// SPDX-License-Identifier: GPL-2.0
/*
 * drivers/base/core.c - core driver model code (device registration, etc)
 *
 * Copyright (c) 2002-3 Patrick Mochel
 * Copyright (c) 2002-3 Open Source Development Labs
 * Copyright (c) 2006 Greg Kroah-Hartman <gregkh@suse.de>
 * Copyright (c) 2006 Novell, Inc.
 */

#include <linux/acpi.h>
#include <linux/cpufreq.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/fwnode.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/kdev_t.h>
#include <linux/notifier.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/genhd.h>
#include <linux/mutex.h>
#include <linux/pm_runtime.h>
#include <linux/netdevice.h>
#include <linux/sched/signal.h>
#include <linux/sysfs.h>

#include "base.h"
#include "power/power.h"

#ifdef CONFIG_SYSFS_DEPRECATED
#ifdef CONFIG_SYSFS_DEPRECATED_V2
long sysfs_deprecated = 1;
#else
long sysfs_deprecated = 0;
#endif
static int __init sysfs_deprecated_setup(char *arg)
{
        return kstrtol(arg, 10, &sysfs_deprecated);
}
early_param("sysfs.deprecated", sysfs_deprecated_setup);
#endif

/* Device links support. */
static LIST_HEAD(wait_for_suppliers);
static DEFINE_MUTEX(wfs_lock);
static LIST_HEAD(deferred_sync);
static unsigned int defer_sync_state_count = 1;
static unsigned int defer_fw_devlink_count;
static LIST_HEAD(deferred_fw_devlink);
static DEFINE_MUTEX(defer_fw_devlink_lock);
static bool fw_devlink_is_permissive(void);

#ifdef CONFIG_SRCU
static DEFINE_MUTEX(device_links_lock);
DEFINE_STATIC_SRCU(device_links_srcu);

static inline void device_links_write_lock(void)
{
        mutex_lock(&device_links_lock);
}

static inline void device_links_write_unlock(void)
{
        mutex_unlock(&device_links_lock);
}

int device_links_read_lock(void) __acquires(&device_links_srcu)
{
        return srcu_read_lock(&device_links_srcu);
}

void device_links_read_unlock(int idx) __releases(&device_links_srcu)
{
        srcu_read_unlock(&device_links_srcu, idx);
}

int device_links_read_lock_held(void)
{
        return srcu_read_lock_held(&device_links_srcu);
}
#else /* !CONFIG_SRCU */
static DECLARE_RWSEM(device_links_lock);

static inline void device_links_write_lock(void)
{
        down_write(&device_links_lock);
}

static inline void device_links_write_unlock(void)
{
        up_write(&device_links_lock);
}

int device_links_read_lock(void)
{
        down_read(&device_links_lock);
        return 0;
}

void device_links_read_unlock(int not_used)
{
        up_read(&device_links_lock);
}

#ifdef CONFIG_DEBUG_LOCK_ALLOC
int device_links_read_lock_held(void)
{
        return lockdep_is_held(&device_links_lock);
}
#endif
#endif /* !CONFIG_SRCU */

/**
 * device_is_dependent - Check if one device depends on another one
 * @dev: Device to check dependencies for.
 * @target: Device to check against.
 *
 * Check if @target depends on @dev or any device dependent on it (its child or
 * its consumer etc).  Return 1 if that is the case or 0 otherwise.
 */
int device_is_dependent(struct device *dev, void *target)
{
        struct device_link *link;
        int ret;

        if (dev == target)
                return 1;

        ret = device_for_each_child(dev, target, device_is_dependent);
        if (ret)
                return ret;

        list_for_each_entry(link, &dev->links.consumers, s_node) {
                if (link->flags == (DL_FLAG_SYNC_STATE_ONLY | DL_FLAG_MANAGED))
                        continue;

                if (link->consumer == target)
                        return 1;

                ret = device_is_dependent(link->consumer, target);
                if (ret)
                        break;
        }
        return ret;
}

static void device_link_init_status(struct device_link *link,
                                    struct device *consumer,
                                    struct device *supplier)
{
        switch (supplier->links.status) {
        case DL_DEV_PROBING:
                switch (consumer->links.status) {
                case DL_DEV_PROBING:
                        /*
                         * A consumer driver can create a link to a supplier
                         * that has not completed its probing yet as long as it
                         * knows that the supplier is already functional (for
                         * example, it has just acquired some resources from the
                         * supplier).
                         */
                        link->status = DL_STATE_CONSUMER_PROBE;
                        break;
                default:
                        link->status = DL_STATE_DORMANT;
                        break;
                }
                break;
        case DL_DEV_DRIVER_BOUND:
                switch (consumer->links.status) {
                case DL_DEV_PROBING:
                        link->status = DL_STATE_CONSUMER_PROBE;
                        break;
                case DL_DEV_DRIVER_BOUND:
                        link->status = DL_STATE_ACTIVE;
                        break;
                default:
                        link->status = DL_STATE_AVAILABLE;
                        break;
                }
                break;
        case DL_DEV_UNBINDING:
                link->status = DL_STATE_SUPPLIER_UNBIND;
                break;
        default:
                link->status = DL_STATE_DORMANT;
                break;
        }
}

static int device_reorder_to_tail(struct device *dev, void *not_used)
{
        struct device_link *link;

        /*
         * Devices that have not been registered yet will be put to the ends
         * of the lists during the registration, so skip them here.
         */
        if (device_is_registered(dev))
                devices_kset_move_last(dev);

        if (device_pm_initialized(dev))
                device_pm_move_last(dev);

        device_for_each_child(dev, NULL, device_reorder_to_tail);
        list_for_each_entry(link, &dev->links.consumers, s_node) {
                if (link->flags == (DL_FLAG_SYNC_STATE_ONLY | DL_FLAG_MANAGED))
                        continue;
                device_reorder_to_tail(link->consumer, NULL);
        }

        return 0;
}

/**
 * device_pm_move_to_tail - Move set of devices to the end of device lists
 * @dev: Device to move
 *
 * This is a device_reorder_to_tail() wrapper taking the requisite locks.
 *
 * It moves the @dev along with all of its children and all of its consumers
 * to the ends of the device_kset and dpm_list, recursively.
 */
void device_pm_move_to_tail(struct device *dev)
{
        int idx;

        idx = device_links_read_lock();
        device_pm_lock();
        device_reorder_to_tail(dev, NULL);
        device_pm_unlock();
        device_links_read_unlock(idx);
}

#define to_devlink(dev) container_of((dev), struct device_link, link_dev)

static ssize_t status_show(struct device *dev,
                          struct device_attribute *attr, char *buf)
{
        char *status;

        switch (to_devlink(dev)->status) {
        case DL_STATE_NONE:
                status = "not tracked"; break;
        case DL_STATE_DORMANT:
                status = "dormant"; break;
        case DL_STATE_AVAILABLE:
                status = "available"; break;
        case DL_STATE_CONSUMER_PROBE:
                status = "consumer probing"; break;
        case DL_STATE_ACTIVE:
                status = "active"; break;
        case DL_STATE_SUPPLIER_UNBIND:
                status = "supplier unbinding"; break;
        default:
                status = "unknown"; break;
        }
        return sprintf(buf, "%s\n", status);
}
static DEVICE_ATTR_RO(status);

static ssize_t auto_remove_on_show(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct device_link *link = to_devlink(dev);
        char *str;

        if (link->flags & DL_FLAG_AUTOREMOVE_SUPPLIER)
                str = "supplier unbind";
        else if (link->flags & DL_FLAG_AUTOREMOVE_CONSUMER)
                str = "consumer unbind";
        else
                str = "never";

        return sprintf(buf, "%s\n", str);
}
static DEVICE_ATTR_RO(auto_remove_on);

static ssize_t runtime_pm_show(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        struct device_link *link = to_devlink(dev);

        return sprintf(buf, "%d\n", !!(link->flags & DL_FLAG_PM_RUNTIME));
}
static DEVICE_ATTR_RO(runtime_pm);

static ssize_t sync_state_only_show(struct device *dev,
                                    struct device_attribute *attr, char *buf)
{
        struct device_link *link = to_devlink(dev);

        return sprintf(buf, "%d\n", !!(link->flags & DL_FLAG_SYNC_STATE_ONLY));
}
static DEVICE_ATTR_RO(sync_state_only);

static struct attribute *devlink_attrs[] = {
        &dev_attr_status.attr,
        &dev_attr_auto_remove_on.attr,
        &dev_attr_runtime_pm.attr,
        &dev_attr_sync_state_only.attr,
        NULL,
};
ATTRIBUTE_GROUPS(devlink);

static void device_link_free(struct device_link *link)
{
        while (refcount_dec_not_one(&link->rpm_active))
                pm_runtime_put(link->supplier);

        put_device(link->consumer);
        put_device(link->supplier);
        kfree(link);
}

#ifdef CONFIG_SRCU
static void __device_link_free_srcu(struct rcu_head *rhead)
{
        device_link_free(container_of(rhead, struct device_link, rcu_head));
}

static void devlink_dev_release(struct device *dev)
{
        struct device_link *link = to_devlink(dev);

        call_srcu(&device_links_srcu, &link->rcu_head, __device_link_free_srcu);
}
#else
static void devlink_dev_release(struct device *dev)
{
        device_link_free(to_devlink(dev));
}
#endif

static struct class devlink_class = {
        .name = "devlink",
        .owner = THIS_MODULE,
        .dev_groups = devlink_groups,
        .dev_release = devlink_dev_release,
};

static int devlink_add_symlinks(struct device *dev,
                                struct class_interface *class_intf)
{
        int ret;
        size_t len;
        struct device_link *link = to_devlink(dev);
        struct device *sup = link->supplier;
        struct device *con = link->consumer;
        char *buf;

        len = max(strlen(dev_name(sup)), strlen(dev_name(con)));
        len += strlen("supplier:") + 1;
        buf = kzalloc(len, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        ret = sysfs_create_link(&link->link_dev.kobj, &sup->kobj, "supplier");
        if (ret)
                goto out;

        ret = sysfs_create_link(&link->link_dev.kobj, &con->kobj, "consumer");
        if (ret)
                goto err_con;

        snprintf(buf, len, "consumer:%s", dev_name(con));
        ret = sysfs_create_link(&sup->kobj, &link->link_dev.kobj, buf);
        if (ret)
                goto err_con_dev;

        snprintf(buf, len, "supplier:%s", dev_name(sup));
        ret = sysfs_create_link(&con->kobj, &link->link_dev.kobj, buf);
        if (ret)
                goto err_sup_dev;

        goto out;

err_sup_dev:
        snprintf(buf, len, "consumer:%s", dev_name(con));
        sysfs_remove_link(&sup->kobj, buf);
err_con_dev:
        sysfs_remove_link(&link->link_dev.kobj, "consumer");
err_con:
        sysfs_remove_link(&link->link_dev.kobj, "supplier");
out:
        kfree(buf);
        return ret;
}

static void devlink_remove_symlinks(struct device *dev,
                                   struct class_interface *class_intf)
{
        struct device_link *link = to_devlink(dev);
        size_t len;
        struct device *sup = link->supplier;
        struct device *con = link->consumer;
        char *buf;

        sysfs_remove_link(&link->link_dev.kobj, "consumer");
        sysfs_remove_link(&link->link_dev.kobj, "supplier");

        len = max(strlen(dev_name(sup)), strlen(dev_name(con)));
        len += strlen("supplier:") + 1;
        buf = kzalloc(len, GFP_KERNEL);
        if (!buf) {
                WARN(1, "Unable to properly free device link symlinks!\n");
                return;
        }

        snprintf(buf, len, "supplier:%s", dev_name(sup));
        sysfs_remove_link(&con->kobj, buf);
        snprintf(buf, len, "consumer:%s", dev_name(con));
        sysfs_remove_link(&sup->kobj, buf);
        kfree(buf);
}

static struct class_interface devlink_class_intf = {
        .class = &devlink_class,
        .add_dev = devlink_add_symlinks,
        .remove_dev = devlink_remove_symlinks,
};

static int __init devlink_class_init(void)
{
        int ret;

        ret = class_register(&devlink_class);
        if (ret)
                return ret;

        ret = class_interface_register(&devlink_class_intf);
        if (ret)
                class_unregister(&devlink_class);

        return ret;
}
postcore_initcall(devlink_class_init);

#define DL_MANAGED_LINK_FLAGS (DL_FLAG_AUTOREMOVE_CONSUMER | \
                               DL_FLAG_AUTOREMOVE_SUPPLIER | \
                               DL_FLAG_AUTOPROBE_CONSUMER  | \
                               DL_FLAG_SYNC_STATE_ONLY)

#define DL_ADD_VALID_FLAGS (DL_MANAGED_LINK_FLAGS | DL_FLAG_STATELESS | \
                            DL_FLAG_PM_RUNTIME | DL_FLAG_RPM_ACTIVE)

/**
 * device_link_add - Create a link between two devices.
 * @consumer: Consumer end of the link.
 * @supplier: Supplier end of the link.
 * @flags: Link flags.
 *
 * The caller is responsible for the proper synchronization of the link creation
 * with runtime PM.  First, setting the DL_FLAG_PM_RUNTIME flag will cause the
 * runtime PM framework to take the link into account.  Second, if the
 * DL_FLAG_RPM_ACTIVE flag is set in addition to it, the supplier devices will
 * be forced into the active metastate and reference-counted upon the creation
 * of the link.  If DL_FLAG_PM_RUNTIME is not set, DL_FLAG_RPM_ACTIVE will be
 * ignored.
 *
 * If DL_FLAG_STATELESS is set in @flags, the caller of this function is
 * expected to release the link returned by it directly with the help of either
 * device_link_del() or device_link_remove().
 *
 * If that flag is not set, however, the caller of this function is handing the
 * management of the link over to the driver core entirely and its return value
 * can only be used to check whether or not the link is present.  In that case,
 * the DL_FLAG_AUTOREMOVE_CONSUMER and DL_FLAG_AUTOREMOVE_SUPPLIER device link
 * flags can be used to indicate to the driver core when the link can be safely
 * deleted.  Namely, setting one of them in @flags indicates to the driver core
 * that the link is not going to be used (by the given caller of this function)
 * after unbinding the consumer or supplier driver, respectively, from its
 * device, so the link can be deleted at that point.  If none of them is set,
 * the link will be maintained until one of the devices pointed to by it (either
 * the consumer or the supplier) is unregistered.
 *
 * Also, if DL_FLAG_STATELESS, DL_FLAG_AUTOREMOVE_CONSUMER and
 * DL_FLAG_AUTOREMOVE_SUPPLIER are not set in @flags (that is, a persistent
 * managed device link is being added), the DL_FLAG_AUTOPROBE_CONSUMER flag can
 * be used to request the driver core to automaticall probe for a consmer
 * driver after successfully binding a driver to the supplier device.
 *
 * The combination of DL_FLAG_STATELESS and one of DL_FLAG_AUTOREMOVE_CONSUMER,
 * DL_FLAG_AUTOREMOVE_SUPPLIER, or DL_FLAG_AUTOPROBE_CONSUMER set in @flags at
 * the same time is invalid and will cause NULL to be returned upfront.
 * However, if a device link between the given @consumer and @supplier pair
 * exists already when this function is called for them, the existing link will
 * be returned regardless of its current type and status (the link's flags may
 * be modified then).  The caller of this function is then expected to treat
 * the link as though it has just been created, so (in particular) if
 * DL_FLAG_STATELESS was passed in @flags, the link needs to be released
 * explicitly when not needed any more (as stated above).
 *
 * A side effect of the link creation is re-ordering of dpm_list and the
 * devices_kset list by moving the consumer device and all devices depending
 * on it to the ends of these lists (that does not happen to devices that have
 * not been registered when this function is called).
 *
 * The supplier device is required to be registered when this function is called
 * and NULL will be returned if that is not the case.  The consumer device need
 * not be registered, however.
 */
struct device_link *device_link_add(struct device *consumer,
                                    struct device *supplier, u32 flags)
{
        struct device_link *link;

        if (!consumer || !supplier || flags & ~DL_ADD_VALID_FLAGS ||
            (flags & DL_FLAG_STATELESS && flags & DL_MANAGED_LINK_FLAGS) ||
            (flags & DL_FLAG_SYNC_STATE_ONLY &&
             flags != DL_FLAG_SYNC_STATE_ONLY) ||
            (flags & DL_FLAG_AUTOPROBE_CONSUMER &&
             flags & (DL_FLAG_AUTOREMOVE_CONSUMER |
                      DL_FLAG_AUTOREMOVE_SUPPLIER)))
                return NULL;

        if (flags & DL_FLAG_PM_RUNTIME && flags & DL_FLAG_RPM_ACTIVE) {
                if (pm_runtime_get_sync(supplier) < 0) {
                        pm_runtime_put_noidle(supplier);
                        return NULL;
                }
        }

        if (!(flags & DL_FLAG_STATELESS))
                flags |= DL_FLAG_MANAGED;

        device_links_write_lock();
        device_pm_lock();

