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 // 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/blkdev.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/swiotlb.h>
 #include <linux/sysfs.h>
 #include <linux/dma-map-ops.h> /* for dma_default_coherent */
 
 #include "base.h"
 #include "physical_location.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;
 static bool fw_devlink_best_effort;
 
 /**
  * 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);
     pr_debug("%pfwP Linked as a fwnode consumer to %pfwP\n",
          con, sup);
 out:
     mutex_unlock(&fwnode_link_lock);
 
     return ret;
 }
 
 /**
  * __fwnode_link_del - Delete a link between two fwnode_handles.
  * @link: the fwnode_link to be deleted
  *
  * The fwnode_link_lock needs to be held when this function is called.
  */
 static void __fwnode_link_del(struct fwnode_link *link)
 {
     pr_debug("%pfwP Dropping the fwnode link to %pfwP\n",
          link->consumer, link->supplier);
     list_del(&link->s_hook);
     list_del(&link->c_hook);
     kfree(link);
 }
 
 /**
  * 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)
         __fwnode_link_del(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)
         __fwnode_link_del(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();
 
     pm_runtime_release_supplier(link);
     /*
      * If supplier_preactivated is set, the link has been dropped between
      * the pm_runtime_get_suppliers() and pm_runtime_put_suppliers() calls
      * in __driver_probe_device().  In that case, drop the supplier's
      * PM-runtime usage counter to remove the reference taken by
      * pm_runtime_get_suppliers().
      */
     if (link->supplier_preactivated)
         pm_runtime_put_noidle(link->supplier);
 
     pm_request_idle(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 || 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(&link->link_dev);
         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 if (!device_is_registered(link->consumer))
         __device_link_del(&link->kref);
     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);
         }
     }
 }
 
 static bool dev_is_best_effort(struct device *dev)
 {
     return (fw_devlink_best_effort && dev->can_match) ||
         (dev->fwnode && (dev->fwnode->flags & FWNODE_FLAG_BEST_EFFORT));
 }
 
 /**
  * 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, fwnode_ret = 0;
     struct fwnode_handle *sup_fw;
 
     /*
      * 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()) {
         sup_fw = list_first_entry(&dev->fwnode->suppliers,
                       struct fwnode_link,
                       c_hook)->supplier;
         if (!dev_is_best_effort(dev)) {
             fwnode_ret = -EPROBE_DEFER;
             dev_err_probe(dev, -EPROBE_DEFER,
                     "wait for supplier %pfwP\n", sup_fw);
         } else {
             fwnode_ret = -EAGAIN;
         }
     }
     mutex_unlock(&fwnode_link_lock);
     if (fwnode_ret == -EPROBE_DEFER)
         return fwnode_ret;
 
     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)) {
 
             if (dev_is_best_effort(dev) &&
                 link->flags & DL_FLAG_INFERRED &&
                 !link->supplier->can_match) {
                 ret = -EAGAIN;
                 continue;
             }
 
             device_links_missing_supplier(dev);
             dev_err_probe(dev, -EPROBE_DEFER,
                       "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 ? ret : fwnode_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 if (dev_is_best_effort(dev) &&
                link->flags & DL_FLAG_INFERRED &&
                link->status != DL_STATE_CONSUMER_PROBE &&
                !link->supplier->can_match) {
             /*
              * When dev_is_best_effort() is true, we ignore device
              * links to suppliers that don't have a driver.  If the
              * consumer device still managed to probe, there's no
              * point in maintaining a device link in a weird state
              * (consumer probed before supplier). So delete it.
              */
             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();
 }
 
 /**
  * wait_for_init_devices_probe - Try to probe any device needed for init
  *
  * Some devices might need to be probed and bound successfully before the kernel
  * boot sequence can finish and move on to init/userspace. For example, a
  * network interface might need to be bound to be able to mount a NFS rootfs.
  *
  * With fw_devlink=on by default, some of these devices might be blocked from
  * probing because they are waiting on a optional supplier that doesn't have a
  * driver. While fw_devlink will eventually identify such devices and unblock
  * the probing automatically, it might be too late by the time it unblocks the
  * probing of devices. For example, the IP4 autoconfig might timeout before
  * fw_devlink unblocks probing of the network interface.
  *
  * This function is available to temporarily try and probe all devices that have
  * a driver even if some of their suppliers haven't been added or don't have
  * drivers.
  *
  * The drivers can then decide which of the suppliers are optional vs mandatory
  * and probe the device if possible. By the time this function returns, all such
  * "best effort" probes are guaranteed to be completed. If a device successfully
  * probes in this mode, we delete all fw_devlink discovered dependencies of that
  * device where the supplier hasn't yet probed successfully because they have to
  * be optional dependencies.
  *
  * Any devices that didn't successfully probe go back to being treated as if
  * this function was never called.
  *
  * This also means that some devices that aren't needed for init and could have
  * waited for their optional supplier to probe (when the supplier's module is
  * loaded later on) would end up probing prematurely with limited functionality.
  * So call this function only when boot would fail without it.
  */
 void __init wait_for_init_devices_probe(void)
 {
     if (!fw_devlink_flags || fw_devlink_is_permissive())
         return;
 
