_class_dev_get, klist_class_dev_put);
160 INIT_LIST_HEAD(&cp->interfaces);
161 kset_init(&cp->glue_dirs);
162 __mutex_init(&cp->mutex, "subsys mutex", key);
163 error = kobject_set_name(&cp->subsys.kobj, "%s", cls->name);
169 /* set the default /sys/dev directory for devices of this class */
171 cls->dev_kobj = sysfs_dev_char_kobj;
173 #if defined(CONFIG_BLOCK)
174 /* let the block class directory show up in the root of sysfs */
175 if (!sysfs_deprecated || cls != &block_class)
176 cp->subsys.kobj.kset = class_kset;
178 cp->subsys.kobj.kset = class_kset;
180 cp->subsys.kobj.ktype = &class_ktype;
184 error = kset_register(&cp->subsys);
189 error = class_add_groups(class_get(cls), cls->class_groups);
193 EXPORT_SYMBOL_GPL(__class_register);
195 void class_unregister(struct class *cls)
197 pr_debug("device class '%s': unregistering\n", cls->name);
198 class_remove_groups(cls, cls->class_groups);
199 kset_unregister(&cls->p->subsys);
202 static void class_create_release(struct class *cls)
204 pr_debug("%s called for %s\n", __func__, cls->name);
209 * class_create - create a struct class structure
210 * @owner: pointer to the module that is to "own" this struct class
211 * @name: pointer to a string for the name of this class.
212 * @key: the lock_class_key for this class; used by mutex lock debugging
214 * This is used to create a struct class pointer that can then be used
215 * in calls to device_create().
217 * Returns &struct class pointer on success, or ERR_PTR() on error.
219 * Note, the pointer created here is to be destroyed when finished by
220 * making a call to class_destroy().
222 struct class *__class_create(struct module *owner, const char *name,
223 struct lock_class_key *key)
228 cls = kzalloc(sizeof(*cls), GFP_KERNEL);
236 cls->class_release = class_create_release;
238 retval = __class_register(cls, key);
246 return ERR_PTR(retval);
248 EXPORT_SYMBOL_GPL(__class_create);
251 * class_destroy - destroys a struct class structure
252 * @cls: pointer to the struct class that is to be destroyed
254 * Note, the pointer to be destroyed must have been created with a call
257 void class_destroy(struct class *cls)
259 if ((cls == NULL) || (IS_ERR(cls)))
262 class_unregister(cls);
266 * class_dev_iter_init - initialize class device iterator
267 * @iter: class iterator to initialize
268 * @class: the class we wanna iterate over
269 * @start: the device to start iterating from, if any
270 * @type: device_type of the devices to iterate over, NULL for all
272 * Initialize class iterator @iter such that it iterates over devices
273 * of @class. If @start is set, the list iteration will start there,
274 * otherwise if it is NULL, the iteration starts at the beginning of
277 void class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
278 struct device *start, const struct device_type *type)
280 struct klist_node *start_knode = NULL;
283 start_knode = &start->knode_class;
284 klist_iter_init_node(&class->p->klist_devices, &iter->ki, start_knode);
287 EXPORT_SYMBOL_GPL(class_dev_iter_init);
290 * class_dev_iter_next - iterate to the next device
291 * @iter: class iterator to proceed
293 * Proceed @iter to the next device and return it. Returns NULL if
294 * iteration is complete.
296 * The returned device is referenced and won't be released till
297 * iterator is proceed to the next device or exited. The caller is
298 * free to do whatever it wants to do with the device including
299 * calling back into class code.
301 struct device *class_dev_iter_next(struct class_dev_iter *iter)
303 struct klist_node *knode;
307 knode = klist_next(&iter->ki);
310 dev = container_of(knode, struct device, knode_class);
311 if (!iter->type || iter->type == dev->type)
315 EXPORT_SYMBOL_GPL(class_dev_iter_next);
318 * class_dev_iter_exit - finish iteration
319 * @iter: class iterator to finish
321 * Finish an iteration. Always call this function after iteration is
322 * complete whether the iteration ran till the end or not.
324 void class_dev_iter_exit(struct class_dev_iter *iter)
326 klist_iter_exit(&iter->ki);
328 EXPORT_SYMBOL_GPL(class_dev_iter_exit);
331 * class_for_each_device - device iterator
332 * @class: the class we're iterating
333 * @start: the device to start with in the list, if any.
334 * @data: data for the callback
335 * @fn: function to be called for each device
337 * Iterate over @class's list of devices, and call @fn for each,
338 * passing it @data. If @start is set, the list iteration will start
339 * there, otherwise if it is NULL, the iteration starts at the
340 * beginning of the list.
342 * We check the return of @fn each time. If it returns anything
343 * other than 0, we break out and return that value.
345 * @fn is allowed to do anything including calling back into class
346 * code. There's no locking restriction.
348 int class_for_each_device(struct class *class, struct device *start,
349 void *data, int (*fn)(struct device *, void *))
351 struct class_dev_iter iter;
358 WARN(1, "%s called for class '%s' before it was initialized",
359 __func__, class->name);
363 class_dev_iter_init(&iter, class, start, NULL);
364 while ((dev = class_dev_iter_next(&iter))) {
365 error = fn(dev, data);
369 class_dev_iter_exit(&iter);
373 EXPORT_SYMBOL_GPL(class_for_each_device);
376 * class_find_device - device iterator for locating a particular device
377 * @class: the class we're iterating
378 * @start: Device to begin with
379 * @data: data for the match function
380 * @match: function to check device
382 * This is similar to the class_for_each_dev() function above, but it
383 * returns a reference to a device that is 'found' for later use, as
384 * determined by the @match callback.
