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 */
26static struct kset *system_kset;
27
28/* /sys/bus */
29static 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
43static 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 */
60struct 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(lock: &bus_kset->list_lock);
69
70 if (list_empty(head: &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;
81done:
82 sp = subsys_get(sp);
83 spin_unlock(lock: &bus_kset->list_lock);
84 return sp;
85}
86
87static 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
96static 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
105static 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
117static 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
129static const struct sysfs_ops driver_sysfs_ops = {
130 .show = drv_attr_show,
131 .store = drv_attr_store,
132};
133
134static 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(objp: drv_priv);
140}
141
142static 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 */
150static 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 /* return -EIO for reading a bus attribute without show() */
156 ssize_t ret = -EIO;
157
158 if (bus_attr->show)
159 ret = bus_attr->show(subsys_priv->bus, buf);
160 return ret;
161}
162
163static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
164 const char *buf, size_t count)
165{
166 struct bus_attribute *bus_attr = to_bus_attr(attr);
167 struct subsys_private *subsys_priv = to_subsys_private(kobj);
168 /* return -EIO for writing a bus attribute without store() */
169 ssize_t ret = -EIO;
170
171 if (bus_attr->store)
172 ret = bus_attr->store(subsys_priv->bus, buf, count);
173 return ret;
174}
175
176static const struct sysfs_ops bus_sysfs_ops = {
177 .show = bus_attr_show,
178 .store = bus_attr_store,
179};
180
181int bus_create_file(const struct bus_type *bus, struct bus_attribute *attr)
182{
183 struct subsys_private *sp = bus_to_subsys(bus);
184 int error;
185
186 if (!sp)
187 return -EINVAL;
188
189 error = sysfs_create_file(kobj: &sp->subsys.kobj, attr: &attr->attr);
190
191 subsys_put(sp);
192 return error;
193}
194EXPORT_SYMBOL_GPL(bus_create_file);
195
196void bus_remove_file(const struct bus_type *bus, struct bus_attribute *attr)
197{
198 struct subsys_private *sp = bus_to_subsys(bus);
199
200 if (!sp)
201 return;
202
203 sysfs_remove_file(kobj: &sp->subsys.kobj, attr: &attr->attr);
204 subsys_put(sp);
205}
206EXPORT_SYMBOL_GPL(bus_remove_file);
207
208static void bus_release(struct kobject *kobj)
209{
210 struct subsys_private *priv = to_subsys_private(kobj);
211
212 lockdep_unregister_key(key: &priv->lock_key);
213 kfree(objp: priv);
214}
215
216static const struct kobj_type bus_ktype = {
217 .sysfs_ops = &bus_sysfs_ops,
218 .release = bus_release,
219};
220
221static int bus_uevent_filter(const struct kobject *kobj)
222{
223 const struct kobj_type *ktype = get_ktype(kobj);
224
225 if (ktype == &bus_ktype)
226 return 1;
227 return 0;
228}
229
230static const struct kset_uevent_ops bus_uevent_ops = {
231 .filter = bus_uevent_filter,
232};
233
234/* Manually detach a device from its associated driver. */
235static ssize_t unbind_store(struct device_driver *drv, const char *buf,
236 size_t count)
237{
238 const struct bus_type *bus = bus_get(bus: drv->bus);
239 struct device *dev;
240 int err = -ENODEV;
241
242 dev = bus_find_device_by_name(bus, NULL, name: buf);
243 if (dev && dev->driver == drv) {
244 device_driver_detach(dev);
245 err = count;
246 }
247 put_device(dev);
248 bus_put(bus);
249 return err;
250}
251static DRIVER_ATTR_IGNORE_LOCKDEP(unbind, 0200, NULL, unbind_store);
252
253/*
254 * Manually attach a device to a driver.
255 * Note: the driver must want to bind to the device,
256 * it is not possible to override the driver's id table.
257 */
258static ssize_t bind_store(struct device_driver *drv, const char *buf,
259 size_t count)
260{
261 const struct bus_type *bus = bus_get(bus: drv->bus);
262 struct device *dev;
263 int err = -ENODEV;
264
265 dev = bus_find_device_by_name(bus, NULL, name: buf);
266 if (dev && driver_match_device(drv, dev)) {
267 err = device_driver_attach(drv, dev);
268 if (!err) {
269 /* success */
270 err = count;
271 }
272 }
273 put_device(dev);
274 bus_put(bus);
275 return err;
276}
277static DRIVER_ATTR_IGNORE_LOCKDEP(bind, 0200, NULL, bind_store);
278
279static ssize_t drivers_autoprobe_show(const struct bus_type *bus, char *buf)
280{
281 struct subsys_private *sp = bus_to_subsys(bus);
282 int ret;
283
284 if (!sp)
285 return -EINVAL;
286
287 ret = sysfs_emit(buf, fmt: "%d\n", sp->drivers_autoprobe);
288 subsys_put(sp);
289 return ret;
290}
291
292static ssize_t drivers_autoprobe_store(const struct bus_type *bus,
293 const char *buf, size_t count)
294{
295 struct subsys_private *sp = bus_to_subsys(bus);
296
297 if (!sp)
298 return -EINVAL;
299
300 if (buf[0] == '0')
301 sp->drivers_autoprobe = 0;
302 else
303 sp->drivers_autoprobe = 1;
304
305 subsys_put(sp);
306 return count;
307}
308
309static ssize_t drivers_probe_store(const struct bus_type *bus,
310 const char *buf, size_t count)
311{
312 struct device *dev;
313 int err = -EINVAL;
314
315 dev = bus_find_device_by_name(bus, NULL, name: buf);
316 if (!dev)
317 return -ENODEV;
318 if (bus_rescan_devices_helper(dev, NULL) == 0)
319 err = count;
320 put_device(dev);
321 return err;
322}
323
324static struct device *next_device(struct klist_iter *i)
325{
326 struct klist_node *n = klist_next(i);
327 struct device *dev = NULL;
328 struct device_private *dev_prv;
329
330 if (n) {
331 dev_prv = to_device_private_bus(n);
332 dev = dev_prv->device;
333 }
334 return dev;
335}
336
337/**
338 * bus_for_each_dev - device iterator.