     /*
      * Wait for all ongoing probes to finish so that the "best effort" is
      * only applied to devices that can't probe otherwise.
      */
     wait_for_device_probe();
 
     pr_info("Trying to probe devices needed for running init ...\n");
     fw_devlink_best_effort = true;
     driver_deferred_probe_trigger();
 
     /*
      * Wait for all "best effort" probes to finish before going back to
      * normal enforcement.
      */
     wait_for_device_probe();
     fw_devlink_best_effort = false;
 }
 
 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;
 
     /*
      * In some cases, a device P might also be a supplier to its child node
      * C. However, this would defer the probe of C until the probe of P
      * completes successfully. This is perfectly fine in the device driver
      * model. device_add() doesn't guarantee probe completion of the device
      * by the time it returns.
      *
      * However, there are a few drivers that assume C will finish probing
      * as soon as it's added and before P finishes probing. So, we provide
      * a flag to let fw_devlink know not to delay the probe of C until the
      * probe of P completes successfully.
      *
      * When such a flag is set, we can't create device links where P is the
      * supplier of C as that would delay the probe of C.
      */
     if (sup_handle->flags & FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD &&
         fwnode_is_ancestor_of(sup_handle, con->fwnode))
         return -EINVAL;
 
     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 and supplier have a cyclic dependency. Since fw_devlink
      * can't tell which of the inferred dependencies are incorrect, don't
      * enforce probe ordering between any of the devices in this cyclic
      * dependency. Do this by relaxing all the fw_devlink device links in
      * this cycle and by treating the fwnode link between the consumer and
      * the supplier as an invalid dependency.
      */
     sup_dev = fwnode_get_next_parent_dev(sup_handle);
     if (sup_dev && device_is_dependent(con, sup_dev)) {
         dev_info(con, "Fixing up cyclic dependency with %pfwP (%s)\n",
              sup_handle, dev_name(sup_dev));
         device_links_write_lock();
         fw_devlink_relax_cycle(con, sup_dev);
         device_links_write_unlock();
         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;
 
         __fwnode_link_del(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;
 
         __fwnode_link_del(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)
 {
     return 1;
 }
 #endif
 
 static void device_platform_notify(struct device *dev)
 {
     acpi_device_notify(dev);
 
     software_node_notify(dev);
 
     if (platform_notify)
         platform_notify(dev);
 }
 
 static void device_platform_notify_remove(struct device *dev)
 {
     acpi_device_notify_remove(dev);
 
     software_node_notify_remove(dev);
 
     if (platform_notify_remove)
         platform_notify_remove(dev);
 }
 
 /**
  * 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_name(dev);
 }
 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 sysfs_emit(buf, "%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 sysfs_emit(buf, "%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 sysfs_emit(buf, "%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);
 
     kfree(dev->dma_range_map);
 
     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 kobject *kobj)
 {
     const 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 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 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;
     int len = 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(&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(&dev->kobj, env);
     if (retval)
         goto out;
 
     /* copy keys to file */
     for (i = 0; i < env->envp_idx; i++)
         len += sysfs_emit_at(buf, len, "%s\n", env->envp[i]);
 out:
     kfree(env);
     return len;
 }
 
 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 sysfs_emit(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);
 
 static ssize_t removable_show(struct device *dev, struct device_attribute *attr,
                   char *buf)
 {
     const char *loc;
 
     switch (dev->removable) {
     case DEVICE_REMOVABLE:
         loc = "removable";
         break;
     case DEVICE_FIXED:
         loc = "fixed";
         break;
     default:
         loc = "unknown";
     }
     return sysfs_emit(buf, "%s\n", loc);
 }
 static DEVICE_ATTR_RO(removable);
 
 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() && dev->fwnode) {
         error = device_create_file(dev, &dev_attr_waiting_for_supplier);
         if (error)
             goto err_remove_dev_online;
     }
 
     if (dev_removable_is_valid(dev)) {
         error = device_create_file(dev, &dev_attr_removable);
         if (error)
             goto err_remove_dev_waiting_for_supplier;
     }
 
     if (dev_add_physical_location(dev)) {
         error = device_add_group(dev,
             &dev_attr_physical_location_group);
         if (error)
             goto err_remove_dev_removable;
     }
 
     return 0;
 
  err_remove_dev_removable:
     device_remove_file(dev, &dev_attr_removable);
  err_remove_dev_waiting_for_supplier:
     device_remove_file(dev, &dev_attr_waiting_for_supplier);
  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;
 
     if (dev->physical_location) {
         device_remove_group(dev, &dev_attr_physical_location_group);
         kfree(dev->physical_location);
     }
 
     device_remove_file(dev, &dev_attr_removable);
     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);
     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, NUMA_NO_NODE);
     INIT_LIST_HEAD(&dev->links.consumers);
     INIT_LIST_HEAD(&dev->links.suppliers);
     INIT_LIST_HEAD(&dev->links.defer_sync);
     dev->links.status = DL_DEV_NO_DRIVER;
 #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
     defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
     defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
     dev->dma_coherent = dma_default_coherent;
 #endif
 #ifdef CONFIG_SWIOTLB
     dev->dma_io_tlb_mem = &io_tlb_default_mem;
 #endif
 }
 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;
 }
 