        /*
         * If the supplier has not been fully registered yet or there is a
         * reverse (non-SYNC_STATE_ONLY) dependency between the consumer and
         * the supplier already in the graph, return NULL. If the link is a
         * SYNC_STATE_ONLY link, we don't check for reverse dependencies
         * because it only affects sync_state() callbacks.
         */
        if (!device_pm_initialized(supplier)
            || (!(flags & DL_FLAG_SYNC_STATE_ONLY) &&
                  device_is_dependent(consumer, supplier))) {
                link = NULL;
                goto out;
        }

        /*
         * DL_FLAG_AUTOREMOVE_SUPPLIER indicates that the link will be needed
         * longer than for DL_FLAG_AUTOREMOVE_CONSUMER and setting them both
         * together doesn't make sense, so prefer DL_FLAG_AUTOREMOVE_SUPPLIER.
         */
        if (flags & DL_FLAG_AUTOREMOVE_SUPPLIER)
                flags &= ~DL_FLAG_AUTOREMOVE_CONSUMER;

        list_for_each_entry(link, &supplier->links.consumers, s_node) {
                if (link->consumer != consumer)
                        continue;

                if (flags & DL_FLAG_PM_RUNTIME) {
                        if (!(link->flags & DL_FLAG_PM_RUNTIME)) {
                                pm_runtime_new_link(consumer);
                                link->flags |= DL_FLAG_PM_RUNTIME;
                        }
                        if (flags & DL_FLAG_RPM_ACTIVE)
                                refcount_inc(&link->rpm_active);
                }

                if (flags & DL_FLAG_STATELESS) {
                        kref_get(&link->kref);
                        if (link->flags & DL_FLAG_SYNC_STATE_ONLY &&
                            !(link->flags & DL_FLAG_STATELESS)) {
                                link->flags |= DL_FLAG_STATELESS;
                                goto reorder;
                        } else {
                                link->flags |= DL_FLAG_STATELESS;
                                goto out;
                        }
                }

                /*
                 * If the life time of the link following from the new flags is
                 * longer than indicated by the flags of the existing link,
                 * update the existing link to stay around longer.
                 */
                if (flags & DL_FLAG_AUTOREMOVE_SUPPLIER) {
                        if (link->flags & DL_FLAG_AUTOREMOVE_CONSUMER) {
                                link->flags &= ~DL_FLAG_AUTOREMOVE_CONSUMER;
                                link->flags |= DL_FLAG_AUTOREMOVE_SUPPLIER;
                        }
                } else if (!(flags & DL_FLAG_AUTOREMOVE_CONSUMER)) {
                        link->flags &= ~(DL_FLAG_AUTOREMOVE_CONSUMER |
                                         DL_FLAG_AUTOREMOVE_SUPPLIER);
                }
                if (!(link->flags & DL_FLAG_MANAGED)) {
                        kref_get(&link->kref);
                        link->flags |= DL_FLAG_MANAGED;
                        device_link_init_status(link, consumer, supplier);
                }
                if (link->flags & DL_FLAG_SYNC_STATE_ONLY &&
                    !(flags & DL_FLAG_SYNC_STATE_ONLY)) {
                        link->flags &= ~DL_FLAG_SYNC_STATE_ONLY;
                        goto reorder;
                }

                goto out;
        }

        link = kzalloc(sizeof(*link), GFP_KERNEL);
        if (!link)
                goto out;

        refcount_set(&link->rpm_active, 1);

        get_device(supplier);
        link->supplier = supplier;
        INIT_LIST_HEAD(&link->s_node);
        get_device(consumer);
        link->consumer = consumer;
        INIT_LIST_HEAD(&link->c_node);
        link->flags = flags;
        kref_init(&link->kref);

        link->link_dev.class = &devlink_class;
        device_set_pm_not_required(&link->link_dev);
        dev_set_name(&link->link_dev, "%s--%s",
                     dev_name(supplier), dev_name(consumer));
        if (device_register(&link->link_dev)) {
                put_device(consumer);
                put_device(supplier);
                kfree(link);
                link = NULL;
                goto out;
        }

        if (flags & DL_FLAG_PM_RUNTIME) {
                if (flags & DL_FLAG_RPM_ACTIVE)
                        refcount_inc(&link->rpm_active);

                pm_runtime_new_link(consumer);
        }

        /* Determine the initial link state. */
        if (flags & DL_FLAG_STATELESS)
                link->status = DL_STATE_NONE;
        else
                device_link_init_status(link, consumer, supplier);

        /*
         * Some callers expect the link creation during consumer driver probe to
         * resume the supplier even without DL_FLAG_RPM_ACTIVE.
         */
        if (link->status == DL_STATE_CONSUMER_PROBE &&
            flags & DL_FLAG_PM_RUNTIME)
                pm_runtime_resume(supplier);

        list_add_tail_rcu(&link->s_node, &supplier->links.consumers);
        list_add_tail_rcu(&link->c_node, &consumer->links.suppliers);

        if (flags & DL_FLAG_SYNC_STATE_ONLY) {
                dev_dbg(consumer,
                        "Linked as a sync state only consumer to %s\n",
                        dev_name(supplier));
                goto out;
        }

reorder:
        /*
         * Move the consumer and all of the devices depending on it to the end
         * of dpm_list and the devices_kset list.
         *
         * It is necessary to hold dpm_list locked throughout all that or else
         * we may end up suspending with a wrong ordering of it.
         */
        device_reorder_to_tail(consumer, NULL);

        dev_dbg(consumer, "Linked as a consumer to %s\n", dev_name(supplier));

out:
        device_pm_unlock();
        device_links_write_unlock();

        if ((flags & DL_FLAG_PM_RUNTIME && flags & DL_FLAG_RPM_ACTIVE) && !link)
                pm_runtime_put(supplier);

        return link;
}
EXPORT_SYMBOL_GPL(device_link_add);

/**
 * device_link_wait_for_supplier - Add device to wait_for_suppliers list
 * @consumer: Consumer device
 *
 * Marks the @consumer device as waiting for suppliers to become available by
 * adding it to the wait_for_suppliers list. The consumer device will never be
 * probed until it's removed from the wait_for_suppliers list.
 *
 * The caller is responsible for adding the links to the supplier devices once
 * they are available and removing the @consumer device from the
 * wait_for_suppliers list once links to all the suppliers have been created.
 *
 * This function is NOT meant to be called from the probe function of the
 * consumer but rather from code that creates/adds the consumer device.
 */
static void device_link_wait_for_supplier(struct device *consumer,
                                          bool need_for_probe)
{
        mutex_lock(&wfs_lock);
        list_add_tail(&consumer->links.needs_suppliers, &wait_for_suppliers);
        consumer->links.need_for_probe = need_for_probe;
        mutex_unlock(&wfs_lock);
}

static void device_link_wait_for_mandatory_supplier(struct device *consumer)
{
        device_link_wait_for_supplier(consumer, true);
}

static void device_link_wait_for_optional_supplier(struct device *consumer)
{
        device_link_wait_for_supplier(consumer, false);
}

/**
 * device_link_add_missing_supplier_links - Add links from consumer devices to
 *                                          supplier devices, leaving any
 *                                          consumer with inactive suppliers on
 *                                          the wait_for_suppliers list
 *
 * Loops through all consumers waiting on suppliers and tries to add all their
 * supplier links. If that succeeds, the consumer device is removed from
 * wait_for_suppliers list. Otherwise, they are left in the wait_for_suppliers
 * list.  Devices left on the wait_for_suppliers list will not be probed.
 *
 * The fwnode add_links callback is expected to return 0 if it has found and
 * added all the supplier links for the consumer device. It should return an
 * error if it isn't able to do so.
 *
 * The caller of device_link_wait_for_supplier() is expected to call this once
 * it's aware of potential suppliers becoming available.
 */
static void device_link_add_missing_supplier_links(void)
{
        struct device *dev, *tmp;

        mutex_lock(&wfs_lock);
        list_for_each_entry_safe(dev, tmp, &wait_for_suppliers,
                                 links.needs_suppliers) {
                int ret = fwnode_call_int_op(dev->fwnode, add_links, dev);
                if (!ret)
                        list_del_init(&dev->links.needs_suppliers);
                else if (ret != -ENODEV || fw_devlink_is_permissive())
                        dev->links.need_for_probe = false;
        }
        mutex_unlock(&wfs_lock);
}

#ifdef CONFIG_SRCU
static void __device_link_del(struct kref *kref)
{
        struct device_link *link = container_of(kref, struct device_link, kref);

        dev_dbg(link->consumer, "Dropping the link to %s\n",
                dev_name(link->supplier));

        if (link->flags & DL_FLAG_PM_RUNTIME)
                pm_runtime_drop_link(link->consumer);

        list_del_rcu(&link->s_node);
        list_del_rcu(&link->c_node);
        device_unregister(&link->link_dev);
}
#else /* !CONFIG_SRCU */
static void __device_link_del(struct kref *kref)
{
        struct device_link *link = container_of(kref, struct device_link, kref);

        dev_info(link->consumer, "Dropping the link to %s\n",
                 dev_name(link->supplier));

        if (link->flags & DL_FLAG_PM_RUNTIME)
                pm_runtime_drop_link(link->consumer);

        list_del(&link->s_node);
        list_del(&link->c_node);
        device_unregister(&link->link_dev);
}
#endif /* !CONFIG_SRCU */

static void device_link_put_kref(struct device_link *link)
{
        if (link->flags & DL_FLAG_STATELESS)
                kref_put(&link->kref, __device_link_del);
        else
                WARN(1, "Unable to drop a managed device link reference\n");
}

/**
 * device_link_del - Delete a stateless link between two devices.
 * @link: Device link to delete.
 *
 * The caller must ensure proper synchronization of this function with runtime
 * PM.  If the link was added multiple times, it needs to be deleted as often.
 * Care is required for hotplugged devices:  Their links are purged on removal
 * and calling device_link_del() is then no longer allowed.
 */
void device_link_del(struct device_link *link)
{
        device_links_write_lock();
        device_link_put_kref(link);
        device_links_write_unlock();
}
EXPORT_SYMBOL_GPL(device_link_del);

/**
 * device_link_remove - Delete a stateless link between two devices.
 * @consumer: Consumer end of the link.
 * @supplier: Supplier end of the link.
 *
 * The caller must ensure proper synchronization of this function with runtime
 * PM.
 */
void device_link_remove(void *consumer, struct device *supplier)
{
        struct device_link *link;

        if (WARN_ON(consumer == supplier))
                return;

        device_links_write_lock();

        list_for_each_entry(link, &supplier->links.consumers, s_node) {
                if (link->consumer == consumer) {
                        device_link_put_kref(link);
                        break;
                }
        }

        device_links_write_unlock();
}
EXPORT_SYMBOL_GPL(device_link_remove);

static void device_links_missing_supplier(struct device *dev)
{
        struct device_link *link;

        list_for_each_entry(link, &dev->links.suppliers, c_node) {
                if (link->status != DL_STATE_CONSUMER_PROBE)
                        continue;

                if (link->supplier->links.status == DL_DEV_DRIVER_BOUND) {
                        WRITE_ONCE(link->status, DL_STATE_AVAILABLE);
                } else {
                        WARN_ON(!(link->flags & DL_FLAG_SYNC_STATE_ONLY));
                        WRITE_ONCE(link->status, DL_STATE_DORMANT);
                }
        }
}

/**
 * device_links_check_suppliers - Check presence of supplier drivers.
 * @dev: Consumer device.
 *
 * Check links from this device to any suppliers.  Walk the list of the device's
 * links to suppliers and see if all of them are available.  If not, simply
 * return -EPROBE_DEFER.
 *
 * We need to guarantee that the supplier will not go away after the check has
 * been positive here.  It only can go away in __device_release_driver() and
 * that function  checks the device's links to consumers.  This means we need to
 * mark the link as "consumer probe in progress" to make the supplier removal
 * wait for us to complete (or bad things may happen).
 *
 * Links without the DL_FLAG_MANAGED flag set are ignored.
 */
int device_links_check_suppliers(struct device *dev)
{
        struct device_link *link;
        int ret = 0;

        /*
         * Device waiting for supplier to become available is not allowed to
         * probe.
         */
        mutex_lock(&wfs_lock);
        if (!list_empty(&dev->links.needs_suppliers) &&
            dev->links.need_for_probe) {
                mutex_unlock(&wfs_lock);
                return -EPROBE_DEFER;
        }
        mutex_unlock(&wfs_lock);

        device_links_write_lock();

        list_for_each_entry(link, &dev->links.suppliers, c_node) {
                if (!(link->flags & DL_FLAG_MANAGED))
                        continue;

                if (link->status != DL_STATE_AVAILABLE &&
                    !(link->flags & DL_FLAG_SYNC_STATE_ONLY)) {
                        device_links_missing_supplier(dev);
                        ret = -EPROBE_DEFER;
                        break;
                }
                WRITE_ONCE(link->status, DL_STATE_CONSUMER_PROBE);
        }
        dev->links.status = DL_DEV_PROBING;

        device_links_write_unlock();
        return ret;
}

/**
 * __device_links_queue_sync_state - Queue a device for sync_state() callback
 * @dev: Device to call sync_state() on
 * @list: List head to queue the @dev on
 *
 * Queues a device for a sync_state() callback when the device links write lock
 * isn't held. This allows the sync_state() execution flow to use device links
 * APIs.  The caller must ensure this function is called with
 * device_links_write_lock() held.
 *
 * This function does a get_device() to make sure the device is not freed while
 * on this list.
 *
 * So the caller must also ensure that device_links_flush_sync_list() is called
 * as soon as the caller releases device_links_write_lock().  This is necessary
 * to make sure the sync_state() is called in a timely fashion and the
 * put_device() is called on this device.
 */
static void __device_links_queue_sync_state(struct device *dev,
                                            struct list_head *list)
{
        struct device_link *link;

        if (!dev_has_sync_state(dev))
                return;
        if (dev->state_synced)
                return;

        list_for_each_entry(link, &dev->links.consumers, s_node) {
                if (!(link->flags & DL_FLAG_MANAGED))
                        continue;
                if (link->status != DL_STATE_ACTIVE)
                        return;
        }

