linux/drivers/base/bus.c

// SPDX-License-Identifier: GPL-2.0
/*
 * bus.c - bus driver management
 *
 * Copyright (c) 2002-3 Patrick Mochel
 * Copyright (c) 2002-3 Open Source Development Labs
 * Copyright (c) 2007 Greg Kroah-Hartman <[email protected]>
 * Copyright (c) 2007 Novell Inc.
 * Copyright (c) 2023 Greg Kroah-Hartman <[email protected]>
 */

#include <linux/async.h>
#include <linux/device/bus.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/mutex.h>
#include <linux/sysfs.h>
#include "base.h"
#include "power/power.h"

/* /sys/devices/system */
static struct kset *system_kset;

/* /sys/bus */
static struct kset *bus_kset;

#define to_bus_attr(_attr) …

/*
 * sysfs bindings for drivers
 */

#define to_drv_attr(_attr) …

#define DRIVER_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) …

static int __must_check bus_rescan_devices_helper(struct device *dev,
						void *data);

/**
 * bus_to_subsys - Turn a struct bus_type into a struct subsys_private
 *
 * @bus: pointer to the struct bus_type to look up
 *
 * The driver core internals needs to work on the subsys_private structure, not
 * the external struct bus_type pointer.  This function walks the list of
 * registered busses in the system and finds the matching one and returns the
 * internal struct subsys_private that relates to that bus.
 *
 * Note, the reference count of the return value is INCREMENTED if it is not
 * NULL.  A call to subsys_put() must be done when finished with the pointer in
 * order for it to be properly freed.
 */
static struct subsys_private *bus_to_subsys(const struct bus_type *bus)
{ … }

static const struct bus_type *bus_get(const struct bus_type *bus)
{ … }

static void bus_put(const struct bus_type *bus)
{ … }

static ssize_t drv_attr_show(struct kobject *kobj, struct attribute *attr,
			     char *buf)
{ … }

static ssize_t drv_attr_store(struct kobject *kobj, struct attribute *attr,
			      const char *buf, size_t count)
{ … }

static const struct sysfs_ops driver_sysfs_ops = …;

static void driver_release(struct kobject *kobj)
{ … }

static const struct kobj_type driver_ktype = …;

/*
 * sysfs bindings for buses
 */
static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,
			     char *buf)
{ … }

static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
			      const char *buf, size_t count)
{ … }

static const struct sysfs_ops bus_sysfs_ops = …;

int bus_create_file(const struct bus_type *bus, struct bus_attribute *attr)
{ … }
EXPORT_SYMBOL_GPL(…);

void bus_remove_file(const struct bus_type *bus, struct bus_attribute *attr)
{ … }
EXPORT_SYMBOL_GPL(…);

static void bus_release(struct kobject *kobj)
{ … }

static const struct kobj_type bus_ktype = …;

static int bus_uevent_filter(const struct kobject *kobj)
{ … }

static const struct kset_uevent_ops bus_uevent_ops = …;

/* Manually detach a device from its associated driver. */
static ssize_t unbind_store(struct device_driver *drv, const char *buf,
			    size_t count)
{ … }
static DRIVER_ATTR_IGNORE_LOCKDEP(unbind, 0200, NULL, unbind_store);

/*
 * Manually attach a device to a driver.
 * Note: the driver must want to bind to the device,
 * it is not possible to override the driver's id table.
 */
static ssize_t bind_store(struct device_driver *drv, const char *buf,
			  size_t count)
{ … }
static DRIVER_ATTR_IGNORE_LOCKDEP(bind, 0200, NULL, bind_store);

static ssize_t drivers_autoprobe_show(const struct bus_type *bus, char *buf)
{ … }

static ssize_t drivers_autoprobe_store(const struct bus_type *bus,
				       const char *buf, size_t count)
{ … }

static ssize_t drivers_probe_store(const struct bus_type *bus,
				   const char *buf, size_t count)
{ … }

