// 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/sched/mm.h>
#include <linux/sysfs.h>
#include <linux/dma-map-ops.h> /* for dma_default_coherent */

#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(deferred_sync);
static unsigned int defer_sync_state_count = 1;
static DEFINE_MUTEX(fwnode_link_lock);
static bool fw_devlink_is_permissive(void);
static bool fw_devlink_drv_reg_done;

/**
 * fwnode_link_add - Create a link between two fwnode_handles.
 * @con: Consumer end of the link.
 * @sup: Supplier end of the link.
 *
 * Create a fwnode link between fwnode handles @con and @sup. The fwnode link
 * represents the detail that the firmware lists @sup fwnode as supplying a
 * resource to @con.
 *
 * The driver core will use the fwnode link to create a device link between the
 * two device objects corresponding to @con and @sup when they are created. The
 * driver core will automatically delete the fwnode link between @con and @sup
 * after doing that.
 *
 * Attempts to create duplicate links between the same pair of fwnode handles
 * are ignored and there is no reference counting.
 */
int fwnode_link_add(struct fwnode_handle *con, struct fwnode_handle *sup)
{
        struct fwnode_link *link;
        int ret = 0;

        mutex_lock(&fwnode_link_lock);

        list_for_each_entry(link, &sup->consumers, s_hook)
                if (link->consumer == con)
                        goto out;

        link = kzalloc(sizeof(*link), GFP_KERNEL);
        if (!link) {
                ret = -ENOMEM;
                goto out;
        }

        link->supplier = sup;
        INIT_LIST_HEAD(&link->s_hook);
        link->consumer = con;
        INIT_LIST_HEAD(&link->c_hook);

        list_add(&link->s_hook, &sup->consumers);
        list_add(&link->c_hook, &con->suppliers);
out:
        mutex_unlock(&fwnode_link_lock);

        return ret;
}

/**
 * fwnode_links_purge_suppliers - Delete all supplier links of fwnode_handle.
 * @fwnode: fwnode whose supplier links need to be deleted
 *
 * Deletes all supplier links connecting directly to @fwnode.
 */
static void fwnode_links_purge_suppliers(struct fwnode_handle *fwnode)
{
        struct fwnode_link *link, *tmp;

        mutex_lock(&fwnode_link_lock);
        list_for_each_entry_safe(link, tmp, &fwnode->suppliers, c_hook) {
                list_del(&link->s_hook);
                list_del(&link->c_hook);
                kfree(link);
        }
        mutex_unlock(&fwnode_link_lock);
}

/**
 * fwnode_links_purge_consumers - Delete all consumer links of fwnode_handle.
 * @fwnode: fwnode whose consumer links need to be deleted
 *
 * Deletes all consumer links connecting directly to @fwnode.
 */
static void fwnode_links_purge_consumers(struct fwnode_handle *fwnode)
{
        struct fwnode_link *link, *tmp;

        mutex_lock(&fwnode_link_lock);
        list_for_each_entry_safe(link, tmp, &fwnode->consumers, s_hook) {
                list_del(&link->s_hook);
                list_del(&link->c_hook);
                kfree(link);
        }
        mutex_unlock(&fwnode_link_lock);
}

/**
 * fwnode_links_purge - Delete all links connected to a fwnode_handle.
 * @fwnode: fwnode whose links needs to be deleted
 *
 * Deletes all links connecting directly to a fwnode.
 */
void fwnode_links_purge(struct fwnode_handle *fwnode)
{
        fwnode_links_purge_suppliers(fwnode);
        fwnode_links_purge_consumers(fwnode);
}

void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode)
{
        struct fwnode_handle *child;

        /* Don't purge consumer links of an added child */
        if (fwnode->dev)
                return;

        fwnode->flags |= FWNODE_FLAG_NOT_DEVICE;
        fwnode_links_purge_consumers(fwnode);

        fwnode_for_each_available_child_node(fwnode, child)
                fw_devlink_purge_absent_suppliers(child);
}
EXPORT_SYMBOL_GPL(fw_devlink_purge_absent_suppliers);

