path: root/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 <gregkh@suse.de>
 * Copyright (c) 2007 Novell Inc.
 * Copyright (c) 2023 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 */

#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) container_of(_attr, struct bus_attribute, attr)

/*
 * sysfs bindings for drivers
 */

#define to_drv_attr(_attr) container_of(_attr, struct driver_attribute, attr)

#define DRIVER_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) \
	struct driver_attribute driver_attr_##_name =		\
		__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)
{
	struct subsys_private *sp = NULL;
	struct kobject *kobj;

	if (!bus || !bus_kset)
		return NULL;

	spin_lock(&bus_kset->list_lock);

	if (list_empty(&bus_kset->list))
		goto done;

	list_for_each_entry(kobj, &bus_kset->list, entry) {
		struct kset *kset = container_of(kobj, struct kset, kobj);

		sp = container_of_const(kset, struct subsys_private, subsys);
		if (sp->bus == bus)
			goto done;
	}
	sp = NULL;
done:
	sp = subsys_get(sp);
	spin_unlock(&bus_kset->list_lock);
	return sp;
}

static const struct bus_type *bus_get(const struct bus_type *bus)
{
	struct subsys_private *sp = bus_to_subsys(bus);

	if (sp