1 // SPDX-License-Identifier: GPL-2.0
3 * bus.c - bus driver management
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.
11 #include <linux/async.h>
12 #include <linux/device/bus.h>
13 #include <linux/device.h>
14 #include <linux/module.h>
15 #include <linux/errno.h>
16 #include <linux/slab.h>
17 #include <linux/init.h>
18 #include <linux/string.h>
19 #include <linux/mutex.h>
20 #include <linux/sysfs.h>
22 #include "power/power.h"
24 /* /sys/devices/system */
25 static struct kset *system_kset;
27 #define to_bus_attr(_attr) container_of(_attr, struct bus_attribute, attr)
30 * sysfs bindings for drivers
33 #define to_drv_attr(_attr) container_of(_attr, struct driver_attribute, attr)
35 #define DRIVER_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) \
36 struct driver_attribute driver_attr_##_name = \
37 __ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store)
39 static int __must_check bus_rescan_devices_helper(struct device *dev,
42 static struct bus_type *bus_get(struct bus_type *bus)
45 kset_get(&bus->p->subsys);
51 static void bus_put(struct bus_type *bus)
54 kset_put(&bus->p->subsys);
57 static ssize_t drv_attr_show(struct kobject *kobj, struct attribute *attr,
60 struct driver_attribute *drv_attr = to_drv_attr(attr);
61 struct driver_private *drv_priv = to_driver(kobj);
65 ret = drv_attr->show(drv_priv->driver, buf);
69 static ssize_t drv_attr_store(struct kobject *kobj, struct attribute *attr,
70 const char *buf, size_t count)
72 struct driver_attribute *drv_attr = to_drv_attr(attr);
73 struct driver_private *drv_priv = to_driver(kobj);
77 ret = drv_attr->store(drv_priv->driver, buf, count);
81 static const struct sysfs_ops driver_sysfs_ops = {
82 .show = drv_attr_show,
83 .store = drv_attr_store,
86 static void driver_release(struct kobject *kobj)
88 struct driver_private *drv_priv = to_driver(kobj);
90 pr_debug("driver: '%s': %s\n", kobject_name(kobj), __func__);
94 static struct kobj_type driver_ktype = {
95 .sysfs_ops = &driver_sysfs_ops,
96 .release = driver_release,
100 * sysfs bindings for buses
102 static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,
105 struct bus_attribute *bus_attr = to_bus_attr(attr);
106 struct subsys_private *subsys_priv = to_subsys_private(kobj);
110 ret = bus_attr->show(subsys_priv->bus, buf);
114 static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
115 const char *buf, size_t count)
117 struct bus_attribute *bus_attr = to_bus_attr(attr);
118 struct subsys_private *subsys_priv = to_subsys_private(kobj);
122 ret = bus_attr->store(subsys_priv->bus, buf, count);
126 static const struct sysfs_ops bus_sysfs_ops = {
127 .show = bus_attr_show,
128 .store = bus_attr_store,
131 int bus_create_file(struct bus_type *bus, struct bus_attribute *attr)
135 error = sysfs_create_file(&bus->p->subsys.kobj, &attr->attr);
141 EXPORT_SYMBOL_GPL(bus_create_file);
143 void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)
146 sysfs_remove_file(&bus->p->subsys.kobj, &attr->attr);
150 EXPORT_SYMBOL_GPL(bus_remove_file);
152 static void bus_release(struct kobject *kobj)
154 struct subsys_private *priv = to_subsys_private(kobj);
155 struct bus_type *bus = priv->bus;
161 static struct kobj_type bus_ktype = {
162 .sysfs_ops = &bus_sysfs_ops,
163 .release = bus_release,
166 static int bus_uevent_filter(struct kset *kset, struct kobject *kobj)
168 struct kobj_type *ktype = get_ktype(kobj);
170 if (ktype == &bus_ktype)
175 static const struct kset_uevent_ops bus_uevent_ops = {
176 .filter = bus_uevent_filter,
179 static struct kset *bus_kset;
181 /* Manually detach a device from its associated driver. */
182 static ssize_t unbind_store(struct device_driver *drv, const char *buf,
185 struct bus_type *bus = bus_get(drv->bus);
189 dev = bus_find_device_by_name(bus, NULL, buf);
190 if (dev && dev->driver == drv) {
191 device_driver_detach(dev);
198 static DRIVER_ATTR_IGNORE_LOCKDEP(unbind, S_IWUSR, NULL, unbind_store);
201 * Manually attach a device to a driver.
