1 /*
2  * class.c - basic device class management
3  *
4  * Copyright (c) 2002-3 Patrick Mochel
5  * Copyright (c) 2002-3 Open Source Development Labs
6  * Copyright (c) 2003-2004 Greg Kroah-Hartman
7  * Copyright (c) 2003-2004 IBM Corp.
8  *
9  * This file is released under the GPLv2
10  *
11  */
12 
13 #include <linux/device.h>
14 #include <linux/module.h>
15 #include <linux/init.h>
16 #include <linux/string.h>
17 #include <linux/kdev_t.h>
18 #include <linux/err.h>
19 #include <linux/slab.h>
20 #include <linux/genhd.h>
21 #include <linux/mutex.h>
22 #include "base.h"
23 
24 #define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
25 
class_attr_show(struct kobject * kobj,struct attribute * attr,char * buf)26 static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
27 			       char *buf)
28 {
29 	struct class_attribute *class_attr = to_class_attr(attr);
30 	struct subsys_private *cp = to_subsys_private(kobj);
31 	ssize_t ret = -EIO;
32 
33 	if (class_attr->show)
34 		ret = class_attr->show(cp->class, class_attr, buf);
35 	return ret;
36 }
37 
class_attr_store(struct kobject * kobj,struct attribute * attr,const char * buf,size_t count)38 static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
39 				const char *buf, size_t count)
40 {
41 	struct class_attribute *class_attr = to_class_attr(attr);
42 	struct subsys_private *cp = to_subsys_private(kobj);
43 	ssize_t ret = -EIO;
44 
45 	if (class_attr->store)
46 		ret = class_attr->store(cp->class, class_attr, buf, count);
47 	return ret;
48 }
49 
class_attr_namespace(struct kobject * kobj,const struct attribute * attr)50 static const void *class_attr_namespace(struct kobject *kobj,
51 					const struct attribute *attr)
52 {
53 	struct class_attribute *class_attr = to_class_attr(attr);
54 	struct subsys_private *cp = to_subsys_private(kobj);
55 	const void *ns = NULL;
56 
57 	if (class_attr->namespace)
58 		ns = class_attr->namespace(cp->class, class_attr);
59 	return ns;
60 }
61 
class_release(struct kobject * kobj)62 static void class_release(struct kobject *kobj)
63 {
64 	struct subsys_private *cp = to_subsys_private(kobj);
65 	struct class *class = cp->class;
66 
67 	pr_debug("class '%s': release.\n", class->name);
68 
69 	if (class->class_release)
70 		class->class_release(class);
71 	else
72 		pr_debug("class '%s' does not have a release() function, "
73 			 "be careful\n", class->name);
74 
75 	kfree(cp);
76 }
77 
class_child_ns_type(struct kobject * kobj)78 static const struct kobj_ns_type_operations *class_child_ns_type(struct kobject *kobj)
79 {
80 	struct subsys_private *cp = to_subsys_private(kobj);
81 	struct class *class = cp->class;
82 
83 	return class->ns_type;
84 }
85 
86 static const struct sysfs_ops class_sysfs_ops = {
87 	.show	   = class_attr_show,
88 	.store	   = class_attr_store,
89 	.namespace = class_attr_namespace,
90 };
91 
92 static struct kobj_type class_ktype = {
93 	.sysfs_ops	= &class_sysfs_ops,
94 	.release	= class_release,
95 	.child_ns_type	= class_child_ns_type,
96 };
97 
98 /* Hotplug events for classes go to the class subsys */
99 static struct kset *class_kset;
100 
101 
class_create_file(struct class * cls,const struct class_attribute * attr)102 int class_create_file(struct class *cls, const struct class_attribute *attr)
103 {
104 	int error;
105 	if (cls)
106 		error = sysfs_create_file(&cls->p->subsys.kobj,
107 					  &attr->attr);
108 	else
109 		error = -EINVAL;
110 	return error;
111 }
112 
class_remove_file(struct class * cls,const struct class_attribute * attr)113 void class_remove_file(struct class *cls, const struct class_attribute *attr)
114 {
115 	if (cls)
116 		sysfs_remove_file(&cls->p->subsys.kobj, &attr->attr);
117 }
118 
class_get(struct class * cls)119 static struct class *class_get(struct class *cls)
120 {