#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);
}

static void device_link_synchronize_removal(void)
{
        synchronize_srcu(&device_links_srcu);
}

static void device_link_remove_from_lists(struct device_link *link)
{
        list_del_rcu(&link->s_node);
        list_del_rcu(&link->c_node);
}
#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

static inline void device_link_synchronize_removal(void)
{
}

static void device_link_remove_from_lists(struct device_link *link)
{
        list_del(&link->s_node);
        list_del(&link->c_node);
}
#endif /* !CONFIG_SRCU */

static bool device_is_ancestor(struct device *dev, struct device *target)
{
        while (target->parent) {
                target = target->parent;
                if (dev == target)
                        return true;
        }
        return false;
}

/**
 * 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;

        /*
         * The "ancestors" check is needed to catch the case when the target
         * device has not been completely initialized yet and it is still
         * missing from the list of children of its parent device.
         */
        if (dev == target || device_is_ancestor(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_INFERRED) ==
                    (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_INFERRED) ==
                    (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)
{
        const char *output;

        switch (to_devlink(dev)->status) {
        case DL_STATE_NONE:
                output = "not tracked";
                break;
        case DL_STATE_DORMANT:
                output = "dormant";
                break;
        case DL_STATE_AVAILABLE:
                output = "available";
                break;
        case DL_STATE_CONSUMER_PROBE:
                output = "consumer probing";
                break;
        case DL_STATE_ACTIVE:
                output = "active";
                break;
        case DL_STATE_SUPPLIER_UNBIND:
                output = "supplier unbinding";
                break;
        default:
                output = "unknown";
                break;
        }

        return sysfs_emit(buf, "%s\n", output);
}
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);
        const char *output;

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

        return sysfs_emit(buf, "%s\n", output);
}
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 sysfs_emit(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 sysfs_emit(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_release_fn(struct work_struct *work)
{
        struct device_link *link = container_of(work, struct device_link, rm_work);

        /* Ensure that all references to the link object have been dropped. */
        device_link_synchronize_removal();

        while (refcount_dec_not_one(&link->rpm_active))
                pm_runtime_put(link->supplier);

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

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

        INIT_WORK(&link->rm_work, device_link_release_fn);
        /*
         * It may take a while to complete this work because of the SRCU
         * synchronization in device_link_release_fn() and if the consumer or
         * supplier devices get deleted when it runs, so put it into the "long"
         * workqueue.
         */
        queue_work(system_long_wq, &link->rm_work);
}

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

        if (device_is_registered(con)) {
                snprintf(buf, len, "supplier:%s:%s", dev_bus_name(sup), dev_name(sup));
                sysfs_remove_link(&con->kobj, buf);
        }
        snprintf(buf, len, "consumer:%s:%s", dev_bus_name(con), 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 | \
                               DL_FLAG_INFERRED)

#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 meta state 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 automatically probe for a consumer
 * 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_INFERRED) != 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;
        }

        /*
         * SYNC_STATE_ONLY links are useless once a consumer device has probed.
         * So, only create it if the consumer hasn't probed yet.
         */
        if (flags & DL_FLAG_SYNC_STATE_ONLY &&
            consumer->links.status != DL_DEV_NO_DRIVER &&
            consumer->links.status != DL_DEV_PROBING) {
                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 (link->flags & DL_FLAG_INFERRED &&
                    !(flags & DL_FLAG_INFERRED))
                        link->flags &= ~DL_FLAG_INFERRED;

                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--%s:%s",
                     dev_bus_name(supplier), dev_name(supplier),
                     dev_bus_name(consumer), 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);

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));

        pm_runtime_drop_link(link);

        device_link_remove_from_lists(link);
        device_unregister(&link->link_dev);
}

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(&fwnode_link_lock);
        if (dev->fwnode && !list_empty(&dev->fwnode->suppliers) &&
            !fw_devlink_is_permissive()) {
                dev_dbg(dev, "probe deferral - wait for supplier %pfwP\n",
                        list_first_entry(&dev->fwnode->suppliers,
                        struct fwnode_link,
                        c_hook)->supplier);
                mutex_unlock(&fwnode_link_lock);
                return -EPROBE_DEFER;
        }
        mutex_unlock(&fwnode_link_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);