        /*
         * Set the flag here to avoid adding the same device to a list more
         * than once. This can happen if new consumers get added to the device
         * and probed before the list is flushed.
         */
        dev->state_synced = true;

        if (WARN_ON(!list_empty(&dev->links.defer_hook)))
                return;

        get_device(dev);
        list_add_tail(&dev->links.defer_hook, list);
}

/**
 * device_links_flush_sync_list - Call sync_state() on a list of devices
 * @list: List of devices to call sync_state() on
 * @dont_lock_dev: Device for which lock is already held by the caller
 *
 * Calls sync_state() on all the devices that have been queued for it. This
 * function is used in conjunction with __device_links_queue_sync_state(). The
 * @dont_lock_dev parameter is useful when this function is called from a
 * context where a device lock is already held.
 */
static void device_links_flush_sync_list(struct list_head *list,
                                         struct device *dont_lock_dev)
{
        struct device *dev, *tmp;

        list_for_each_entry_safe(dev, tmp, list, links.defer_hook) {
                list_del_init(&dev->links.defer_hook);

                if (dev != dont_lock_dev)
                        device_lock(dev);

                if (dev->bus->sync_state)
                        dev->bus->sync_state(dev);
                else if (dev->driver && dev->driver->sync_state)
                        dev->driver->sync_state(dev);

                if (dev != dont_lock_dev)
                        device_unlock(dev);

                put_device(dev);
        }
}

void device_links_supplier_sync_state_pause(void)
{
        device_links_write_lock();
        defer_sync_state_count++;
        device_links_write_unlock();
}

void device_links_supplier_sync_state_resume(void)
{
        struct device *dev, *tmp;
        LIST_HEAD(sync_list);

        device_links_write_lock();
        if (!defer_sync_state_count) {
                WARN(true, "Unmatched sync_state pause/resume!");
                goto out;
        }
        defer_sync_state_count--;
        if (defer_sync_state_count)
                goto out;

        list_for_each_entry_safe(dev, tmp, &deferred_sync, links.defer_hook) {
                /*
                 * Delete from deferred_sync list before queuing it to
                 * sync_list because defer_hook is used for both lists.
                 */
                list_del_init(&dev->links.defer_hook);
                __device_links_queue_sync_state(dev, &sync_list);
        }
out:
        device_links_write_unlock();

        device_links_flush_sync_list(&sync_list, NULL);
}

static int sync_state_resume_initcall(void)
{
        device_links_supplier_sync_state_resume();
        return 0;
}
late_initcall(sync_state_resume_initcall);

static void __device_links_supplier_defer_sync(struct device *sup)
{
        if (list_empty(&sup->links.defer_hook) && dev_has_sync_state(sup))
                list_add_tail(&sup->links.defer_hook, &deferred_sync);
}

static void device_link_drop_managed(struct device_link *link)
{
        link->flags &= ~DL_FLAG_MANAGED;
        WRITE_ONCE(link->status, DL_STATE_NONE);
        kref_put(&link->kref, __device_link_del);
}

static ssize_t waiting_for_supplier_show(struct device *dev,
                                         struct device_attribute *attr,
                                         char *buf)
{
        bool val;

        device_lock(dev);
        mutex_lock(&wfs_lock);
        val = !list_empty(&dev->links.needs_suppliers)
              && dev->links.need_for_probe;
        mutex_unlock(&wfs_lock);
        device_unlock(dev);
        return sprintf(buf, "%u\n", val);
}
static DEVICE_ATTR_RO(waiting_for_supplier);

/**
 * device_links_driver_bound - Update device links after probing its driver.
 * @dev: Device to update the links for.
 *
 * The probe has been successful, so update links from this device to any
 * consumers by changing their status to "available".
 *
 * Also change the status of @dev's links to suppliers to "active".
 *
 * Links without the DL_FLAG_MANAGED flag set are ignored.
 */
void device_links_driver_bound(struct device *dev)
{
        struct device_link *link, *ln;
        LIST_HEAD(sync_list);

        /*
         * If a device probes successfully, it's expected to have created all
         * the device links it needs to or make new device links as it needs
         * them. So, it no longer needs to wait on any suppliers.
         */
        mutex_lock(&wfs_lock);
        list_del_init(&dev->links.needs_suppliers);
        mutex_unlock(&wfs_lock);
        device_remove_file(dev, &dev_attr_waiting_for_supplier);

        device_links_write_lock();

        list_for_each_entry(link, &dev->links.consumers, s_node) {
                if (!(link->flags & DL_FLAG_MANAGED))
                        continue;

                /*
                 * Links created during consumer probe may be in the "consumer
                 * probe" state to start with if the supplier is still probing
                 * when they are created and they may become "active" if the
                 * consumer probe returns first.  Skip them here.
                 */
                if (link->status == DL_STATE_CONSUMER_PROBE ||
                    link->status == DL_STATE_ACTIVE)
                        continue;

                WARN_ON(link->status != DL_STATE_DORMANT);
                WRITE_ONCE(link->status, DL_STATE_AVAILABLE);

                if (link->flags & DL_FLAG_AUTOPROBE_CONSUMER)
                        driver_deferred_probe_add(link->consumer);
        }

        if (defer_sync_state_count)
                __device_links_supplier_defer_sync(dev);
        else
                __device_links_queue_sync_state(dev, &sync_list);

        list_for_each_entry_safe(link, ln, &dev->links.suppliers, c_node) {
                struct device *supplier;

                if (!(link->flags & DL_FLAG_MANAGED))
                        continue;

                supplier = link->supplier;
                if (link->flags & DL_FLAG_SYNC_STATE_ONLY) {
                        /*
                         * When DL_FLAG_SYNC_STATE_ONLY is set, it means no
                         * other DL_MANAGED_LINK_FLAGS have been set. So, it's
                         * save to drop the managed link completely.
                         */
                        device_link_drop_managed(link);
                } else {
                        WARN_ON(link->status != DL_STATE_CONSUMER_PROBE);
                        WRITE_ONCE(link->status, DL_STATE_ACTIVE);
                }

                /*
                 * This needs to be done even for the deleted
                 * DL_FLAG_SYNC_STATE_ONLY device link in case it was the last
                 * device link that was preventing the supplier from getting a
                 * sync_state() call.
                 */
                if (defer_sync_state_count)
                        __device_links_supplier_defer_sync(supplier);
                else
                        __device_links_queue_sync_state(supplier, &sync_list);
        }

        dev->links.status = DL_DEV_DRIVER_BOUND;

        device_links_write_unlock();

        device_links_flush_sync_list(&sync_list, dev);
}

/**
 * __device_links_no_driver - Update links of a device without a driver.
 * @dev: Device without a drvier.
 *
 * Delete all non-persistent links from this device to any suppliers.
 *
 * Persistent links stay around, but their status is changed to "available",
 * unless they already are in the "supplier unbind in progress" state in which
 * case they need not be updated.
 *
 * Links without the DL_FLAG_MANAGED flag set are ignored.
 */
static void __device_links_no_driver(struct device *dev)
{
        struct device_link *link, *ln;

        list_for_each_entry_safe_reverse(link, ln, &dev->links.suppliers, c_node) {
                if (!(link->flags & DL_FLAG_MANAGED))
                        continue;

                if (link->flags & DL_FLAG_AUTOREMOVE_CONSUMER) {
                        device_link_drop_managed(link);
                        continue;
                }

                if (link->status != DL_STATE_CONSUMER_PROBE &&
                    link->status != DL_STATE_ACTIVE)
                        continue;

                if (link->supplier->links.status == DL_DEV_DRIVER_BOUND) {
                        WRITE_ONCE(link->status, DL_STATE_AVAILABLE);
                } else {
                        WARN_ON(!(link->flags & DL_FLAG_SYNC_STATE_ONLY));
                        WRITE_ONCE(link->status, DL_STATE_DORMANT);
                }
        }

        dev->links.status = DL_DEV_NO_DRIVER;
}

/**
 * device_links_no_driver - Update links after failing driver probe.
 * @dev: Device whose driver has just failed to probe.
 *
 * Clean up leftover links to consumers for @dev and invoke
 * %__device_links_no_driver() to update links to suppliers for it as
 * appropriate.
 *
 * Links without the DL_FLAG_MANAGED flag set are ignored.
 */
void device_links_no_driver(struct device *dev)
{
        struct device_link *link;

        device_links_write_lock();

        list_for_each_entry(link, &dev->links.consumers, s_node) {
                if (!(link->flags & DL_FLAG_MANAGED))
                        continue;

                /*
                 * The probe has failed, so if the status of the link is
                 * "consumer probe" or "active", it must have been added by
                 * a probing consumer while this device was still probing.
                 * Change its state to "dormant", as it represents a valid
                 * relationship, but it is not functionally meaningful.
                 */
                if (link->status == DL_STATE_CONSUMER_PROBE ||
                    link->status == DL_STATE_ACTIVE)
                        WRITE_ONCE(link->status, DL_STATE_DORMANT);
        }

        __device_links_no_driver(dev);

        device_links_write_unlock();
}

/**
 * device_links_driver_cleanup - Update links after driver removal.
 * @dev: Device whose driver has just gone away.
 *
 * Update links to consumers for @dev by changing their status to "dormant" and
 * invoke %__device_links_no_driver() to update links to suppliers for it as
 * appropriate.
 *
 * Links without the DL_FLAG_MANAGED flag set are ignored.
 */
void device_links_driver_cleanup(struct device *dev)
{
        struct device_link *link, *ln;

        device_links_write_lock();

        list_for_each_entry_safe(link, ln, &dev->links.consumers, s_node) {
                if (!(link->flags & DL_FLAG_MANAGED))
                        continue;

                WARN_ON(link->flags & DL_FLAG_AUTOREMOVE_CONSUMER);
                WARN_ON(link->status != DL_STATE_SUPPLIER_UNBIND);

                /*
                 * autoremove the links between this @dev and its consumer
                 * devices that are not active, i.e. where the link state
                 * has moved to DL_STATE_SUPPLIER_UNBIND.
                 */
                if (link->status == DL_STATE_SUPPLIER_UNBIND &&
                    link->flags & DL_FLAG_AUTOREMOVE_SUPPLIER)
                        device_link_drop_managed(link);

                WRITE_ONCE(link->status, DL_STATE_DORMANT);
        }

        list_del_init(&dev->links.defer_hook);
        __device_links_no_driver(dev);

        device_links_write_unlock();
}

/**
 * device_links_busy - Check if there are any busy links to consumers.
 * @dev: Device to check.
 *
 * Check each consumer of the device and return 'true' if its link's status
 * is one of "consumer probe" or "active" (meaning that the given consumer is
 * probing right now or its driver is present).  Otherwise, change the link
 * state to "supplier unbind" to prevent the consumer from being probed
 * successfully going forward.
 *
 * Return 'false' if there are no probing or active consumers.
 *
 * Links without the DL_FLAG_MANAGED flag set are ignored.
 */
bool device_links_busy(struct device *dev)
{
        struct device_link *link;
        bool ret = false;

        device_links_write_lock();

        list_for_each_entry(link, &dev->links.consumers, s_node) {
                if (!(link->flags & DL_FLAG_MANAGED))
                        continue;

                if (link->status == DL_STATE_CONSUMER_PROBE
                    || link->status == DL_STATE_ACTIVE) {
                        ret = true;
                        break;
                }
                WRITE_ONCE(link->status, DL_STATE_SUPPLIER_UNBIND);
        }

        dev->links.status = DL_DEV_UNBINDING;

        device_links_write_unlock();
        return ret;
}

/**
 * device_links_unbind_consumers - Force unbind consumers of the given device.
 * @dev: Device to unbind the consumers of.
 *
 * Walk the list of links to consumers for @dev and if any of them is in the
 * "consumer probe" state, wait for all device probes in progress to complete
 * and start over.
 *
 * If that's not the case, change the status of the link to "supplier unbind"
 * and check if the link was in the "active" state.  If so, force the consumer
 * driver to unbind and start over (the consumer will not re-probe as we have
 * changed the state of the link already).
 *
 * Links without the DL_FLAG_MANAGED flag set are ignored.
 */
void device_links_unbind_consumers(struct device *dev)
{
        struct device_link *link;

 start:
        device_links_write_lock();

        list_for_each_entry(link, &dev->links.consumers, s_node) {
                enum device_link_state status;

                if (!(link->flags & DL_FLAG_MANAGED) ||
                    link->flags & DL_FLAG_SYNC_STATE_ONLY)
                        continue;

                status = link->status;
                if (status == DL_STATE_CONSUMER_PROBE) {
                        device_links_write_unlock();

                        wait_for_device_probe();
                        goto start;
                }
                WRITE_ONCE(link->status, DL_STATE_SUPPLIER_UNBIND);
                if (status == DL_STATE_ACTIVE) {
                        struct device *consumer = link->consumer;

                        get_device(consumer);

                        device_links_write_unlock();

                        device_release_driver_internal(consumer, NULL,
                                                       consumer->parent);
                        put_device(consumer);
                        goto start;
                }
        }

        device_links_write_unlock();
}

/**
 * device_links_purge - Delete existing links to other devices.
 * @dev: Target device.
 */
static void device_links_purge(struct device *dev)
{
        struct device_link *link, *ln;

        if (dev->class == &devlink_class)
                return;

        mutex_lock(&wfs_lock);
        list_del(&dev->links.needs_suppliers);
        mutex_unlock(&wfs_lock);