202 * Note: the driver must want to bind to the device,
203 * it is not possible to override the driver's id table.
205 static ssize_t bind_store(struct device_driver *drv, const char *buf,
208 struct bus_type *bus = bus_get(drv->bus);
212 dev = bus_find_device_by_name(bus, NULL, buf);
213 if (dev && dev->driver == NULL && driver_match_device(drv, dev)) {
214 err = device_driver_attach(drv, dev);
219 } else if (err == 0) {
220 /* driver didn't accept device */
228 static DRIVER_ATTR_IGNORE_LOCKDEP(bind, S_IWUSR, NULL, bind_store);
230 static ssize_t drivers_autoprobe_show(struct bus_type *bus, char *buf)
232 return sysfs_emit(buf, "%d\n", bus->p->drivers_autoprobe);
235 static ssize_t drivers_autoprobe_store(struct bus_type *bus,
236 const char *buf, size_t count)
239 bus->p->drivers_autoprobe = 0;
241 bus->p->drivers_autoprobe = 1;
245 static ssize_t drivers_probe_store(struct bus_type *bus,
246 const char *buf, size_t count)
251 dev = bus_find_device_by_name(bus, NULL, buf);
254 if (bus_rescan_devices_helper(dev, NULL) == 0)
260 static struct device *next_device(struct klist_iter *i)
262 struct klist_node *n = klist_next(i);
263 struct device *dev = NULL;
264 struct device_private *dev_prv;
267 dev_prv = to_device_private_bus(n);
268 dev = dev_prv->device;
274 * bus_for_each_dev - device iterator.
276 * @start: device to start iterating from.
277 * @data: data for the callback.
278 * @fn: function to be called for each device.
280 * Iterate over @bus's list of devices, and call @fn for each,
281 * passing it @data. If @start is not NULL, we use that device to
282 * begin iterating from.
284 * We check the return of @fn each time. If it returns anything
285 * other than 0, we break out and return that value.
287 * NOTE: The device that returns a non-zero value is not retained
288 * in any way, nor is its refcount incremented. If the caller needs
289 * to retain this data, it should do so, and increment the reference
290 * count in the supplied callback.
292 int bus_for_each_dev(struct bus_type *bus, struct device *start,
293 void *data, int (*fn)(struct device *, void *))
302 klist_iter_init_node(&bus->p->klist_devices, &i,
303 (start ? &start->p->knode_bus : NULL));
304 while (!error && (dev = next_device(&i)))
305 error = fn(dev, data);
309 EXPORT_SYMBOL_GPL(bus_for_each_dev);
312 * bus_find_device - device iterator for locating a particular device.
314 * @start: Device to begin with
315 * @data: Data to pass to match function
316 * @match: Callback function to check device
318 * This is similar to the bus_for_each_dev() function above, but it
319 * returns a reference to a device that is 'found' for later use, as
320 * determined by the @match callback.
322 * The callback should return 0 if the device doesn't match and non-zero
323 * if it does. If the callback returns non-zero, this function will
324 * return to the caller and not iterate over any more devices.
326 struct device *bus_find_device(struct bus_type *bus,
327 struct device *start, const void *data,
328 int (*match)(struct device *dev, const void *data))
336 klist_iter_init_node(&bus->p->klist_devices, &i,
337 (start ? &start->p->knode_bus : NULL));
338 while ((dev = next_device(&i)))
339 if (match(dev, data) && get_device(dev))
344 EXPORT_SYMBOL_GPL(bus_find_device);
347 * subsys_find_device_by_id - find a device with a specific enumeration number
349 * @id: index 'id' in struct device
350 * @hint: device to check first
352 * Check the hint's next object and if it is a match return it directly,
353 * otherwise, fall back to a full list search. Either way a reference for
354 * the returned object is taken.
356 struct device *subsys_find_device_by_id(struct bus_type *subsys, unsigned int id,
366 klist_iter_init_node(&subsys->p->klist_devices, &i, &hint->p->knode_bus);
367 dev = next_device(&i);
368 if (dev && dev->id == id && get_device(dev)) {
375 klist_iter_init_node(&subsys->p->klist_devices, &i, NULL);
376 while ((dev = next_device(&i))) {
377 if (dev->id == id && get_device(dev)) {
385 EXPORT_SYMBOL_GPL(subsys_find_device_by_id);
387 static struct device_driver *next_driver(struct klist_iter *i)
389 struct klist_node *n = klist_next(i);
390 struct driver_private *drv_priv;
393 drv_priv = container_of(n, struct driver_private, knode_bus);
394 return drv_priv->driver;
400 * bus_for_each_drv - driver iterator
401 * @bus: bus we're dealing with.