                        dev_dbg(dev, "probe deferral - supplier %s not ready\n",
                                dev_name(link->supplier));
                        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_sync)))
                return;

        get_device(dev);
        list_add_tail(&dev->links.defer_sync, 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_sync) {
                list_del_init(&dev->links.defer_sync);

                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_sync) {
                /*
                 * Delete from deferred_sync list before queuing it to
                 * sync_list because defer_sync is used for both lists.
                 */
                list_del_init(&dev->links.defer_sync);
                __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_sync) && dev_has_sync_state(sup))
                list_add_tail(&sup->links.defer_sync, &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);
        val = !list_empty(&dev->fwnode->suppliers);
        device_unlock(dev);
        return sysfs_emit(buf, "%u\n", val);
}
static DEVICE_ATTR_RO(waiting_for_supplier);

/**
 * device_links_force_bind - Prepares device to be force bound
 * @dev: Consumer device.
 *
 * device_bind_driver() force binds a device to a driver without calling any
 * driver probe functions. So the consumer really isn't going to wait for any
 * supplier before it's bound to the driver. We still want the device link
 * states to be sensible when this happens.
 *
 * In preparation for device_bind_driver(), this function goes through each
 * supplier device links and checks if the supplier is bound. If it is, then
 * the device link status is set to CONSUMER_PROBE. Otherwise, the device link
 * is dropped. Links without the DL_FLAG_MANAGED flag set are ignored.
 */
void device_links_force_bind(struct device *dev)
{
        struct device_link *link, *ln;

        device_links_write_lock();

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

                if (link->status != DL_STATE_AVAILABLE) {
                        device_link_drop_managed(link);
                        continue;
                }
                WRITE_ONCE(link->status, DL_STATE_CONSUMER_PROBE);
        }
        dev->links.status = DL_DEV_PROBING;

        device_links_write_unlock();
}

/**
 * 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 binds successfully, it's expected to have created all
         * the device links it needs to or make new device links as it needs
         * them. So, fw_devlink no longer needs to create device links to any
         * of the device's suppliers.
         *
         * Also, if a child firmware node of this bound device is not added as
         * a device by now, assume it is never going to be added and make sure
         * other devices don't defer probe indefinitely by waiting for such a
         * child device.
         */
        if (dev->fwnode && dev->fwnode->dev == dev) {
                struct fwnode_handle *child;
                fwnode_links_purge_suppliers(dev->fwnode);
                fwnode_for_each_available_child_node(dev->fwnode, child)
                        fw_devlink_purge_absent_suppliers(child);
        }
        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_sync);
        __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;

        /*
         * 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();
}

#define FW_DEVLINK_FLAGS_PERMISSIVE     (DL_FLAG_INFERRED | \
                                         DL_FLAG_SYNC_STATE_ONLY)
#define FW_DEVLINK_FLAGS_ON             (DL_FLAG_INFERRED | \
                                         DL_FLAG_AUTOPROBE_CONSUMER)
#define FW_DEVLINK_FLAGS_RPM            (FW_DEVLINK_FLAGS_ON | \
                                         DL_FLAG_PM_RUNTIME)

static u32 fw_devlink_flags = FW_DEVLINK_FLAGS_ON;
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 = FW_DEVLINK_FLAGS_PERMISSIVE;
        } else if (strcmp(arg, "on") == 0) {
                fw_devlink_flags = FW_DEVLINK_FLAGS_ON;
        } else if (strcmp(arg, "rpm") == 0) {
                fw_devlink_flags = FW_DEVLINK_FLAGS_RPM;
        }
        return 0;
}
early_param("fw_devlink", fw_devlink_setup);

static bool fw_devlink_strict;
static int __init fw_devlink_strict_setup(char *arg)
{
        return strtobool(arg, &fw_devlink_strict);
}
early_param("fw_devlink.strict", fw_devlink_strict_setup);

u32 fw_devlink_get_flags(void)
{
        return fw_devlink_flags;
}

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

bool fw_devlink_is_strict(void)
{
        return fw_devlink_strict && !fw_devlink_is_permissive();
}

static void fw_devlink_parse_fwnode(struct fwnode_handle *fwnode)
{
        if (fwnode->flags & FWNODE_FLAG_LINKS_ADDED)
                return;