339 * @bus: bus type.
340 * @start: device to start iterating from.
341 * @data: data for the callback.
342 * @fn: function to be called for each device.
343 *
344 * Iterate over @bus's list of devices, and call @fn for each,
345 * passing it @data. If @start is not NULL, we use that device to
346 * begin iterating from.
347 *
348 * We check the return of @fn each time. If it returns anything
349 * other than 0, we break out and return that value.
350 *
351 * NOTE: The device that returns a non-zero value is not retained
352 * in any way, nor is its refcount incremented. If the caller needs
353 * to retain this data, it should do so, and increment the reference
354 * count in the supplied callback.
355 */
356int bus_for_each_dev(const struct bus_type *bus, struct device *start,
357 void *data, device_iter_t fn)
358{
359 struct subsys_private *sp = bus_to_subsys(bus);
360 struct klist_iter i;
361 struct device *dev;
362 int error = 0;
363
364 if (!sp)
365 return -EINVAL;
366
367 klist_iter_init_node(k: &sp->klist_devices, i: &i,
368 n: (start ? &start->p->knode_bus : NULL));
369 while (!error && (dev = next_device(i: &i)))
370 error = fn(dev, data);
371 klist_iter_exit(i: &i);
372 subsys_put(sp);
373 return error;
374}
375EXPORT_SYMBOL_GPL(bus_for_each_dev);
376
377/**
378 * bus_find_device - device iterator for locating a particular device.
379 * @bus: bus type
380 * @start: Device to begin with
381 * @data: Data to pass to match function
382 * @match: Callback function to check device
383 *
384 * This is similar to the bus_for_each_dev() function above, but it
385 * returns a reference to a device that is 'found' for later use, as
386 * determined by the @match callback.
387 *
388 * The callback should return 0 if the device doesn't match and non-zero
389 * if it does. If the callback returns non-zero, this function will
390 * return to the caller and not iterate over any more devices.
391 */
392struct device *bus_find_device(const struct bus_type *bus,
393 struct device *start, const void *data,
394 device_match_t match)
395{
396 struct subsys_private *sp = bus_to_subsys(bus);
397 struct klist_iter i;
398 struct device *dev;
399
400 if (!sp)
401 return NULL;
402
403 klist_iter_init_node(k: &sp->klist_devices, i: &i,
404 n: (start ? &start->p->knode_bus : NULL));
405 while ((dev = next_device(i: &i))) {
406 if (match(dev, data)) {
407 get_device(dev);
408 break;
409 }
410 }
411 klist_iter_exit(i: &i);
412 subsys_put(sp);
413 return dev;
414}
415EXPORT_SYMBOL_GPL(bus_find_device);
416
417static struct device_driver *next_driver(struct klist_iter *i)
418{
419 struct klist_node *n = klist_next(i);
420 struct driver_private *drv_priv;
421
422 if (n) {
423 drv_priv = container_of(n, struct driver_private, knode_bus);
424 return drv_priv->driver;
425 }
426 return NULL;
427}
428
429/**
430 * bus_for_each_drv - driver iterator
431 * @bus: bus we're dealing with.
432 * @start: driver to start iterating on.
433 * @data: data to pass to the callback.
434 * @fn: function to call for each driver.
435 *
436 * This is nearly identical to the device iterator above.
437 * We iterate over each driver that belongs to @bus, and call
438 * @fn for each. If @fn returns anything but 0, we break out
439 * and return it. If @start is not NULL, we use it as the head
440 * of the list.
441 *
442 * NOTE: we don't return the driver that returns a non-zero
443 * value, nor do we leave the reference count incremented for that
444 * driver. If the caller needs to know that info, it must set it
445 * in the callback. It must also be sure to increment the refcount
446 * so it doesn't disappear before returning to the caller.
447 */
448int bus_for_each_drv(const struct bus_type *bus, struct device_driver *start,
449 void *data, int (*fn)(struct device_driver *, void *))
450{
451 struct subsys_private *sp = bus_to_subsys(bus);
452 struct klist_iter i;
453 struct device_driver *drv;
454 int error = 0;
455
456 if (!sp)
457 return -EINVAL;
458
459 klist_iter_init_node(k: &sp->klist_drivers, i: &i,
460 n: start ? &start->p->knode_bus : NULL);
461 while ((drv = next_driver(i: &i)) && !error)
462 error = fn(drv, data);
463 klist_iter_exit(i: &i);
464 subsys_put(sp);
465 return error;
466}
467EXPORT_SYMBOL_GPL(bus_for_each_drv);
468
469/**
470 * bus_add_device - add device to bus
471 * @dev: device being added
472 *
473 * - Add device's bus attributes.
