1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * attribute_container.c - implementation of a simple container for classes
4  *
5  * Copyright (c) 2005 - James Bottomley <James.Bottomley@steeleye.com>
6  *
7  * The basic idea here is to enable a device to be attached to an
8  * aritrary numer of classes without having to allocate storage for them.
9  * Instead, the contained classes select the devices they need to attach
10  * to via a matching function.
11  */
12 
13 #include <linux/attribute_container.h>
14 #include <linux/device.h>
15 #include <linux/kernel.h>
16 #include <linux/slab.h>
17 #include <linux/list.h>
18 #include <linux/module.h>
19 #include <linux/mutex.h>
20 
21 #include "base.h"
22 
23 /* This is a private structure used to tie the classdev and the
24  * container .. it should never be visible outside this file */
25 struct internal_container {
26 	struct klist_node node;
27 	struct attribute_container *cont;
28 	struct device classdev;
29 };
30 
31 static void internal_container_klist_get(struct klist_node *n)
32 {
33 	struct internal_container *ic =
34 		container_of(n, struct internal_container, node);
35 	get_device(&ic->classdev);
36 }
37 
38 static void internal_container_klist_put(struct klist_node *n)
39 {
40 	struct internal_container *ic =
41 		container_of(n, struct internal_container, node);
42 	put_device(&ic->classdev);
43 }
44 
45 
46 /**
47  * attribute_container_classdev_to_container - given a classdev, return the container
48  *
49  * @classdev: the class device created by attribute_container_add_device.
50  *
51  * Returns the container associated with this classdev.
52  */
53 struct attribute_container *
54 attribute_container_classdev_to_container(struct device *classdev)
55 {
56 	struct internal_container *ic =
57 		container_of(classdev, struct internal_container, classdev);
58 	return ic->cont;
59 }
60 EXPORT_SYMBOL_GPL(attribute_container_classdev_to_container);
61 
62 static LIST_HEAD(attribute_container_list);
63 
64 static DEFINE_MUTEX(attribute_container_mutex);
65 
66 /**
67  * attribute_container_register - register an attribute container
68  *
69  * @cont: The container to register.  This must be allocated by the
70  *        callee and should also be zeroed by it.
71  */
72 int
73 attribute_container_register(struct attribute_container *cont)
74 {
75 	INIT_LIST_HEAD(&cont->node);
76 	klist_init(&cont->containers, internal_container_klist_get,
77 		   internal_container_klist_put);
78 
79 	mutex_lock(&attribute_container_mutex);
80 	list_add_tail(&cont->node, &attribute_container_list);
81 	mutex_unlock(&attribute_container_mutex);
82 
83 	return 0;
84 }
85 EXPORT_SYMBOL_GPL(attribute_container_register);
86 
87 /**
88  * attribute_container_unregister - remove a container registration
89  *
90  * @cont: previously registered container to remove
91  */
92 int
93 attribute_container_unregister(struct attribute_container *cont)
94 {
95 	int retval = -EBUSY;
96 
97 	mutex_lock(&attribute_container_mutex);
98 	spin_lock(&cont->containers.k_lock);
99 	if (!list_empty(&cont->containers.k_list))
100 		goto out;
101 	retval = 0;
102 	list_del(&cont->node);
103  out:
104 	spin_unlock(&cont->containers.k_lock);
105 	mutex_unlock(&attribute_container_mutex);
106 	return retval;
107 
108 }
109 EXPORT_SYMBOL_GPL(attribute_container_unregister);
110 
111 /* private function used as class release */
112 static void attribute_container_release(struct device *classdev)
113 {
114 	struct internal_container *ic
115 		= container_of(classdev, struct internal_container, classdev);
116 	struct device *dev = classdev->parent;
117 
118 	kfree(ic);
119 	put_device(dev);
120 }
121 
122 /**
123  * attribute_container_add_device - see if any container is interested in dev
124  *
125  * @dev: device to add attributes to
126  * @fn:	 function to trigger addition of class device.
127  *
128  * This function allocates storage for the class device(s) to be
129  * attached to dev (one for each matching attribute_container).  If no
130  * fn is provided, the code will simply register the class device via
131  * device_add.  If a function is provided, it is expected to add
132  * the class device at the appropriate time.  One of the things that
133  * might be necessary is to allocate and initialise the classdev and
134  * then add it a later time.  To do this, call this routine for
135  * allocation and initialisation and then use
136  * attribute_container_device_trigger() to call device_add() on
137  * it.  Note: after this, the class device contains a reference to dev
138  * which is not relinquished until the release of the classdev.