121 	if (cls)
122 		kset_get(&cls->p->subsys);
123 	return cls;
124 }
125 
class_put(struct class * cls)126 static void class_put(struct class *cls)
127 {
128 	if (cls)
129 		kset_put(&cls->p->subsys);
130 }
131 
add_class_attrs(struct class * cls)132 static int add_class_attrs(struct class *cls)
133 {
134 	int i;
135 	int error = 0;
136 
137 	if (cls->class_attrs) {
138 		for (i = 0; attr_name(cls->class_attrs[i]); i++) {
139 			error = class_create_file(cls, &cls->class_attrs[i]);
140 			if (error)
141 				goto error;
142 		}
143 	}
144 done:
145 	return error;
146 error:
147 	while (--i >= 0)
148 		class_remove_file(cls, &cls->class_attrs[i]);
149 	goto done;
150 }
151 
remove_class_attrs(struct class * cls)152 static void remove_class_attrs(struct class *cls)
153 {
154 	int i;
155 
156 	if (cls->class_attrs) {
157 		for (i = 0; attr_name(cls->class_attrs[i]); i++)
158 			class_remove_file(cls, &cls->class_attrs[i]);
159 	}
160 }
161 
klist_class_dev_get(struct klist_node * n)162 static void klist_class_dev_get(struct klist_node *n)
163 {
164 	struct device *dev = container_of(n, struct device, knode_class);
165 
166 	get_device(dev);
167 }
168 
klist_class_dev_put(struct klist_node * n)169 static void klist_class_dev_put(struct klist_node *n)
170 {
171 	struct device *dev = container_of(n, struct device, knode_class);
172 
173 	put_device(dev);
174 }
175 
__class_register(struct class * cls,struct lock_class_key * key)176 int __class_register(struct class *cls, struct lock_class_key *key)
177 {
178 	struct subsys_private *cp;
179 	int error;
180 
181 	pr_debug("device class '%s': registering\n", cls->name);
182 
183 	cp = kzalloc(sizeof(*cp), GFP_KERNEL);
184 	if (!cp)
185 		return -ENOMEM;
186 	klist_init(&cp->klist_devices, klist_class_dev_get, klist_class_dev_put);
187 	INIT_LIST_HEAD(&cp->interfaces);
188 	kset_init(&cp->glue_dirs);
189 	__mutex_init(&cp->mutex, "subsys mutex", key);
190 	error = kobject_set_name(&cp->subsys.kobj, "%s", cls->name);
191 	if (error) {
192 		kfree(cp);
193 		return error;
194 	}
195 
196 	/* set the default /sys/dev directory for devices of this class */
197 	if (!cls->dev_kobj)
198 		cls->dev_kobj = sysfs_dev_char_kobj;
199 
200 #if defined(CONFIG_BLOCK)
201 	/* let the block class directory show up in the root of sysfs */
202 	if (!sysfs_deprecated || cls != &block_class)
203 		cp->subsys.kobj.kset = class_kset;
204 #else
205 	cp->subsys.kobj.kset = class_kset;
206 #endif
207 	cp->subsys.kobj.ktype = &class_ktype;
208 	cp->class = cls;
209 	cls->p = cp;
210 
211 	error = kset_register(&cp->subsys);
212 	if (error) {
213 		kfree(cp);
214 		return error;
215 	}
216 	error = add_class_attrs(class_get(cls));
217 	class_put(cls);
218 	return error;
219 }
220 EXPORT_SYMBOL_GPL(__class_register);
221 
class_unregister(struct class * cls)222 void class_unregister(struct class *cls)
223 {
224 	pr_debug("device class '%s': unregistering\n", cls->name);
225 	remove_class_attrs(cls);
226 	kset_unregister(&cls->p->subsys);
227 }
228 
class_create_release(struct class * cls)229 static void class_create_release(struct class *cls)
230 {
231 	pr_debug("%s called for %s\n", __func__, cls->name);
232 	kfree(cls);
233 }
234 
235 /**
236  * class_create - create a struct class structure
237  * @owner: pointer to the module that is to "own" this struct class
238  * @name: pointer to a string for the name of this class.
239  * @key: the lock_class_key for this class; used by mutex lock debugging
240  *
241  * This is used to create a struct class pointer that can then be used
242  * in calls to device_create().
243  *
244  * Returns &struct class pointer on success, or ERR_PTR() on error.
245  *
246  * Note, the pointer created here is to be destroyed when finished by
247  * making a call to class_destroy().
