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 */
60static 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(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 ssize_t ret = 0;
156
157 if (bus_attr->show)
158 ret = bus_attr->show(subsys_priv->bus, buf);
159 return ret;
160}
161
162static 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
174static const struct sysfs_ops bus_sysfs_ops = {
175 .show = bus_attr_show,
176 .store = bus_attr_store,
177};
178
179int 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(kobj: &sp->subsys.kobj, attr: &attr->attr);
188
189 subsys_put(sp);
190 return error;
191}
192EXPORT_SYMBOL_GPL(bus_create_file);
193
194void 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(kobj: &sp->subsys.kobj, attr: &attr->attr);
202 subsys_put(sp);
203}
204EXPORT_SYMBOL_GPL(bus_remove_file);
205
206static void bus_release(struct kobject *kobj)
207{
208 struct subsys_private *priv = to_subsys_private(kobj);
209
210 lockdep_unregister_key(key: &priv->lock_key);
211 kfree(objp: priv);
212}
213
214static const struct kobj_type bus_ktype = {
215 .sysfs_ops = &bus_sysfs_ops,
216 .release = bus_release,
217};
218
219static 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
228static const struct kset_uevent_ops bus_uevent_ops = {
229 .filter = bus_uevent_filter,
230};
231
232/* Manually detach a device from its associated driver. */
233static ssize_t unbind_store(struct device_driver *drv, const char *buf,
234 size_t count)
235{
236 const struct bus_type *bus = bus_get(bus: drv->bus);
237 struct device *dev;
238 int err = -ENODEV;
239
240 dev = bus_find_device_by_name(bus, NULL, name: 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}
249static 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 */
256static ssize_t bind_store(struct device_driver *drv, const char *buf,
257 size_t count)
258{
259 const struct bus_type *bus = bus_get(bus: drv->bus);
260 struct device *dev;
261 int err = -ENODEV;
262
263 dev = bus_find_device_by_name(bus, NULL, name: 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}
275static DRIVER_ATTR_IGNORE_LOCKDEP(bind, 0200, NULL, bind_store);
276
277static 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, fmt: "%d\n", sp->drivers_autoprobe);
286 subsys_put(sp);
287 return ret;
288}
289
290static 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
307static 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, name: 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
322static 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 */
354int 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(k: &sp->klist_devices, i: &i,
366 n: (start ? &start->p->knode_bus : NULL));
367 while (!error && (dev = next_device(i: &i)))
368 error = fn(dev, data);
369 klist_iter_exit(i: &i);
370 subsys_put(sp);
371 return error;
372}
373EXPORT_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 */
390struct 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(k: &sp->klist_devices, i: &i,
402 n: (start ? &start->p->knode_bus : NULL));
403 while ((dev = next_device(i: &i)))
404 if (match(dev, data) && get_device(dev))
405 break;
406 klist_iter_exit(i: &i);
407 subsys_put(sp);
408 return dev;
409}
410EXPORT_SYMBOL_GPL(bus_find_device);
411
412static 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 */
443int 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(k: &sp->klist_drivers, i: &i,
455 n: start ? &start->p->knode_bus : NULL);
456 while ((drv = next_driver(i: &i)) && !error)
457 error = fn(drv, data);
458 klist_iter_exit(i: &i);
459 subsys_put(sp);
460 return error;
461}
462EXPORT_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 */
472int bus_add_device(struct device *dev)
473{
474 struct subsys_private *sp = bus_to_subsys(bus: 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, groups: sp->bus->dev_groups);
494 if (error)
495 goto out_put;
496
497 error = sysfs_create_link(kobj: &sp->devices_kset->kobj, target: &dev->kobj, name: dev_name(dev));
498 if (error)
499 goto out_groups;
500
501 error = sysfs_create_link(kobj: &dev->kobj, target: &sp->subsys.kobj, name: "subsystem");
502 if (error)
503 goto out_subsys;
504
505 klist_add_tail(n: &dev->p->knode_bus, k: &sp->klist_devices);
506 return 0;
507
508out_subsys:
509 sysfs_remove_link(kobj: &sp->devices_kset->kobj, name: dev_name(dev));
510out_groups:
511 device_remove_groups(dev, groups: sp->bus->dev_groups);
512out_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 */
523void bus_probe_device(struct device *dev)
524{
525 struct subsys_private *sp = bus_to_subsys(bus: 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(lock: &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 */
552void bus_remove_device(struct device *dev)
553{
554 struct subsys_private *sp = bus_to_subsys(bus: 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(lock: &sp->mutex);
565
566 sysfs_remove_link(kobj: &dev->kobj, name: "subsystem");
567 sysfs_remove_link(kobj: &sp->devices_kset->kobj, name: dev_name(dev));
568 device_remove_groups(dev, groups: dev->bus->dev_groups);
569 if (klist_node_attached(n: &dev->p->knode_bus))
570 klist_del(n: &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
585static int __must_check add_bind_files(struct device_driver *drv)
586{
587 int ret;
588
589 ret = driver_create_file(driver: drv, attr: &driver_attr_unbind);
590 if (ret == 0) {
591 ret = driver_create_file(driver: drv, attr: &driver_attr_bind);
592 if (ret)
593 driver_remove_file(driver: drv, attr: &driver_attr_unbind);
594 }
595 return ret;
596}
597
598static void remove_bind_files(struct device_driver *drv)
599{
600 driver_remove_file(driver: drv, attr: &driver_attr_bind);
601 driver_remove_file(driver: drv, attr: &driver_attr_unbind);
602}
603
604static BUS_ATTR_WO(drivers_probe);
605static BUS_ATTR_RW(drivers_autoprobe);
606
607static 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);
618out:
619 return retval;
620}
621
622static 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
628static 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(kobj: &drv->p->kobj, buf, count);
634 return rc ? rc : count;
635}
636static DRIVER_ATTR_WO(uevent);
637
638/**
639 * bus_add_driver - Add a driver to the bus.