139  */
140 void
141 attribute_container_add_device(struct device *dev,
142 			       int (*fn)(struct attribute_container *,
143 					 struct device *,
144 					 struct device *))
145 {
146 	struct attribute_container *cont;
147 
148 	mutex_lock(&attribute_container_mutex);
149 	list_for_each_entry(cont, &attribute_container_list, node) {
150 		struct internal_container *ic;
151 
152 		if (attribute_container_no_classdevs(cont))
153 			continue;
154 
155 		if (!cont->match(cont, dev))
156 			continue;
157 
158 		ic = kzalloc(sizeof(*ic), GFP_KERNEL);
159 		if (!ic) {
160 			dev_err(dev, "failed to allocate class container\n");
161 			continue;
162 		}
163 
164 		ic->cont = cont;
165 		device_initialize(&ic->classdev);
166 		ic->classdev.parent = get_device(dev);
167 		ic->classdev.class = cont->class;
168 		cont->class->dev_release = attribute_container_release;
169 		dev_set_name(&ic->classdev, "%s", dev_name(dev));
170 		if (fn)
171 			fn(cont, dev, &ic->classdev);
172 		else
173 			attribute_container_add_class_device(&ic->classdev);
174 		klist_add_tail(&ic->node, &cont->containers);
175 	}
176 	mutex_unlock(&attribute_container_mutex);
177 }
178 
179 /* FIXME: can't break out of this unless klist_iter_exit is also
180  * called before doing the break
181  */
182 #define klist_for_each_entry(pos, head, member, iter) \
183 	for (klist_iter_init(head, iter); (pos = ({ \
184 		struct klist_node *n = klist_next(iter); \
185 		n ? container_of(n, typeof(*pos), member) : \
186 			({ klist_iter_exit(iter) ; NULL; }); \
187 	})) != NULL;)
188 
189 
190 /**
191  * attribute_container_remove_device - make device eligible for removal.
192  *
193  * @dev:  The generic device
194  * @fn:	  A function to call to remove the device
195  *
196  * This routine triggers device removal.  If fn is NULL, then it is
197  * simply done via device_unregister (note that if something
198  * still has a reference to the classdev, then the memory occupied
199  * will not be freed until the classdev is released).  If you want a
200  * two phase release: remove from visibility and then delete the
201  * device, then you should use this routine with a fn that calls
202  * device_del() and then use attribute_container_device_trigger()
203  * to do the final put on the classdev.
204  */
205 void
206 attribute_container_remove_device(struct device *dev,
207 				  void (*fn)(struct attribute_container *,
208 					     struct device *,
209 					     struct device *))
210 {
211 	struct attribute_container *cont;
212 
213 	mutex_lock(&attribute_container_mutex);
214 	list_for_each_entry(cont, &attribute_container_list, node) {
215 		struct internal_container *ic;
216 		struct klist_iter iter;
217 
218 		if (attribute_container_no_classdevs(cont))
219 			continue;
220 
221 		if (!cont->match(cont, dev))
222 			continue;
223 
224 		klist_for_each_entry(ic, &cont->containers, node, &iter) {
225 			if (dev != ic->classdev.parent)
226 				continue;
227 			klist_del(&ic->node);
228 			if (fn)
229 				fn(cont, dev, &ic->classdev);
230 			else {
231 				attribute_container_remove_attrs(&ic->classdev);
232 				device_unregister(&ic->classdev);
233 			}
234 		}
235 	}
236 	mutex_unlock(&attribute_container_mutex);
237 }
238 
239 static int
240 do_attribute_container_device_trigger_safe(struct device *dev,
241 					   struct attribute_container *cont,
242 					   int (*fn)(struct attribute_container *,
243 						     struct device *, struct device *),
244 					   int (*undo)(struct attribute_container *,
245 						       struct device *, struct device *))
246 {
247 	int ret;
248 	struct internal_container *ic, *failed;
249 	struct klist_iter iter;
250 
251 	if (attribute_container_no_classdevs(cont))
252 		return fn(cont, dev, NULL);
253 
254 	klist_for_each_entry(ic, &cont->containers, node, &iter) {
255 		if (dev == ic->classdev.parent) {
256 			ret = fn(cont, dev, &ic->classdev);
257 			if (ret) {
258 				failed = ic;
259 				klist_iter_exit(&iter);
260 				goto fail;
261 			}
262 		}
263 	}
264 	return 0;
265 
266 fail:
267 	if (!undo)
268 		return ret;
269 
270 	/* Attempt to undo the work partially done. */
271 	klist_for_each_entry(ic, &cont->containers, node, &iter) {
272 		if (ic == failed) {
273 			klist_iter_exit(&iter);
274 			break;
275 		}
276 		if (dev == ic->classdev.parent)
277 			undo(cont, dev, &ic->classdev);
278 	}
279 	return ret;
280 }
281 
282 /**
283  * attribute_container_device_trigger_safe - execute a trigger for each
284  * matching classdev or fail all of them.
