1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * bus.c - bus driver management
4  *
5  * Copyright (c) 2002-3 Patrick Mochel
6  * Copyright (c) 2002-3 Open Source Development Labs
7  * Copyright (c) 2007 Greg Kroah-Hartman <gregkh@suse.de>
8  * Copyright (c) 2007 Novell Inc.
9  * Copyright (c) 2023 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
10  */
11 
12 #include <linux/async.h>
13 #include <linux/device/bus.h>
14 #include <linux/device.h>
15 #include <linux/module.h>
16 #include <linux/errno.h>
17 #include <linux/slab.h>
18 #include <linux/init.h>
19 #include <linux/string.h>
20 #include <linux/mutex.h>
21 #include <linux/sysfs.h>
22 #include "base.h"
23 #include "power/power.h"
24 
25 /* /sys/devices/system */
26 static struct kset *system_kset;
27 
28 /* /sys/bus */
29 static struct kset *bus_kset;
30 
31 #define to_bus_attr(_attr) container_of(_attr, struct bus_attribute, attr)
32 
33 /*
34  * sysfs bindings for drivers
35  */
36 
37 #define to_drv_attr(_attr) container_of(_attr, struct driver_attribute, attr)
38 
39 #define DRIVER_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) \
40 	struct driver_attribute driver_attr_##_name =		\
41 		__ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store)
42 
43 static int __must_check bus_rescan_devices_helper(struct device *dev,
44 						void *data);
45 
46 /**
47  * bus_to_subsys - Turn a struct bus_type into a struct subsys_private
48  *
49  * @bus: pointer to the struct bus_type to look up
50  *
51  * The driver core internals needs to work on the subsys_private structure, not
52  * the external struct bus_type pointer.  This function walks the list of
53  * registered busses in the system and finds the matching one and returns the
54  * internal struct subsys_private that relates to that bus.
55  *
56  * Note, the reference count of the return value is INCREMENTED if it is not
57  * NULL.  A call to subsys_put() must be done when finished with the pointer in
58  * order for it to be properly freed.
59  */
bus_to_subsys(const struct bus_type * bus)60 static struct subsys_private *bus_to_subsys(const struct bus_type *bus)
61 {
62 	struct subsys_private *sp = NULL;
63 	struct kobject *kobj;
64 
65 	if (!bus || !bus_kset)
66 		return NULL;
67 
68 	spin_lock(&bus_kset->list_lock);
69 
70 	if (list_empty(&bus_kset->list))
71 		goto done;
72 
73 	list_for_each_entry(kobj, &bus_kset->list, entry) {
74 		struct kset *kset = container_of(kobj, struct kset, kobj);
75 
76 		sp = container_of_const(kset, struct subsys_private, subsys);
77 		if (sp->bus == bus)
78 			goto done;
79 	}
80 	sp = NULL;
81 done:
82 	sp = subsys_get(sp);
83 	spin_unlock(&bus_kset->list_lock);
84 	return sp;
85 }
86 
bus_get(const struct bus_type * bus)87 static const struct bus_type *bus_get(const struct bus_type *bus)
88 {
89 	struct subsys_private *sp = bus_to_subsys(bus);
90 
91 	if (sp)
92 		return bus;
93 	return NULL;
94 }
95 
bus_put(const struct bus_type * bus)96 static void bus_put(const struct bus_type *bus)
97 {
98 	struct subsys_private *sp = bus_to_subsys(bus);
99 
100 	/* two puts are required as the call to bus_to_subsys incremented it again */
101 	subsys_put(sp);
102 	subsys_put(sp);
103 }
104 
drv_attr_show(struct kobject * kobj,struct attribute * attr,char * buf)105 static ssize_t drv_attr_show(struct kobject *kobj, struct attribute *attr,
106 			     char *buf)
107 {
108 	struct driver_attribute *drv_attr = to_drv_attr(attr);
109 	struct driver_private *drv_priv = to_driver(kobj);
110 	ssize_t ret = -EIO;
111 
112 	if (drv_attr->show)
113 		ret = drv_attr->show(drv_priv->driver, buf);
114 	return ret;
115 }
116 
drv_attr_store(struct kobject * kobj,struct attribute * attr,const char * buf,size_t count)117 static ssize_t drv_attr_store(struct kobject *kobj, struct attribute *attr,
118 			      const char *buf, size_t count)
119 {
120 	struct driver_attribute *drv_attr = to_drv_attr(attr);
121 	struct driver_private *drv_priv = to_driver(kobj);
122 	ssize_t ret = -EIO;
123 
124 	if (drv_attr->store)
125 		ret = drv_attr->store(drv_priv->driver, buf, count);
126 	return ret;
127 }
128 
129 static const struct sysfs_ops driver_sysfs_ops = {
130 	.show	= drv_attr_show,
131 	.store	= drv_attr_store,
132 };
133 
driver_release(struct kobject * kobj)134 static void driver_release(struct kobject *kobj)
135 {
136 	struct driver_private *drv_priv = to_driver(kobj);
137 
138 	pr_debug("driver: '%s': %s\n", kobject_name(kobj), __func__);
139 	kfree(drv_priv);
140 }
141 
142 static const struct kobj_type driver_ktype = {
143 	.sysfs_ops	= &driver_sysfs_ops,
144 	.release	= driver_release,
145 };
146 
147 /*
148  * sysfs bindings for buses
149  */
bus_attr_show(struct kobject * kobj,struct attribute * attr,char * buf)150 static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,
151 			     char *buf)
152 {
153 	struct bus_attribute *bus_attr = to_bus_attr(attr);
154 	struct subsys_private *subsys_priv = to_subsys_private(kobj);
155 	ssize_t ret = 0;
156 
157 	if (bus_attr->show)
158 		ret = bus_attr->show(subsys_priv->bus, buf);
159 	return ret;
160 }
161 
bus_attr_store(struct kobject * kobj,struct attribute * attr,const char * buf,size_t count)162 static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
163 			      const char *buf, size_t count)
164 {
165 	struct bus_attribute *bus_attr = to_bus_attr(attr);
166 	struct subsys_private *subsys_priv = to_subsys_private(kobj);
167 	ssize_t ret = 0;
168 
169 	if (bus_attr->store)
170 		ret = bus_attr->store(subsys_priv->bus, buf, count);