640 * @drv: driver.
641 */
642int bus_add_driver(struct device_driver *drv)
643{
644 struct subsys_private *sp = bus_to_subsys(bus: 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(size: sizeof(*priv), GFP_KERNEL);
658 if (!priv) {
659 error = -ENOMEM;
660 goto out_put_bus;
661 }
662 klist_init(k: &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(kobj: &priv->kobj, ktype: &driver_ktype, NULL,
667 fmt: "%s", drv->name);
668 if (error)
669 goto out_unregister;
670
671 klist_add_tail(n: &priv->knode_bus, k: &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(mod: drv->owner, drv);
678
679 error = driver_create_file(driver: drv, attr: &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, groups: 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
702out_del_list:
703 klist_del(n: &priv->knode_bus);
704out_unregister:
705 kobject_put(kobj: &priv->kobj);
706 /* drv->p is freed in driver_release() */
707 drv->p = NULL;
708out_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 */
721void bus_remove_driver(struct device_driver *drv)
722{
723 struct subsys_private *sp = bus_to_subsys(bus: 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, groups: sp->bus->drv_groups);
733 driver_remove_file(driver: drv, attr: &driver_attr_uevent);
734 klist_remove(n: &drv->p->knode_bus);
735 driver_detach(drv);
736 module_remove_driver(drv);
737 kobject_put(kobj: &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 */
749static 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: dev->parent);
757 ret = device_attach(dev);
758 if (dev->parent && dev->bus->need_parent_lock)
759 device_unlock(dev: 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 */
772int bus_rescan_devices(const struct bus_type *bus)
773{
774 return bus_for_each_dev(bus, NULL, NULL, bus_rescan_devices_helper);
775}
776EXPORT_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 */
787int device_reprobe(struct device *dev)
788{
789 if (dev->driver)
790 device_driver_detach(dev);
791 return bus_rescan_devices_helper(dev, NULL);
792}
793EXPORT_SYMBOL_GPL(device_reprobe);
794
795static 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
803static 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
811static 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(kobj: &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 */
833static 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 */
844int 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(size: 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(kobj: bus_kobj, name: "%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(kset: &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(name: "devices", NULL, parent_kobj: 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(name: "drivers", NULL, parent_kobj: bus_kobj);
883 if (!priv->drivers_kset) {
884 retval = -ENOMEM;
885 goto bus_drivers_fail;
886 }
887
888 INIT_LIST_HEAD(list: &priv->interfaces);
889 key = &priv->lock_key;
890 lockdep_register_key(key);
891 __mutex_init(lock: &priv->mutex, name: "subsys mutex", key);
892 klist_init(k: &priv->klist_devices, get: klist_devices_get, put: klist_devices_put);
893 klist_init(k: &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(kobj: bus_kobj, groups: 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
906bus_groups_fail:
907 remove_probe_files(bus);
908bus_probe_files_fail:
909 kset_unregister(kset: priv->drivers_kset);
910bus_drivers_fail:
911 kset_unregister(kset: priv->devices_kset);
912bus_devices_fail:
913 bus_remove_file(bus, &bus_attr_uevent);
914bus_uevent_fail:
915 kset_unregister(kset: &priv->subsys);
916out:
917 kfree(objp: priv);
918 return retval;
919}
920EXPORT_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 */
929void 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(dev: sp->dev_root);
940
941 bus_kobj = &sp->subsys.kobj;
942 sysfs_remove_groups(kobj: bus_kobj, groups: bus->bus_groups);
943 remove_probe_files(bus);
944 bus_remove_file(bus, &bus_attr_uevent);
945
946 kset_unregister(kset: sp->drivers_kset);
947 kset_unregister(kset: sp->devices_kset);
948 kset_unregister(kset: &sp->subsys);
949 subsys_put(sp);
950}
951EXPORT_SYMBOL_GPL(bus_unregister);
952
953int 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(nh: &sp->bus_notifier, nb);
962 subsys_put(sp);
963 return retval;
964}
965EXPORT_SYMBOL_GPL(bus_register_notifier);
966
967int 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(nh: &sp->bus_notifier, nb);