        /*
         * Delete all of the remaining links from this device to any other
         * devices (either consumers or suppliers).
         */
        device_links_write_lock();

        list_for_each_entry_safe_reverse(link, ln, &dev->links.suppliers, c_node) {
                WARN_ON(link->status == DL_STATE_ACTIVE);
                __device_link_del(&link->kref);
        }

        list_for_each_entry_safe_reverse(link, ln, &dev->links.consumers, s_node) {
                WARN_ON(link->status != DL_STATE_DORMANT &&
                        link->status != DL_STATE_NONE);
                __device_link_del(&link->kref);
        }

        device_links_write_unlock();
}

static u32 fw_devlink_flags = DL_FLAG_SYNC_STATE_ONLY;
static int __init fw_devlink_setup(char *arg)
{
        if (!arg)
                return -EINVAL;

        if (strcmp(arg, "off") == 0) {
                fw_devlink_flags = 0;
        } else if (strcmp(arg, "permissive") == 0) {
                fw_devlink_flags = DL_FLAG_SYNC_STATE_ONLY;
        } else if (strcmp(arg, "on") == 0) {
                fw_devlink_flags = DL_FLAG_AUTOPROBE_CONSUMER;
        } else if (strcmp(arg, "rpm") == 0) {
                fw_devlink_flags = DL_FLAG_AUTOPROBE_CONSUMER |
                                   DL_FLAG_PM_RUNTIME;
        }
        return 0;
}
early_param("fw_devlink", fw_devlink_setup);

u32 fw_devlink_get_flags(void)
{
        return fw_devlink_flags;
}

static bool fw_devlink_is_permissive(void)
{
        return fw_devlink_flags == DL_FLAG_SYNC_STATE_ONLY;
}

static void fw_devlink_link_device(struct device *dev)
{
        int fw_ret;

        if (!fw_devlink_flags)
                return;

        mutex_lock(&defer_fw_devlink_lock);
        if (!defer_fw_devlink_count)
                device_link_add_missing_supplier_links();

        /*
         * The device's fwnode not having add_links() doesn't affect if other
         * consumers can find this device as a supplier.  So, this check is
         * intentionally placed after device_link_add_missing_supplier_links().
         */
        if (!fwnode_has_op(dev->fwnode, add_links))
                goto out;

        /*
         * If fw_devlink is being deferred, assume all devices have mandatory
         * suppliers they need to link to later. Then, when the fw_devlink is
         * resumed, all these devices will get a chance to try and link to any
         * suppliers they have.
         */
        if (!defer_fw_devlink_count) {
                fw_ret = fwnode_call_int_op(dev->fwnode, add_links, dev);
                if (fw_ret == -ENODEV && fw_devlink_is_permissive())
                        fw_ret = -EAGAIN;
        } else {
                fw_ret = -ENODEV;
                /*
                 * defer_hook is not used to add device to deferred_sync list
                 * until device is bound. Since deferred fw devlink also blocks
                 * probing, same list hook can be used for deferred_fw_devlink.
                 */
                list_add_tail(&dev->links.defer_hook, &deferred_fw_devlink);
        }

        if (fw_ret == -ENODEV)
                device_link_wait_for_mandatory_supplier(dev);
        else if (fw_ret)
                device_link_wait_for_optional_supplier(dev);

out:
        mutex_unlock(&defer_fw_devlink_lock);
}

/**
 * fw_devlink_pause - Pause parsing of fwnode to create device links
 *
 * Calling this function defers any fwnode parsing to create device links until
 * fw_devlink_resume() is called. Both these functions are ref counted and the
 * caller needs to match the calls.
 *
 * While fw_devlink is paused:
 * - Any device that is added won't have its fwnode parsed to create device
 *   links.
 * - The probe of the device will also be deferred during this period.
 * - Any devices that were already added, but waiting for suppliers won't be
 *   able to link to newly added devices.
 *
 * Once fw_devlink_resume():
 * - All the fwnodes that was not parsed will be parsed.
 * - All the devices that were deferred probing will be reattempted if they
 *   aren't waiting for any more suppliers.
 *
 * This pair of functions, is mainly meant to optimize the parsing of fwnodes
 * when a lot of devices that need to link to each other are added in a short
 * interval of time. For example, adding all the top level devices in a system.
 *
 * For example, if N devices are added and:
 * - All the consumers are added before their suppliers
 * - All the suppliers of the N devices are part of the N devices
 *
 * Then:
 *
 * - With the use of fw_devlink_pause() and fw_devlink_resume(), each device
 *   will only need one parsing of its fwnode because it is guaranteed to find
 *   all the supplier devices already registered and ready to link to. It won't
 *   have to do another pass later to find one or more suppliers it couldn't
 *   find in the first parse of the fwnode. So, we'll only need O(N) fwnode
 *   parses.
 *
 * - Without the use of fw_devlink_pause() and fw_devlink_resume(), we would
 *   end up doing O(N^2) parses of fwnodes because every device that's added is
 *   guaranteed to trigger a parse of the fwnode of every device added before
 *   it. This O(N^2) parse is made worse by the fact that when a fwnode of a
 *   device is parsed, all it descendant devices might need to have their
 *   fwnodes parsed too (even if the devices themselves aren't added).
 */
void fw_devlink_pause(void)
{
        mutex_lock(&defer_fw_devlink_lock);
        defer_fw_devlink_count++;
        mutex_unlock(&defer_fw_devlink_lock);
}

/** fw_devlink_resume - Resume parsing of fwnode to create device links
 *
 * This function is used in conjunction with fw_devlink_pause() and is ref
 * counted. See documentation for fw_devlink_pause() for more details.
 */
void fw_devlink_resume(void)
{
        struct device *dev, *tmp;
        LIST_HEAD(probe_list);

        mutex_lock(&defer_fw_devlink_lock);
        if (!defer_fw_devlink_count) {
                WARN(true, "Unmatched fw_devlink pause/resume!");
                goto out;
        }

        defer_fw_devlink_count--;
        if (defer_fw_devlink_count)
                goto out;

        device_link_add_missing_supplier_links();
        list_splice_tail_init(&deferred_fw_devlink, &probe_list);
out:
        mutex_unlock(&defer_fw_devlink_lock);

        /*
         * bus_probe_device() can cause new devices to get added and they'll
         * try to grab defer_fw_devlink_lock. So, this needs to be done outside
         * the defer_fw_devlink_lock.
         */
        list_for_each_entry_safe(dev, tmp, &probe_list, links.defer_hook) {
                list_del_init(&dev->links.defer_hook);
                bus_probe_device(dev);
        }
}
/* Device links support end. */

int (*platform_notify)(struct device *dev) = NULL;
int (*platform_notify_remove)(struct device *dev) = NULL;
static struct kobject *dev_kobj;
struct kobject *sysfs_dev_char_kobj;
struct kobject *sysfs_dev_block_kobj;

static DEFINE_MUTEX(device_hotplug_lock);

void lock_device_hotplug(void)
{
        mutex_lock(&device_hotplug_lock);
}

void unlock_device_hotplug(void)
{
        mutex_unlock(&device_hotplug_lock);
}

int lock_device_hotplug_sysfs(void)
{
        if (mutex_trylock(&device_hotplug_lock))
                return 0;

        /* Avoid busy looping (5 ms of sleep should do). */
        msleep(5);
        return restart_syscall();
}

#ifdef CONFIG_BLOCK
static inline int device_is_not_partition(struct device *dev)
{
        return !(dev->type == &part_type);
}
#else
static inline int device_is_not_partition(struct device *dev)
{
        return 1;
}
#endif

static int
device_platform_notify(struct device *dev, enum kobject_action action)
{
        int ret;

        ret = acpi_platform_notify(dev, action);
        if (ret)
                return ret;

        ret = software_node_notify(dev, action);
        if (ret)
                return ret;

        if (platform_notify && action == KOBJ_ADD)
                platform_notify(dev);
        else if (platform_notify_remove && action == KOBJ_REMOVE)
                platform_notify_remove(dev);
        return 0;
}

/**
 * dev_driver_string - Return a device's driver name, if at all possible
 * @dev: struct device to get the name of
 *
 * Will return the device's driver's name if it is bound to a device.  If
 * the device is not bound to a driver, it will return the name of the bus
 * it is attached to.  If it is not attached to a bus either, an empty
 * string will be returned.
 */
const char *dev_driver_string(const struct device *dev)
{
        struct device_driver *drv;

        /* dev->driver can change to NULL underneath us because of unbinding,
         * so be careful about accessing it.  dev->bus and dev->class should
         * never change once they are set, so they don't need special care.
         */
        drv = READ_ONCE(dev->driver);
        return drv ? drv->name :
                        (dev->bus ? dev->bus->name :
                        (dev->class ? dev->class->name : ""));
}
EXPORT_SYMBOL(dev_driver_string);

#define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)

static ssize_t dev_attr_show(struct kobject *kobj, struct attribute *attr,
                             char *buf)
{
        struct device_attribute *dev_attr = to_dev_attr(attr);
        struct device *dev = kobj_to_dev(kobj);
        ssize_t ret = -EIO;

        if (dev_attr->show)
                ret = dev_attr->show(dev, dev_attr, buf);
        if (ret >= (ssize_t)PAGE_SIZE) {
                printk("dev_attr_show: %pS returned bad count\n",
                                dev_attr->show);
        }
        return ret;
}

static ssize_t dev_attr_store(struct kobject *kobj, struct attribute *attr,
                              const char *buf, size_t count)
{
        struct device_attribute *dev_attr = to_dev_attr(attr);
        struct device *dev = kobj_to_dev(kobj);
        ssize_t ret = -EIO;

        if (dev_attr->store)
                ret = dev_attr->store(dev, dev_attr, buf, count);
        return ret;
}

static const struct sysfs_ops dev_sysfs_ops = {
        .show   = dev_attr_show,
        .store  = dev_attr_store,
};

#define to_ext_attr(x) container_of(x, struct dev_ext_attribute, attr)

ssize_t device_store_ulong(struct device *dev,
                           struct device_attribute *attr,
                           const char *buf, size_t size)
{
        struct dev_ext_attribute *ea = to_ext_attr(attr);
        int ret;
        unsigned long new;

        ret = kstrtoul(buf, 0, &new);
        if (ret)
                return ret;
        *(unsigned long *)(ea->var) = new;
        /* Always return full write size even if we didn't consume all */
        return size;
}
EXPORT_SYMBOL_GPL(device_store_ulong);

ssize_t device_show_ulong(struct device *dev,
                          struct device_attribute *attr,
                          char *buf)
{
        struct dev_ext_attribute *ea = to_ext_attr(attr);
        return snprintf(buf, PAGE_SIZE, "%lx\n", *(unsigned long *)(ea->var));
}
EXPORT_SYMBOL_GPL(device_show_ulong);

ssize_t device_store_int(struct device *dev,
                         struct device_attribute *attr,
                         const char *buf, size_t size)
{
        struct dev_ext_attribute *ea = to_ext_attr(attr);
        int ret;
        long new;

        ret = kstrtol(buf, 0, &new);
        if (ret)
                return ret;

        if (new > INT_MAX || new < INT_MIN)
                return -EINVAL;
        *(int *)(ea->var) = new;
        /* Always return full write size even if we didn't consume all */
        return size;
}
EXPORT_SYMBOL_GPL(device_store_int);

ssize_t device_show_int(struct device *dev,
                        struct device_attribute *attr,
                        char *buf)
{
        struct dev_ext_attribute *ea = to_ext_attr(attr);

        return snprintf(buf, PAGE_SIZE, "%d\n", *(int *)(ea->var));
}
EXPORT_SYMBOL_GPL(device_show_int);

ssize_t device_store_bool(struct device *dev, struct device_attribute *attr,
                          const char *buf, size_t size)
{
        struct dev_ext_attribute *ea = to_ext_attr(attr);

        if (strtobool(buf, ea->var) < 0)
                return -EINVAL;

        return size;
}
EXPORT_SYMBOL_GPL(device_store_bool);

ssize_t device_show_bool(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct dev_ext_attribute *ea = to_ext_attr(attr);

        return snprintf(buf, PAGE_SIZE, "%d\n", *(bool *)(ea->var));
}
EXPORT_SYMBOL_GPL(device_show_bool);

/**
 * device_release - free device structure.
 * @kobj: device's kobject.
 *
 * This is called once the reference count for the object
 * reaches 0. We forward the call to the device's release
 * method, which should handle actually freeing the structure.
 */
static void device_release(struct kobject *kobj)
{
        struct device *dev = kobj_to_dev(kobj);
        struct device_private *p = dev->p;

        /*
         * Some platform devices are driven without driver attached
         * and managed resources may have been acquired.  Make sure
         * all resources are released.
         *
         * Drivers still can add resources into device after device
         * is deleted but alive, so release devres here to avoid
         * possible memory leak.
         */
        devres_release_all(dev);

        if (dev->release)
                dev->release(dev);
        else if (dev->type && dev->type->release)
                dev->type->release(dev);
        else if (dev->class && dev->class->dev_release)
                dev->class->dev_release(dev);
        else
                WARN(1, KERN_ERR "Device '%s' does not have a release() function, it is broken and must be fixed. See Documentation/core-api/kobject.rst.\n",
                        dev_name(dev));
        kfree(p);
}

static const void *device_namespace(struct kobject *kobj)
{
        struct device *dev = kobj_to_dev(kobj);
        const void *ns = NULL;

        if (dev->class && dev->class->ns_type)
                ns = dev->class->namespace(dev);

        return ns;
}

static void device_get_ownership(struct kobject *kobj, kuid_t *uid, kgid_t *gid)
{
        struct device *dev = kobj_to_dev(kobj);

        if (dev->class && dev->class->get_ownership)
                dev->class->get_ownership(dev, uid, gid);
}

static struct kobj_type device_ktype = {
        .release        = device_release,
        .sysfs_ops      = &dev_sysfs_ops,
        .namespace      = device_namespace,
        .get_ownership  = device_get_ownership,
};


static int dev_uevent_filter(struct kset *kset, struct kobject *kobj)
{
        struct kobj_type *ktype = get_ktype(kobj);

        if (ktype == &device_ktype) {
                struct device *dev = kobj_to_dev(kobj);
                if (dev->bus)
                        return 1;
                if (dev->class)
                        return 1;
        }
        return 0;
}

static const char *dev_uevent_name(struct kset *kset, struct kobject *kobj)
{
        struct device *dev = kobj_to_dev(kobj);

        if (dev->bus)
                return dev->bus->name;
        if (dev->class)
                return dev->class->name;
        return NULL;
}

static int dev_uevent(struct kset *kset, struct kobject *kobj,
                      struct kobj_uevent_env *env)
{
        struct device *dev = kobj_to_dev(kobj);
        int retval = 0;

        /* add device node properties if present */
        if (MAJOR(dev->devt)) {
                const char *tmp;
                const char *name;
                umode_t mode = 0;
                kuid_t uid = GLOBAL_ROOT_UID;
                kgid_t gid = GLOBAL_ROOT_GID;

                add_uevent_var(env, "MAJOR=%u", MAJOR(dev->devt));
                add_uevent_var(env, "MINOR=%u", MINOR(dev->devt));
                name = device_get_devnode(dev, &mode, &uid, &gid, &tmp);
                if (name) {
                        add_uevent_var(env, "DEVNAME=%s", name);
                        if (mode)
                                add_uevent_var(env, "DEVMODE=%#o", mode & 0777);
                        if (!uid_eq(uid, GLOBAL_ROOT_UID))
                                add_uevent_var(env, "DEVUID=%u", from_kuid(&init_user_ns, uid));
                        if (!gid_eq(gid, GLOBAL_ROOT_GID))
                                add_uevent_var(env, "DEVGID=%u", from_kgid(&init_user_ns, gid));
                        kfree(tmp);
                }
        }

        if (dev->type && dev->type->name)
                add_uevent_var(env, "DEVTYPE=%s", dev->type->name);

        if (dev->driver)
                add_uevent_var(env, "DRIVER=%s", dev->driver->name);

        /* Add common DT information about the device */
        of_device_uevent(dev, env);