static struct device *next_device(struct klist_iter *i)
{ … }

/**
 * bus_for_each_dev - device iterator.
 * @bus: bus type.
 * @start: device to start iterating from.
 * @data: data for the callback.
 * @fn: function to be called for each device.
 *
 * Iterate over @bus's list of devices, and call @fn for each,
 * passing it @data. If @start is not NULL, we use that device to
 * begin iterating from.
 *
 * We check the return of @fn each time. If it returns anything
 * other than 0, we break out and return that value.
 *
 * NOTE: The device that returns a non-zero value is not retained
 * in any way, nor is its refcount incremented. If the caller needs
 * to retain this data, it should do so, and increment the reference
 * count in the supplied callback.
 */
int bus_for_each_dev(const struct bus_type *bus, struct device *start,
		     void *data, int (*fn)(struct device *, void *))
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * bus_find_device - device iterator for locating a particular device.
 * @bus: bus type
 * @start: Device to begin with
 * @data: Data to pass to match function
 * @match: Callback function to check device
 *
 * This is similar to the bus_for_each_dev() function above, but it
 * returns a reference to a device that is 'found' for later use, as
 * determined by the @match callback.
 *
 * The callback should return 0 if the device doesn't match and non-zero
 * if it does.  If the callback returns non-zero, this function will
 * return to the caller and not iterate over any more devices.
 */
struct device *bus_find_device(const struct bus_type *bus,
			       struct device *start, const void *data,
			       int (*match)(struct device *dev, const void *data))
{ … }
EXPORT_SYMBOL_GPL(…);

static struct device_driver *next_driver(struct klist_iter *i)
{ … }

/**
 * bus_for_each_drv - driver iterator
 * @bus: bus we're dealing with.
 * @start: driver to start iterating on.
 * @data: data to pass to the callback.
 * @fn: function to call for each driver.
 *
 * This is nearly identical to the device iterator above.
 * We iterate over each driver that belongs to @bus, and call
 * @fn for each. If @fn returns anything but 0, we break out
 * and return it. If @start is not NULL, we use it as the head
 * of the list.
 *
 * NOTE: we don't return the driver that returns a non-zero
 * value, nor do we leave the reference count incremented for that
 * driver. If the caller needs to know that info, it must set it
 * in the callback. It must also be sure to increment the refcount
 * so it doesn't disappear before returning to the caller.
 */
int bus_for_each_drv(const struct bus_type *bus, struct device_driver *start,
		     void *data, int (*fn)(struct device_driver *, void *))
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * bus_add_device - add device to bus
 * @dev: device being added
 *
 * - Add device's bus attributes.
 * - Create links to device's bus.
 * - Add the device to its bus's list of devices.
 */
int bus_add_device(struct device *dev)
{ … }

/**
 * bus_probe_device - probe drivers for a new device
 * @dev: device to probe
 *
 * - Automatically probe for a driver if the bus allows it.
 */
void bus_probe_device(struct device *dev)
{ … }

/**
 * bus_remove_device - remove device from bus
 * @dev: device to be removed
 *
 * - Remove device from all interfaces.
 * - Remove symlink from bus' directory.
 * - Delete device from bus's list.
 * - Detach from its driver.
 * - Drop reference taken in bus_add_device().
 */
void bus_remove_device(struct device *dev)
{ … }

static int __must_check add_bind_files(struct device_driver *drv)
{ … }

static void remove_bind_files(struct device_driver *drv)
{ … }

static BUS_ATTR_WO(drivers_probe);
static BUS_ATTR_RW(drivers_autoprobe);

static int add_probe_files(const struct bus_type *bus)
{ … }

static void remove_probe_files(const struct bus_type *bus)
{ … }

static ssize_t uevent_store(struct device_driver *drv, const char *buf,
			    size_t count)
{ … }
static DRIVER_ATTR_WO(uevent);

/**
 * bus_add_driver - Add a driver to the bus.
 * @drv: driver.
 */
int bus_add_driver(struct device_driver *drv)
{ … }