        fwnode_call_int_op(fwnode, add_links);
        fwnode->flags |= FWNODE_FLAG_LINKS_ADDED;
}

static void fw_devlink_parse_fwtree(struct fwnode_handle *fwnode)
{
        struct fwnode_handle *child = NULL;

        fw_devlink_parse_fwnode(fwnode);

        while ((child = fwnode_get_next_available_child_node(fwnode, child)))
                fw_devlink_parse_fwtree(child);
}

static void fw_devlink_relax_link(struct device_link *link)
{
        if (!(link->flags & DL_FLAG_INFERRED))
                return;

        if (link->flags == (DL_FLAG_MANAGED | FW_DEVLINK_FLAGS_PERMISSIVE))
                return;

        pm_runtime_drop_link(link);
        link->flags = DL_FLAG_MANAGED | FW_DEVLINK_FLAGS_PERMISSIVE;
        dev_dbg(link->consumer, "Relaxing link with %s\n",
                dev_name(link->supplier));
}

static int fw_devlink_no_driver(struct device *dev, void *data)
{
        struct device_link *link = to_devlink(dev);

        if (!link->supplier->can_match)
                fw_devlink_relax_link(link);

        return 0;
}

void fw_devlink_drivers_done(void)
{
        fw_devlink_drv_reg_done = true;
        device_links_write_lock();
        class_for_each_device(&devlink_class, NULL, NULL,
                              fw_devlink_no_driver);
        device_links_write_unlock();
}

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

        if (!fw_devlink_flags || fw_devlink_is_permissive())
                return;

        device_links_write_lock();
        list_for_each_entry(link, &dev->links.consumers, s_node)
                fw_devlink_relax_link(link);
        device_links_write_unlock();
}

/**
 * fw_devlink_relax_cycle - Convert cyclic links to SYNC_STATE_ONLY links
 * @con: Device to check dependencies for.
 * @sup: Device to check against.
 *
 * Check if @sup depends on @con or any device dependent on it (its child or
 * its consumer etc).  When such a cyclic dependency is found, convert all
 * device links created solely by fw_devlink into SYNC_STATE_ONLY device links.
 * This is the equivalent of doing fw_devlink=permissive just between the
 * devices in the cycle. We need to do this because, at this point, fw_devlink
 * can't tell which of these dependencies is not a real dependency.
 *
 * Return 1 if a cycle is found. Otherwise, return 0.
 */
static int fw_devlink_relax_cycle(struct device *con, void *sup)
{
        struct device_link *link;
        int ret;

        if (con == sup)
                return 1;

        ret = device_for_each_child(con, sup, fw_devlink_relax_cycle);
        if (ret)
                return ret;

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

                if (!fw_devlink_relax_cycle(link->consumer, sup))
                        continue;

                ret = 1;

                fw_devlink_relax_link(link);
        }
        return ret;
}

/**
 * fw_devlink_create_devlink - Create a device link from a consumer to fwnode
 * @con: consumer device for the device link
 * @sup_handle: fwnode handle of supplier
 * @flags: devlink flags
 *
 * This function will try to create a device link between the consumer device
 * @con and the supplier device represented by @sup_handle.
 *
 * The supplier has to be provided as a fwnode because incorrect cycles in
 * fwnode links can sometimes cause the supplier device to never be created.
 * This function detects such cases and returns an error if it cannot create a
 * device link from the consumer to a missing supplier.
 *
 * Returns,
 * 0 on successfully creating a device link
 * -EINVAL if the device link cannot be created as expected
 * -EAGAIN if the device link cannot be created right now, but it may be
 *  possible to do that in the future
 */
static int fw_devlink_create_devlink(struct device *con,
                                     struct fwnode_handle *sup_handle, u32 flags)
{
        struct device *sup_dev;
        int ret = 0;

        sup_dev = get_dev_from_fwnode(sup_handle);
        if (sup_dev) {
                /*
                 * If it's one of those drivers that don't actually bind to
                 * their device using driver core, then don't wait on this
                 * supplier device indefinitely.
                 */
                if (sup_dev->links.status == DL_DEV_NO_DRIVER &&
                    sup_handle->flags & FWNODE_FLAG_INITIALIZED) {
                        ret = -EINVAL;
                        goto out;
                }