285  *
286  * @dev:  The generic device to run the trigger for
287  * @fn:   the function to execute for each classdev.
288  * @undo: A function to undo the work previously done in case of error
289  *
290  * This function is a safe version of
291  * attribute_container_device_trigger. It stops on the first error and
292  * undo the partial work that has been done, on previous classdev.  It
293  * is guaranteed that either they all succeeded, or none of them
294  * succeeded.
295  */
296 int
297 attribute_container_device_trigger_safe(struct device *dev,
298 					int (*fn)(struct attribute_container *,
299 						  struct device *,
300 						  struct device *),
301 					int (*undo)(struct attribute_container *,
302 						    struct device *,
303 						    struct device *))
304 {
305 	struct attribute_container *cont, *failed = NULL;
306 	int ret = 0;
307 
308 	mutex_lock(&attribute_container_mutex);
309 
310 	list_for_each_entry(cont, &attribute_container_list, node) {
311 
312 		if (!cont->match(cont, dev))
313 			continue;
314 
315 		ret = do_attribute_container_device_trigger_safe(dev, cont,
316 								 fn, undo);
317 		if (ret) {
318 			failed = cont;
319 			break;
320 		}
321 	}
322 
323 	if (ret && !WARN_ON(!undo)) {
324 		list_for_each_entry(cont, &attribute_container_list, node) {
325 
326 			if (failed == cont)
327 				break;
328 
329 			if (!cont->match(cont, dev))
330 				continue;
331 
332 			do_attribute_container_device_trigger_safe(dev, cont,
333 								   undo, NULL);
334 		}
335 	}
336 
337 	mutex_unlock(&attribute_container_mutex);
338 	return ret;
339 
340 }
341 
342 /**
343  * attribute_container_device_trigger - execute a trigger for each matching classdev
344  *
345  * @dev:  The generic device to run the trigger for
346  * @fn:   the function to execute for each classdev.
347  *
348  * This function is for executing a trigger when you need to know both
349  * the container and the classdev.  If you only care about the
350  * container, then use attribute_container_trigger() instead.
351  */
352 void
353 attribute_container_device_trigger(struct device *dev,
354 				   int (*fn)(struct attribute_container *,
355 					     struct device *,
356 					     struct device *))
357 {
358 	struct attribute_container *cont;
359 
360 	mutex_lock(&attribute_container_mutex);
361 	list_for_each_entry(cont, &attribute_container_list, node) {
362 		struct internal_container *ic;
363 		struct klist_iter iter;
364 
365 		if (!cont->match(cont, dev))
366 			continue;
367 
368 		if (attribute_container_no_classdevs(cont)) {
369 			fn(cont, dev, NULL);
370 			continue;
371 		}
372 
373 		klist_for_each_entry(ic, &cont->containers, node, &iter) {
374 			if (dev == ic->classdev.parent)
375 				fn(cont, dev, &ic->classdev);
376 		}
377 	}
378 	mutex_unlock(&attribute_container_mutex);
379 }
380 
381 /**
382  * attribute_container_trigger - trigger a function for each matching container
383  *
384  * @dev:  The generic device to activate the trigger for
385  * @fn:	  the function to trigger
386  *
387  * This routine triggers a function that only needs to know the
388  * matching containers (not the classdev) associated with a device.
389  * It is more lightweight than attribute_container_device_trigger, so
390  * should be used in preference unless the triggering function
391  * actually needs to know the classdev.