402 * @start: driver to start iterating on.
403 * @data: data to pass to the callback.
404 * @fn: function to call for each driver.
406 * This is nearly identical to the device iterator above.
407 * We iterate over each driver that belongs to @bus, and call
408 * @fn for each. If @fn returns anything but 0, we break out
409 * and return it. If @start is not NULL, we use it as the head
412 * NOTE: we don't return the driver that returns a non-zero
413 * value, nor do we leave the reference count incremented for that
414 * driver. If the caller needs to know that info, it must set it
415 * in the callback. It must also be sure to increment the refcount
416 * so it doesn't disappear before returning to the caller.
418 int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,
419 void *data, int (*fn)(struct device_driver *, void *))
422 struct device_driver *drv;
428 klist_iter_init_node(&bus->p->klist_drivers, &i,
429 start ? &start->p->knode_bus : NULL);
430 while ((drv = next_driver(&i)) && !error)
431 error = fn(drv, data);
435 EXPORT_SYMBOL_GPL(bus_for_each_drv);
438 * bus_add_device - add device to bus
439 * @dev: device being added
441 * - Add device's bus attributes.
442 * - Create links to device's bus.
443 * - Add the device to its bus's list of devices.
445 int bus_add_device(struct device *dev)
447 struct bus_type *bus = bus_get(dev->bus);
451 pr_debug("bus: '%s': add device %s\n", bus->name, dev_name(dev));
452 error = device_add_groups(dev, bus->dev_groups);
455 error = sysfs_create_link(&bus->p->devices_kset->kobj,
456 &dev->kobj, dev_name(dev));
459 error = sysfs_create_link(&dev->kobj,
460 &dev->bus->p->subsys.kobj, "subsystem");
463 klist_add_tail(&dev->p->knode_bus, &bus->p->klist_devices);
468 sysfs_remove_link(&bus->p->devices_kset->kobj, dev_name(dev));
470 device_remove_groups(dev, bus->dev_groups);
477 * bus_probe_device - probe drivers for a new device
478 * @dev: device to probe
480 * - Automatically probe for a driver if the bus allows it.
482 void bus_probe_device(struct device *dev)
484 struct bus_type *bus = dev->bus;
485 struct subsys_interface *sif;
490 if (bus->p->drivers_autoprobe)
491 device_initial_probe(dev);
493 mutex_lock(&bus->p->mutex);
494 list_for_each_entry(sif, &bus->p->interfaces, node)
496 sif->add_dev(dev, sif);
497 mutex_unlock(&bus->p->mutex);
501 * bus_remove_device - remove device from bus
502 * @dev: device to be removed
504 * - Remove device from all interfaces.
505 * - Remove symlink from bus' directory.
506 * - Delete device from bus's list.
507 * - Detach from its driver.
508 * - Drop reference taken in bus_add_device().
510 void bus_remove_device(struct device *dev)
512 struct bus_type *bus = dev->bus;
513 struct subsys_interface *sif;
518 mutex_lock(&bus->p->mutex);
519 list_for_each_entry(sif, &bus->p->interfaces, node)
521 sif->remove_dev(dev, sif);
522 mutex_unlock(&bus->p->mutex);
524 sysfs_remove_link(&dev->kobj, "subsystem");
525 sysfs_remove_link(&dev->bus->p->devices_kset->kobj,
527 device_remove_groups(dev, dev->bus->dev_groups);
528 if (klist_node_attached(&dev->p->knode_bus))
529 klist_del(&dev->p->knode_bus);
531 pr_debug("bus: '%s': remove device %s\n",
532 dev->bus->name, dev_name(dev));
533 device_release_driver(dev);
537 static int __must_check add_bind_files(struct device_driver *drv)
541 ret = driver_create_file(drv, &driver_attr_unbind);
543 ret = driver_create_file(drv, &driver_attr_bind);
545 driver_remove_file(drv, &driver_attr_unbind);
550 static void remove_bind_files(struct device_driver *drv)
552 driver_remove_file(drv, &driver_attr_bind);
553 driver_remove_file(drv, &driver_attr_unbind);
556 static BUS_ATTR_WO(drivers_probe);
557 static BUS_ATTR_RW(drivers_autoprobe);
559 static int add_probe_files(struct bus_type *bus)
563 retval = bus_create_file(bus, &bus_attr_drivers_probe);
567 retval = bus_create_file(bus, &bus_attr_drivers_autoprobe);
569 bus_remove_file(bus, &bus_attr_drivers_probe);
574 static void remove_probe_files(struct bus_type *bus)
576 bus_remove_file(bus, &bus_attr_drivers_autoprobe);
577 bus_remove_file(bus, &bus_attr_drivers_probe);
580 static ssize_t uevent_store(struct device_driver *drv, const char *buf,
585 rc = kobject_synth_uevent(&drv->p->kobj, buf, count);
586 return rc ? rc : count;
588 static DRIVER_ATTR_WO(uevent);
591 * bus_add_driver - Add a driver to the bus.