474 * - Create links to device's bus.
475 * - Add the device to its bus's list of devices.
476 */
477int bus_add_device(struct device *dev)
478{
479 struct subsys_private *sp = bus_to_subsys(bus: dev->bus);
480 int error;
481
482 if (!sp) {
483 /*
484 * This is a normal operation for many devices that do not
485 * have a bus assigned to them, just say that all went
486 * well.
487 */
488 return 0;
489 }
490
491 /*
492 * Reference in sp is now incremented and will be dropped when
493 * the device is removed from the bus
494 */
495
496 pr_debug("bus: '%s': add device %s\n", sp->bus->name, dev_name(dev));
497
498 error = device_add_groups(dev, groups: sp->bus->dev_groups);
499 if (error)
500 goto out_put;
501
502 error = sysfs_create_link(kobj: &sp->devices_kset->kobj, target: &dev->kobj, name: dev_name(dev));
503 if (error)
504 goto out_groups;
505
506 error = sysfs_create_link(kobj: &dev->kobj, target: &sp->subsys.kobj, name: "subsystem");
507 if (error)
508 goto out_subsys;
509
510 klist_add_tail(n: &dev->p->knode_bus, k: &sp->klist_devices);
511 return 0;
512
513out_subsys:
514 sysfs_remove_link(kobj: &sp->devices_kset->kobj, name: dev_name(dev));
515out_groups:
516 device_remove_groups(dev, groups: sp->bus->dev_groups);
517out_put:
518 subsys_put(sp);
519 return error;
520}
521
522/**
523 * bus_probe_device - probe drivers for a new device
524 * @dev: device to probe
525 *
526 * - Automatically probe for a driver if the bus allows it.
527 */
528void bus_probe_device(struct device *dev)
529{
530 struct subsys_private *sp = bus_to_subsys(bus: dev->bus);
531 struct subsys_interface *sif;
532
533 if (!sp)
534 return;
535
536 if (sp->drivers_autoprobe)
537 device_initial_probe(dev);
538
539 mutex_lock(lock: &sp->mutex);
540 list_for_each_entry(sif, &sp->interfaces, node)
541 if (sif->add_dev)
542 sif->add_dev(dev, sif);
543 mutex_unlock(lock: &sp->mutex);
544 subsys_put(sp);
545}
546
547/**
548 * bus_remove_device - remove device from bus
549 * @dev: device to be removed
550 *
551 * - Remove device from all interfaces.
552 * - Remove symlink from bus' directory.
553 * - Delete device from bus's list.
554 * - Detach from its driver.
555 * - Drop reference taken in bus_add_device().
556 */
557void bus_remove_device(struct device *dev)
558{
559 struct subsys_private *sp = bus_to_subsys(bus: dev->bus);
560 struct subsys_interface *sif;
561
562 if (!sp)
563 return;
564
565 mutex_lock(lock: &sp->mutex);
566 list_for_each_entry(sif, &sp->interfaces, node)
567 if (sif->remove_dev)
568 sif->remove_dev(dev, sif);
569 mutex_unlock(lock: &sp->mutex);
570
571 sysfs_remove_link(kobj: &dev->kobj, name: "subsystem");
572 sysfs_remove_link(kobj: &sp->devices_kset->kobj, name: dev_name(dev));
573 device_remove_groups(dev, groups: dev->bus->dev_groups);
574 if (klist_node_attached(n: &dev->p->knode_bus))
575 klist_del(n: &dev->p->knode_bus);
576
577 pr_debug("bus: '%s': remove device %s\n",
578 dev->bus->name, dev_name(dev));
579 device_release_driver(dev);
580
581 /*
582 * Decrement the reference count twice, once for the bus_to_subsys()
583 * call in the start of this function, and the second one from the
584 * reference increment in bus_add_device()
585 */
586 subsys_put(sp);
587 subsys_put(sp);
588}
589
590static int __must_check add_bind_files(struct device_driver *drv)
591{
592 int ret;
593
594 ret = driver_create_file(driver: drv, attr: &driver_attr_unbind);
595 if (ret == 0) {
596 ret = driver_create_file(driver: drv, attr: &driver_attr_bind);
597 if (ret)
598 driver_remove_file(driver: drv, attr: &driver_attr_unbind);
599 }
600 return ret;
601}
602
603static void remove_bind_files(struct device_driver *drv)
604{
605 driver_remove_file(driver: drv, attr: &driver_attr_bind);
606 driver_remove_file(driver: drv, attr: &driver_attr_unbind);
607}
608
609static BUS_ATTR_WO(drivers_probe);
610static BUS_ATTR_RW(drivers_autoprobe);
611
612static int add_probe_files(const struct bus_type *bus)
613{
614 int retval;
615
616 retval = bus_create_file(bus, &bus_attr_drivers_probe);
617 if (retval)
618 goto out;
619
620 retval = bus_create_file(bus, &bus_attr_drivers_autoprobe);
621 if (retval)
622 bus_remove_file(bus, &bus_attr_drivers_probe);
623out:
624 return retval;
625}
626
627static void remove_probe_files(const struct bus_type *bus)
628{
629 bus_remove_file(bus, &bus_attr_drivers_autoprobe);
630 bus_remove_file(bus, &bus_attr_drivers_probe);
631}
632
633static ssize_t uevent_store(struct device_driver *drv, const char *buf,
634 size_t count)
635{
636 int rc;
637
638 rc = kobject_synth_uevent(kobj: &drv->p->kobj, buf, count);
639 return rc ? rc : count;
640}
641static DRIVER_ATTR_WO(uevent);
642
643/**
644 * bus_add_driver - Add a driver to the bus.