        /* have the bus specific function add its stuff */
        if (dev->bus && dev->bus->uevent) {
                retval = dev->bus->uevent(dev, env);
                if (retval)
                        pr_debug("device: '%s': %s: bus uevent() returned %d\n",
                                 dev_name(dev), __func__, retval);
        }

        /* have the class specific function add its stuff */
        if (dev->class && dev->class->dev_uevent) {
                retval = dev->class->dev_uevent(dev, env);
                if (retval)
                        pr_debug("device: '%s': %s: class uevent() "
                                 "returned %d\n", dev_name(dev),
                                 __func__, retval);
        }

        /* have the device type specific function add its stuff */
        if (dev->type && dev->type->uevent) {
                retval = dev->type->uevent(dev, env);
                if (retval)
                        pr_debug("device: '%s': %s: dev_type uevent() "
                                 "returned %d\n", dev_name(dev),
                                 __func__, retval);
        }

        return retval;
}

static const struct kset_uevent_ops device_uevent_ops = {
        .filter =       dev_uevent_filter,
        .name =         dev_uevent_name,
        .uevent =       dev_uevent,
};

static ssize_t uevent_show(struct device *dev, struct device_attribute *attr,
                           char *buf)
{
        struct kobject *top_kobj;
        struct kset *kset;
        struct kobj_uevent_env *env = NULL;
        int i;
        size_t count = 0;
        int retval;

        /* search the kset, the device belongs to */
        top_kobj = &dev->kobj;
        while (!top_kobj->kset && top_kobj->parent)
                top_kobj = top_kobj->parent;
        if (!top_kobj->kset)
                goto out;

        kset = top_kobj->kset;
        if (!kset->uevent_ops || !kset->uevent_ops->uevent)
                goto out;

        /* respect filter */
        if (kset->uevent_ops && kset->uevent_ops->filter)
                if (!kset->uevent_ops->filter(kset, &dev->kobj))
                        goto out;

        env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
        if (!env)
                return -ENOMEM;

        /* let the kset specific function add its keys */
        retval = kset->uevent_ops->uevent(kset, &dev->kobj, env);
        if (retval)
                goto out;

        /* copy keys to file */
        for (i = 0; i < env->envp_idx; i++)
                count += sprintf(&buf[count], "%s\n", env->envp[i]);
out:
        kfree(env);
        return count;
}

static ssize_t uevent_store(struct device *dev, struct device_attribute *attr,
                            const char *buf, size_t count)
{
        int rc;

        rc = kobject_synth_uevent(&dev->kobj, buf, count);

        if (rc) {
                dev_err(dev, "uevent: failed to send synthetic uevent\n");
                return rc;
        }

        return count;
}
static DEVICE_ATTR_RW(uevent);

static ssize_t online_show(struct device *dev, struct device_attribute *attr,
                           char *buf)
{
        bool val;

        device_lock(dev);
        val = !dev->offline;
        device_unlock(dev);
        return sprintf(buf, "%u\n", val);
}

static ssize_t online_store(struct device *dev, struct device_attribute *attr,
                            const char *buf, size_t count)
{

        bool val;
        int ret;

        ret = strtobool(buf, &val);
        if (ret < 0)
                return ret;

        ret = lock_device_hotplug_sysfs();
        if (ret)
                return ret;

        ret = val ? device_online(dev) : device_offline(dev);
        unlock_device_hotplug();
        return ret < 0 ? ret : count;
}
static DEVICE_ATTR_RW(online);

int device_add_groups(struct device *dev, const struct attribute_group **groups)
{
        return sysfs_create_groups(&dev->kobj, groups);
}
EXPORT_SYMBOL_GPL(device_add_groups);

void device_remove_groups(struct device *dev,
                          const struct attribute_group **groups)
{
        sysfs_remove_groups(&dev->kobj, groups);
}
EXPORT_SYMBOL_GPL(device_remove_groups);

union device_attr_group_devres {
        const struct attribute_group *group;
        const struct attribute_group **groups;
};

static int devm_attr_group_match(struct device *dev, void *res, void *data)
{
        return ((union device_attr_group_devres *)res)->group == data;
}

static void devm_attr_group_remove(struct device *dev, void *res)
{
        union device_attr_group_devres *devres = res;
        const struct attribute_group *group = devres->group;

        dev_dbg(dev, "%s: removing group %p\n", __func__, group);
        sysfs_remove_group(&dev->kobj, group);
}

static void devm_attr_groups_remove(struct device *dev, void *res)
{
        union device_attr_group_devres *devres = res;
        const struct attribute_group **groups = devres->groups;

        dev_dbg(dev, "%s: removing groups %p\n", __func__, groups);
        sysfs_remove_groups(&dev->kobj, groups);
}

/**
 * devm_device_add_group - given a device, create a managed attribute group
 * @dev:        The device to create the group for
 * @grp:        The attribute group to create
 *
 * This function creates a group for the first time.  It will explicitly
 * warn and error if any of the attribute files being created already exist.
 *
 * Returns 0 on success or error code on failure.
 */
int devm_device_add_group(struct device *dev, const struct attribute_group *grp)
{
        union device_attr_group_devres *devres;
        int error;

        devres = devres_alloc(devm_attr_group_remove,
                              sizeof(*devres), GFP_KERNEL);
        if (!devres)
                return -ENOMEM;

        error = sysfs_create_group(&dev->kobj, grp);
        if (error) {
                devres_free(devres);
                return error;
        }

        devres->group = grp;
        devres_add(dev, devres);
        return 0;
}
EXPORT_SYMBOL_GPL(devm_device_add_group);

/**
 * devm_device_remove_group: remove a managed group from a device
 * @dev:        device to remove the group from
 * @grp:        group to remove
 *
 * This function removes a group of attributes from a device. The attributes
 * previously have to have been created for this group, otherwise it will fail.
 */
void devm_device_remove_group(struct device *dev,
                              const struct attribute_group *grp)
{
        WARN_ON(devres_release(dev, devm_attr_group_remove,
                               devm_attr_group_match,
                               /* cast away const */ (void *)grp));
}
EXPORT_SYMBOL_GPL(devm_device_remove_group);

/**
 * devm_device_add_groups - create a bunch of managed attribute groups
 * @dev:        The device to create the group for
 * @groups:     The attribute groups to create, NULL terminated
 *
 * This function creates a bunch of managed attribute groups.  If an error
 * occurs when creating a group, all previously created groups will be
 * removed, unwinding everything back to the original state when this
 * function was called.  It will explicitly warn and error if any of the
 * attribute files being created already exist.
 *
 * Returns 0 on success or error code from sysfs_create_group on failure.
 */
int devm_device_add_groups(struct device *dev,
                           const struct attribute_group **groups)
{
        union device_attr_group_devres *devres;
        int error;

        devres = devres_alloc(devm_attr_groups_remove,
                              sizeof(*devres), GFP_KERNEL);
        if (!devres)
                return -ENOMEM;

        error = sysfs_create_groups(&dev->kobj, groups);
        if (error) {
                devres_free(devres);
                return error;
        }

        devres->groups = groups;
        devres_add(dev, devres);
        return 0;
}
EXPORT_SYMBOL_GPL(devm_device_add_groups);

/**
 * devm_device_remove_groups - remove a list of managed groups
 *
 * @dev:        The device for the groups to be removed from
 * @groups:     NULL terminated list of groups to be removed
 *
 * If groups is not NULL, remove the specified groups from the device.
 */
void devm_device_remove_groups(struct device *dev,
                               const struct attribute_group **groups)
{
        WARN_ON(devres_release(dev, devm_attr_groups_remove,
                               devm_attr_group_match,
                               /* cast away const */ (void *)groups));
}
EXPORT_SYMBOL_GPL(devm_device_remove_groups);

static int device_add_attrs(struct device *dev)
{
        struct class *class = dev->class;
        const struct device_type *type = dev->type;
        int error;

        if (class) {
                error = device_add_groups(dev, class->dev_groups);
                if (error)
                        return error;
        }

        if (type) {
                error = device_add_groups(dev, type->groups);
                if (error)
                        goto err_remove_class_groups;
        }

        error = device_add_groups(dev, dev->groups);
        if (error)
                goto err_remove_type_groups;

        if (device_supports_offline(dev) && !dev->offline_disabled) {
                error = device_create_file(dev, &dev_attr_online);
                if (error)
                        goto err_remove_dev_groups;
        }

        if (fw_devlink_flags && !fw_devlink_is_permissive()) {
                error = device_create_file(dev, &dev_attr_waiting_for_supplier);
                if (error)
                        goto err_remove_dev_online;
        }

        return 0;

 err_remove_dev_online:
        device_remove_file(dev, &dev_attr_online);
 err_remove_dev_groups:
        device_remove_groups(dev, dev->groups);
 err_remove_type_groups:
        if (type)
                device_remove_groups(dev, type->groups);
 err_remove_class_groups:
        if (class)
                device_remove_groups(dev, class->dev_groups);

        return error;
}

static void device_remove_attrs(struct device *dev)
{
        struct class *class = dev->class;
        const struct device_type *type = dev->type;

        device_remove_file(dev, &dev_attr_waiting_for_supplier);
        device_remove_file(dev, &dev_attr_online);
        device_remove_groups(dev, dev->groups);

        if (type)
                device_remove_groups(dev, type->groups);

        if (class)
                device_remove_groups(dev, class->dev_groups);
}

static ssize_t dev_show(struct device *dev, struct device_attribute *attr,
                        char *buf)
{
        return print_dev_t(buf, dev->devt);
}
static DEVICE_ATTR_RO(dev);

/* /sys/devices/ */
struct kset *devices_kset;

/**
 * devices_kset_move_before - Move device in the devices_kset's list.
 * @deva: Device to move.
 * @devb: Device @deva should come before.
 */
static void devices_kset_move_before(struct device *deva, struct device *devb)
{
        if (!devices_kset)
                return;
        pr_debug("devices_kset: Moving %s before %s\n",
                 dev_name(deva), dev_name(devb));
        spin_lock(&devices_kset->list_lock);
        list_move_tail(&deva->kobj.entry, &devb->kobj.entry);
        spin_unlock(&devices_kset->list_lock);
}

/**
 * devices_kset_move_after - Move device in the devices_kset's list.
 * @deva: Device to move
 * @devb: Device @deva should come after.
 */
static void devices_kset_move_after(struct device *deva, struct device *devb)
{
        if (!devices_kset)
                return;
        pr_debug("devices_kset: Moving %s after %s\n",
                 dev_name(deva), dev_name(devb));
        spin_lock(&devices_kset->list_lock);
        list_move(&deva->kobj.entry, &devb->kobj.entry);
        spin_unlock(&devices_kset->list_lock);
}

/**
 * devices_kset_move_last - move the device to the end of devices_kset's list.
 * @dev: device to move
 */
void devices_kset_move_last(struct device *dev)
{
        if (!devices_kset)
                return;
        pr_debug("devices_kset: Moving %s to end of list\n", dev_name(dev));
        spin_lock(&devices_kset->list_lock);
        list_move_tail(&dev->kobj.entry, &devices_kset->list);
        spin_unlock(&devices_kset->list_lock);
}

/**
 * device_create_file - create sysfs attribute file for device.
 * @dev: device.
 * @attr: device attribute descriptor.
 */
int device_create_file(struct device *dev,
                       const struct device_attribute *attr)
{
        int error = 0;

        if (dev) {
                WARN(((attr->attr.mode & S_IWUGO) && !attr->store),
                        "Attribute %s: write permission without 'store'\n",
                        attr->attr.name);
                WARN(((attr->attr.mode & S_IRUGO) && !attr->show),
                        "Attribute %s: read permission without 'show'\n",
                        attr->attr.name);
                error = sysfs_create_file(&dev->kobj, &attr->attr);
        }

        return error;
}
EXPORT_SYMBOL_GPL(device_create_file);

/**
 * device_remove_file - remove sysfs attribute file.
 * @dev: device.
 * @attr: device attribute descriptor.
 */
void device_remove_file(struct device *dev,
                        const struct device_attribute *attr)
{
        if (dev)
                sysfs_remove_file(&dev->kobj, &attr->attr);
}
EXPORT_SYMBOL_GPL(device_remove_file);

/**
 * device_remove_file_self - remove sysfs attribute file from its own method.
 * @dev: device.
 * @attr: device attribute descriptor.
 *
 * See kernfs_remove_self() for details.
 */
bool device_remove_file_self(struct device *dev,
                             const struct device_attribute *attr)
{
        if (dev)
                return sysfs_remove_file_self(&dev->kobj, &attr->attr);
        else
                return false;
}
EXPORT_SYMBOL_GPL(device_remove_file_self);

/**
 * device_create_bin_file - create sysfs binary attribute file for device.
 * @dev: device.
 * @attr: device binary attribute descriptor.
 */
int device_create_bin_file(struct device *dev,
                           const struct bin_attribute *attr)
{
        int error = -EINVAL;
        if (dev)
                error = sysfs_create_bin_file(&dev->kobj, attr);
        return error;
}
EXPORT_SYMBOL_GPL(device_create_bin_file);

/**
 * device_remove_bin_file - remove sysfs binary attribute file
 * @dev: device.
 * @attr: device binary attribute descriptor.
 */
void device_remove_bin_file(struct device *dev,
                            const struct bin_attribute *attr)
{
        if (dev)
                sysfs_remove_bin_file(&dev->kobj, attr);
}
EXPORT_SYMBOL_GPL(device_remove_bin_file);

static void klist_children_get(struct klist_node *n)
{
        struct device_private *p = to_device_private_parent(n);
        struct device *dev = p->device;

        get_device(dev);
}

static void klist_children_put(struct klist_node *n)
{
        struct device_private *p = to_device_private_parent(n);
        struct device *dev = p->device;

        put_device(dev);
}

/**
 * device_initialize - init device structure.
 * @dev: device.
 *
 * This prepares the device for use by other layers by initializing
 * its fields.
 * It is the first half of device_register(), if called by
 * that function, though it can also be called separately, so one
 * may use @dev's fields. In particular, get_device()/put_device()
 * may be used for reference counting of @dev after calling this
 * function.
 *
 * All fields in @dev must be initialized by the caller to 0, except
 * for those explicitly set to some other value.  The simplest
 * approach is to use kzalloc() to allocate the structure containing
 * @dev.
 *
 * NOTE: Use put_device() to give up your reference instead of freeing
 * @dev directly once you have called this function.
 */
void device_initialize(struct device *dev)
{
        dev->kobj.kset = devices_kset;
        kobject_init(&dev->kobj, &device_ktype);
        INIT_LIST_HEAD(&dev->dma_pools);
        mutex_init(&dev->mutex);
#ifdef CONFIG_PROVE_LOCKING
        mutex_init(&dev->lockdep_mutex);
#endif
        lockdep_set_novalidate_class(&dev->mutex);
        spin_lock_init(&dev->devres_lock);
        INIT_LIST_HEAD(&dev->devres_head);
        device_pm_init(dev);
        set_dev_node(dev, -1);
#ifdef CONFIG_GENERIC_MSI_IRQ
        INIT_LIST_HEAD(&dev->msi_list);
#endif
        INIT_LIST_HEAD(&dev->links.consumers);
        INIT_LIST_HEAD(&dev->links.suppliers);
        INIT_LIST_HEAD(&dev->links.needs_suppliers);
        INIT_LIST_HEAD(&dev->links.defer_hook);
        dev->links.status = DL_DEV_NO_DRIVER;
}
EXPORT_SYMBOL_GPL(device_initialize);

struct kobject *virtual_device_parent(struct device *dev)
{
        static struct kobject *virtual_dir = NULL;

        if (!virtual_dir)
                virtual_dir = kobject_create_and_add("virtual",
                                                     &devices_kset->kobj);

        return virtual_dir;
}

struct class_dir {
        struct kobject kobj;
        struct class *class;
};