171 	return ret;
172 }
173 
174 static const struct sysfs_ops bus_sysfs_ops = {
175 	.show	= bus_attr_show,
176 	.store	= bus_attr_store,
177 };
178 
bus_create_file(const struct bus_type * bus,struct bus_attribute * attr)179 int bus_create_file(const struct bus_type *bus, struct bus_attribute *attr)
180 {
181 	struct subsys_private *sp = bus_to_subsys(bus);
182 	int error;
183 
184 	if (!sp)
185 		return -EINVAL;
186 
187 	error = sysfs_create_file(&sp->subsys.kobj, &attr->attr);
188 
189 	subsys_put(sp);
190 	return error;
191 }
192 EXPORT_SYMBOL_GPL(bus_create_file);
193 
bus_remove_file(const struct bus_type * bus,struct bus_attribute * attr)194 void bus_remove_file(const struct bus_type *bus, struct bus_attribute *attr)
195 {
196 	struct subsys_private *sp = bus_to_subsys(bus);
197 
198 	if (!sp)
199 		return;
200 
201 	sysfs_remove_file(&sp->subsys.kobj, &attr->attr);
202 	subsys_put(sp);
203 }
204 EXPORT_SYMBOL_GPL(bus_remove_file);
205 
bus_release(struct kobject * kobj)206 static void bus_release(struct kobject *kobj)
207 {
208 	struct subsys_private *priv = to_subsys_private(kobj);
209 
210 	lockdep_unregister_key(&priv->lock_key);
211 	kfree(priv);
212 }
213 
214 static const struct kobj_type bus_ktype = {
215 	.sysfs_ops	= &bus_sysfs_ops,
216 	.release	= bus_release,
217 };
218 
bus_uevent_filter(const struct kobject * kobj)219 static int bus_uevent_filter(const struct kobject *kobj)
220 {
221 	const struct kobj_type *ktype = get_ktype(kobj);
222 
223 	if (ktype == &bus_ktype)
224 		return 1;
225 	return 0;
226 }
227 
228 static const struct kset_uevent_ops bus_uevent_ops = {
229 	.filter = bus_uevent_filter,
230 };
231 
232 /* Manually detach a device from its associated driver. */
unbind_store(struct device_driver * drv,const char * buf,size_t count)233 static ssize_t unbind_store(struct device_driver *drv, const char *buf,
234 			    size_t count)
235 {
236 	const struct bus_type *bus = bus_get(drv->bus);
237 	struct device *dev;
238 	int err = -ENODEV;
239 
240 	dev = bus_find_device_by_name(bus, NULL, buf);
241 	if (dev && dev->driver == drv) {
242 		device_driver_detach(dev);
243 		err = count;
244 	}
245 	put_device(dev);
246 	bus_put(bus);
247 	return err;
248 }
249 static DRIVER_ATTR_IGNORE_LOCKDEP(unbind, 0200, NULL, unbind_store);
250 
251 /*
252  * Manually attach a device to a driver.
253  * Note: the driver must want to bind to the device,
254  * it is not possible to override the driver's id table.
255  */
bind_store(struct device_driver * drv,const char * buf,size_t count)256 static ssize_t bind_store(struct device_driver *drv, const char *buf,
257 			  size_t count)
258 {
259 	const struct bus_type *bus = bus_get(drv->bus);
260 	struct device *dev;
261 	int err = -ENODEV;
262 
263 	dev = bus_find_device_by_name(bus, NULL, buf);
264 	if (dev && driver_match_device(drv, dev)) {
265 		err = device_driver_attach(drv, dev);
266 		if (!err) {
267 			/* success */
268 			err = count;
269 		}
270 	}
271 	put_device(dev);
272 	bus_put(bus);
273 	return err;
274 }
275 static DRIVER_ATTR_IGNORE_LOCKDEP(bind, 0200, NULL, bind_store);
276 
drivers_autoprobe_show(const struct bus_type * bus,char * buf)277 static ssize_t drivers_autoprobe_show(const struct bus_type *bus, char *buf)
278 {
279 	struct subsys_private *sp = bus_to_subsys(bus);
280 	int ret;
281 
282 	if (!sp)
283 		return -EINVAL;
284 
285 	ret = sysfs_emit(buf, "%d\n", sp->drivers_autoprobe);
286 	subsys_put(sp);
287 	return ret;
288 }
289 
drivers_autoprobe_store(const struct bus_type * bus,const char * buf,size_t count)290 static ssize_t drivers_autoprobe_store(const struct bus_type *bus,
291 				       const char *buf, size_t count)
292 {
293 	struct subsys_private *sp = bus_to_subsys(bus);
294 
295 	if (!sp)
296 		return -EINVAL;
297 
298 	if (buf[0] == '0')
299 		sp->drivers_autoprobe = 0;
300 	else
301 		sp->drivers_autoprobe = 1;
302 
303 	subsys_put(sp);
304 	return count;
305 }
306 
drivers_probe_store(const struct bus_type * bus,const char * buf,size_t count)307 static ssize_t drivers_probe_store(const struct bus_type *bus,
308 				   const char *buf, size_t count)
309 {
310 	struct device *dev;
311 	int err = -EINVAL;
312 
313 	dev = bus_find_device_by_name(bus, NULL, buf);
314 	if (!dev)
315 		return -ENODEV;
316 	if (bus_rescan_devices_helper(dev, NULL) == 0)
317 		err = count;
318 	put_device(dev);
319 	return err;
320 }
321 
next_device(struct klist_iter * i)322 static struct device *next_device(struct klist_iter *i)
323 {
324 	struct klist_node *n = klist_next(i);
325 	struct device *dev = NULL;
326 	struct device_private *dev_prv;
327 
328 	if (n) {
329 		dev_prv = to_device_private_bus(n);
330 		dev = dev_prv->device;
331 	}
332 	return dev;
333 }
334 
335 /**
336  * bus_for_each_dev - device iterator.
337  * @bus: bus type.
338  * @start: device to start iterating from.
339  * @data: data for the callback.
340  * @fn: function to be called for each device.
341  *
342  * Iterate over @bus's list of devices, and call @fn for each,
343  * passing it @data. If @start is not NULL, we use that device to
344  * begin iterating from.
345  *
346  * We check the return of @fn each time. If it returns anything
347  * other than 0, we break out and return that value.
348  *
349  * NOTE: The device that returns a non-zero value is not retained
350  * in any way, nor is its refcount incremented. If the caller needs
351  * to retain this data, it should do so, and increment the reference
352  * count in the supplied callback.