386 * The callback should return 0 if the device doesn't match and non-zero
387 * if it does. If the callback returns non-zero, this function will
388 * return to the caller and not iterate over any more devices.
390 * Note, you will need to drop the reference with put_device() after use.
392 * @match is allowed to do anything including calling back into class
393 * code. There's no locking restriction.
395 struct device *class_find_device(struct class *class, struct device *start,
397 int (*match)(struct device *, const void *))
399 struct class_dev_iter iter;
405 WARN(1, "%s called for class '%s' before it was initialized",
406 __func__, class->name);
410 class_dev_iter_init(&iter, class, start, NULL);
411 while ((dev = class_dev_iter_next(&iter))) {
412 if (match(dev, data)) {
417 class_dev_iter_exit(&iter);
421 EXPORT_SYMBOL_GPL(class_find_device);
423 int class_interface_register(struct class_interface *class_intf)
425 struct class *parent;
426 struct class_dev_iter iter;
429 if (!class_intf || !class_intf->class)
432 parent = class_get(class_intf->class);
436 mutex_lock(&parent->p->mutex);
437 list_add_tail(&class_intf->node, &parent->p->interfaces);
438 if (class_intf->add_dev) {
439 class_dev_iter_init(&iter, parent, NULL, NULL);
440 while ((dev = class_dev_iter_next(&iter)))
441 class_intf->add_dev(dev, class_intf);
442 class_dev_iter_exit(&iter);
444 mutex_unlock(&parent->p->mutex);
449 void class_interface_unregister(struct class_interface *class_intf)
451 struct class *parent = class_intf->class;
452 struct class_dev_iter iter;
458 mutex_lock(&parent->p->mutex);
459 list_del_init(&class_intf->node);
460 if (class_intf->remove_dev) {
461 class_dev_iter_init(&iter, parent, NULL, NULL);
462 while ((dev = class_dev_iter_next(&iter)))
463 class_intf->remove_dev(dev, class_intf);
464 class_dev_iter_exit(&iter);
466 mutex_unlock(&parent->p->mutex);
471 ssize_t show_class_attr_string(struct class *class,
472 struct class_attribute *attr, char *buf)
474 struct class_attribute_string *cs;
476 cs = container_of(attr, struct class_attribute_string, attr);
477 return snprintf(buf, PAGE_SIZE, "%s\n", cs->str);
480 EXPORT_SYMBOL_GPL(show_class_attr_string);
482 struct class_compat {
483 struct kobject *kobj;
487 * class_compat_register - register a compatibility class
488 * @name: the name of the class
490 * Compatibility class are meant as a temporary user-space compatibility
491 * workaround when converting a family of class devices to a bus devices.
493 struct class_compat *class_compat_register(const char *name)
495 struct class_compat *cls;
497 cls = kmalloc(sizeof(struct class_compat), GFP_KERNEL);
500 cls->kobj = kobject_create_and_add(name, &class_kset->kobj);
507 EXPORT_SYMBOL_GPL(class_compat_register);
510 * class_compat_unregister - unregister a compatibility class
511 * @cls: the class to unregister
513 void class_compat_unregister(struct class_compat *cls)
515 kobject_put(cls->kobj);
518 EXPORT_SYMBOL_GPL(class_compat_unregister);
521 * class_compat_create_link - create a compatibility class device link to
523 * @cls: the compatibility class
524 * @dev: the target bus device
525 * @device_link: an optional device to which a "device" link should be created
527 int class_compat_create_link(struct class_compat *cls, struct device *dev,
528 struct device *device_link)
532 error = sysfs_create_link(cls->kobj, &dev->kobj, dev_name(dev));
537 * Optionally add a "device" link (typically to the parent), as a
538 * class device would have one and we want to provide as much
539 * backwards compatibility as possible.
542 error = sysfs_create_link(&dev->kobj, &device_link->kobj,
545 sysfs_remove_link(cls->kobj, dev_name(dev));
550 EXPORT_SYMBOL_GPL(class_compat_create_link);
553 * class_compat_remove_link - remove a compatibility class device link to
555 * @cls: the compatibility class
556 * @dev: the target bus device
557 * @device_link: an optional device to which a "device" link was previously
560 void class_compat_remove_link(struct class_compat *cls, struct device *dev,
561 struct device *device_link)
564 sysfs_remove_link(&dev->kobj, "device");
565 sysfs_remove_link(cls->kobj, dev_name(dev));
567 EXPORT_SYMBOL_GPL(class_compat_remove_link);
569 int __init classes_init(void)
571 class_kset = kset_create_and_add("class", NULL, NULL);
577 EXPORT_SYMBOL_GPL(class_create_file_ns);
578 EXPORT_SYMBOL_GPL(class_remove_file_ns);
579 EXPORT_SYMBOL_GPL(class_unregister);
580 EXPORT_SYMBOL_GPL(class_destroy);
582 EXPORT_SYMBOL_GPL(class_interface_register);
583 EXPORT_SYMBOL_GPL(class_interface_unregister);