975 subsys_put(sp);
976 return retval;
977}
978EXPORT_SYMBOL_GPL(bus_unregister_notifier);
979
980void bus_notify(struct device *dev, enum bus_notifier_event value)
981{
982 struct subsys_private *sp = bus_to_subsys(bus: dev->bus);
983
984 if (!sp)
985 return;
986
987 blocking_notifier_call_chain(nh: &sp->bus_notifier, val: value, v: dev);
988 subsys_put(sp);
989}
990
991struct 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}
1004EXPORT_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 */
1013static 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(list: &a->p->knode_bus.n_node,
1026 head: &b->p->knode_bus.n_node);
1027 return;
1028 }
1029 }
1030 list_move_tail(list: &a->p->knode_bus.n_node, head: list);
1031}
1032
1033void 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(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(a: dev, list: &sorted_devices, compare);
1053 }
1054 list_splice(list: &sorted_devices, head: &device_klist->k_list);
1055 spin_unlock(lock: &device_klist->k_lock);
1056 subsys_put(sp);
1057}
1058EXPORT_SYMBOL_GPL(bus_sort_breadthfirst);
1059
1060struct 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 */
1077static 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(k: &sp->klist_devices, i: &iter->ki, n: 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 */
1100static 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(i: &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 */
1122static void subsys_dev_iter_exit(struct subsys_dev_iter *iter)
1123{
1124 klist_iter_exit(i: &iter->ki);
1125}
1126
1127int 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(bus: 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(new: &sif->node, head: &sp->interfaces);
1147 if (sif->add_dev) {
1148 subsys_dev_iter_init(iter: &iter, sp, NULL, NULL);
1149 while ((dev = subsys_dev_iter_next(iter: &iter)))
1150 sif->add_dev(dev, sif);
1151 subsys_dev_iter_exit(iter: &iter);
1152 }
1153 mutex_unlock(lock: &sp->mutex);
1154
1155 return 0;
1156}
1157EXPORT_SYMBOL_GPL(subsys_interface_register);
1158
1159void 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(bus: sif->subsys);
1169 if (!sp)
1170 return;
1171
1172 mutex_lock(&sp->mutex);
1173 list_del_init(entry: &sif->node);
1174 if (sif->remove_dev) {
1175 subsys_dev_iter_init(iter: &iter, sp, NULL, NULL);
1176 while ((dev = subsys_dev_iter_next(iter: &iter)))
1177 sif->remove_dev(dev, sif);
1178 subsys_dev_iter_exit(iter: &iter);
1179 }
1180 mutex_unlock(lock: &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}
1190EXPORT_SYMBOL_GPL(subsys_interface_unregister);
1191
1192static void system_root_device_release(struct device *dev)
1193{
1194 kfree(objp: dev);
1195}
1196
1197static 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(bus: subsys);
1210 if (!sp) {
1211 err = -EINVAL;
1212 goto err_sp;
1213 }
1214
1215 dev = kzalloc(size: sizeof(struct device), GFP_KERNEL);
1216 if (!dev) {
1217 err = -ENOMEM;
1218 goto err_dev;
1219 }
1220
1221 err = dev_set_name(dev, name: "%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
1237err_dev_reg:
1238 put_device(dev);
1239 dev = NULL;
1240err_name:
1241 kfree(objp: dev);
1242err_dev:
1243 subsys_put(sp);
1244err_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 */
1267int subsys_system_register(struct bus_type *subsys,
1268 const struct attribute_group **groups)
1269{
1270 return subsys_register(subsys, groups, parent_of_root: &system_kset->kobj);
1271}
1272EXPORT_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 */
1285int 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, parent_of_root: virtual_dir);
1295}
1296EXPORT_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 */
1310struct 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(kobj: k);
1328 return priv->driver;
1329}
1330EXPORT_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 */
1336bool 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 */
1360struct 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(dev: sp->dev_root);
1369 subsys_put(sp);
1370 return dev_root;
1371}
1372EXPORT_SYMBOL_GPL(bus_get_dev_root);
1373
1374int __init buses_init(void)
1375{
1376 bus_kset = kset_create_and_add(name: "bus", u: &bus_uevent_ops, NULL);
1377 if (!bus_kset)
1378 return -ENOMEM;
1379
1380 system_kset = kset_create_and_add(name: "system", NULL, parent_kobj: &devices_kset->kobj);
1381 if (!system_kset)
1382 return -ENOMEM;
1383
1384 return 0;
1385}
1386

source code of linux/drivers/base/bus.c