594 int bus_add_driver(struct device_driver *drv)
596 struct bus_type *bus;
597 struct driver_private *priv;
600 bus = bus_get(drv->bus);
604 pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);
606 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
611 klist_init(&priv->klist_devices, NULL, NULL);
614 priv->kobj.kset = bus->p->drivers_kset;
615 error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
620 klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
621 if (drv->bus->p->drivers_autoprobe) {
622 error = driver_attach(drv);
626 module_add_driver(drv->owner, drv);
628 error = driver_create_file(drv, &driver_attr_uevent);
630 printk(KERN_ERR "%s: uevent attr (%s) failed\n",
631 __func__, drv->name);
633 error = driver_add_groups(drv, bus->drv_groups);
635 /* How the hell do we get out of this pickle? Give up */
636 printk(KERN_ERR "%s: driver_create_groups(%s) failed\n",
637 __func__, drv->name);
640 if (!drv->suppress_bind_attrs) {
641 error = add_bind_files(drv);
644 printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
645 __func__, drv->name);
652 klist_del(&priv->knode_bus);
654 kobject_put(&priv->kobj);
655 /* drv->p is freed in driver_release() */
663 * bus_remove_driver - delete driver from bus's knowledge.
666 * Detach the driver from the devices it controls, and remove
667 * it from its bus's list of drivers. Finally, we drop the reference
668 * to the bus we took in bus_add_driver().
670 void bus_remove_driver(struct device_driver *drv)
675 if (!drv->suppress_bind_attrs)
676 remove_bind_files(drv);
677 driver_remove_groups(drv, drv->bus->drv_groups);
678 driver_remove_file(drv, &driver_attr_uevent);
679 klist_remove(&drv->p->knode_bus);
680 pr_debug("bus: '%s': remove driver %s\n", drv->bus->name, drv->name);
682 module_remove_driver(drv);
683 kobject_put(&drv->p->kobj);
687 /* Helper for bus_rescan_devices's iter */
688 static int __must_check bus_rescan_devices_helper(struct device *dev,
694 if (dev->parent && dev->bus->need_parent_lock)
695 device_lock(dev->parent);
696 ret = device_attach(dev);
697 if (dev->parent && dev->bus->need_parent_lock)
698 device_unlock(dev->parent);
700 return ret < 0 ? ret : 0;
704 * bus_rescan_devices - rescan devices on the bus for possible drivers
705 * @bus: the bus to scan.
707 * This function will look for devices on the bus with no driver
708 * attached and rescan it against existing drivers to see if it matches
709 * any by calling device_attach() for the unbound devices.
711 int bus_rescan_devices(struct bus_type *bus)
713 return bus_for_each_dev(bus, NULL, NULL, bus_rescan_devices_helper);
715 EXPORT_SYMBOL_GPL(bus_rescan_devices);
718 * device_reprobe - remove driver for a device and probe for a new driver
719 * @dev: the device to reprobe
721 * This function detaches the attached driver (if any) for the given
722 * device and restarts the driver probing process. It is intended
723 * to use if probing criteria changed during a devices lifetime and
724 * driver attachment should change accordingly.
726 int device_reprobe(struct device *dev)
729 device_driver_detach(dev);
730 return bus_rescan_devices_helper(dev, NULL);
732 EXPORT_SYMBOL_GPL(device_reprobe);
735 * find_bus - locate bus by name.