#define to_class_dir(obj) container_of(obj, struct class_dir, kobj)

static void class_dir_release(struct kobject *kobj)
{
        struct class_dir *dir = to_class_dir(kobj);
        kfree(dir);
}

static const
struct kobj_ns_type_operations *class_dir_child_ns_type(struct kobject *kobj)
{
        struct class_dir *dir = to_class_dir(kobj);
        return dir->class->ns_type;
}

static struct kobj_type class_dir_ktype = {
        .release        = class_dir_release,
        .sysfs_ops      = &kobj_sysfs_ops,
        .child_ns_type  = class_dir_child_ns_type
};

static struct kobject *
class_dir_create_and_add(struct class *class, struct kobject *parent_kobj)
{
        struct class_dir *dir;
        int retval;

        dir = kzalloc(sizeof(*dir), GFP_KERNEL);
        if (!dir)
                return ERR_PTR(-ENOMEM);

        dir->class = class;
        kobject_init(&dir->kobj, &class_dir_ktype);

        dir->kobj.kset = &class->p->glue_dirs;

        retval = kobject_add(&dir->kobj, parent_kobj, "%s", class->name);
        if (retval < 0) {
                kobject_put(&dir->kobj);
                return ERR_PTR(retval);
        }
        return &dir->kobj;
}

static DEFINE_MUTEX(gdp_mutex);

static struct kobject *get_device_parent(struct device *dev,
                                         struct device *parent)
{
        if (dev->class) {
                struct kobject *kobj = NULL;
                struct kobject *parent_kobj;
                struct kobject *k;

#ifdef CONFIG_BLOCK
                /* block disks show up in /sys/block */
                if (sysfs_deprecated && dev->class == &block_class) {
                        if (parent && parent->class == &block_class)
                                return &parent->kobj;
                        return &block_class.p->subsys.kobj;
                }
#endif

                /*
                 * If we have no parent, we live in "virtual".
                 * Class-devices with a non class-device as parent, live
                 * in a "glue" directory to prevent namespace collisions.
                 */
                if (parent == NULL)
                        parent_kobj = virtual_device_parent(dev);
                else if (parent->class && !dev->class->ns_type)
                        return &parent->kobj;
                else
                        parent_kobj = &parent->kobj;

                mutex_lock(&gdp_mutex);

                /* find our class-directory at the parent and reference it */
                spin_lock(&dev->class->p->glue_dirs.list_lock);
                list_for_each_entry(k, &dev->class->p->glue_dirs.list, entry)
                        if (k->parent == parent_kobj) {
                                kobj = kobject_get(k);
                                break;
                        }
                spin_unlock(&dev->class->p->glue_dirs.list_lock);
                if (kobj) {
                        mutex_unlock(&gdp_mutex);
                        return kobj;
                }

                /* or create a new class-directory at the parent device */
                k = class_dir_create_and_add(dev->class, parent_kobj);
                /* do not emit an uevent for this simple "glue" directory */
                mutex_unlock(&gdp_mutex);
                return k;
        }

        /* subsystems can specify a default root directory for their devices */
        if (!parent && dev->bus && dev->bus->dev_root)
                return &dev->bus->dev_root->kobj;

        if (parent)
                return &parent->kobj;
        return NULL;
}

static inline bool live_in_glue_dir(struct kobject *kobj,
                                    struct device *dev)
{
        if (!kobj || !dev->class ||
            kobj->kset != &dev->class->p->glue_dirs)
                return false;
        return true;
}

static inline struct kobject *get_glue_dir(struct device *dev)
{
        return dev->kobj.parent;
}

/*
 * make sure cleaning up dir as the last step, we need to make
 * sure .release handler of kobject is run with holding the
 * global lock
 */
static void cleanup_glue_dir(struct device *dev, struct kobject *glue_dir)
{
        unsigned int ref;

        /* see if we live in a "glue" directory */
        if (!live_in_glue_dir(glue_dir, dev))
                return;

        mutex_lock(&gdp_mutex);
        /**
         * There is a race condition between removing glue directory
         * and adding a new device under the glue directory.
         *
         * CPU1:                                         CPU2:
         *
         * device_add()
         *   get_device_parent()
         *     class_dir_create_and_add()
         *       kobject_add_internal()
         *         create_dir()    // create glue_dir
         *
         *                                               device_add()
         *                                                 get_device_parent()
         *                                                   kobject_get() // get glue_dir
         *
         * device_del()
         *   cleanup_glue_dir()
         *     kobject_del(glue_dir)
         *
         *                                               kobject_add()
         *                                                 kobject_add_internal()
         *                                                   create_dir() // in glue_dir
         *                                                     sysfs_create_dir_ns()
         *                                                       kernfs_create_dir_ns(sd)
         *
         *       sysfs_remove_dir() // glue_dir->sd=NULL
         *       sysfs_put()        // free glue_dir->sd
         *
         *                                                         // sd is freed
         *                                                         kernfs_new_node(sd)
         *                                                           kernfs_get(glue_dir)
         *                                                           kernfs_add_one()
         *                                                           kernfs_put()
         *
         * Before CPU1 remove last child device under glue dir, if CPU2 add
         * a new device under glue dir, the glue_dir kobject reference count
         * will be increase to 2 in kobject_get(k). And CPU2 has been called
         * kernfs_create_dir_ns(). Meanwhile, CPU1 call sysfs_remove_dir()
         * and sysfs_put(). This result in glue_dir->sd is freed.
         *
         * Then the CPU2 will see a stale "empty" but still potentially used
         * glue dir around in kernfs_new_node().
         *
         * In order to avoid this happening, we also should make sure that
         * kernfs_node for glue_dir is released in CPU1 only when refcount
         * for glue_dir kobj is 1.
         */
        ref = kref_read(&glue_dir->kref);
        if (!kobject_has_children(glue_dir) && !--ref)
                kobject_del(glue_dir);
        kobject_put(glue_dir);
        mutex_unlock(&gdp_mutex);
}

static int device_add_class_symlinks(struct device *dev)
{
        struct device_node *of_node = dev_of_node(dev);
        int error;

        if (of_node) {
                error = sysfs_create_link(&dev->kobj, of_node_kobj(of_node), "of_node");
                if (error)
                        dev_warn(dev, "Error %d creating of_node link\n",error);
                /* An error here doesn't warrant bringing down the device */
        }

        if (!dev->class)
                return 0;

        error = sysfs_create_link(&dev->kobj,
                                  &dev->class->p->subsys.kobj,
                                  "subsystem");
        if (error)
                goto out_devnode;

        if (dev->parent && device_is_not_partition(dev)) {
                error = sysfs_create_link(&dev->kobj, &dev->parent->kobj,
                                          "device");
                if (error)
                        goto out_subsys;
        }

#ifdef CONFIG_BLOCK
        /* /sys/block has directories and does not need symlinks */
        if (sysfs_deprecated && dev->class == &block_class)
                return 0;
#endif

        /* link in the class directory pointing to the device */
        error = sysfs_create_link(&dev->class->p->subsys.kobj,
                                  &dev->kobj, dev_name(dev));
        if (error)
                goto out_device;

        return 0;

out_device:
        sysfs_remove_link(&dev->kobj, "device");

out_subsys:
        sysfs_remove_link(&dev->kobj, "subsystem");
out_devnode:
        sysfs_remove_link(&dev->kobj, "of_node");
        return error;
}

static void device_remove_class_symlinks(struct device *dev)
{
        if (dev_of_node(dev))
                sysfs_remove_link(&dev->kobj, "of_node");

        if (!dev->class)
                return;

        if (dev->parent && device_is_not_partition(dev))
                sysfs_remove_link(&dev->kobj, "device");
        sysfs_remove_link(&dev->kobj, "subsystem");
#ifdef CONFIG_BLOCK
        if (sysfs_deprecated && dev->class == &block_class)
                return;
#endif
        sysfs_delete_link(&dev->class->p->subsys.kobj, &dev->kobj, dev_name(dev));
}

/**
 * dev_set_name - set a device name
 * @dev: device
 * @fmt: format string for the device's name
 */
int dev_set_name(struct device *dev, const char *fmt, ...)
{
        va_list vargs;
        int err;

        va_start(vargs, fmt);
        err = kobject_set_name_vargs(&dev->kobj, fmt, vargs);
        va_end(vargs);
        return err;
}
EXPORT_SYMBOL_GPL(dev_set_name);

/**
 * device_to_dev_kobj - select a /sys/dev/ directory for the device
 * @dev: device
 *
 * By default we select char/ for new entries.  Setting class->dev_obj
 * to NULL prevents an entry from being created.  class->dev_kobj must
 * be set (or cleared) before any devices are registered to the class
 * otherwise device_create_sys_dev_entry() and
 * device_remove_sys_dev_entry() will disagree about the presence of
 * the link.
 */
static struct kobject *device_to_dev_kobj(struct device *dev)
{
        struct kobject *kobj;

        if (dev->class)
                kobj = dev->class->dev_kobj;
        else
                kobj = sysfs_dev_char_kobj;

        return kobj;
}

static int device_create_sys_dev_entry(struct device *dev)
{
        struct kobject *kobj = device_to_dev_kobj(dev);
        int error = 0;
        char devt_str[15];

        if (kobj) {
                format_dev_t(devt_str, dev->devt);
                error = sysfs_create_link(kobj, &dev->kobj, devt_str);
        }

        return error;
}

static void device_remove_sys_dev_entry(struct device *dev)
{
        struct kobject *kobj = device_to_dev_kobj(dev);
        char devt_str[15];

        if (kobj) {
                format_dev_t(devt_str, dev->devt);
                sysfs_remove_link(kobj, devt_str);
        }
}

static int device_private_init(struct device *dev)
{
        dev->p = kzalloc(sizeof(*dev->p), GFP_KERNEL);
        if (!dev->p)
                return -ENOMEM;
        dev->p->device = dev;
        klist_init(&dev->p->klist_children, klist_children_get,
                   klist_children_put);
        INIT_LIST_HEAD(&dev->p->deferred_probe);
        return 0;
}

/**
 * device_add - add device to device hierarchy.
 * @dev: device.
 *
 * This is part 2 of device_register(), though may be called
 * separately _iff_ device_initialize() has been called separately.
 *
 * This adds @dev to the kobject hierarchy via kobject_add(), adds it
 * to the global and sibling lists for the device, then
 * adds it to the other relevant subsystems of the driver model.
 *
 * Do not call this routine or device_register() more than once for
 * any device structure.  The driver model core is not designed to work
 * with devices that get unregistered and then spring back to life.
 * (Among other things, it's very hard to guarantee that all references
 * to the previous incarnation of @dev have been dropped.)  Allocate
 * and register a fresh new struct device instead.
 *
 * NOTE: _Never_ directly free @dev after calling this function, even
 * if it returned an error! Always use put_device() to give up your
 * reference instead.
 *
 * Rule of thumb is: if device_add() succeeds, you should call
 * device_del() when you want to get rid of it. If device_add() has
 * *not* succeeded, use *only* put_device() to drop the reference
 * count.
 */
int device_add(struct device *dev)
{
        struct device *parent;
        struct kobject *kobj;
        struct class_interface *class_intf;
        int error = -EINVAL;
        struct kobject *glue_dir = NULL;

        dev = get_device(dev);
        if (!dev)
                goto done;

        if (!dev->p) {
                error = device_private_init(dev);
                if (error)
                        goto done;
        }

        /*
         * for statically allocated devices, which should all be converted
         * some day, we need to initialize the name. We prevent reading back
         * the name, and force the use of dev_name()
         */
        if (dev->init_name) {
                dev_set_name(dev, "%s", dev->init_name);
                dev->init_name = NULL;
        }

        /* subsystems can specify simple device enumeration */
        if (!dev_name(dev) && dev->bus && dev->bus->dev_name)
                dev_set_name(dev, "%s%u", dev->bus->dev_name, dev->id);

        if (!dev_name(dev)) {
                error = -EINVAL;
                goto name_error;
        }

        pr_debug("device: '%s': %s\n", dev_name(dev), __func__);

        parent = get_device(dev->parent);
        kobj = get_device_parent(dev, parent);
        if (IS_ERR(kobj)) {
                error = PTR_ERR(kobj);
                goto parent_error;
        }
        if (kobj)
                dev->kobj.parent = kobj;

        /* use parent numa_node */
        if (parent && (dev_to_node(dev) == NUMA_NO_NODE))
                set_dev_node(dev, dev_to_node(parent));

        /* first, register with generic layer. */
        /* we require the name to be set before, and pass NULL */
        error = kobject_add(&dev->kobj, dev->kobj.parent, NULL);
        if (error) {
                glue_dir = get_glue_dir(dev);
                goto Error;
        }

        /* notify platform of device entry */
        error = device_platform_notify(dev, KOBJ_ADD);
        if (error)
                goto platform_error;

        error = device_create_file(dev, &dev_attr_uevent);
        if (error)
                goto attrError;

        error = device_add_class_symlinks(dev);
        if (error)
                goto SymlinkError;
        error = device_add_attrs(dev);
        if (error)
                goto AttrsError;
        error = bus_add_device(dev);
        if (error)
                goto BusError;
        error = dpm_sysfs_add(dev);
        if (error)
                goto DPMError;
        device_pm_add(dev);

        if (MAJOR(dev->devt)) {
                error = device_create_file(dev, &dev_attr_dev);
                if (error)
                        goto DevAttrError;

                error = device_create_sys_dev_entry(dev);
                if (error)
                        goto SysEntryError;

                devtmpfs_create_node(dev);
        }

        /* Notify clients of device addition.  This call must come
         * after dpm_sysfs_add() and before kobject_uevent().
         */
        if (dev->bus)
                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
                                             BUS_NOTIFY_ADD_DEVICE, dev);

        kobject_uevent(&dev->kobj, KOBJ_ADD);

        /*
         * Check if any of the other devices (consumers) have been waiting for
         * this device (supplier) to be added so that they can create a device
         * link to it.
         *
         * This needs to happen after device_pm_add() because device_link_add()
         * requires the supplier be registered before it's called.
         *
         * But this also needs to happen before bus_probe_device() to make sure
         * waiting consumers can link to it before the driver is bound to the
         * device and the driver sync_state callback is called for this device.
         */
        if (dev->fwnode && !dev->fwnode->dev) {
                dev->fwnode->dev = dev;
                fw_devlink_link_device(dev);
        }

        bus_probe_device(dev);
        if (parent)
                klist_add_tail(&dev->p->knode_parent,
                               &parent->p->klist_children);

        if (dev->class) {
                mutex_lock(&dev->class->p->mutex);
                /* tie the class to the device */
                klist_add_tail(&dev->p->knode_class,
                               &dev->class->p->klist_devices);