353  */
bus_for_each_dev(const struct bus_type * bus,struct device * start,void * data,int (* fn)(struct device *,void *))354 int bus_for_each_dev(const struct bus_type *bus, struct device *start,
355 		     void *data, int (*fn)(struct device *, void *))
356 {
357 	struct subsys_private *sp = bus_to_subsys(bus);
358 	struct klist_iter i;
359 	struct device *dev;
360 	int error = 0;
361 
362 	if (!sp)
363 		return -EINVAL;
364 
365 	klist_iter_init_node(&sp->klist_devices, &i,
366 			     (start ? &start->p->knode_bus : NULL));
367 	while (!error && (dev = next_device(&i)))
368 		error = fn(dev, data);
369 	klist_iter_exit(&i);
370 	subsys_put(sp);
371 	return error;
372 }
373 EXPORT_SYMBOL_GPL(bus_for_each_dev);
374 
375 /**
376  * bus_find_device - device iterator for locating a particular device.
377  * @bus: bus type
378  * @start: Device to begin with
379  * @data: Data to pass to match function
380  * @match: Callback function to check device
381  *
382  * This is similar to the bus_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.
385  *
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.
389  */
bus_find_device(const struct bus_type * bus,struct device * start,const void * data,int (* match)(struct device * dev,const void * data))390 struct device *bus_find_device(const struct bus_type *bus,
391 			       struct device *start, const void *data,
392 			       int (*match)(struct device *dev, const void *data))
393 {
394 	struct subsys_private *sp = bus_to_subsys(bus);
395 	struct klist_iter i;
396 	struct device *dev;
397 
398 	if (!sp)
399 		return NULL;
400 
401 	klist_iter_init_node(&sp->klist_devices, &i,
402 			     (start ? &start->p->knode_bus : NULL));
403 	while ((dev = next_device(&i)))
404 		if (match(dev, data) && get_device(dev))
405 			break;
406 	klist_iter_exit(&i);
407 	subsys_put(sp);
408 	return dev;
409 }
410 EXPORT_SYMBOL_GPL(bus_find_device);
411 
next_driver(struct klist_iter * i)412 static struct device_driver *next_driver(struct klist_iter *i)
413 {
414 	struct klist_node *n = klist_next(i);
415 	struct driver_private *drv_priv;
416 
417 	if (n) {
418 		drv_priv = container_of(n, struct driver_private, knode_bus);
419 		return drv_priv->driver;
420 	}
421 	return NULL;
422 }
423 
424 /**
425  * bus_for_each_drv - driver iterator
426  * @bus: bus we're dealing with.
427  * @start: driver to start iterating on.
428  * @data: data to pass to the callback.
429  * @fn: function to call for each driver.
430  *
431  * This is nearly identical to the device iterator above.
432  * We iterate over each driver that belongs to @bus, and call
433  * @fn for each. If @fn returns anything but 0, we break out
434  * and return it. If @start is not NULL, we use it as the head
435  * of the list.
436  *
437  * NOTE: we don't return the driver that returns a non-zero
438  * value, nor do we leave the reference count incremented for that
439  * driver. If the caller needs to know that info, it must set it
440  * in the callback. It must also be sure to increment the refcount
441  * so it doesn't disappear before returning to the caller.
442  */
bus_for_each_drv(const struct bus_type * bus,struct device_driver * start,void * data,int (* fn)(struct device_driver *,void *))443 int bus_for_each_drv(const struct bus_type *bus, struct device_driver *start,
444 		     void *data, int (*fn)(struct device_driver *, void *))
445 {
446 	struct subsys_private *sp = bus_to_subsys(bus);
447 	struct klist_iter i;
448 	struct device_driver *drv;
449 	int error = 0;
450 
451 	if (!sp)
452 		return -EINVAL;
453 
454 	klist_iter_init_node(&sp->klist_drivers, &i,
455 			     start ? &start->p->knode_bus : NULL);
456 	while ((drv = next_driver(&i)) && !error)
457 		error = fn(drv, data);
458 	klist_iter_exit(&i);
459 	subsys_put(sp);
460 	return error;
461 }
462 EXPORT_SYMBOL_GPL(bus_for_each_drv);
463 
464 /**
465  * bus_add_device - add device to bus
466  * @dev: device being added
467  *
468  * - Add device's bus attributes.
469  * - Create links to device's bus.
470  * - Add the device to its bus's list of devices.
471  */
bus_add_device(struct device * dev)472 int bus_add_device(struct device *dev)
473 {
474 	struct subsys_private *sp = bus_to_subsys(dev->bus);
475 	int error;
476 
477 	if (!sp) {
478 		/*
479 		 * This is a normal operation for many devices that do not
480 		 * have a bus assigned to them, just say that all went
481 		 * well.
482 		 */
483 		return 0;
484 	}
485 
486 	/*
487 	 * Reference in sp is now incremented and will be dropped when
488 	 * the device is removed from the bus
489 	 */
490 
491 	pr_debug("bus: '%s': add device %s\n", sp->bus->name, dev_name(dev));
492 
493 	error = device_add_groups(dev, sp->bus->dev_groups);
494 	if (error)
495 		goto out_put;
496 
497 	error = sysfs_create_link(&sp->devices_kset->kobj, &dev->kobj, dev_name(dev));
498 	if (error)
499 		goto out_groups;
500 
501 	error = sysfs_create_link(&dev->kobj, &sp->subsys.kobj, "subsystem");
502 	if (error)
503 		goto out_subsys;
504 
505 	klist_add_tail(&dev->p->knode_bus, &sp->klist_devices);
506 	return 0;
507 
508 out_subsys:
509 	sysfs_remove_link(&sp->devices_kset->kobj, dev_name(dev));
510 out_groups:
511 	device_remove_groups(dev, sp->bus->dev_groups);
512 out_put:
513 	subsys_put(sp);
514 	return error;
515 }
516 
517 /**
518  * bus_probe_device - probe drivers for a new device
519  * @dev: device to probe
520  *
521  * - Automatically probe for a driver if the bus allows it.
522  */
bus_probe_device(struct device * dev)523 void bus_probe_device(struct device *dev)
524 {
525 	struct subsys_private *sp = bus_to_subsys(dev->bus);
526 	struct subsys_interface *sif;
527 
528 	if (!sp)
529 		return;
530 
531 	if (sp->drivers_autoprobe)
532 		device_initial_probe(dev);
533 
534 	mutex_lock(&sp->mutex);
535 	list_for_each_entry(sif, &sp->interfaces, node)
536 		if (sif->add_dev)
537 			sif->add_dev(dev, sif);
538 	mutex_unlock(&sp->mutex);
539 	subsys_put(sp);
540 }
541 
542 /**
543  * bus_remove_device - remove device from bus
544  * @dev: device to be removed
545  *
546  * - Remove device from all interfaces.