736 * @name: name of bus.
738 * Call kset_find_obj() to iterate over list of buses to
739 * find a bus by name. Return bus if found.
741 * Note that kset_find_obj increments bus' reference count.
744 struct bus_type *find_bus(char *name)
746 struct kobject *k = kset_find_obj(bus_kset, name);
747 return k ? to_bus(k) : NULL;
751 static int bus_add_groups(struct bus_type *bus,
752 const struct attribute_group **groups)
754 return sysfs_create_groups(&bus->p->subsys.kobj, groups);
757 static void bus_remove_groups(struct bus_type *bus,
758 const struct attribute_group **groups)
760 sysfs_remove_groups(&bus->p->subsys.kobj, groups);
763 static void klist_devices_get(struct klist_node *n)
765 struct device_private *dev_prv = to_device_private_bus(n);
766 struct device *dev = dev_prv->device;
771 static void klist_devices_put(struct klist_node *n)
773 struct device_private *dev_prv = to_device_private_bus(n);
774 struct device *dev = dev_prv->device;
779 static ssize_t bus_uevent_store(struct bus_type *bus,
780 const char *buf, size_t count)
784 rc = kobject_synth_uevent(&bus->p->subsys.kobj, buf, count);
785 return rc ? rc : count;
788 * "open code" the old BUS_ATTR() macro here. We want to use BUS_ATTR_WO()
789 * here, but can not use it as earlier in the file we have
790 * DEVICE_ATTR_WO(uevent), which would cause a clash with the with the store
793 static struct bus_attribute bus_attr_uevent = __ATTR(uevent, S_IWUSR, NULL,
797 * bus_register - register a driver-core subsystem
798 * @bus: bus to register
800 * Once we have that, we register the bus with the kobject
801 * infrastructure, then register the children subsystems it has:
802 * the devices and drivers that belong to the subsystem.
804 int bus_register(struct bus_type *bus)
807 struct subsys_private *priv;
808 struct lock_class_key *key = &bus->lock_key;
810 priv = kzalloc(sizeof(struct subsys_private), GFP_KERNEL);
817 BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);
819 retval = kobject_set_name(&priv->subsys.kobj, "%s", bus->name);
823 priv->subsys.kobj.kset = bus_kset;
824 priv->subsys.kobj.ktype = &bus_ktype;
825 priv->drivers_autoprobe = 1;
827 retval = kset_register(&priv->subsys);
831 retval = bus_create_file(bus, &bus_attr_uevent);
833 goto bus_uevent_fail;
835 priv->devices_kset = kset_create_and_add("devices", NULL,
837 if (!priv->devices_kset) {
839 goto bus_devices_fail;
842 priv->drivers_kset = kset_create_and_add("drivers", NULL,
844 if (!priv->drivers_kset) {
846 goto bus_drivers_fail;
849 INIT_LIST_HEAD(&priv->interfaces);
850 __mutex_init(&priv->mutex, "subsys mutex", key);
851 klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);
852 klist_init(&priv->klist_drivers, NULL, NULL);
854 retval = add_probe_files(bus);
856 goto bus_probe_files_fail;
858 retval = bus_add_groups(bus, bus->bus_groups);
860 goto bus_groups_fail;
862 pr_debug("bus: '%s': registered\n", bus->name);
866 remove_probe_files(bus);
867 bus_probe_files_fail:
868 kset_unregister(bus->p->drivers_kset);
870 kset_unregister(bus->p->devices_kset);
872 bus_remove_file(bus, &bus_attr_uevent);
874 kset_unregister(&bus->p->subsys);
880 EXPORT_SYMBOL_GPL(bus_register);
883 * bus_unregister - remove a bus from the system
886 * Unregister the child subsystems and the bus itself.