/**
 * bus_remove_driver - delete driver from bus's knowledge.
 * @drv: driver.
 *
 * Detach the driver from the devices it controls, and remove
 * it from its bus's list of drivers. Finally, we drop the reference
 * to the bus we took in bus_add_driver().
 */
void bus_remove_driver(struct device_driver *drv)
{ … }

/* Helper for bus_rescan_devices's iter */
static int __must_check bus_rescan_devices_helper(struct device *dev,
						  void *data)
{ … }

/**
 * bus_rescan_devices - rescan devices on the bus for possible drivers
 * @bus: the bus to scan.
 *
 * This function will look for devices on the bus with no driver
 * attached and rescan it against existing drivers to see if it matches
 * any by calling device_attach() for the unbound devices.
 */
int bus_rescan_devices(const struct bus_type *bus)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * device_reprobe - remove driver for a device and probe for a new driver
 * @dev: the device to reprobe
 *
 * This function detaches the attached driver (if any) for the given
 * device and restarts the driver probing process.  It is intended
 * to use if probing criteria changed during a devices lifetime and
 * driver attachment should change accordingly.
 */
int device_reprobe(struct device *dev)
{ … }
EXPORT_SYMBOL_GPL(…);

static void klist_devices_get(struct klist_node *n)
{ … }

static void klist_devices_put(struct klist_node *n)
{ … }

static ssize_t bus_uevent_store(const struct bus_type *bus,
				const char *buf, size_t count)
{ … }
/*
 * "open code" the old BUS_ATTR() macro here.  We want to use BUS_ATTR_WO()
 * here, but can not use it as earlier in the file we have
 * DEVICE_ATTR_WO(uevent), which would cause a clash with the with the store
 * function name.
 */
static struct bus_attribute bus_attr_uevent = …;

/**
 * bus_register - register a driver-core subsystem
 * @bus: bus to register
 *
 * Once we have that, we register the bus with the kobject
 * infrastructure, then register the children subsystems it has:
 * the devices and drivers that belong to the subsystem.
 */
int bus_register(const struct bus_type *bus)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * bus_unregister - remove a bus from the system
 * @bus: bus.
 *
 * Unregister the child subsystems and the bus itself.
 * Finally, we call bus_put() to release the refcount
 */
void bus_unregister(const struct bus_type *bus)
{ … }
EXPORT_SYMBOL_GPL(…);

int bus_register_notifier(const struct bus_type *bus, struct notifier_block *nb)
{ … }
EXPORT_SYMBOL_GPL(…);

int bus_unregister_notifier(const struct bus_type *bus, struct notifier_block *nb)
{ … }
EXPORT_SYMBOL_GPL(…);

void bus_notify(struct device *dev, enum bus_notifier_event value)
{ … }

struct kset *bus_get_kset(const struct bus_type *bus)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * Yes, this forcibly breaks the klist abstraction temporarily.  It
 * just wants to sort the klist, not change reference counts and
 * take/drop locks rapidly in the process.  It does all this while
 * holding the lock for the list, so objects can't otherwise be
 * added/removed while we're swizzling.
 */
static void device_insertion_sort_klist(struct device *a, struct list_head *list,
					int (*compare)(const struct device *a,
							const struct device *b))
{ … }

void bus_sort_breadthfirst(const struct bus_type *bus,
			   int (*compare)(const struct device *a,
					  const struct device *b))
{ … }
EXPORT_SYMBOL_GPL(…);

struct subsys_dev_iter { … };

/**
 * subsys_dev_iter_init - initialize subsys device iterator
 * @iter: subsys iterator to initialize
 * @sp: the subsys private (i.e. bus) we wanna iterate over
 * @start: the device to start iterating from, if any
 * @type: device_type of the devices to iterate over, NULL for all
 *
 * Initialize subsys iterator @iter such that it iterates over devices
 * of @subsys.  If @start is set, the list iteration will start there,
 * otherwise if it is NULL, the iteration starts at the beginning of
 * the list.
 */
static void subsys_dev_iter_init(struct subsys_dev_iter *iter, struct subsys_private *sp,
				 struct device *start, const struct device_type *type)
{ … }