547  * - Remove symlink from bus' directory.
548  * - Delete device from bus's list.
549  * - Detach from its driver.
550  * - Drop reference taken in bus_add_device().
551  */
bus_remove_device(struct device * dev)552 void bus_remove_device(struct device *dev)
553 {
554 	struct subsys_private *sp = bus_to_subsys(dev->bus);
555 	struct subsys_interface *sif;
556 
557 	if (!sp)
558 		return;
559 
560 	mutex_lock(&sp->mutex);
561 	list_for_each_entry(sif, &sp->interfaces, node)
562 		if (sif->remove_dev)
563 			sif->remove_dev(dev, sif);
564 	mutex_unlock(&sp->mutex);
565 
566 	sysfs_remove_link(&dev->kobj, "subsystem");
567 	sysfs_remove_link(&sp->devices_kset->kobj, dev_name(dev));
568 	device_remove_groups(dev, dev->bus->dev_groups);
569 	if (klist_node_attached(&dev->p->knode_bus))
570 		klist_del(&dev->p->knode_bus);
571 
572 	pr_debug("bus: '%s': remove device %s\n",
573 		 dev->bus->name, dev_name(dev));
574 	device_release_driver(dev);
575 
576 	/*
577 	 * Decrement the reference count twice, once for the bus_to_subsys()
578 	 * call in the start of this function, and the second one from the
579 	 * reference increment in bus_add_device()
580 	 */
581 	subsys_put(sp);
582 	subsys_put(sp);
583 }
584 
add_bind_files(struct device_driver * drv)585 static int __must_check add_bind_files(struct device_driver *drv)
586 {
587 	int ret;
588 
589 	ret = driver_create_file(drv, &driver_attr_unbind);
590 	if (ret == 0) {
591 		ret = driver_create_file(drv, &driver_attr_bind);
592 		if (ret)
593 			driver_remove_file(drv, &driver_attr_unbind);
594 	}
595 	return ret;
596 }
597 
remove_bind_files(struct device_driver * drv)598 static void remove_bind_files(struct device_driver *drv)
599 {
600 	driver_remove_file(drv, &driver_attr_bind);
601 	driver_remove_file(drv, &driver_attr_unbind);
602 }
603 
604 static BUS_ATTR_WO(drivers_probe);
605 static BUS_ATTR_RW(drivers_autoprobe);
606 
add_probe_files(const struct bus_type * bus)607 static int add_probe_files(const struct bus_type *bus)
608 {
609 	int retval;
610 
611 	retval = bus_create_file(bus, &bus_attr_drivers_probe);
612 	if (retval)
613 		goto out;
614 
615 	retval = bus_create_file(bus, &bus_attr_drivers_autoprobe);
616 	if (retval)
617 		bus_remove_file(bus, &bus_attr_drivers_probe);
618 out:
619 	return retval;
620 }
621 
remove_probe_files(const struct bus_type * bus)622 static void remove_probe_files(const struct bus_type *bus)
623 {
624 	bus_remove_file(bus, &bus_attr_drivers_autoprobe);
625 	bus_remove_file(bus, &bus_attr_drivers_probe);
626 }
627 
uevent_store(struct device_driver * drv,const char * buf,size_t count)628 static ssize_t uevent_store(struct device_driver *drv, const char *buf,
629 			    size_t count)
630 {
631 	int rc;
632 
633 	rc = kobject_synth_uevent(&drv->p->kobj, buf, count);
634 	return rc ? rc : count;
635 }
636 static DRIVER_ATTR_WO(uevent);
637 
638 /**
639  * bus_add_driver - Add a driver to the bus.
640  * @drv: driver.
641  */
bus_add_driver(struct device_driver * drv)642 int bus_add_driver(struct device_driver *drv)
643 {
644 	struct subsys_private *sp = bus_to_subsys(drv->bus);
645 	struct driver_private *priv;
646 	int error = 0;
647 
648 	if (!sp)
649 		return -EINVAL;
650 
651 	/*
652 	 * Reference in sp is now incremented and will be dropped when
653 	 * the driver is removed from the bus
654 	 */
655 	pr_debug("bus: '%s': add driver %s\n", sp->bus->name, drv->name);
656 
657 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
658 	if (!priv) {
659 		error = -ENOMEM;
660 		goto out_put_bus;
661 	}
662 	klist_init(&priv->klist_devices, NULL, NULL);
663 	priv->driver = drv;
664 	drv->p = priv;
665 	priv->kobj.kset = sp->drivers_kset;
666 	error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
667 				     "%s", drv->name);
668 	if (error)
669 		goto out_unregister;
670 
671 	klist_add_tail(&priv->knode_bus, &sp->klist_drivers);
672 	if (sp->drivers_autoprobe) {
673 		error = driver_attach(drv);
674 		if (error)
675 			goto out_del_list;
676 	}
677 	module_add_driver(drv->owner, drv);
678 
679 	error = driver_create_file(drv, &driver_attr_uevent);
680 	if (error) {
681 		printk(KERN_ERR "%s: uevent attr (%s) failed\n",
682 			__func__, drv->name);
683 	}
684 	error = driver_add_groups(drv, sp->bus->drv_groups);
685 	if (error) {
686 		/* How the hell do we get out of this pickle? Give up */
687 		printk(KERN_ERR "%s: driver_add_groups(%s) failed\n",
688 			__func__, drv->name);
689 	}
690 
691 	if (!drv->suppress_bind_attrs) {
692 		error = add_bind_files(drv);
693 		if (error) {
694 			/* Ditto */
695 			printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
696 				__func__, drv->name);
697 		}
698 	}
699 
700 	return 0;
701 
702 out_del_list:
703 	klist_del(&priv->knode_bus);
704 out_unregister:
705 	kobject_put(&priv->kobj);
706 	/* drv->p is freed in driver_release()  */
707 	drv->p = NULL;
708 out_put_bus:
709 	subsys_put(sp);
710 	return error;
711 }
712 
713 /**
714  * bus_remove_driver - delete driver from bus's knowledge.
715  * @drv: driver.