887 * Finally, we call bus_put() to release the refcount
889 void bus_unregister(struct bus_type *bus)
891 pr_debug("bus: '%s': unregistering\n", bus->name);
893 device_unregister(bus->dev_root);
894 bus_remove_groups(bus, bus->bus_groups);
895 remove_probe_files(bus);
896 kset_unregister(bus->p->drivers_kset);
897 kset_unregister(bus->p->devices_kset);
898 bus_remove_file(bus, &bus_attr_uevent);
899 kset_unregister(&bus->p->subsys);
901 EXPORT_SYMBOL_GPL(bus_unregister);
903 int bus_register_notifier(struct bus_type *bus, struct notifier_block *nb)
905 return blocking_notifier_chain_register(&bus->p->bus_notifier, nb);
907 EXPORT_SYMBOL_GPL(bus_register_notifier);
909 int bus_unregister_notifier(struct bus_type *bus, struct notifier_block *nb)
911 return blocking_notifier_chain_unregister(&bus->p->bus_notifier, nb);
913 EXPORT_SYMBOL_GPL(bus_unregister_notifier);
915 struct kset *bus_get_kset(struct bus_type *bus)
917 return &bus->p->subsys;
919 EXPORT_SYMBOL_GPL(bus_get_kset);
921 struct klist *bus_get_device_klist(struct bus_type *bus)
923 return &bus->p->klist_devices;
925 EXPORT_SYMBOL_GPL(bus_get_device_klist);
928 * Yes, this forcibly breaks the klist abstraction temporarily. It
929 * just wants to sort the klist, not change reference counts and
930 * take/drop locks rapidly in the process. It does all this while
931 * holding the lock for the list, so objects can't otherwise be
932 * added/removed while we're swizzling.
934 static void device_insertion_sort_klist(struct device *a, struct list_head *list,
935 int (*compare)(const struct device *a,
936 const struct device *b))
938 struct klist_node *n;
939 struct device_private *dev_prv;
942 list_for_each_entry(n, list, n_node) {
943 dev_prv = to_device_private_bus(n);
945 if (compare(a, b) <= 0) {
946 list_move_tail(&a->p->knode_bus.n_node,
947 &b->p->knode_bus.n_node);
951 list_move_tail(&a->p->knode_bus.n_node, list);
954 void bus_sort_breadthfirst(struct bus_type *bus,
955 int (*compare)(const struct device *a,
956 const struct device *b))
958 LIST_HEAD(sorted_devices);
959 struct klist_node *n, *tmp;
960 struct device_private *dev_prv;
962 struct klist *device_klist;
964 device_klist = bus_get_device_klist(bus);
966 spin_lock(&device_klist->k_lock);
967 list_for_each_entry_safe(n, tmp, &device_klist->k_list, n_node) {
968 dev_prv = to_device_private_bus(n);
969 dev = dev_prv->device;
970 device_insertion_sort_klist(dev, &sorted_devices, compare);
972 list_splice(&sorted_devices, &device_klist->k_list);
973 spin_unlock(&device_klist->k_lock);
975 EXPORT_SYMBOL_GPL(bus_sort_breadthfirst);
978 * subsys_dev_iter_init - initialize subsys device iterator
979 * @iter: subsys iterator to initialize
980 * @subsys: the subsys we wanna iterate over
981 * @start: the device to start iterating from, if any
982 * @type: device_type of the devices to iterate over, NULL for all
984 * Initialize subsys iterator @iter such that it iterates over devices
985 * of @subsys. If @start is set, the list iteration will start there,
986 * otherwise if it is NULL, the iteration starts at the beginning of
989 void subsys_dev_iter_init(struct subsys_dev_iter *iter, struct bus_type *subsys,
990 struct device *start, const struct device_type *type)
992 struct klist_node *start_knode = NULL;
995 start_knode = &start->p->knode_bus;
996 klist_iter_init_node(&subsys->p->klist_devices, &iter->ki, start_knode);
999 EXPORT_SYMBOL_GPL(subsys_dev_iter_init);
1002 * subsys_dev_iter_next - iterate to the next device
1003 * @iter: subsys iterator to proceed
1005 * Proceed @iter to the next device and return it. Returns NULL if
1006 * iteration is complete.
1008 * The returned device is referenced and won't be released till
1009 * iterator is proceed to the next device or exited. The caller is
1010 * free to do whatever it wants to do with the device including
1011 * calling back into subsys code.
1013 struct device *subsys_dev_iter_next(struct subsys_dev_iter *iter)
1015 struct klist_node *knode;
1019 knode = klist_next(&iter->ki);
1022 dev = to_device_private_bus(knode)->device;
1023 if (!iter->type || iter->type == dev->type)
1027 EXPORT_SYMBOL_GPL(subsys_dev_iter_next);
1030 * subsys_dev_iter_exit - finish iteration
1031 * @iter: subsys iterator to finish
1033 * Finish an iteration. Always call this function after iteration is
1034 * complete whether the iteration ran till the end or not.