                /* notify any interfaces that the device is here */
                list_for_each_entry(class_intf,
                                    &dev->class->p->interfaces, node)
                        if (class_intf->add_dev)
                                class_intf->add_dev(dev, class_intf);
                mutex_unlock(&dev->class->p->mutex);
        }
done:
        put_device(dev);
        return error;
 SysEntryError:
        if (MAJOR(dev->devt))
                device_remove_file(dev, &dev_attr_dev);
 DevAttrError:
        device_pm_remove(dev);
        dpm_sysfs_remove(dev);
 DPMError:
        bus_remove_device(dev);
 BusError:
        device_remove_attrs(dev);
 AttrsError:
        device_remove_class_symlinks(dev);
 SymlinkError:
        device_remove_file(dev, &dev_attr_uevent);
 attrError:
        device_platform_notify(dev, KOBJ_REMOVE);
platform_error:
        kobject_uevent(&dev->kobj, KOBJ_REMOVE);
        glue_dir = get_glue_dir(dev);
        kobject_del(&dev->kobj);
 Error:
        cleanup_glue_dir(dev, glue_dir);
parent_error:
        put_device(parent);
name_error:
        kfree(dev->p);
        dev->p = NULL;
        goto done;
}
EXPORT_SYMBOL_GPL(device_add);

/**
 * device_register - register a device with the system.
 * @dev: pointer to the device structure
 *
 * This happens in two clean steps - initialize the device
 * and add it to the system. The two steps can be called
 * separately, but this is the easiest and most common.
 * I.e. you should only call the two helpers separately if
 * have a clearly defined need to use and refcount the device
 * before it is added to the hierarchy.
 *
 * For more information, see the kerneldoc for device_initialize()
 * and device_add().
 *
 * NOTE: _Never_ directly free @dev after calling this function, even
 * if it returned an error! Always use put_device() to give up the
 * reference initialized in this function instead.
 */
int device_register(struct device *dev)
{
        device_initialize(dev);
        return device_add(dev);
}

EXPORT_SYMBOL_GPL(device_register);

/**
 * get_device - increment reference count for device.
 * @dev: device.
 *
 * This simply forwards the call to kobject_get(), though
 * we do take care to provide for the case that we get a NULL
 * pointer passed in.
 */
struct device *get_device(struct device *dev)
{
        return dev ? kobj_to_dev(kobject_get(&dev->kobj)) : NULL;
}
EXPORT_SYMBOL_GPL(get_device);

/**
 * put_device - decrement reference count.
 * @dev: device in question.
 */
void put_device(struct device *dev)
{
        /* might_sleep(); */
        if (dev)
                kobject_put(&dev->kobj);
}
EXPORT_SYMBOL_GPL(put_device);

bool kill_device(struct device *dev)
{
        /*
         * Require the device lock and set the "dead" flag to guarantee that
         * the update behavior is consistent with the other bitfields near
         * it and that we cannot have an asynchronous probe routine trying
         * to run while we are tearing out the bus/class/sysfs from
         * underneath the device.
         */
        lockdep_assert_held(&dev->mutex);

        if (dev->p->dead)
                return false;
        dev->p->dead = true;
        return true;
}
EXPORT_SYMBOL_GPL(kill_device);

/**
 * device_del - delete device from system.
 * @dev: device.
 *
 * This is the first part of the device unregistration
 * sequence. This removes the device from the lists we control
 * from here, has it removed from the other driver model
 * subsystems it was added to in device_add(), and removes it
 * from the kobject hierarchy.
 *
 * NOTE: this should be called manually _iff_ device_add() was
 * also called manually.
 */
void device_del(struct device *dev)
{
        struct device *parent = dev->parent;
        struct kobject *glue_dir = NULL;
        struct class_interface *class_intf;

        device_lock(dev);
        kill_device(dev);
        device_unlock(dev);

        if (dev->fwnode && dev->fwnode->dev == dev)
                dev->fwnode->dev = NULL;

        /* Notify clients of device removal.  This call must come
         * before dpm_sysfs_remove().
         */
        if (dev->bus)
                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
                                             BUS_NOTIFY_DEL_DEVICE, dev);

        dpm_sysfs_remove(dev);
        if (parent)
                klist_del(&dev->p->knode_parent);
        if (MAJOR(dev->devt)) {
                devtmpfs_delete_node(dev);
                device_remove_sys_dev_entry(dev);
                device_remove_file(dev, &dev_attr_dev);
        }
        if (dev->class) {
                device_remove_class_symlinks(dev);

                mutex_lock(&dev->class->p->mutex);
                /* notify any interfaces that the device is now gone */
                list_for_each_entry(class_intf,
                                    &dev->class->p->interfaces, node)
                        if (class_intf->remove_dev)
                                class_intf->remove_dev(dev, class_intf);
                /* remove the device from the class list */
                klist_del(&dev->p->knode_class);
                mutex_unlock(&dev->class->p->mutex);
        }
        device_remove_file(dev, &dev_attr_uevent);
        device_remove_attrs(dev);
        bus_remove_device(dev);
        device_pm_remove(dev);
        driver_deferred_probe_del(dev);
        device_platform_notify(dev, KOBJ_REMOVE);
        device_remove_properties(dev);
        device_links_purge(dev);

        if (dev->bus)
                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
                                             BUS_NOTIFY_REMOVED_DEVICE, dev);
        kobject_uevent(&dev->kobj, KOBJ_REMOVE);
        glue_dir = get_glue_dir(dev);
        kobject_del(&dev->kobj);
        cleanup_glue_dir(dev, glue_dir);
        put_device(parent);
}
EXPORT_SYMBOL_GPL(device_del);

/**
 * device_unregister - unregister device from system.
 * @dev: device going away.
 *
 * We do this in two parts, like we do device_register(). First,
 * we remove it from all the subsystems with device_del(), then
 * we decrement the reference count via put_device(). If that
 * is the final reference count, the device will be cleaned up
 * via device_release() above. Otherwise, the structure will
 * stick around until the final reference to the device is dropped.
 */
void device_unregister(struct device *dev)
{
        pr_debug("device: '%s': %s\n", dev_name(dev), __func__);
        device_del(dev);
        put_device(dev);
}
EXPORT_SYMBOL_GPL(device_unregister);

static struct device *prev_device(struct klist_iter *i)
{
        struct klist_node *n = klist_prev(i);
        struct device *dev = NULL;
        struct device_private *p;

        if (n) {
                p = to_device_private_parent(n);
                dev = p->device;
        }
        return dev;
}

static struct device *next_device(struct klist_iter *i)
{
        struct klist_node *n = klist_next(i);
        struct device *dev = NULL;
        struct device_private *p;

        if (n) {
                p = to_device_private_parent(n);
                dev = p->device;
        }
        return dev;
}

/**
 * device_get_devnode - path of device node file
 * @dev: device
 * @mode: returned file access mode
 * @uid: returned file owner
 * @gid: returned file group
 * @tmp: possibly allocated string
 *
 * Return the relative path of a possible device node.
 * Non-default names may need to allocate a memory to compose
 * a name. This memory is returned in tmp and needs to be
 * freed by the caller.
 */
const char *device_get_devnode(struct device *dev,
                               umode_t *mode, kuid_t *uid, kgid_t *gid,
                               const char **tmp)
{
        char *s;

        *tmp = NULL;

        /* the device type may provide a specific name */
        if (dev->type && dev->type->devnode)
                *tmp = dev->type->devnode(dev, mode, uid, gid);
        if (*tmp)
                return *tmp;

        /* the class may provide a specific name */
        if (dev->class && dev->class->devnode)
                *tmp = dev->class->devnode(dev, mode);
        if (*tmp)
                return *tmp;

        /* return name without allocation, tmp == NULL */
        if (strchr(dev_name(dev), '!') == NULL)
                return dev_name(dev);

        /* replace '!' in the name with '/' */
        s = kstrdup(dev_name(dev), GFP_KERNEL);
        if (!s)
                return NULL;
        strreplace(s, '!', '/');
        return *tmp = s;
}

/**
 * device_for_each_child - device child iterator.
 * @parent: parent struct device.
 * @fn: function to be called for each device.
 * @data: data for the callback.
 *
 * Iterate over @parent's child devices, and call @fn for each,
 * passing it @data.
 *
 * We check the return of @fn each time. If it returns anything
 * other than 0, we break out and return that value.
 */
int device_for_each_child(struct device *parent, void *data,
                          int (*fn)(struct device *dev, void *data))
{
        struct klist_iter i;
        struct device *child;
        int error = 0;

        if (!parent->p)
                return 0;

        klist_iter_init(&parent->p->klist_children, &i);
        while (!error && (child = next_device(&i)))
                error = fn(child, data);
        klist_iter_exit(&i);
        return error;
}
EXPORT_SYMBOL_GPL(device_for_each_child);

/**
 * device_for_each_child_reverse - device child iterator in reversed order.
 * @parent: parent struct device.
 * @fn: function to be called for each device.
 * @data: data for the callback.
 *
 * Iterate over @parent's child devices, and call @fn for each,
 * passing it @data.
 *
 * We check the return of @fn each time. If it returns anything
 * other than 0, we break out and return that value.
 */
int device_for_each_child_reverse(struct device *parent, void *data,
                                  int (*fn)(struct device *dev, void *data))
{
        struct klist_iter i;
        struct device *child;
        int error = 0;

        if (!parent->p)
                return 0;

        klist_iter_init(&parent->p->klist_children, &i);
        while ((child = prev_device(&i)) && !error)
                error = fn(child, data);
        klist_iter_exit(&i);
        return error;
}
EXPORT_SYMBOL_GPL(device_for_each_child_reverse);

/**
 * device_find_child - device iterator for locating a particular device.
 * @parent: parent struct device
 * @match: Callback function to check device
 * @data: Data to pass to match function
 *
 * This is similar to the device_for_each_child() 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 and a reference to the
 * current device can be obtained, this function will return to the caller
 * and not iterate over any more devices.
 *
 * NOTE: you will need to drop the reference with put_device() after use.
 */
struct device *device_find_child(struct device *parent, void *data,
                                 int (*match)(struct device *dev, void *data))
{
        struct klist_iter i;
        struct device *child;

        if (!parent)
                return NULL;

        klist_iter_init(&parent->p->klist_children, &i);
        while ((child = next_device(&i)))
                if (match(child, data) && get_device(child))
                        break;
        klist_iter_exit(&i);
        return child;
}
EXPORT_SYMBOL_GPL(device_find_child);

/**
 * device_find_child_by_name - device iterator for locating a child device.
 * @parent: parent struct device
 * @name: name of the child device
 *
 * This is similar to the device_find_child() function above, but it
 * returns a reference to a device that has the name @name.
 *
 * NOTE: you will need to drop the reference with put_device() after use.
 */
struct device *device_find_child_by_name(struct device *parent,
                                         const char *name)
{
        struct klist_iter i;
        struct device *child;

        if (!parent)
                return NULL;

        klist_iter_init(&parent->p->klist_children, &i);
        while ((child = next_device(&i)))
                if (!strcmp(dev_name(child), name) && get_device(child))
                        break;
        klist_iter_exit(&i);
        return child;
}
EXPORT_SYMBOL_GPL(device_find_child_by_name);

int __init devices_init(void)
{
        devices_kset = kset_create_and_add("devices", &device_uevent_ops, NULL);
        if (!devices_kset)
                return -ENOMEM;
        dev_kobj = kobject_create_and_add("dev", NULL);
        if (!dev_kobj)
                goto dev_kobj_err;
        sysfs_dev_block_kobj = kobject_create_and_add("block", dev_kobj);
        if (!sysfs_dev_block_kobj)
                goto block_kobj_err;
        sysfs_dev_char_kobj = kobject_create_and_add("char", dev_kobj);
        if (!sysfs_dev_char_kobj)
                goto char_kobj_err;

        return 0;

 char_kobj_err:
        kobject_put(sysfs_dev_block_kobj);
 block_kobj_err:
        kobject_put(dev_kobj);
 dev_kobj_err:
        kset_unregister(devices_kset);
        return -ENOMEM;
}

static int device_check_offline(struct device *dev, void *not_used)
{
        int ret;

        ret = device_for_each_child(dev, NULL, device_check_offline);
        if (ret)
                return ret;

        return device_supports_offline(dev) && !dev->offline ? -EBUSY : 0;
}

/**
 * device_offline - Prepare the device for hot-removal.
 * @dev: Device to be put offline.
 *
 * Execute the device bus type's .offline() callback, if present, to prepare
 * the device for a subsequent hot-removal.  If that succeeds, the device must
 * not be used until either it is removed or its bus type's .online() callback
 * is executed.
 *
 * Call under device_hotplug_lock.
 */
int device_offline(struct device *dev)
{
        int ret;

        if (dev->offline_disabled)
                return -EPERM;

        ret = device_for_each_child(dev, NULL, device_check_offline);
        if (ret)
                return ret;

        device_lock(dev);
        if (device_supports_offline(dev)) {
                if (dev->offline) {
                        ret = 1;
                } else {
                        ret = dev->bus->offline(dev);
                        if (!ret) {
                                kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
                                dev->offline = true;
                        }
                }
        }
        device_unlock(dev);

        return ret;
}

/**
 * device_online - Put the device back online after successful device_offline().
 * @dev: Device to be put back online.
 *
 * If device_offline() has been successfully executed for @dev, but the device
 * has not been removed subsequently, execute its bus type's .online() callback
 * to indicate that the device can be used again.
 *
 * Call under device_hotplug_lock.
 */
int device_online(struct device *dev)
{
        int ret = 0;

        device_lock(dev);
        if (device_supports_offline(dev)) {
                if (dev->offline) {
                        ret = dev->bus->online(dev);
                        if (!ret) {
                                kobject_uevent(&dev->kobj, KOBJ_ONLINE);
                                dev->offline = false;
                        }
                } else {
                        ret = 1;
                }
        }
        device_unlock(dev);

        return ret;
}

struct root_device {
        struct device dev;
        struct module *owner;
};

static inline struct root_device *to_root_device(struct device *d)
{
        return container_of(d, struct root_device, dev);
}

static void root_device_release(struct device *dev)
{
        kfree(to_root_device(dev));
}

/**
 * __root_device_register - allocate and register a root device
 * @name: root device name
 * @owner: owner module of the root device, usually THIS_MODULE
 *
 * This function allocates a root device and registers it
 * using device_register(). In order to free the returned
 * device, use root_device_unregister().
 *
 * Root devices are dummy devices which allow other devices
 * to be grouped under /sys/devices. Use this function to
 * allocate a root device and then use it as the parent of
 * any device which should appear under /sys/devices/{name}
 *
 * The /sys/devices/{name} directory will also contain a
 * 'module' symlink which points to the @owner directory
 * in sysfs.
 *
 * Returns &struct device pointer on success, or ERR_PTR() on error.
 *
 * Note: You probably want to use root_device_register().
 */
struct device *__root_device_register(const char *name, struct module *owner)
{
        struct root_device *root;
        int err = -ENOMEM;

        root = kzalloc(sizeof(struct root_device), GFP_KERNEL);
        if (!root)
                return ERR_PTR(err);

        err = dev_set_name(&root->dev, "%s", name);
        if (err) {
                kfree(root);
                return ERR_PTR(err);
        }

        root->dev.release = root_device_release;

        err = device_register(&root->dev);
        if (err) {
                put_device(&root->dev);
                return ERR_PTR(err);
        }