716  *
717  * Detach the driver from the devices it controls, and remove
718  * it from its bus's list of drivers. Finally, we drop the reference
719  * to the bus we took in bus_add_driver().
720  */
bus_remove_driver(struct device_driver * drv)721 void bus_remove_driver(struct device_driver *drv)
722 {
723 	struct subsys_private *sp = bus_to_subsys(drv->bus);
724 
725 	if (!sp)
726 		return;
727 
728 	pr_debug("bus: '%s': remove driver %s\n", sp->bus->name, drv->name);
729 
730 	if (!drv->suppress_bind_attrs)
731 		remove_bind_files(drv);
732 	driver_remove_groups(drv, sp->bus->drv_groups);
733 	driver_remove_file(drv, &driver_attr_uevent);
734 	klist_remove(&drv->p->knode_bus);
735 	driver_detach(drv);
736 	module_remove_driver(drv);
737 	kobject_put(&drv->p->kobj);
738 
739 	/*
740 	 * Decrement the reference count twice, once for the bus_to_subsys()
741 	 * call in the start of this function, and the second one from the
742 	 * reference increment in bus_add_driver()
743 	 */
744 	subsys_put(sp);
745 	subsys_put(sp);
746 }
747 
748 /* Helper for bus_rescan_devices's iter */
bus_rescan_devices_helper(struct device * dev,void * data)749 static int __must_check bus_rescan_devices_helper(struct device *dev,
750 						  void *data)
751 {
752 	int ret = 0;
753 
754 	if (!dev->driver) {
755 		if (dev->parent && dev->bus->need_parent_lock)
756 			device_lock(dev->parent);
757 		ret = device_attach(dev);
758 		if (dev->parent && dev->bus->need_parent_lock)
759 			device_unlock(dev->parent);
760 	}
761 	return ret < 0 ? ret : 0;
762 }
763 
764 /**
765  * bus_rescan_devices - rescan devices on the bus for possible drivers
766  * @bus: the bus to scan.
767  *
768  * This function will look for devices on the bus with no driver
769  * attached and rescan it against existing drivers to see if it matches
770  * any by calling device_attach() for the unbound devices.
771  */
bus_rescan_devices(const struct bus_type * bus)772 int bus_rescan_devices(const struct bus_type *bus)
773 {
774 	return bus_for_each_dev(bus, NULL, NULL, bus_rescan_devices_helper);
775 }
776 EXPORT_SYMBOL_GPL(bus_rescan_devices);
777 
778 /**
779  * device_reprobe - remove driver for a device and probe for a new driver
780  * @dev: the device to reprobe
781  *
782  * This function detaches the attached driver (if any) for the given
783  * device and restarts the driver probing process.  It is intended
784  * to use if probing criteria changed during a devices lifetime and
785  * driver attachment should change accordingly.
786  */
device_reprobe(struct device * dev)787 int device_reprobe(struct device *dev)
788 {
789 	if (dev->driver)
790 		device_driver_detach(dev);
791 	return bus_rescan_devices_helper(dev, NULL);
792 }
793 EXPORT_SYMBOL_GPL(device_reprobe);
794 
klist_devices_get(struct klist_node * n)795 static void klist_devices_get(struct klist_node *n)
796 {
797 	struct device_private *dev_prv = to_device_private_bus(n);
798 	struct device *dev = dev_prv->device;
799 
800 	get_device(dev);
801 }
802 
klist_devices_put(struct klist_node * n)803 static void klist_devices_put(struct klist_node *n)
804 {
805 	struct device_private *dev_prv = to_device_private_bus(n);
806 	struct device *dev = dev_prv->device;
807 
808 	put_device(dev);
809 }
810 
bus_uevent_store(const struct bus_type * bus,const char * buf,size_t count)811 static ssize_t bus_uevent_store(const struct bus_type *bus,
812 				const char *buf, size_t count)
813 {
814 	struct subsys_private *sp = bus_to_subsys(bus);
815 	int ret;
816 
817 	if (!sp)
818 		return -EINVAL;
819 
820 	ret = kobject_synth_uevent(&sp->subsys.kobj, buf, count);
821 	subsys_put(sp);
822 
823 	if (ret)
824 		return ret;
825 	return count;
826 }
827 /*
828  * "open code" the old BUS_ATTR() macro here.  We want to use BUS_ATTR_WO()
829  * here, but can not use it as earlier in the file we have
830  * DEVICE_ATTR_WO(uevent), which would cause a clash with the with the store
831  * function name.
832  */
833 static struct bus_attribute bus_attr_uevent = __ATTR(uevent, 0200, NULL,
834 						     bus_uevent_store);
835 
836 /**
837  * bus_register - register a driver-core subsystem
838  * @bus: bus to register
839  *
840  * Once we have that, we register the bus with the kobject
841  * infrastructure, then register the children subsystems it has:
842  * the devices and drivers that belong to the subsystem.
843  */
bus_register(const struct bus_type * bus)844 int bus_register(const struct bus_type *bus)
845 {
846 	int retval;
847 	struct subsys_private *priv;
848 	struct kobject *bus_kobj;
849 	struct lock_class_key *key;
850 
851 	priv = kzalloc(sizeof(struct subsys_private), GFP_KERNEL);
852 	if (!priv)
853 		return -ENOMEM;
854 
855 	priv->bus = bus;
856 
857 	BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);
858 
859 	bus_kobj = &priv->subsys.kobj;
860 	retval = kobject_set_name(bus_kobj, "%s", bus->name);
861 	if (retval)
862 		goto out;
863 
864 	bus_kobj->kset = bus_kset;
865 	bus_kobj->ktype = &bus_ktype;
866 	priv->drivers_autoprobe = 1;
867 
868 	retval = kset_register(&priv->subsys);
869 	if (retval)
870 		goto out;
871 
872 	retval = bus_create_file(bus, &bus_attr_uevent);
873 	if (retval)
874 		goto bus_uevent_fail;
875 
876 	priv->devices_kset = kset_create_and_add("devices", NULL, bus_kobj);
877 	if (!priv->devices_kset) {
878 		retval = -ENOMEM;
879 		goto bus_devices_fail;
880 	}
881 
882 	priv->drivers_kset = kset_create_and_add("drivers", NULL, bus_kobj);
883 	if (!priv->drivers_kset) {
884 		retval = -ENOMEM;
885 		goto bus_drivers_fail;
886 	}
887 
888 	INIT_LIST_HEAD(&priv->interfaces);
889 	key = &priv->lock_key;
890 	lockdep_register_key(key);
891 	__mutex_init(&priv->mutex, "subsys mutex", key);
892 	klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);
893 	klist_init(&priv->klist_drivers, NULL, NULL);
894 
895 	retval = add_probe_files(bus);
896 	if (retval)
897 		goto bus_probe_files_fail;
898 
899 	retval = sysfs_create_groups(bus_kobj, bus->bus_groups);
900 	if (retval)
901 		goto bus_groups_fail;
902 
903 	pr_debug("bus: '%s': registered\n", bus->name);
904 	return 0;
905 
906 bus_groups_fail:
907 	remove_probe_files(bus);
908 bus_probe_files_fail:
909 	kset_unregister(priv->drivers_kset);
910 bus_drivers_fail:
911 	kset_unregister(priv->devices_kset);
912 bus_devices_fail:
913 	bus_remove_file(bus, &bus_attr_uevent);
914 bus_uevent_fail:
915 	kset_unregister(&priv->subsys);
916 out:
917 	kfree(priv);
918 	return retval;
919 }
920 EXPORT_SYMBOL_GPL(bus_register);
921 
922 /**
923  * bus_unregister - remove a bus from the system
924  * @bus: bus.