248  */
__class_create(struct module * owner,const char * name,struct lock_class_key * key)249 struct class *__class_create(struct module *owner, const char *name,
250 			     struct lock_class_key *key)
251 {
252 	struct class *cls;
253 	int retval;
254 
255 	cls = kzalloc(sizeof(*cls), GFP_KERNEL);
256 	if (!cls) {
257 		retval = -ENOMEM;
258 		goto error;
259 	}
260 
261 	cls->name = name;
262 	cls->owner = owner;
263 	cls->class_release = class_create_release;
264 
265 	retval = __class_register(cls, key);
266 	if (retval)
267 		goto error;
268 
269 	return cls;
270 
271 error:
272 	kfree(cls);
273 	return ERR_PTR(retval);
274 }
275 EXPORT_SYMBOL_GPL(__class_create);
276 
277 /**
278  * class_destroy - destroys a struct class structure
279  * @cls: pointer to the struct class that is to be destroyed
280  *
281  * Note, the pointer to be destroyed must have been created with a call
282  * to class_create().
283  */
class_destroy(struct class * cls)284 void class_destroy(struct class *cls)
285 {
286 	if ((cls == NULL) || (IS_ERR(cls)))
287 		return;
288 
289 	class_unregister(cls);
290 }
291 
292 /**
293  * class_dev_iter_init - initialize class device iterator
294  * @iter: class iterator to initialize
295  * @class: the class we wanna iterate over
296  * @start: the device to start iterating from, if any
297  * @type: device_type of the devices to iterate over, NULL for all
298  *
299  * Initialize class iterator @iter such that it iterates over devices
300  * of @class.  If @start is set, the list iteration will start there,
301  * otherwise if it is NULL, the iteration starts at the beginning of
302  * the list.
303  */
class_dev_iter_init(struct class_dev_iter * iter,struct class * class,struct device * start,const struct device_type * type)304 void class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
305 			 struct device *start, const struct device_type *type)
306 {
307 	struct klist_node *start_knode = NULL;
308 
309 	if (start)
310 		start_knode = &start->knode_class;
311 	klist_iter_init_node(&class->p->klist_devices, &iter->ki, start_knode);
312 	iter->type = type;
313 }
314 EXPORT_SYMBOL_GPL(class_dev_iter_init);
315 
316 /**
317  * class_dev_iter_next - iterate to the next device
318  * @iter: class iterator to proceed
319  *
320  * Proceed @iter to the next device and return it.  Returns NULL if
321  * iteration is complete.
322  *
323  * The returned device is referenced and won't be released till
324  * iterator is proceed to the next device or exited.  The caller is
325  * free to do whatever it wants to do with the device including
326  * calling back into class code.
327  */
class_dev_iter_next(struct class_dev_iter * iter)328 struct device *class_dev_iter_next(struct class_dev_iter *iter)
329 {
330 	struct klist_node *knode;
331 	struct device *dev;
332 
333 	while (1) {
334 		knode = klist_next(&iter->ki);
335 		if (!knode)
336 			return NULL;
337 		dev = container_of(knode, struct device, knode_class);
338 		if (!iter->type || iter->type == dev->type)
339 			return dev;
340 	}
341 }
342 EXPORT_SYMBOL_GPL(class_dev_iter_next);
343 
344 /**
345  * class_dev_iter_exit - finish iteration
346  * @iter: class iterator to finish
347  *
348  * Finish an iteration.  Always call this function after iteration is
349  * complete whether the iteration ran till the end or not.
350  */
class_dev_iter_exit(struct class_dev_iter * iter)351 void class_dev_iter_exit(struct class_dev_iter *iter)
352 {
353 	klist_iter_exit(&iter->ki);
354 }
355 EXPORT_SYMBOL_GPL(class_dev_iter_exit);
356 
357 /**
358  * class_for_each_device - device iterator
359  * @class: the class we're iterating
360  * @start: the device to start with in the list, if any.
361  * @data: data for the callback
362  * @fn: function to be called for each device
363  *
364  * Iterate over @class's list of devices, and call @fn for each,
365  * passing it @data.  If @start is set, the list iteration will start
366  * there, otherwise if it is NULL, the iteration starts at the
367  * beginning of the list.
368  *
369  * We check the return of @fn each time. If it returns anything
370  * other than 0, we break out and return that value.
