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// SPDX-License-Identifier: GPL-2.0
* bus.h - the bus-specific portions of the driver model
* Copyright (c) 2001-2003 Patrick Mochel <>
* Copyright (c) 2004-2009 Greg Kroah-Hartman <>
* Copyright (c) 2008-2009 Novell Inc.
* Copyright (c) 2012-2019 Greg Kroah-Hartman <>
* Copyright (c) 2012-2019 Linux Foundation
* See Documentation/driver-api/driver-model/ for more information.
#ifndef _DEVICE_BUS_H_
#define _DEVICE_BUS_H_
#include <linux/kobject.h>
#include <linux/klist.h>
#include <linux/pm.h>
struct device_driver;
struct fwnode_handle;
* struct bus_type - The bus type of the device
* @name: The name of the bus.
* @dev_name: Used for subsystems to enumerate devices like ("foo%u", dev->id).
* @dev_root: Default device to use as the parent.
* @bus_groups: Default attributes of the bus.
* @dev_groups: Default attributes of the devices on the bus.
* @drv_groups: Default attributes of the device drivers on the bus.
* @match: Called, perhaps multiple times, whenever a new device or driver
* is added for this bus. It should return a positive value if the
* given device can be handled by the given driver and zero
* otherwise. It may also return error code if determining that
* the driver supports the device is not possible. In case of
* -EPROBE_DEFER it will queue the device for deferred probing.
* @uevent: Called when a device is added, removed, or a few other things
* that generate uevents to add the environment variables.
* @probe: Called when a new device or driver add to this bus, and callback
* the specific driver's probe to initial the matched device.
* @sync_state: Called to sync device state to software state after all the
* state tracking consumers linked to this device (present at
* the time of late_initcall) have successfully bound to a
* driver. If the device has no consumers, this function will
* be called at late_initcall_sync level. If the device has
* consumers that are never bound to a driver, this function
* will never get called until they do.
* @remove: Called when a device removed from this bus.
* @shutdown: Called at shut-down time to quiesce the device.
* @online: Called to put the device back online (after offlining it).
* @offline: Called to put the device offline for hot-removal. May fail.
* @suspend: Called when a device on this bus wants to go to sleep mode.
* @resume: Called to bring a device on this bus out of sleep mode.
* @num_vf: Called to find out how many virtual functions a device on this
* bus supports.
* @dma_configure: Called to setup DMA configuration on a device on
* this bus.
* @pm: Power management operations of this bus, callback the specific
* device driver's pm-ops.
* @iommu_ops: IOMMU specific operations for this bus, used to attach IOMMU
* driver implementations to a bus and allow the driver to do
* bus-specific setup
* @p: The private data of the driver core, only the driver core can
* touch this.
* @lock_key: Lock class key for use by the lock validator
* @need_parent_lock: When probing or removing a device on this bus, the
* device core should lock the device's parent.
* A bus is a channel between the processor and one or more devices. For the
* purposes of the device model, all devices are connected via a bus, even if
* it is an internal, virtual, "platform" bus. Buses can plug into each other.
* A USB controller is usually a PCI device, for example. The device model
* represents the actual connections between buses and the devices they control.
* A bus is represented by the bus_type structure. It contains the name, the
* default attributes, the bus' methods, PM operations, and the driver core's
* private data.
struct bus_type {
const char *name;
const char *dev_name;
struct device *dev_root;
const struct attribute_group **bus_groups;
const struct attribute_group **dev_groups;
const struct attribute_group **drv_groups;
int (*match)(struct device *dev, struct device_driver *drv);
int (*uevent)(struct device *dev, struct kobj_uevent_env *env);
int (*probe)(struct device *dev);
void (*sync_state)(struct device *dev);
int (*remove)(struct device *dev);
void (*shutdown)(struct device *dev);
int (*online)(struct device *dev);
int (*offline)(struct device *dev);
int (*suspend)(struct device *dev, pm_message_t state);
int (*resume)(struct device *dev);
int (*num_vf)(struct device *dev);
int (*dma_configure)(struct device *dev);
const struct dev_pm_ops *pm;
const struct iommu_ops *iommu_ops;
struct subsys_private *p;
struct lock_class_key lock_key;
bool need_parent_lock;
extern int __must_check bus_register(struct bus_type *bus);
extern void bus_unregister(struct bus_type *bus);
extern int __must_check bus_rescan_devices(struct bus_type *bus);
struct bus_attribute {
struct attribute attr;
ssize_t (*show)(struct bus_type *bus, char *buf);
ssize_t (*store)(struct bus_type *bus, const char *buf, size_t count);
#define BUS_ATTR_RW(_name) \
struct bus_attribute bus_attr_##_name = __ATTR_RW(_name)
#define BUS_ATTR_RO(_name) \
struct bus_attribute bus_attr_##_name = __ATTR_RO(_name)
#define BUS_ATTR_WO(_name) \
struct bus_attribute bus_attr_##_name = __ATTR_WO(_name)
extern int __must_check bus_create_file(struct bus_type *,
struct bus_attribute *);
extern void bus_remove_file(struct bus_type *, struct bus_attribute *);
/* Generic device matching functions that all busses can use to match with */
int device_match_name(struct device *dev, const void *name);
int device_match_of_node(struct device *dev, const void *np);
int device_match_fwnode(struct device *dev, const void *fwnode);
int device_match_devt(struct device *dev, const void *pdevt);
int device_match_acpi_dev(struct device *dev, const void *adev);
int device_match_any(struct device *dev, const void *unused);
/* iterator helpers for buses */
struct subsys_dev_iter {
struct klist_iter ki;
const struct device_type *type;
void subsys_dev_iter_init(struct subsys_dev_iter *iter,
struct bus_type *subsys,
struct device *start,
const struct device_type *type);
struct device *subsys_dev_iter_next(struct subsys_dev_iter *iter);
void subsys_dev_iter_exit(struct subsys_dev_iter *iter);
int bus_for_each_dev(struct bus_type *bus, struct device *start, void *data,
int (*fn)(struct device *dev, void *data));
struct device *bus_find_device(struct bus_type *bus, struct device *start,
const void *data,
int (*match)(struct device *dev, const void *data));
* bus_find_device_by_name - device iterator for locating a particular device
* of a specific name.