925  *
926  * Unregister the child subsystems and the bus itself.
927  * Finally, we call bus_put() to release the refcount
928  */
bus_unregister(const struct bus_type * bus)929 void bus_unregister(const struct bus_type *bus)
930 {
931 	struct subsys_private *sp = bus_to_subsys(bus);
932 	struct kobject *bus_kobj;
933 
934 	if (!sp)
935 		return;
936 
937 	pr_debug("bus: '%s': unregistering\n", bus->name);
938 	if (sp->dev_root)
939 		device_unregister(sp->dev_root);
940 
941 	bus_kobj = &sp->subsys.kobj;
942 	sysfs_remove_groups(bus_kobj, bus->bus_groups);
943 	remove_probe_files(bus);
944 	bus_remove_file(bus, &bus_attr_uevent);
945 
946 	kset_unregister(sp->drivers_kset);
947 	kset_unregister(sp->devices_kset);
948 	kset_unregister(&sp->subsys);
949 	subsys_put(sp);
950 }
951 EXPORT_SYMBOL_GPL(bus_unregister);
952 
bus_register_notifier(const struct bus_type * bus,struct notifier_block * nb)953 int bus_register_notifier(const struct bus_type *bus, struct notifier_block *nb)
954 {
955 	struct subsys_private *sp = bus_to_subsys(bus);
956 	int retval;
957 
958 	if (!sp)
959 		return -EINVAL;
960 
961 	retval = blocking_notifier_chain_register(&sp->bus_notifier, nb);
962 	subsys_put(sp);
963 	return retval;
964 }
965 EXPORT_SYMBOL_GPL(bus_register_notifier);
966 
bus_unregister_notifier(const struct bus_type * bus,struct notifier_block * nb)967 int bus_unregister_notifier(const struct bus_type *bus, struct notifier_block *nb)
968 {
969 	struct subsys_private *sp = bus_to_subsys(bus);
970 	int retval;
971 
972 	if (!sp)
973 		return -EINVAL;
974 	retval = blocking_notifier_chain_unregister(&sp->bus_notifier, nb);
975 	subsys_put(sp);
976 	return retval;
977 }
978 EXPORT_SYMBOL_GPL(bus_unregister_notifier);
979 
bus_notify(struct device * dev,enum bus_notifier_event value)980 void bus_notify(struct device *dev, enum bus_notifier_event value)
981 {
982 	struct subsys_private *sp = bus_to_subsys(dev->bus);
983 
984 	if (!sp)
985 		return;
986 
987 	blocking_notifier_call_chain(&sp->bus_notifier, value, dev);
988 	subsys_put(sp);
989 }
990 
bus_get_kset(const struct bus_type * bus)991 struct kset *bus_get_kset(const struct bus_type *bus)
992 {
993 	struct subsys_private *sp = bus_to_subsys(bus);
994 	struct kset *kset;
995 
996 	if (!sp)
997 		return NULL;
998 
999 	kset = &sp->subsys;
1000 	subsys_put(sp);
1001 
1002 	return kset;
1003 }
1004 EXPORT_SYMBOL_GPL(bus_get_kset);
1005 
1006 /*
1007  * Yes, this forcibly breaks the klist abstraction temporarily.  It
1008  * just wants to sort the klist, not change reference counts and
1009  * take/drop locks rapidly in the process.  It does all this while
1010  * holding the lock for the list, so objects can't otherwise be
1011  * added/removed while we're swizzling.
1012  */
device_insertion_sort_klist(struct device * a,struct list_head * list,int (* compare)(const struct device * a,const struct device * b))1013 static void device_insertion_sort_klist(struct device *a, struct list_head *list,
1014 					int (*compare)(const struct device *a,
1015 							const struct device *b))
1016 {
1017 	struct klist_node *n;
1018 	struct device_private *dev_prv;
1019 	struct device *b;
1020 
1021 	list_for_each_entry(n, list, n_node) {
1022 		dev_prv = to_device_private_bus(n);
1023 		b = dev_prv->device;
1024 		if (compare(a, b) <= 0) {
1025 			list_move_tail(&a->p->knode_bus.n_node,
1026 				       &b->p->knode_bus.n_node);
1027 			return;
1028 		}
1029 	}
1030 	list_move_tail(&a->p->knode_bus.n_node, list);
1031 }
1032 
bus_sort_breadthfirst(struct bus_type * bus,int (* compare)(const struct device * a,const struct device * b))1033 void bus_sort_breadthfirst(struct bus_type *bus,
1034 			   int (*compare)(const struct device *a,
1035 					  const struct device *b))
1036 {
1037 	struct subsys_private *sp = bus_to_subsys(bus);
1038 	LIST_HEAD(sorted_devices);
1039 	struct klist_node *n, *tmp;
1040 	struct device_private *dev_prv;
1041 	struct device *dev;
1042 	struct klist *device_klist;
1043 
1044 	if (!sp)
1045 		return;
1046 	device_klist = &sp->klist_devices;
1047 
1048 	spin_lock(&device_klist->k_lock);
1049 	list_for_each_entry_safe(n, tmp, &device_klist->k_list, n_node) {
1050 		dev_prv = to_device_private_bus(n);
1051 		dev = dev_prv->device;
1052 		device_insertion_sort_klist(dev, &sorted_devices, compare);
1053 	}
1054 	list_splice(&sorted_devices, &device_klist->k_list);
1055 	spin_unlock(&device_klist->k_lock);
1056 	subsys_put(sp);
1057 }
1058 EXPORT_SYMBOL_GPL(bus_sort_breadthfirst);
1059 
1060 struct subsys_dev_iter {
1061 	struct klist_iter		ki;
1062 	const struct device_type	*type;
1063 };
1064 
1065 /**
1066  * subsys_dev_iter_init - initialize subsys device iterator
1067  * @iter: subsys iterator to initialize
1068  * @sp: the subsys private (i.e. bus) we wanna iterate over
1069  * @start: the device to start iterating from, if any
1070  * @type: device_type of the devices to iterate over, NULL for all
1071  *
1072  * Initialize subsys iterator @iter such that it iterates over devices
1073  * of @subsys.  If @start is set, the list iteration will start there,
1074  * otherwise if it is NULL, the iteration starts at the beginning of
1075  * the list.