371  *
372  * @fn is allowed to do anything including calling back into class
373  * code.  There's no locking restriction.
374  */
class_for_each_device(struct class * class,struct device * start,void * data,int (* fn)(struct device *,void *))375 int class_for_each_device(struct class *class, struct device *start,
376 			  void *data, int (*fn)(struct device *, void *))
377 {
378 	struct class_dev_iter iter;
379 	struct device *dev;
380 	int error = 0;
381 
382 	if (!class)
383 		return -EINVAL;
384 	if (!class->p) {
385 		WARN(1, "%s called for class '%s' before it was initialized",
386 		     __func__, class->name);
387 		return -EINVAL;
388 	}
389 
390 	class_dev_iter_init(&iter, class, start, NULL);
391 	while ((dev = class_dev_iter_next(&iter))) {
392 		error = fn(dev, data);
393 		if (error)
394 			break;
395 	}
396 	class_dev_iter_exit(&iter);
397 
398 	return error;
399 }
400 EXPORT_SYMBOL_GPL(class_for_each_device);
401 
402 /**
403  * class_find_device - device iterator for locating a particular device
404  * @class: the class we're iterating
405  * @start: Device to begin with
406  * @data: data for the match function
407  * @match: function to check device
408  *
409  * This is similar to the class_for_each_dev() function above, but it
410  * returns a reference to a device that is 'found' for later use, as
411  * determined by the @match callback.
412  *
413  * The callback should return 0 if the device doesn't match and non-zero
414  * if it does.  If the callback returns non-zero, this function will
415  * return to the caller and not iterate over any more devices.
416  *
417  * Note, you will need to drop the reference with put_device() after use.
418  *
419  * @fn is allowed to do anything including calling back into class
420  * code.  There's no locking restriction.
421  */
class_find_device(struct class * class,struct device * start,void * data,int (* match)(struct device *,void *))422 struct device *class_find_device(struct class *class, struct device *start,
423 				 void *data,
424 				 int (*match)(struct device *, void *))
425 {
426 	struct class_dev_iter iter;
427 	struct device *dev;
428 
429 	if (!class)
430 		return NULL;
431 	if (!class->p) {
432 		WARN(1, "%s called for class '%s' before it was initialized",
433 		     __func__, class->name);
434 		return NULL;
435 	}
436 
437 	class_dev_iter_init(&iter, class, start, NULL);
438 	while ((dev = class_dev_iter_next(&iter))) {
439 		if (match(dev, data)) {
440 			get_device(dev);
441 			break;
442 		}
443 	}
444 	class_dev_iter_exit(&iter);
445 
446 	return dev;
447 }
448 EXPORT_SYMBOL_GPL(class_find_device);
449 
class_interface_register(struct class_interface * class_intf)450 int class_interface_register(struct class_interface *class_intf)
451 {
452 	struct class *parent;
453 	struct class_dev_iter iter;
454 	struct device *dev;
455 
456 	if (!class_intf || !class_intf->class)
457 		return -ENODEV;
458 
459 	parent = class_get(class_intf->class);
460 	if (!parent)
461 		return -EINVAL;
462 
463 	mutex_lock(&parent->p->mutex);
464 	list_add_tail(&class_intf->node, &parent->p->interfaces);
465 	if (class_intf->add_dev) {
466 		class_dev_iter_init(&iter, parent, NULL, NULL);
467 		while ((dev = class_dev_iter_next(&iter)))
468 			class_intf->add_dev(dev, class_intf);
469 		class_dev_iter_exit(&iter);
470 	}
471 	mutex_unlock(&parent->p->mutex);
472 
473 	return 0;
474 }
475 
class_interface_unregister(struct class_interface * class_intf)476 void class_interface_unregister(struct class_interface *class_intf)
477 {
478 	struct class *parent = class_intf->class;
479 	struct class_dev_iter iter;
480 	struct device *dev;
481 
482 	if (!parent)
483 		return;
484 
485 	mutex_lock(&parent->p->mutex);
486 	list_del_init(&class_intf->node);
487 	if (class_intf->remove_dev) {
488 		class_dev_iter_init(&iter, parent, NULL, NULL);
489 		while ((dev = class_dev_iter_next(&iter)))
490 			class_intf->remove_dev(dev, class_intf);
491 		class_dev_iter_exit(&iter);
492 	}
493 	mutex_unlock(&parent->p->mutex);
494 
495 	class_put(parent);
496 }
497 
show_class_attr_string(struct class * class,struct class_attribute * attr,char * buf)498 ssize_t show_class_attr_string(struct class *class,
499 			       struct class_attribute *attr, char *buf)
500 {
501 	struct class_attribute_string *cs;
502 	cs = container_of(attr, struct class_attribute_string, attr);
503 	return snprintf(buf, PAGE_SIZE, "%s\n", cs->str);
504 }
505 
506 EXPORT_SYMBOL_GPL(show_class_attr_string);
507 
508 struct class_compat {
509 	struct kobject *kobj;
510 };
511 
512 /**
513  * class_compat_register - register a compatibility class
514  * @name: the name of the class
515  *
516  * Compatibility class are meant as a temporary user-space compatibility
517  * workaround when converting a family of class devices to a bus devices.