                /*
                 * If this fails, it is due to cycles in device links.  Just
                 * give up on this link and treat it as invalid.
                 */
                if (!device_link_add(con, sup_dev, flags) &&
                    !(flags & DL_FLAG_SYNC_STATE_ONLY)) {
                        dev_info(con, "Fixing up cyclic dependency with %s\n",
                                 dev_name(sup_dev));
                        device_links_write_lock();
                        fw_devlink_relax_cycle(con, sup_dev);
                        device_links_write_unlock();
                        device_link_add(con, sup_dev,
                                        FW_DEVLINK_FLAGS_PERMISSIVE);
                        ret = -EINVAL;
                }

                goto out;
        }

        /* Supplier that's already initialized without a struct device. */
        if (sup_handle->flags & FWNODE_FLAG_INITIALIZED)
                return -EINVAL;

        /*
         * DL_FLAG_SYNC_STATE_ONLY doesn't block probing and supports
         * cycles. So cycle detection isn't necessary and shouldn't be
         * done.
         */
        if (flags & DL_FLAG_SYNC_STATE_ONLY)
                return -EAGAIN;

        /*
         * If we can't find the supplier device from its fwnode, it might be
         * due to a cyclic dependency between fwnodes. Some of these cycles can
         * be broken by applying logic. Check for these types of cycles and
         * break them so that devices in the cycle probe properly.
         *
         * If the supplier's parent is dependent on the consumer, then
         * the consumer-supplier dependency is a false dependency. So,
         * treat it as an invalid link.
         */
        sup_dev = fwnode_get_next_parent_dev(sup_handle);
        if (sup_dev && device_is_dependent(con, sup_dev)) {
                dev_dbg(con, "Not linking to %pfwP - False link\n",
                        sup_handle);
                ret = -EINVAL;
        } else {
                /*
                 * Can't check for cycles or no cycles. So let's try
                 * again later.
                 */
                ret = -EAGAIN;
        }

out:
        put_device(sup_dev);
        return ret;
}

/**
 * __fw_devlink_link_to_consumers - Create device links to consumers of a device
 * @dev: Device that needs to be linked to its consumers
 *
 * This function looks at all the consumer fwnodes of @dev and creates device
 * links between the consumer device and @dev (supplier).
 *
 * If the consumer device has not been added yet, then this function creates a
 * SYNC_STATE_ONLY link between @dev (supplier) and the closest ancestor device
 * of the consumer fwnode. This is necessary to make sure @dev doesn't get a
 * sync_state() callback before the real consumer device gets to be added and
 * then probed.
 *
 * Once device links are created from the real consumer to @dev (supplier), the
 * fwnode links are deleted.
 */
static void __fw_devlink_link_to_consumers(struct device *dev)
{
        struct fwnode_handle *fwnode = dev->fwnode;
        struct fwnode_link *link, *tmp;

        list_for_each_entry_safe(link, tmp, &fwnode->consumers, s_hook) {
                u32 dl_flags = fw_devlink_get_flags();
                struct device *con_dev;
                bool own_link = true;
                int ret;

                con_dev = get_dev_from_fwnode(link->consumer);
                /*
                 * If consumer device is not available yet, make a "proxy"
                 * SYNC_STATE_ONLY link from the consumer's parent device to
                 * the supplier device. This is necessary to make sure the
                 * supplier doesn't get a sync_state() callback before the real
                 * consumer can create a device link to the supplier.
                 *
                 * This proxy link step is needed to handle the case where the
                 * consumer's parent device is added before the supplier.
                 */
                if (!con_dev) {
                        con_dev = fwnode_get_next_parent_dev(link->consumer);
                        /*
                         * However, if the consumer's parent device is also the
                         * parent of the supplier, don't create a
                         * consumer-supplier link from the parent to its child
                         * device. Such a dependency is impossible.
                         */
                        if (con_dev &&
                            fwnode_is_ancestor_of(con_dev->fwnode, fwnode)) {
                                put_device(con_dev);
                                con_dev = NULL;
                        } else {
                                own_link = false;
                                dl_flags = FW_DEVLINK_FLAGS_PERMISSIVE;
                        }
                }

                if (!con_dev)
                        continue;

                ret = fw_devlink_create_devlink(con_dev, fwnode, dl_flags);
                put_device(con_dev);
                if (!own_link || ret == -EAGAIN)
                        continue;

                list_del(&link->s_hook);
                list_del(&link->c_hook);
                kfree(link);
        }
}