* @bus: bus type
* @start: Device to begin with
* @name: name of the device to match
static inline struct device *bus_find_device_by_name(struct bus_type *bus,
struct device *start,
const char *name)
return bus_find_device(bus, start, name, device_match_name);
* bus_find_device_by_of_node : device iterator for locating a particular device
* matching the of_node.
* @bus: bus type
* @np: of_node of the device to match.
static inline struct device *
bus_find_device_by_of_node(struct bus_type *bus, const struct device_node *np)
return bus_find_device(bus, NULL, np, device_match_of_node);
* bus_find_device_by_fwnode : device iterator for locating a particular device
* matching the fwnode.
* @bus: bus type
* @fwnode: fwnode of the device to match.
static inline struct device *
bus_find_device_by_fwnode(struct bus_type *bus, const struct fwnode_handle *fwnode)
return bus_find_device(bus, NULL, fwnode, device_match_fwnode);
* bus_find_device_by_devt : device iterator for locating a particular device
* matching the device type.
* @bus: bus type
* @devt: device type of the device to match.
static inline struct device *bus_find_device_by_devt(struct bus_type *bus,
dev_t devt)
return bus_find_device(bus, NULL, &devt, device_match_devt);
* bus_find_next_device - Find the next device after a given device in a
* given bus.
* @bus: bus type
* @cur: device to begin the search with.
static inline struct device *
bus_find_next_device(struct bus_type *bus,struct device *cur)
return bus_find_device(bus, cur, NULL, device_match_any);
struct acpi_device;
* bus_find_device_by_acpi_dev : device iterator for locating a particular device
* matching the ACPI COMPANION device.
* @bus: bus type
* @adev: ACPI COMPANION device to match.
static inline struct device *
bus_find_device_by_acpi_dev(struct bus_type *bus, const struct acpi_device *adev)
return bus_find_device(bus, NULL, adev, device_match_acpi_dev);
static inline struct device *
bus_find_device_by_acpi_dev(struct bus_type *bus, const void *adev)
return NULL;
struct device *subsys_find_device_by_id(struct bus_type *bus, unsigned int id,
struct device *hint);
int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,
void *data, int (*fn)(struct device_driver *, void *));
void bus_sort_breadthfirst(struct bus_type *bus,
int (*compare)(const struct device *a,
const struct device *b));
* Bus notifiers: Get notified of addition/removal of devices
* and binding/unbinding of drivers to devices.
* In the long run, it should be a replacement for the platform
* notify hooks.
struct notifier_block;
extern int bus_register_notifier(struct bus_type *bus,
struct notifier_block *nb);
extern int bus_unregister_notifier(struct bus_type *bus,
struct notifier_block *nb);
/* All 4 notifers below get called with the target struct device *
* as an argument. Note that those functions are likely to be called
* with the device lock held in the core, so be careful.
#define BUS_NOTIFY_ADD_DEVICE 0x00000001 /* device added */
#define BUS_NOTIFY_DEL_DEVICE 0x00000002 /* device to be removed */
#define BUS_NOTIFY_REMOVED_DEVICE 0x00000003 /* device removed */
#define BUS_NOTIFY_BIND_DRIVER 0x00000004 /* driver about to be
bound */
#define BUS_NOTIFY_BOUND_DRIVER 0x00000005 /* driver bound to device */
#define BUS_NOTIFY_UNBIND_DRIVER 0x00000006 /* driver about to be
unbound */
#define BUS_NOTIFY_UNBOUND_DRIVER 0x00000007 /* driver is unbound
from the device */
#define BUS_NOTIFY_DRIVER_NOT_BOUND 0x00000008 /* driver fails to be bound */
extern struct kset *bus_get_kset(struct bus_type *bus);
extern struct klist *bus_get_device_klist(struct bus_type *bus);