1036 void subsys_dev_iter_exit(struct subsys_dev_iter *iter)
1038 klist_iter_exit(&iter->ki);
1040 EXPORT_SYMBOL_GPL(subsys_dev_iter_exit);
1042 int subsys_interface_register(struct subsys_interface *sif)
1044 struct bus_type *subsys;
1045 struct subsys_dev_iter iter;
1048 if (!sif || !sif->subsys)
1051 subsys = bus_get(sif->subsys);
1055 mutex_lock(&subsys->p->mutex);
1056 list_add_tail(&sif->node, &subsys->p->interfaces);
1058 subsys_dev_iter_init(&iter, subsys, NULL, NULL);
1059 while ((dev = subsys_dev_iter_next(&iter)))
1060 sif->add_dev(dev, sif);
1061 subsys_dev_iter_exit(&iter);
1063 mutex_unlock(&subsys->p->mutex);
1067 EXPORT_SYMBOL_GPL(subsys_interface_register);
1069 void subsys_interface_unregister(struct subsys_interface *sif)
1071 struct bus_type *subsys;
1072 struct subsys_dev_iter iter;
1075 if (!sif || !sif->subsys)
1078 subsys = sif->subsys;
1080 mutex_lock(&subsys->p->mutex);
1081 list_del_init(&sif->node);
1082 if (sif->remove_dev) {
1083 subsys_dev_iter_init(&iter, subsys, NULL, NULL);
1084 while ((dev = subsys_dev_iter_next(&iter)))
1085 sif->remove_dev(dev, sif);
1086 subsys_dev_iter_exit(&iter);
1088 mutex_unlock(&subsys->p->mutex);
1092 EXPORT_SYMBOL_GPL(subsys_interface_unregister);
1094 static void system_root_device_release(struct device *dev)
1099 static int subsys_register(struct bus_type *subsys,
1100 const struct attribute_group **groups,
1101 struct kobject *parent_of_root)
1106 err = bus_register(subsys);
1110 dev = kzalloc(sizeof(struct device), GFP_KERNEL);
1116 err = dev_set_name(dev, "%s", subsys->name);
1120 dev->kobj.parent = parent_of_root;
1121 dev->groups = groups;
1122 dev->release = system_root_device_release;
1124 err = device_register(dev);
1128 subsys->dev_root = dev;
1137 bus_unregister(subsys);
1142 * subsys_system_register - register a subsystem at /sys/devices/system/
1143 * @subsys: system subsystem
1144 * @groups: default attributes for the root device
1146 * All 'system' subsystems have a /sys/devices/system/<name> root device
1147 * with the name of the subsystem. The root device can carry subsystem-
1148 * wide attributes. All registered devices are below this single root
1149 * device and are named after the subsystem with a simple enumeration
1150 * number appended. The registered devices are not explicitly named;
1151 * only 'id' in the device needs to be set.
1153 * Do not use this interface for anything new, it exists for compatibility
1154 * with bad ideas only. New subsystems should use plain subsystems; and
1155 * add the subsystem-wide attributes should be added to the subsystem
1156 * directory itself and not some create fake root-device placed in
1157 * /sys/devices/system/<name>.
1159 int subsys_system_register(struct bus_type *subsys,
1160 const struct attribute_group **groups)
1162 return subsys_register(subsys, groups, &system_kset->kobj);
1164 EXPORT_SYMBOL_GPL(subsys_system_register);
1167 * subsys_virtual_register - register a subsystem at /sys/devices/virtual/
1168 * @subsys: virtual subsystem
1169 * @groups: default attributes for the root device
1171 * All 'virtual' subsystems have a /sys/devices/system/<name> root device
1172 * with the name of the subystem. The root device can carry subsystem-wide
1173 * attributes. All registered devices are below this single root device.
1174 * There's no restriction on device naming. This is for kernel software
1175 * constructs which need sysfs interface.
1177 int subsys_virtual_register(struct bus_type *subsys,
1178 const struct attribute_group **groups)
1180 struct kobject *virtual_dir;
1182 virtual_dir = virtual_device_parent(NULL);
1186 return subsys_register(subsys, groups, virtual_dir);
1188 EXPORT_SYMBOL_GPL(subsys_virtual_register);
1190 int __init buses_init(void)
1192 bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);
1196 system_kset = kset_create_and_add("system", NULL, &devices_kset->kobj);