392  */
393 void
394 attribute_container_trigger(struct device *dev,
395 			    int (*fn)(struct attribute_container *,
396 				      struct device *))
397 {
398 	struct attribute_container *cont;
399 
400 	mutex_lock(&attribute_container_mutex);
401 	list_for_each_entry(cont, &attribute_container_list, node) {
402 		if (cont->match(cont, dev))
403 			fn(cont, dev);
404 	}
405 	mutex_unlock(&attribute_container_mutex);
406 }
407 
408 /**
409  * attribute_container_add_attrs - add attributes
410  *
411  * @classdev: The class device
412  *
413  * This simply creates all the class device sysfs files from the
414  * attributes listed in the container
415  */
416 int
417 attribute_container_add_attrs(struct device *classdev)
418 {
419 	struct attribute_container *cont =
420 		attribute_container_classdev_to_container(classdev);
421 	struct device_attribute **attrs = cont->attrs;
422 	int i, error;
423 
424 	BUG_ON(attrs && cont->grp);
425 
426 	if (!attrs && !cont->grp)
427 		return 0;
428 
429 	if (cont->grp)
430 		return sysfs_create_group(&classdev->kobj, cont->grp);
431 
432 	for (i = 0; attrs[i]; i++) {
433 		sysfs_attr_init(&attrs[i]->attr);
434 		error = device_create_file(classdev, attrs[i]);
435 		if (error)
436 			return error;
437 	}
438 
439 	return 0;
440 }
441 
442 /**
443  * attribute_container_add_class_device - same function as device_add
444  *
445  * @classdev:	the class device to add
446  *
447  * This performs essentially the same function as device_add except for
448  * attribute containers, namely add the classdev to the system and then
449  * create the attribute files
450  */
451 int
452 attribute_container_add_class_device(struct device *classdev)
453 {
454 	int error = device_add(classdev);
455 
456 	if (error)
457 		return error;
458 	return attribute_container_add_attrs(classdev);
459 }
460 
461 /**
462  * attribute_container_add_class_device_adapter - simple adapter for triggers
463  *
464  * @cont: the container to register.
465  * @dev:  the generic device to activate the trigger for
466  * @classdev:	the class device to add
467  *
468  * This function is identical to attribute_container_add_class_device except
469  * that it is designed to be called from the triggers
470  */
471 int
472 attribute_container_add_class_device_adapter(struct attribute_container *cont,
473 					     struct device *dev,
474 					     struct device *classdev)
475 {
476 	return attribute_container_add_class_device(classdev);
477 }
478 
479 /**
480  * attribute_container_remove_attrs - remove any attribute files
481  *
482  * @classdev: The class device to remove the files from
483  *
484  */
485 void
486 attribute_container_remove_attrs(struct device *classdev)
487 {
488 	struct attribute_container *cont =
489 		attribute_container_classdev_to_container(classdev);
490 	struct device_attribute **attrs = cont->attrs;
491 	int i;
492 
493 	if (!attrs && !cont->grp)
494 		return;
495 
496 	if (cont->grp) {
497 		sysfs_remove_group(&classdev->kobj, cont->grp);
498 		return ;
499 	}
500 
501 	for (i = 0; attrs[i]; i++)
502 		device_remove_file(classdev, attrs[i]);
503 }
504 
505 /**
506  * attribute_container_class_device_del - equivalent of class_device_del
507  *
508  * @classdev: the class device
509  *
510  * This function simply removes all the attribute files and then calls
511  * device_del.
512  */
513 void
514 attribute_container_class_device_del(struct device *classdev)
515 {
516 	attribute_container_remove_attrs(classdev);
517 	device_del(classdev);
518 }
519 
520 /**
521  * attribute_container_find_class_device - find the corresponding class_device
522  *
523  * @cont:	the container
524  * @dev:	the generic device
525  *
526  * Looks up the device in the container's list of class devices and returns
527  * the corresponding class_device.
528  */
529 struct device *
530 attribute_container_find_class_device(struct attribute_container *cont,
531 				      struct device *dev)
532 {
533 	struct device *cdev = NULL;
534 	struct internal_container *ic;
535 	struct klist_iter iter;
536 
537 	klist_for_each_entry(ic, &cont->containers, node, &iter) {
538 		if (ic->classdev.parent == dev) {
539 			cdev = &ic->classdev;
540 			/* FIXME: must exit iterator then break */
541 			klist_iter_exit(&iter);
542 			break;
543 		}
544 	}
545 
546 	return cdev;
547 }
548 EXPORT_SYMBOL_GPL(attribute_container_find_class_device);
549