1076  */
subsys_dev_iter_init(struct subsys_dev_iter * iter,struct subsys_private * sp,struct device * start,const struct device_type * type)1077 static void subsys_dev_iter_init(struct subsys_dev_iter *iter, struct subsys_private *sp,
1078 				 struct device *start, const struct device_type *type)
1079 {
1080 	struct klist_node *start_knode = NULL;
1081 
1082 	if (start)
1083 		start_knode = &start->p->knode_bus;
1084 	klist_iter_init_node(&sp->klist_devices, &iter->ki, start_knode);
1085 	iter->type = type;
1086 }
1087 
1088 /**
1089  * subsys_dev_iter_next - iterate to the next device
1090  * @iter: subsys iterator to proceed
1091  *
1092  * Proceed @iter to the next device and return it.  Returns NULL if
1093  * iteration is complete.
1094  *
1095  * The returned device is referenced and won't be released till
1096  * iterator is proceed to the next device or exited.  The caller is
1097  * free to do whatever it wants to do with the device including
1098  * calling back into subsys code.
1099  */
subsys_dev_iter_next(struct subsys_dev_iter * iter)1100 static struct device *subsys_dev_iter_next(struct subsys_dev_iter *iter)
1101 {
1102 	struct klist_node *knode;
1103 	struct device *dev;
1104 
1105 	for (;;) {
1106 		knode = klist_next(&iter->ki);
1107 		if (!knode)
1108 			return NULL;
1109 		dev = to_device_private_bus(knode)->device;
1110 		if (!iter->type || iter->type == dev->type)
1111 			return dev;
1112 	}
1113 }
1114 
1115 /**
1116  * subsys_dev_iter_exit - finish iteration
1117  * @iter: subsys iterator to finish
1118  *
1119  * Finish an iteration.  Always call this function after iteration is
1120  * complete whether the iteration ran till the end or not.
1121  */
subsys_dev_iter_exit(struct subsys_dev_iter * iter)1122 static void subsys_dev_iter_exit(struct subsys_dev_iter *iter)
1123 {
1124 	klist_iter_exit(&iter->ki);
1125 }
1126 
subsys_interface_register(struct subsys_interface * sif)1127 int subsys_interface_register(struct subsys_interface *sif)
1128 {
1129 	struct subsys_private *sp;
1130 	struct subsys_dev_iter iter;
1131 	struct device *dev;
1132 
1133 	if (!sif || !sif->subsys)
1134 		return -ENODEV;
1135 
1136 	sp = bus_to_subsys(sif->subsys);
1137 	if (!sp)
1138 		return -EINVAL;
1139 
1140 	/*
1141 	 * Reference in sp is now incremented and will be dropped when
1142 	 * the interface is removed from the bus
1143 	 */
1144 
1145 	mutex_lock(&sp->mutex);
1146 	list_add_tail(&sif->node, &sp->interfaces);
1147 	if (sif->add_dev) {
1148 		subsys_dev_iter_init(&iter, sp, NULL, NULL);
1149 		while ((dev = subsys_dev_iter_next(&iter)))
1150 			sif->add_dev(dev, sif);
1151 		subsys_dev_iter_exit(&iter);
1152 	}
1153 	mutex_unlock(&sp->mutex);
1154 
1155 	return 0;
1156 }
1157 EXPORT_SYMBOL_GPL(subsys_interface_register);
1158 
subsys_interface_unregister(struct subsys_interface * sif)1159 void subsys_interface_unregister(struct subsys_interface *sif)
1160 {
1161 	struct subsys_private *sp;
1162 	struct subsys_dev_iter iter;
1163 	struct device *dev;
1164 
1165 	if (!sif || !sif->subsys)
1166 		return;
1167 
1168 	sp = bus_to_subsys(sif->subsys);
1169 	if (!sp)
1170 		return;
1171 
1172 	mutex_lock(&sp->mutex);
1173 	list_del_init(&sif->node);
1174 	if (sif->remove_dev) {
1175 		subsys_dev_iter_init(&iter, sp, NULL, NULL);
1176 		while ((dev = subsys_dev_iter_next(&iter)))
1177 			sif->remove_dev(dev, sif);
1178 		subsys_dev_iter_exit(&iter);
1179 	}
1180 	mutex_unlock(&sp->mutex);
1181 
1182 	/*
1183 	 * Decrement the reference count twice, once for the bus_to_subsys()
1184 	 * call in the start of this function, and the second one from the
1185 	 * reference increment in subsys_interface_register()
1186 	 */
1187 	subsys_put(sp);
1188 	subsys_put(sp);
1189 }
1190 EXPORT_SYMBOL_GPL(subsys_interface_unregister);
1191 
system_root_device_release(struct device * dev)1192 static void system_root_device_release(struct device *dev)
1193 {
1194 	kfree(dev);
1195 }
1196 
subsys_register(struct bus_type * subsys,const struct attribute_group ** groups,struct kobject * parent_of_root)1197 static int subsys_register(struct bus_type *subsys,
1198 			   const struct attribute_group **groups,
1199 			   struct kobject *parent_of_root)
1200 {
1201 	struct subsys_private *sp;
1202 	struct device *dev;
1203 	int err;
1204 
1205 	err = bus_register(subsys);
1206 	if (err < 0)
1207 		return err;
1208 
1209 	sp = bus_to_subsys(subsys);
1210 	if (!sp) {
1211 		err = -EINVAL;
1212 		goto err_sp;
1213 	}
1214 
1215 	dev = kzalloc(sizeof(struct device), GFP_KERNEL);
1216 	if (!dev) {
1217 		err = -ENOMEM;
1218 		goto err_dev;
1219 	}
1220 
1221 	err = dev_set_name(dev, "%s", subsys->name);
1222 	if (err < 0)
1223 		goto err_name;
1224 
1225 	dev->kobj.parent = parent_of_root;
1226 	dev->groups = groups;
1227 	dev->release = system_root_device_release;
1228 
1229 	err = device_register(dev);
1230 	if (err < 0)
1231 		goto err_dev_reg;
1232 
1233 	sp->dev_root = dev;
1234 	subsys_put(sp);
1235 	return 0;
1236 
1237 err_dev_reg:
1238 	put_device(dev);
1239 	dev = NULL;
1240 err_name:
1241 	kfree(dev);
1242 err_dev:
1243 	subsys_put(sp);
1244 err_sp:
1245 	bus_unregister(subsys);
1246 	return err;
1247 }
1248 
1249 /**
1250  * subsys_system_register - register a subsystem at /sys/devices/system/
1251  * @subsys: system subsystem
1252  * @groups: default attributes for the root device
1253  *
1254  * All 'system' subsystems have a /sys/devices/system/<name> root device
1255  * with the name of the subsystem. The root device can carry subsystem-
1256  * wide attributes. All registered devices are below this single root
1257  * device and are named after the subsystem with a simple enumeration
1258  * number appended. The registered devices are not explicitly named;
1259  * only 'id' in the device needs to be set.