645 * @drv: driver.
646 */
647int bus_add_driver(struct device_driver *drv)
648{
649 struct subsys_private *sp = bus_to_subsys(bus: drv->bus);
650 struct driver_private *priv;
651 int error = 0;
652
653 if (!sp)
654 return -EINVAL;
655
656 /*
657 * Reference in sp is now incremented and will be dropped when
658 * the driver is removed from the bus
659 */
660 pr_debug("bus: '%s': add driver %s\n", sp->bus->name, drv->name);
661
662 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
663 if (!priv) {
664 error = -ENOMEM;
665 goto out_put_bus;
666 }
667 klist_init(k: &priv->klist_devices, NULL, NULL);
668 priv->driver = drv;
669 drv->p = priv;
670 priv->kobj.kset = sp->drivers_kset;
671 error = kobject_init_and_add(kobj: &priv->kobj, ktype: &driver_ktype, NULL,
672 fmt: "%s", drv->name);
673 if (error)
674 goto out_unregister;
675
676 klist_add_tail(n: &priv->knode_bus, k: &sp->klist_drivers);
677 if (sp->drivers_autoprobe) {
678 error = driver_attach(drv);
679 if (error)
680 goto out_del_list;
681 }
682 error = module_add_driver(mod: drv->owner, drv);
683 if (error) {
684 printk(KERN_ERR "%s: failed to create module links for %s\n",
685 __func__, drv->name);
686 goto out_detach;
687 }
688
689 error = driver_create_file(driver: drv, attr: &driver_attr_uevent);
690 if (error) {
691 printk(KERN_ERR "%s: uevent attr (%s) failed\n",
692 __func__, drv->name);
693 }
694 error = driver_add_groups(drv, groups: sp->bus->drv_groups);
695 if (error) {
696 /* How the hell do we get out of this pickle? Give up */
697 printk(KERN_ERR "%s: driver_add_groups(%s) failed\n",
698 __func__, drv->name);
699 }
700
701 if (!drv->suppress_bind_attrs) {
702 error = add_bind_files(drv);
703 if (error) {
704 /* Ditto */
705 printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
706 __func__, drv->name);
707 }
708 }
709
710 return 0;
711
712out_detach:
713 driver_detach(drv);
714out_del_list:
715 klist_del(n: &priv->knode_bus);
716out_unregister:
717 kobject_put(kobj: &priv->kobj);
718 /* drv->p is freed in driver_release() */
719 drv->p = NULL;
720out_put_bus:
721 subsys_put(sp);
722 return error;
723}
724
725/**
726 * bus_remove_driver - delete driver from bus's knowledge.
727 * @drv: driver.
728 *
729 * Detach the driver from the devices it controls, and remove
730 * it from its bus's list of drivers. Finally, we drop the reference
731 * to the bus we took in bus_add_driver().
732 */
733void bus_remove_driver(struct device_driver *drv)
734{
735 struct subsys_private *sp = bus_to_subsys(bus: drv->bus);
736
737 if (!sp)
738 return;
739
740 pr_debug("bus: '%s': remove driver %s\n", sp->bus->name, drv->name);
741
742 if (!drv->suppress_bind_attrs)
743 remove_bind_files(drv);
744 driver_remove_groups(drv, groups: sp->bus->drv_groups);
745 driver_remove_file(driver: drv, attr: &driver_attr_uevent);
746 klist_remove(n: &drv->p->knode_bus);
747 driver_detach(drv);
748 module_remove_driver(drv);
749 kobject_put(kobj: &drv->p->kobj);
750
751 /*
752 * Decrement the reference count twice, once for the bus_to_subsys()
753 * call in the start of this function, and the second one from the
754 * reference increment in bus_add_driver()
755 */
756 subsys_put(sp);
757 subsys_put(sp);
758}
759
760/* Helper for bus_rescan_devices's iter */
761static int __must_check bus_rescan_devices_helper(struct device *dev,
762 void *data)
763{
764 int ret = 0;
765
766 if (!dev->driver) {
767 if (dev->parent && dev->bus->need_parent_lock)
768 device_lock(dev: dev->parent);
769 ret = device_attach(dev);
770 if (dev->parent && dev->bus->need_parent_lock)
771 device_unlock(dev: dev->parent);
772 }
773 return ret < 0 ? ret : 0;
774}
775
776/**
777 * bus_rescan_devices - rescan devices on the bus for possible drivers
778 * @bus: the bus to scan.
779 *
780 * This function will look for devices on the bus with no driver
781 * attached and rescan it against existing drivers to see if it matches
782 * any by calling device_attach() for the unbound devices.