/**
 * __fw_devlink_link_to_suppliers - Create device links to suppliers of a device
 * @dev: The consumer device that needs to be linked to its suppliers
 * @fwnode: Root of the fwnode tree that is used to create device links
 *
 * This function looks at all the supplier fwnodes of fwnode tree rooted at
 * @fwnode and creates device links between @dev (consumer) and all the
 * supplier devices of the entire fwnode tree at @fwnode.
 *
 * The function creates normal (non-SYNC_STATE_ONLY) device links between @dev
 * and the real suppliers of @dev. Once these device links are created, the
 * fwnode links are deleted. When such device links are successfully created,
 * this function is called recursively on those supplier devices. This is
 * needed to detect and break some invalid cycles in fwnode links.  See
 * fw_devlink_create_devlink() for more details.
 *
 * In addition, it also looks at all the suppliers of the entire fwnode tree
 * because some of the child devices of @dev that have not been added yet
 * (because @dev hasn't probed) might already have their suppliers added to
 * driver core. So, this function creates SYNC_STATE_ONLY device links between
 * @dev (consumer) and these suppliers to make sure they don't execute their
 * sync_state() callbacks before these child devices have a chance to create
 * their device links. The fwnode links that correspond to the child devices
 * aren't delete because they are needed later to create the device links
 * between the real consumer and supplier devices.
 */
static void __fw_devlink_link_to_suppliers(struct device *dev,
                                           struct fwnode_handle *fwnode)
{
        bool own_link = (dev->fwnode == fwnode);
        struct fwnode_link *link, *tmp;
        struct fwnode_handle *child = NULL;
        u32 dl_flags;

        if (own_link)
                dl_flags = fw_devlink_get_flags();
        else
                dl_flags = FW_DEVLINK_FLAGS_PERMISSIVE;

        list_for_each_entry_safe(link, tmp, &fwnode->suppliers, c_hook) {
                int ret;
                struct device *sup_dev;
                struct fwnode_handle *sup = link->supplier;

                ret = fw_devlink_create_devlink(dev, sup, dl_flags);
                if (!own_link || ret == -EAGAIN)
                        continue;

                list_del(&link->s_hook);
                list_del(&link->c_hook);
                kfree(link);

                /* If no device link was created, nothing more to do. */
                if (ret)
                        continue;

                /*
                 * If a device link was successfully created to a supplier, we
                 * now need to try and link the supplier to all its suppliers.
                 *
                 * This is needed to detect and delete false dependencies in
                 * fwnode links that haven't been converted to a device link
                 * yet. See comments in fw_devlink_create_devlink() for more
                 * details on the false dependency.
                 *
                 * Without deleting these false dependencies, some devices will
                 * never probe because they'll keep waiting for their false
                 * dependency fwnode links to be converted to device links.
                 */
                sup_dev = get_dev_from_fwnode(sup);
                __fw_devlink_link_to_suppliers(sup_dev, sup_dev->fwnode);
                put_device(sup_dev);
        }

        /*
         * Make "proxy" SYNC_STATE_ONLY device links to represent the needs of
         * all the descendants. This proxy link step is needed to handle the
         * case where the supplier is added before the consumer's parent device
         * (@dev).
         */
        while ((child = fwnode_get_next_available_child_node(fwnode, child)))
                __fw_devlink_link_to_suppliers(dev, child);
}

static void fw_devlink_link_device(struct device *dev)
{
        struct fwnode_handle *fwnode = dev->fwnode;

        if (!fw_devlink_flags)
                return;

        fw_devlink_parse_fwtree(fwnode);

        mutex_lock(&fwnode_link_lock);
        __fw_devlink_link_to_consumers(dev);
        __fw_devlink_link_to_suppliers(dev, fwnode);
        mutex_unlock(&fwnode_link_lock);
}

/* 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)
{