/**
 * subsys_dev_iter_next - iterate to the next device
 * @iter: subsys iterator to proceed
 *
 * Proceed @iter to the next device and return it.  Returns NULL if
 * iteration is complete.
 *
 * The returned device is referenced and won't be released till
 * iterator is proceed to the next device or exited.  The caller is
 * free to do whatever it wants to do with the device including
 * calling back into subsys code.
 */
static struct device *subsys_dev_iter_next(struct subsys_dev_iter *iter)
{ … }

/**
 * subsys_dev_iter_exit - finish iteration
 * @iter: subsys iterator to finish
 *
 * Finish an iteration.  Always call this function after iteration is
 * complete whether the iteration ran till the end or not.
 */
static void subsys_dev_iter_exit(struct subsys_dev_iter *iter)
{ … }

int subsys_interface_register(struct subsys_interface *sif)
{ … }
EXPORT_SYMBOL_GPL(…);

void subsys_interface_unregister(struct subsys_interface *sif)
{ … }
EXPORT_SYMBOL_GPL(…);

static void system_root_device_release(struct device *dev)
{ … }

static int subsys_register(const struct bus_type *subsys,
			   const struct attribute_group **groups,
			   struct kobject *parent_of_root)
{ … }

/**
 * subsys_system_register - register a subsystem at /sys/devices/system/
 * @subsys: system subsystem
 * @groups: default attributes for the root device
 *
 * All 'system' subsystems have a /sys/devices/system/<name> root device
 * with the name of the subsystem. The root device can carry subsystem-
 * wide attributes. All registered devices are below this single root
 * device and are named after the subsystem with a simple enumeration
 * number appended. The registered devices are not explicitly named;
 * only 'id' in the device needs to be set.
 *
 * Do not use this interface for anything new, it exists for compatibility
 * with bad ideas only. New subsystems should use plain subsystems; and
 * add the subsystem-wide attributes should be added to the subsystem
 * directory itself and not some create fake root-device placed in
 * /sys/devices/system/<name>.
 */
int subsys_system_register(const struct bus_type *subsys,
			   const struct attribute_group **groups)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * subsys_virtual_register - register a subsystem at /sys/devices/virtual/
 * @subsys: virtual subsystem
 * @groups: default attributes for the root device
 *
 * All 'virtual' subsystems have a /sys/devices/system/<name> root device
 * with the name of the subystem.  The root device can carry subsystem-wide
 * attributes.  All registered devices are below this single root device.
 * There's no restriction on device naming.  This is for kernel software
 * constructs which need sysfs interface.
 */
int subsys_virtual_register(const struct bus_type *subsys,
			    const struct attribute_group **groups)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * driver_find - locate driver on a bus by its name.
 * @name: name of the driver.
 * @bus: bus to scan for the driver.
 *
 * Call kset_find_obj() to iterate over list of drivers on
 * a bus to find driver by name. Return driver if found.
 *
 * This routine provides no locking to prevent the driver it returns
 * from being unregistered or unloaded while the caller is using it.
 * The caller is responsible for preventing this.
 */
struct device_driver *driver_find(const char *name, const struct bus_type *bus)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * Warning, the value could go to "removed" instantly after calling this function, so be very
 * careful when calling it...
 */
bool bus_is_registered(const struct bus_type *bus)
{ … }

/**
 * bus_get_dev_root - return a pointer to the "device root" of a bus
 * @bus: bus to return the device root of.
 *
 * If a bus has a "device root" structure, return it, WITH THE REFERENCE
 * COUNT INCREMENTED.
 *
 * Note, when finished with the device, a call to put_device() is required.
 *
 * If the device root is not present (or bus is not a valid pointer), NULL
 * will be returned.
 */
struct device *bus_get_dev_root(const struct bus_type *bus)
{ … }
EXPORT_SYMBOL_GPL(…);

int __init buses_init(void)
{ … }