783 */
784int bus_rescan_devices(const struct bus_type *bus)
785{
786 return bus_for_each_dev(bus, NULL, NULL, bus_rescan_devices_helper);
787}
788EXPORT_SYMBOL_GPL(bus_rescan_devices);
789
790/**
791 * device_reprobe - remove driver for a device and probe for a new driver
792 * @dev: the device to reprobe
793 *
794 * This function detaches the attached driver (if any) for the given
795 * device and restarts the driver probing process. It is intended
796 * to use if probing criteria changed during a devices lifetime and
797 * driver attachment should change accordingly.
798 */
799int device_reprobe(struct device *dev)
800{
801 if (dev->driver)
802 device_driver_detach(dev);
803 return bus_rescan_devices_helper(dev, NULL);
804}
805EXPORT_SYMBOL_GPL(device_reprobe);
806
807static void klist_devices_get(struct klist_node *n)
808{
809 struct device_private *dev_prv = to_device_private_bus(n);
810 struct device *dev = dev_prv->device;
811
812 get_device(dev);
813}
814
815static void klist_devices_put(struct klist_node *n)
816{
817 struct device_private *dev_prv = to_device_private_bus(n);
818 struct device *dev = dev_prv->device;
819
820 put_device(dev);
821}
822
823static ssize_t bus_uevent_store(const struct bus_type *bus,
824 const char *buf, size_t count)
825{
826 struct subsys_private *sp = bus_to_subsys(bus);
827 int ret;
828
829 if (!sp)
830 return -EINVAL;
831
832 ret = kobject_synth_uevent(kobj: &sp->subsys.kobj, buf, count);
833 subsys_put(sp);
834
835 if (ret)
836 return ret;
837 return count;
838}
839/*
840 * "open code" the old BUS_ATTR() macro here. We want to use BUS_ATTR_WO()
841 * here, but can not use it as earlier in the file we have
842 * DEVICE_ATTR_WO(uevent), which would cause a clash with the with the store
843 * function name.
844 */
845static struct bus_attribute bus_attr_uevent = __ATTR(uevent, 0200, NULL,
846 bus_uevent_store);
847
848/**
849 * bus_register - register a driver-core subsystem
850 * @bus: bus to register
851 *
852 * Once we have that, we register the bus with the kobject
853 * infrastructure, then register the children subsystems it has:
854 * the devices and drivers that belong to the subsystem.
855 */
856int bus_register(const struct bus_type *bus)
857{
858 int retval;
859 struct subsys_private *priv;
860 struct kobject *bus_kobj;
861 struct lock_class_key *key;
862
863 priv = kzalloc(sizeof(struct subsys_private), GFP_KERNEL);
864 if (!priv)
865 return -ENOMEM;
866
867 priv->bus = bus;
868
869 BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);
870
871 bus_kobj = &priv->subsys.kobj;
872 retval = kobject_set_name(kobj: bus_kobj, name: "%s", bus->name);
873 if (retval)
874 goto out;
875
876 bus_kobj->kset = bus_kset;
877 bus_kobj->ktype = &bus_ktype;
878 priv->drivers_autoprobe = 1;
879
880 retval = kset_register(kset: &priv->subsys);
881 if (retval)
882 goto out;
883
884 retval = bus_create_file(bus, &bus_attr_uevent);
885 if (retval)
886 goto bus_uevent_fail;
887
888 priv->devices_kset = kset_create_and_add(name: "devices", NULL, parent_kobj: bus_kobj);
889 if (!priv->devices_kset) {
890 retval = -ENOMEM;
891 goto bus_devices_fail;
892 }
893
894 priv->drivers_kset = kset_create_and_add(name: "drivers", NULL, parent_kobj: bus_kobj);
895 if (!priv->drivers_kset) {
896 retval = -ENOMEM;
897 goto bus_drivers_fail;
898 }
899
900 INIT_LIST_HEAD(list: &priv->interfaces);
901 key = &priv->lock_key;
902 lockdep_register_key(key);
903 __mutex_init(lock: &priv->mutex, name: "subsys mutex", key);
904 klist_init(k: &priv->klist_devices, get: klist_devices_get, put: klist_devices_put);
905 klist_init(k: &priv->klist_drivers, NULL, NULL);
906
907 retval = add_probe_files(bus);
908 if (retval)
909 goto bus_probe_files_fail;
910
911 retval = sysfs_create_groups(kobj: bus_kobj, groups: bus->bus_groups);
912 if (retval)
913 goto bus_groups_fail;
914
915 pr_debug("bus: '%s': registered\n", bus->name);
916 return 0;
917
918bus_groups_fail:
919 remove_probe_files(bus);
920bus_probe_files_fail:
921 kset_unregister(kset: priv->drivers_kset);
922bus_drivers_fail:
923 kset_unregister(kset: priv->devices_kset);
924bus_devices_fail:
925 bus_remove_file(bus, &bus_attr_uevent);
926bus_uevent_fail:
927 kset_unregister(kset: &priv->subsys);
928 /* Above kset_unregister() will kfree @priv */
929 priv = NULL;
930out:
931 kfree(objp: priv);
932 return retval;
933}
934EXPORT_SYMBOL_GPL(bus_register);
935
936/**
937 * bus_unregister - remove a bus from the system
938 * @bus: bus.
939 *
940 * Unregister the child subsystems and the bus itself.