1260  *
1261  * Do not use this interface for anything new, it exists for compatibility
1262  * with bad ideas only. New subsystems should use plain subsystems; and
1263  * add the subsystem-wide attributes should be added to the subsystem
1264  * directory itself and not some create fake root-device placed in
1265  * /sys/devices/system/<name>.
1266  */
subsys_system_register(struct bus_type * subsys,const struct attribute_group ** groups)1267 int subsys_system_register(struct bus_type *subsys,
1268 			   const struct attribute_group **groups)
1269 {
1270 	return subsys_register(subsys, groups, &system_kset->kobj);
1271 }
1272 EXPORT_SYMBOL_GPL(subsys_system_register);
1273 
1274 /**
1275  * subsys_virtual_register - register a subsystem at /sys/devices/virtual/
1276  * @subsys: virtual subsystem
1277  * @groups: default attributes for the root device
1278  *
1279  * All 'virtual' subsystems have a /sys/devices/system/<name> root device
1280  * with the name of the subystem.  The root device can carry subsystem-wide
1281  * attributes.  All registered devices are below this single root device.
1282  * There's no restriction on device naming.  This is for kernel software
1283  * constructs which need sysfs interface.
1284  */
subsys_virtual_register(struct bus_type * subsys,const struct attribute_group ** groups)1285 int subsys_virtual_register(struct bus_type *subsys,
1286 			    const struct attribute_group **groups)
1287 {
1288 	struct kobject *virtual_dir;
1289 
1290 	virtual_dir = virtual_device_parent(NULL);
1291 	if (!virtual_dir)
1292 		return -ENOMEM;
1293 
1294 	return subsys_register(subsys, groups, virtual_dir);
1295 }
1296 EXPORT_SYMBOL_GPL(subsys_virtual_register);
1297 
1298 /**
1299  * driver_find - locate driver on a bus by its name.
1300  * @name: name of the driver.
1301  * @bus: bus to scan for the driver.
1302  *
1303  * Call kset_find_obj() to iterate over list of drivers on
1304  * a bus to find driver by name. Return driver if found.
1305  *
1306  * This routine provides no locking to prevent the driver it returns
1307  * from being unregistered or unloaded while the caller is using it.
1308  * The caller is responsible for preventing this.
1309  */
driver_find(const char * name,const struct bus_type * bus)1310 struct device_driver *driver_find(const char *name, const struct bus_type *bus)
1311 {
1312 	struct subsys_private *sp = bus_to_subsys(bus);
1313 	struct kobject *k;
1314 	struct driver_private *priv;
1315 
1316 	if (!sp)
1317 		return NULL;
1318 
1319 	k = kset_find_obj(sp->drivers_kset, name);
1320 	subsys_put(sp);
1321 	if (!k)
1322 		return NULL;
1323 
1324 	priv = to_driver(k);
1325 
1326 	/* Drop reference added by kset_find_obj() */
1327 	kobject_put(k);
1328 	return priv->driver;
1329 }
1330 EXPORT_SYMBOL_GPL(driver_find);
1331 
1332 /*
1333  * Warning, the value could go to "removed" instantly after calling this function, so be very
1334  * careful when calling it...
1335  */
bus_is_registered(const struct bus_type * bus)1336 bool bus_is_registered(const struct bus_type *bus)
1337 {
1338 	struct subsys_private *sp = bus_to_subsys(bus);
1339 	bool is_initialized = false;
1340 
1341 	if (sp) {
1342 		is_initialized = true;
1343 		subsys_put(sp);
1344 	}
1345 	return is_initialized;
1346 }
1347 
1348 /**
1349  * bus_get_dev_root - return a pointer to the "device root" of a bus
1350  * @bus: bus to return the device root of.
1351  *
1352  * If a bus has a "device root" structure, return it, WITH THE REFERENCE
1353  * COUNT INCREMENTED.
1354  *
1355  * Note, when finished with the device, a call to put_device() is required.
1356  *
1357  * If the device root is not present (or bus is not a valid pointer), NULL
1358  * will be returned.
1359  */
bus_get_dev_root(const struct bus_type * bus)1360 struct device *bus_get_dev_root(const struct bus_type *bus)
1361 {
1362 	struct subsys_private *sp = bus_to_subsys(bus);
1363 	struct device *dev_root;
1364 
1365 	if (!sp)
1366 		return NULL;
1367 
1368 	dev_root = get_device(sp->dev_root);
1369 	subsys_put(sp);
1370 	return dev_root;
1371 }
1372 EXPORT_SYMBOL_GPL(bus_get_dev_root);
1373 
buses_init(void)1374 int __init buses_init(void)
1375 {
1376 	bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);
1377 	if (!bus_kset)
1378 		return -ENOMEM;
1379 
1380 	system_kset = kset_create_and_add("system", NULL, &devices_kset->kobj);
1381 	if (!system_kset)
1382 		return -ENOMEM;
1383 
1384 	return 0;
1385 }
1386