518  */
class_compat_register(const char * name)519 struct class_compat *class_compat_register(const char *name)
520 {
521 	struct class_compat *cls;
522 
523 	cls = kmalloc(sizeof(struct class_compat), GFP_KERNEL);
524 	if (!cls)
525 		return NULL;
526 	cls->kobj = kobject_create_and_add(name, &class_kset->kobj);
527 	if (!cls->kobj) {
528 		kfree(cls);
529 		return NULL;
530 	}
531 	return cls;
532 }
533 EXPORT_SYMBOL_GPL(class_compat_register);
534 
535 /**
536  * class_compat_unregister - unregister a compatibility class
537  * @cls: the class to unregister
538  */
class_compat_unregister(struct class_compat * cls)539 void class_compat_unregister(struct class_compat *cls)
540 {
541 	kobject_put(cls->kobj);
542 	kfree(cls);
543 }
544 EXPORT_SYMBOL_GPL(class_compat_unregister);
545 
546 /**
547  * class_compat_create_link - create a compatibility class device link to
548  *			      a bus device
549  * @cls: the compatibility class
550  * @dev: the target bus device
551  * @device_link: an optional device to which a "device" link should be created
552  */
class_compat_create_link(struct class_compat * cls,struct device * dev,struct device * device_link)553 int class_compat_create_link(struct class_compat *cls, struct device *dev,
554 			     struct device *device_link)
555 {
556 	int error;
557 
558 	error = sysfs_create_link(cls->kobj, &dev->kobj, dev_name(dev));
559 	if (error)
560 		return error;
561 
562 	/*
563 	 * Optionally add a "device" link (typically to the parent), as a
564 	 * class device would have one and we want to provide as much
565 	 * backwards compatibility as possible.
566 	 */
567 	if (device_link) {
568 		error = sysfs_create_link(&dev->kobj, &device_link->kobj,
569 					  "device");
570 		if (error)
571 			sysfs_remove_link(cls->kobj, dev_name(dev));
572 	}
573 
574 	return error;
575 }
576 EXPORT_SYMBOL_GPL(class_compat_create_link);
577 
578 /**
579  * class_compat_remove_link - remove a compatibility class device link to
580  *			      a bus device
581  * @cls: the compatibility class
582  * @dev: the target bus device
583  * @device_link: an optional device to which a "device" link was previously
584  * 		 created
585  */
class_compat_remove_link(struct class_compat * cls,struct device * dev,struct device * device_link)586 void class_compat_remove_link(struct class_compat *cls, struct device *dev,
587 			      struct device *device_link)
588 {
589 	if (device_link)
590 		sysfs_remove_link(&dev->kobj, "device");
591 	sysfs_remove_link(cls->kobj, dev_name(dev));
592 }
593 EXPORT_SYMBOL_GPL(class_compat_remove_link);
594 
classes_init(void)595 int __init classes_init(void)
596 {
597 	class_kset = kset_create_and_add("class", NULL, NULL);
598 	if (!class_kset)
599 		return -ENOMEM;
600 	return 0;
601 }
602 
603 EXPORT_SYMBOL_GPL(class_create_file);
604 EXPORT_SYMBOL_GPL(class_remove_file);
605 EXPORT_SYMBOL_GPL(class_unregister);
606 EXPORT_SYMBOL_GPL(class_destroy);
607 
608 EXPORT_SYMBOL_GPL(class_interface_register);
609 EXPORT_SYMBOL_GPL(class_interface_unregister);
610