941 * Finally, we call bus_put() to release the refcount
942 */
943void bus_unregister(const struct bus_type *bus)
944{
945 struct subsys_private *sp = bus_to_subsys(bus);
946 struct kobject *bus_kobj;
947
948 if (!sp)
949 return;
950
951 pr_debug("bus: '%s': unregistering\n", bus->name);
952 if (sp->dev_root)
953 device_unregister(dev: sp->dev_root);
954
955 bus_kobj = &sp->subsys.kobj;
956 sysfs_remove_groups(kobj: bus_kobj, groups: bus->bus_groups);
957 remove_probe_files(bus);
958 bus_remove_file(bus, &bus_attr_uevent);
959
960 kset_unregister(kset: sp->drivers_kset);
961 kset_unregister(kset: sp->devices_kset);
962 kset_unregister(kset: &sp->subsys);
963 subsys_put(sp);
964}
965EXPORT_SYMBOL_GPL(bus_unregister);
966
967int bus_register_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
975 retval = blocking_notifier_chain_register(nh: &sp->bus_notifier, nb);
976 subsys_put(sp);
977 return retval;
978}
979EXPORT_SYMBOL_GPL(bus_register_notifier);
980
981int bus_unregister_notifier(const struct bus_type *bus, struct notifier_block *nb)
982{
983 struct subsys_private *sp = bus_to_subsys(bus);
984 int retval;
985
986 if (!sp)
987 return -EINVAL;
988 retval = blocking_notifier_chain_unregister(nh: &sp->bus_notifier, nb);
989 subsys_put(sp);
990 return retval;
991}
992EXPORT_SYMBOL_GPL(bus_unregister_notifier);
993
994void bus_notify(struct device *dev, enum bus_notifier_event value)
995{
996 struct subsys_private *sp = bus_to_subsys(bus: dev->bus);
997
998 if (!sp)
999 return;
1000
1001 blocking_notifier_call_chain(nh: &sp->bus_notifier, val: value, v: dev);
1002 subsys_put(sp);
1003}
1004
1005struct kset *bus_get_kset(const struct bus_type *bus)
1006{
1007 struct subsys_private *sp = bus_to_subsys(bus);
1008 struct kset *kset;
1009
1010 if (!sp)
1011 return NULL;
1012
1013 kset = &sp->subsys;
1014 subsys_put(sp);
1015
1016 return kset;
1017}
1018EXPORT_SYMBOL_GPL(bus_get_kset);
1019
1020/*
1021 * Yes, this forcibly breaks the klist abstraction temporarily. It
1022 * just wants to sort the klist, not change reference counts and
1023 * take/drop locks rapidly in the process. It does all this while
1024 * holding the lock for the list, so objects can't otherwise be
1025 * added/removed while we're swizzling.
1026 */
1027static void device_insertion_sort_klist(struct device *a, struct list_head *list,
1028 int (*compare)(const struct device *a,
1029 const struct device *b))
1030{
1031 struct klist_node *n;
1032 struct device_private *dev_prv;
1033 struct device *b;
1034
1035 list_for_each_entry(n, list, n_node) {
1036 dev_prv = to_device_private_bus(n);
1037 b = dev_prv->device;
1038 if (compare(a, b) <= 0) {
1039 list_move_tail(list: &a->p->knode_bus.n_node,
1040 head: &b->p->knode_bus.n_node);
1041 return;
1042 }
1043 }
1044 list_move_tail(list: &a->p->knode_bus.n_node, head: list);
1045}
1046
1047void bus_sort_breadthfirst(const struct bus_type *bus,
1048 int (*compare)(const struct device *a,
1049 const struct device *b))
1050{
1051 struct subsys_private *sp = bus_to_subsys(bus);
1052 LIST_HEAD(sorted_devices);
1053 struct klist_node *n, *tmp;
1054 struct device_private *dev_prv;
1055 struct device *dev;
1056 struct klist *device_klist;
1057
1058 if (!sp)
1059 return;
1060 device_klist = &sp->klist_devices;
1061
1062 spin_lock(lock: &device_klist->k_lock);
1063 list_for_each_entry_safe(n, tmp, &device_klist->k_list, n_node) {
1064 dev_prv = to_device_private_bus(n);
1065 dev = dev_prv->device;
1066 device_insertion_sort_klist(a: dev, list: &sorted_devices, compare);
1067 }
1068 list_splice(list: &sorted_devices, head: &device_klist->k_list);
1069 spin_unlock(lock: &device_klist->k_lock);
1070 subsys_put(sp);
1071}
1072EXPORT_SYMBOL_GPL(bus_sort_breadthfirst);
1073
1074struct subsys_dev_iter {
1075 struct klist_iter ki;
1076 const struct device_type *type;
1077};
1078
1079/**
1080 * subsys_dev_iter_init - initialize subsys device iterator
1081 * @iter: subsys iterator to initialize
1082 * @sp: the subsys private (i.e. bus) we wanna iterate over
1083 * @start: the device to start iterating from, if any
1084 * @type: device_type of the devices to iterate over, NULL for all
1085 *
1086 * Initialize subsys iterator @iter such that it iterates over devices
1087 * of @subsys. If @start is set, the list iteration will start there,
1088 * otherwise if it is NULL, the iteration starts at the beginning of
1089 * the list.