#ifdef CONFIG_MODULES   /* gotta find a "cleaner" way to do this */
        if (owner) {
                struct module_kobject *mk = &owner->mkobj;

                err = sysfs_create_link(&root->dev.kobj, &mk->kobj, "module");
                if (err) {
                        device_unregister(&root->dev);
                        return ERR_PTR(err);
                }
                root->owner = owner;
        }
#endif

        return &root->dev;
}
EXPORT_SYMBOL_GPL(__root_device_register);

/**
 * root_device_unregister - unregister and free a root device
 * @dev: device going away
 *
 * This function unregisters and cleans up a device that was created by
 * root_device_register().
 */
void root_device_unregister(struct device *dev)
{
        struct root_device *root = to_root_device(dev);

        if (root->owner)
                sysfs_remove_link(&root->dev.kobj, "module");

        device_unregister(dev);
}
EXPORT_SYMBOL_GPL(root_device_unregister);


static void device_create_release(struct device *dev)
{
        pr_debug("device: '%s': %s\n", dev_name(dev), __func__);
        kfree(dev);
}

static __printf(6, 0) struct device *
device_create_groups_vargs(struct class *class, struct device *parent,
                           dev_t devt, void *drvdata,
                           const struct attribute_group **groups,
                           const char *fmt, va_list args)
{
        struct device *dev = NULL;
        int retval = -ENODEV;

        if (class == NULL || IS_ERR(class))
                goto error;

        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
        if (!dev) {
                retval = -ENOMEM;
                goto error;
        }

        device_initialize(dev);
        dev->devt = devt;
        dev->class = class;
        dev->parent = parent;
        dev->groups = groups;
        dev->release = device_create_release;
        dev_set_drvdata(dev, drvdata);

        retval = kobject_set_name_vargs(&dev->kobj, fmt, args);
        if (retval)
                goto error;

        retval = device_add(dev);
        if (retval)
                goto error;

        return dev;

error:
        put_device(dev);
        return ERR_PTR(retval);
}

/**
 * device_create - creates a device and registers it with sysfs
 * @class: pointer to the struct class that this device should be registered to
 * @parent: pointer to the parent struct device of this new device, if any
 * @devt: the dev_t for the char device to be added
 * @drvdata: the data to be added to the device for callbacks
 * @fmt: string for the device's name
 *
 * This function can be used by char device classes.  A struct device
 * will be created in sysfs, registered to the specified class.
 *
 * A "dev" file will be created, showing the dev_t for the device, if
 * the dev_t is not 0,0.
 * If a pointer to a parent struct device is passed in, the newly created
 * struct device will be a child of that device in sysfs.
 * The pointer to the struct device will be returned from the call.
 * Any further sysfs files that might be required can be created using this
 * pointer.
 *
 * Returns &struct device pointer on success, or ERR_PTR() on error.
 *
 * Note: the struct class passed to this function must have previously
 * been created with a call to class_create().
 */
struct device *device_create(struct class *class, struct device *parent,
                             dev_t devt, void *drvdata, const char *fmt, ...)
{
        va_list vargs;
        struct device *dev;

        va_start(vargs, fmt);
        dev = device_create_groups_vargs(class, parent, devt, drvdata, NULL,
                                          fmt, vargs);
        va_end(vargs);
        return dev;
}
EXPORT_SYMBOL_GPL(device_create);

/**
 * device_create_with_groups - creates a device and registers it with sysfs
 * @class: pointer to the struct class that this device should be registered to
 * @parent: pointer to the parent struct device of this new device, if any
 * @devt: the dev_t for the char device to be added
 * @drvdata: the data to be added to the device for callbacks
 * @groups: NULL-terminated list of attribute groups to be created
 * @fmt: string for the device's name
 *
 * This function can be used by char device classes.  A struct device
 * will be created in sysfs, registered to the specified class.
 * Additional attributes specified in the groups parameter will also
 * be created automatically.
 *
 * A "dev" file will be created, showing the dev_t for the device, if
 * the dev_t is not 0,0.
 * If a pointer to a parent struct device is passed in, the newly created
 * struct device will be a child of that device in sysfs.
 * The pointer to the struct device will be returned from the call.
 * Any further sysfs files that might be required can be created using this
 * pointer.
 *
 * Returns &struct device pointer on success, or ERR_PTR() on error.
 *
 * Note: the struct class passed to this function must have previously
 * been created with a call to class_create().
 */
struct device *device_create_with_groups(struct class *class,
                                         struct device *parent, dev_t devt,
                                         void *drvdata,
                                         const struct attribute_group **groups,
                                         const char *fmt, ...)
{
        va_list vargs;
        struct device *dev;

        va_start(vargs, fmt);
        dev = device_create_groups_vargs(class, parent, devt, drvdata, groups,
                                         fmt, vargs);
        va_end(vargs);
        return dev;
}
EXPORT_SYMBOL_GPL(device_create_with_groups);

/**
 * device_destroy - removes a device that was created with device_create()
 * @class: pointer to the struct class that this device was registered with
 * @devt: the dev_t of the device that was previously registered
 *
 * This call unregisters and cleans up a device that was created with a
 * call to device_create().
 */
void device_destroy(struct class *class, dev_t devt)
{
        struct device *dev;

        dev = class_find_device_by_devt(class, devt);
        if (dev) {
                put_device(dev);
                device_unregister(dev);
        }
}
EXPORT_SYMBOL_GPL(device_destroy);

/**
 * device_rename - renames a device
 * @dev: the pointer to the struct device to be renamed
 * @new_name: the new name of the device
 *
 * It is the responsibility of the caller to provide mutual
 * exclusion between two different calls of device_rename
 * on the same device to ensure that new_name is valid and
 * won't conflict with other devices.
 *
 * Note: Don't call this function.  Currently, the networking layer calls this
 * function, but that will change.  The following text from Kay Sievers offers
 * some insight:
 *
 * Renaming devices is racy at many levels, symlinks and other stuff are not
 * replaced atomically, and you get a "move" uevent, but it's not easy to
 * connect the event to the old and new device. Device nodes are not renamed at
 * all, there isn't even support for that in the kernel now.
 *
 * In the meantime, during renaming, your target name might be taken by another
 * driver, creating conflicts. Or the old name is taken directly after you
 * renamed it -- then you get events for the same DEVPATH, before you even see
 * the "move" event. It's just a mess, and nothing new should ever rely on
 * kernel device renaming. Besides that, it's not even implemented now for
 * other things than (driver-core wise very simple) network devices.
 *
 * We are currently about to change network renaming in udev to completely
 * disallow renaming of devices in the same namespace as the kernel uses,
 * because we can't solve the problems properly, that arise with swapping names
 * of multiple interfaces without races. Means, renaming of eth[0-9]* will only
 * be allowed to some other name than eth[0-9]*, for the aforementioned
 * reasons.
 *
 * Make up a "real" name in the driver before you register anything, or add
 * some other attributes for userspace to find the device, or use udev to add
 * symlinks -- but never rename kernel devices later, it's a complete mess. We
 * don't even want to get into that and try to implement the missing pieces in
 * the core. We really have other pieces to fix in the driver core mess. :)
 */
int device_rename(struct device *dev, const char *new_name)
{
        struct kobject *kobj = &dev->kobj;
        char *old_device_name = NULL;
        int error;

        dev = get_device(dev);
        if (!dev)
                return -EINVAL;

        dev_dbg(dev, "renaming to %s\n", new_name);

        old_device_name = kstrdup(dev_name(dev), GFP_KERNEL);
        if (!old_device_name) {
                error = -ENOMEM;
                goto out;
        }

        if (dev->class) {
                error = sysfs_rename_link_ns(&dev->class->p->subsys.kobj,
                                             kobj, old_device_name,
                                             new_name, kobject_namespace(kobj));
                if (error)
                        goto out;
        }

        error = kobject_rename(kobj, new_name);
        if (error)
                goto out;

out:
        put_device(dev);

        kfree(old_device_name);

        return error;
}
EXPORT_SYMBOL_GPL(device_rename);

static int device_move_class_links(struct device *dev,
                                   struct device *old_parent,
                                   struct device *new_parent)
{
        int error = 0;

        if (old_parent)
                sysfs_remove_link(&dev->kobj, "device");
        if (new_parent)
                error = sysfs_create_link(&dev->kobj, &new_parent->kobj,
                                          "device");
        return error;
}

/**
 * device_move - moves a device to a new parent
 * @dev: the pointer to the struct device to be moved
 * @new_parent: the new parent of the device (can be NULL)
 * @dpm_order: how to reorder the dpm_list
 */
int device_move(struct device *dev, struct device *new_parent,
                enum dpm_order dpm_order)
{
        int error;
        struct device *old_parent;
        struct kobject *new_parent_kobj;

        dev = get_device(dev);
        if (!dev)
                return -EINVAL;

        device_pm_lock();
        new_parent = get_device(new_parent);
        new_parent_kobj = get_device_parent(dev, new_parent);
        if (IS_ERR(new_parent_kobj)) {
                error = PTR_ERR(new_parent_kobj);
                put_device(new_parent);
                goto out;
        }

        pr_debug("device: '%s': %s: moving to '%s'\n", dev_name(dev),
                 __func__, new_parent ? dev_name(new_parent) : "<NULL>");
        error = kobject_move(&dev->kobj, new_parent_kobj);
        if (error) {
                cleanup_glue_dir(dev, new_parent_kobj);
                put_device(new_parent);
                goto out;
        }
        old_parent = dev->parent;
        dev->parent = new_parent;
        if (old_parent)
                klist_remove(&dev->p->knode_parent);
        if (new_parent) {
                klist_add_tail(&dev->p->knode_parent,
                               &new_parent->p->klist_children);
                set_dev_node(dev, dev_to_node(new_parent));
        }

        if (dev->class) {
                error = device_move_class_links(dev, old_parent, new_parent);
                if (error) {
                        /* We ignore errors on cleanup since we're hosed anyway... */
                        device_move_class_links(dev, new_parent, old_parent);
                        if (!kobject_move(&dev->kobj, &old_parent->kobj)) {
                                if (new_parent)
                                        klist_remove(&dev->p->knode_parent);
                                dev->parent = old_parent;
                                if (old_parent) {
                                        klist_add_tail(&dev->p->knode_parent,
                                                       &old_parent->p->klist_children);
                                        set_dev_node(dev, dev_to_node(old_parent));
                                }
                        }
                        cleanup_glue_dir(dev, new_parent_kobj);
                        put_device(new_parent);
                        goto out;
                }
        }
        switch (dpm_order) {
        case DPM_ORDER_NONE:
                break;
        case DPM_ORDER_DEV_AFTER_PARENT:
                device_pm_move_after(dev, new_parent);
                devices_kset_move_after(dev, new_parent);
                break;
        case DPM_ORDER_PARENT_BEFORE_DEV:
                device_pm_move_before(new_parent, dev);
                devices_kset_move_before(new_parent, dev);
                break;
        case DPM_ORDER_DEV_LAST:
                device_pm_move_last(dev);
                devices_kset_move_last(dev);
                break;
        }

        put_device(old_parent);
out:
        device_pm_unlock();
        put_device(dev);
        return error;
}
EXPORT_SYMBOL_GPL(device_move);

static int device_attrs_change_owner(struct device *dev, kuid_t kuid,
                                     kgid_t kgid)
{
        struct kobject *kobj = &dev->kobj;
        struct class *class = dev->class;
        const struct device_type *type = dev->type;
        int error;

        if (class) {
                /*
                 * Change the device groups of the device class for @dev to
                 * @kuid/@kgid.
                 */
                error = sysfs_groups_change_owner(kobj, class->dev_groups, kuid,
                                                  kgid);
                if (error)
                        return error;
        }

        if (type) {
                /*
                 * Change the device groups of the device type for @dev to
                 * @kuid/@kgid.
                 */
                error = sysfs_groups_change_owner(kobj, type->groups, kuid,
                                                  kgid);
                if (error)
                        return error;
        }

        /* Change the device groups of @dev to @kuid/@kgid. */
        error = sysfs_groups_change_owner(kobj, dev->groups, kuid, kgid);
        if (error)
                return error;

        if (device_supports_offline(dev) && !dev->offline_disabled) {
                /* Change online device attributes of @dev to @kuid/@kgid. */
                error = sysfs_file_change_owner(kobj, dev_attr_online.attr.name,
                                                kuid, kgid);
                if (error)
                        return error;
        }

        return 0;
}

/**
 * device_change_owner - change the owner of an existing device.
 * @dev: device.
 * @kuid: new owner's kuid
 * @kgid: new owner's kgid
 *
 * This changes the owner of @dev and its corresponding sysfs entries to
 * @kuid/@kgid. This function closely mirrors how @dev was added via driver
 * core.
 *
 * Returns 0 on success or error code on failure.
 */
int device_change_owner(struct device *dev, kuid_t kuid, kgid_t kgid)
{
        int error;
        struct kobject *kobj = &dev->kobj;

        dev = get_device(dev);
        if (!dev)
                return -EINVAL;

        /*
         * Change the kobject and the default attributes and groups of the
         * ktype associated with it to @kuid/@kgid.
         */
        error = sysfs_change_owner(kobj, kuid, kgid);
        if (error)
                goto out;

        /*
         * Change the uevent file for @dev to the new owner. The uevent file
         * was created in a separate step when @dev got added and we mirror
         * that step here.
         */
        error = sysfs_file_change_owner(kobj, dev_attr_uevent.attr.name, kuid,
                                        kgid);
        if (error)
                goto out;

        /*
         * Change the device groups, the device groups associated with the
         * device class, and the groups associated with the device type of @dev
         * to @kuid/@kgid.
         */
        error = device_attrs_change_owner(dev, kuid, kgid);
        if (error)
                goto out;

        error = dpm_sysfs_change_owner(dev, kuid, kgid);
        if (error)
                goto out;

#ifdef CONFIG_BLOCK
        if (sysfs_deprecated && dev->class == &block_class)
                goto out;
#endif

        /*
         * Change the owner of the symlink located in the class directory of
         * the device class associated with @dev which points to the actual
         * directory entry for @dev to @kuid/@kgid. This ensures that the
         * symlink shows the same permissions as its target.
         */
        error = sysfs_link_change_owner(&dev->class->p->subsys.kobj, &dev->kobj,
                                        dev_name(dev), kuid, kgid);
        if (error)
                goto out;

out:
        put_device(dev);
        return error;
}
EXPORT_SYMBOL_GPL(device_change_owner);

/**
 * device_shutdown - call ->shutdown() on each device to shutdown.
 */
void device_shutdown(void)
{
        struct device *dev, *parent;

        wait_for_device_probe();
        device_block_probing();

        cpufreq_suspend();

        spin_lock(&devices_kset->list_lock);
        /*