1090 */
1091static void subsys_dev_iter_init(struct subsys_dev_iter *iter, struct subsys_private *sp,
1092 struct device *start, const struct device_type *type)
1093{
1094 struct klist_node *start_knode = NULL;
1095
1096 if (start)
1097 start_knode = &start->p->knode_bus;
1098 klist_iter_init_node(k: &sp->klist_devices, i: &iter->ki, n: start_knode);
1099 iter->type = type;
1100}
1101
1102/**
1103 * subsys_dev_iter_next - iterate to the next device
1104 * @iter: subsys iterator to proceed
1105 *
1106 * Proceed @iter to the next device and return it. Returns NULL if
1107 * iteration is complete.
1108 *
1109 * The returned device is referenced and won't be released till
1110 * iterator is proceed to the next device or exited. The caller is
1111 * free to do whatever it wants to do with the device including
1112 * calling back into subsys code.
1113 */
1114static struct device *subsys_dev_iter_next(struct subsys_dev_iter *iter)
1115{
1116 struct klist_node *knode;
1117 struct device *dev;
1118
1119 for (;;) {
1120 knode = klist_next(i: &iter->ki);
1121 if (!knode)
1122 return NULL;
1123 dev = to_device_private_bus(knode)->device;
1124 if (!iter->type || iter->type == dev->type)
1125 return dev;
1126 }
1127}
1128
1129/**
1130 * subsys_dev_iter_exit - finish iteration
1131 * @iter: subsys iterator to finish
1132 *
1133 * Finish an iteration. Always call this function after iteration is
1134 * complete whether the iteration ran till the end or not.
1135 */
1136static void subsys_dev_iter_exit(struct subsys_dev_iter *iter)
1137{
1138 klist_iter_exit(i: &iter->ki);
1139}
1140
1141int subsys_interface_register(struct subsys_interface *sif)
1142{
1143 struct subsys_private *sp;
1144 struct subsys_dev_iter iter;
1145 struct device *dev;
1146
1147 if (!sif || !sif->subsys)
1148 return -ENODEV;
1149
1150 sp = bus_to_subsys(bus: sif->subsys);
1151 if (!sp)
1152 return -EINVAL;
1153
1154 /*
1155 * Reference in sp is now incremented and will be dropped when
1156 * the interface is removed from the bus
1157 */
1158
1159 mutex_lock(lock: &sp->mutex);
1160 list_add_tail(new: &sif->node, head: &sp->interfaces);
1161 if (sif->add_dev) {
1162 subsys_dev_iter_init(iter: &iter, sp, NULL, NULL);
1163 while ((dev = subsys_dev_iter_next(iter: &iter)))
1164 sif->add_dev(dev, sif);
1165 subsys_dev_iter_exit(iter: &iter);
1166 }
1167 mutex_unlock(lock: &sp->mutex);
1168
1169 return 0;
1170}
1171EXPORT_SYMBOL_GPL(subsys_interface_register);
1172
1173void subsys_interface_unregister(struct subsys_interface *sif)
1174{
1175 struct subsys_private *sp;
1176 struct subsys_dev_iter iter;
1177 struct device *dev;
1178
1179 if (!sif || !sif->subsys)
1180 return;
1181
1182 sp = bus_to_subsys(bus: sif->subsys);
1183 if (!sp)
1184 return;
1185
1186 mutex_lock(lock: &sp->mutex);
1187 list_del_init(entry: &sif->node);
1188 if (sif->remove_dev) {
1189 subsys_dev_iter_init(iter: &iter, sp, NULL, NULL);
1190 while ((dev = subsys_dev_iter_next(iter: &iter)))
1191 sif->remove_dev(dev, sif);
1192 subsys_dev_iter_exit(iter: &iter);
1193 }
1194 mutex_unlock(lock: &sp->mutex);
1195
1196 /*
1197 * Decrement the reference count twice, once for the bus_to_subsys()
1198 * call in the start of this function, and the second one from the
1199 * reference increment in subsys_interface_register()
1200 */
1201 subsys_put(sp);
1202 subsys_put(sp);
1203}
1204EXPORT_SYMBOL_GPL(subsys_interface_unregister);
1205
1206static void system_root_device_release(struct device *dev)
1207{
1208 kfree(objp: dev);
1209}
1210
1211static int subsys_register(const struct bus_type *subsys,
1212 const struct attribute_group **groups,
1213 struct kobject *parent_of_root)
1214{
1215 struct subsys_private *sp;
1216 struct device *dev;
1217 int err;
1218
1219 err = bus_register(subsys);
1220 if (err < 0)
1221 return err;
1222
1223 sp = bus_to_subsys(bus: subsys);
1224 if (!sp) {
1225 err = -EINVAL;
1226 goto err_sp;
1227 }
1228
1229 dev = kzalloc(sizeof(struct device), GFP_KERNEL);
1230 if (!dev) {
1231 err = -ENOMEM;
1232 goto err_dev;
1233 }
1234
1235 err = dev_set_name(dev, name: "%s", subsys->name);
1236 if (err < 0)
1237 goto err_name;
1238
1239 dev->kobj.parent = parent_of_root;
1240 dev->groups = groups;
1241 dev->release = system_root_device_release;
1242
1243 err = device_register(dev);
1244 if (err < 0)
1245 goto err_dev_reg;
1246
1247 sp->dev_root = dev;
1248 subsys_put(sp);
1249 return 0;
1250
1251err_dev_reg:
1252 put_device(dev);
1253 dev = NULL;
1254err_name:
1255 kfree(objp: dev);
1256err_dev:
1257 subsys_put(sp);
1258err_sp:
1259 bus_unregister(subsys);
1260 return err;
1261}
1262
1263/**
1264 * subsys_system_register - register a subsystem at /sys/devices/system/
1265 * @subsys: system subsystem
1266 * @groups: default attributes for the root device
1267 *
1268 * All 'system' subsystems have a /sys/devices/system/<name> root device
1269 * with the name of the subsystem. The root device can carry subsystem-
1270 * wide attributes. All registered devices are below this single root
1271 * device and are named after the subsystem with a simple enumeration
1272 * number appended. The registered devices are not explicitly named;
1273 * only 'id' in the device needs to be set.
1274 *
1275 * Do not use this interface for anything new, it exists for compatibility
1276 * with bad ideas only. New subsystems should use plain subsystems; and
1277 * add the subsystem-wide attributes should be added to the subsystem
1278 * directory itself and not some create fake root-device placed in
1279 * /sys/devices/system/<name>.
1280 */
1281int subsys_system_register(const struct bus_type *subsys,
1282 const struct attribute_group **groups)
1283{
1284 return subsys_register(subsys, groups, parent_of_root: &system_kset->kobj);
1285}
1286EXPORT_SYMBOL_GPL(subsys_system_register);
1287
1288/**
1289 * subsys_virtual_register - register a subsystem at /sys/devices/virtual/
1290 * @subsys: virtual subsystem
1291 * @groups: default attributes for the root device
1292 *
1293 * All 'virtual' subsystems have a /sys/devices/system/<name> root device
1294 * with the name of the subsystem. The root device can carry subsystem-wide
1295 * attributes. All registered devices are below this single root device.
1296 * There's no restriction on device naming. This is for kernel software
1297 * constructs which need sysfs interface.
1298 */
1299int subsys_virtual_register(const struct bus_type *subsys,
1300 const struct attribute_group **groups)
1301{
1302 struct kobject *virtual_dir;
1303
1304 virtual_dir = virtual_device_parent();
1305 if (!virtual_dir)
1306 return -ENOMEM;
1307
1308 return subsys_register(subsys, groups, parent_of_root: virtual_dir);
1309}
1310EXPORT_SYMBOL_GPL(subsys_virtual_register);
1311
1312/**
1313 * driver_find - locate driver on a bus by its name.
1314 * @name: name of the driver.
1315 * @bus: bus to scan for the driver.
1316 *
1317 * Call kset_find_obj() to iterate over list of drivers on
1318 * a bus to find driver by name. Return driver if found.
1319 *
1320 * This routine provides no locking to prevent the driver it returns
1321 * from being unregistered or unloaded while the caller is using it.
1322 * The caller is responsible for preventing this.
1323 */
1324struct device_driver *driver_find(const char *name, const struct bus_type *bus)
1325{
1326 struct subsys_private *sp = bus_to_subsys(bus);
1327 struct kobject *k;
1328 struct driver_private *priv;
1329
1330 if (!sp)
1331 return NULL;
1332
1333 k = kset_find_obj(sp->drivers_kset, name);
1334 subsys_put(sp);
1335 if (!k)
1336 return NULL;
1337
1338 priv = to_driver(k);
1339
1340 /* Drop reference added by kset_find_obj() */
1341 kobject_put(kobj: k);
1342 return priv->driver;
1343}
1344EXPORT_SYMBOL_GPL(driver_find);
1345
1346/*
1347 * Warning, the value could go to "removed" instantly after calling this function, so be very
1348 * careful when calling it...
1349 */
1350bool bus_is_registered(const struct bus_type *bus)
1351{
1352 struct subsys_private *sp = bus_to_subsys(bus);
1353 bool is_initialized = false;
1354
1355 if (sp) {
1356 is_initialized = true;
1357 subsys_put(sp);
1358 }
1359 return is_initialized;
1360}
1361
1362/**
1363 * bus_get_dev_root - return a pointer to the "device root" of a bus
1364 * @bus: bus to return the device root of.
1365 *
1366 * If a bus has a "device root" structure, return it, WITH THE REFERENCE
1367 * COUNT INCREMENTED.
1368 *
1369 * Note, when finished with the device, a call to put_device() is required.
1370 *
1371 * If the device root is not present (or bus is not a valid pointer), NULL
1372 * will be returned.
1373 */
1374struct device *bus_get_dev_root(const struct bus_type *bus)
1375{
1376 struct subsys_private *sp = bus_to_subsys(bus);
1377 struct device *dev_root;
1378
1379 if (!sp)
1380 return NULL;
1381
1382 dev_root = get_device(dev: sp->dev_root);
1383 subsys_put(sp);
1384 return dev_root;
1385}
1386EXPORT_SYMBOL_GPL(bus_get_dev_root);
1387
1388int __init buses_init(void)
1389{
1390 bus_kset = kset_create_and_add(name: "bus", u: &bus_uevent_ops, NULL);
1391 if (!bus_kset)
1392 return -ENOMEM;
1393
1394 system_kset = kset_create_and_add(name: "system", NULL, parent_kobj: &devices_kset->kobj);
1395 if (!system_kset) {
1396 /* Do error handling here as devices_init() do */
1397 kset_unregister(kset: bus_kset);
1398 bus_kset = NULL;
1399 pr_err("%s: failed to create and add kset 'bus'\n", __func__);
1400 return -ENOMEM;
1401 }
1402
1403 return 0;
1404}
1405