 /**
  * kobject_has_children - Returns whether a kobject has children.
  * @kobj: the object to test
  *
  * This will return whether a kobject has other kobjects as children.
  *
  * It does NOT account for the presence of attribute files, only sub
  * directories. It also assumes there is no concurrent addition or
  * removal of such children, and thus relies on external locking.
  */
 static inline bool kobject_has_children(struct kobject *kobj)
 {
     WARN_ON_ONCE(kref_read(&kobj->kref) == 0);
 
     return kobj->sd && kobj->sd->dir.subdirs;
 }
 
 /*
  * 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 */
     device_platform_notify(dev);
 
     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 all driver registration is done and a newly added device doesn't
      * match with any driver, don't block its consumers from probing in
      * case the consumer device is able to operate without this supplier.
      */
     if (dev->fwnode && fw_devlink_drv_reg_done && !dev->can_match)
         fw_devlink_unblock_consumers(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_remove(dev);
     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.
      */
     device_lock_assert(dev);
 
     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;
     unsigned int noio_flag;
 
     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().
      */
     noio_flag = memalloc_noio_save();
     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_remove(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);
     memalloc_noio_restore(noio_flag);
     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 (sysfs_streq(dev_name(child), name) && get_device(child))
             break;
     klist_iter_exit(&i);
     return child;
 }
 EXPORT_SYMBOL_GPL(device_find_child_by_name);
 
 static int match_any(struct device *dev, void *unused)
 {
     return 1;
 }
 
 /**
  * device_find_any_child - device iterator for locating a child device, if any.
  * @parent: parent struct device
  *
  * This is similar to the device_find_child() function above, but it
  * returns a reference to a child device, if any.
  *
  * NOTE: you will need to drop the reference with put_device() after use.
  */
 struct device *device_find_any_child(struct device *parent)
 {
     return device_find_child(parent, NULL, match_any);
 }
 EXPORT_SYMBOL_GPL(device_find_any_child);
 
 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);
     /*
      * Walk the devices list backward, shutting down each in turn.
      * Beware that device unplug events may also start pulling
      * devices offline, even as the system is shutting down.
      */
     while (!list_empty(&devices_kset->list)) {
         dev = list_entry(devices_kset->list.prev, struct device,
                 kobj.entry);
 
         /*
          * hold reference count of device's parent to
          * prevent it from being freed because parent's
          * lock is to be held
          */
         parent = get_device(dev->parent);
         get_device(dev);
         /*
          * Make sure the device is off the kset list, in the
          * event that dev->*->shutdown() doesn't remove it.
          */
         list_del_init(&dev->kobj.entry);
         spin_unlock(&devices_kset->list_lock);
 
         /* hold lock to avoid race with probe/release */
         if (parent)
             device_lock(parent);
         device_lock(dev);
 
         /* Don't allow any more runtime suspends */
         pm_runtime_get_noresume(dev);
         pm_runtime_barrier(dev);
 
         if (dev->class && dev->class->shutdown_pre) {
             if (initcall_debug)
                 dev_info(dev, "shutdown_pre\n");
             dev->class->shutdown_pre(dev);
         }
         if (dev->bus && dev->bus->shutdown) {
             if (initcall_debug)
                 dev_info(dev, "shutdown\n");
             dev->bus->shutdown(dev);
         } else if (dev->driver && dev->driver->shutdown) {
             if (initcall_debug)
                 dev_info(dev, "shutdown\n");
             dev->driver->shutdown(dev);
         }
 
         device_unlock(dev);
         if (parent)
             device_unlock(parent);
 
         put_device(dev);
         put_device(parent);
 
         spin_lock(&devices_kset->list_lock);
     }
     spin_unlock(&devices_kset->list_lock);
 }
 
 /*
  * Device logging functions
  */
 
 #ifdef CONFIG_PRINTK
 static void
 set_dev_info(const struct device *dev, struct dev_printk_info *dev_info)
 {
     const char *subsys;
 
     memset(dev_info, 0, sizeof(*dev_info));
 
     if (dev->class)
         subsys = dev->class->name;
     else if (dev->bus)
         subsys = dev->bus->name;
     else
         return;
 
     strscpy(dev_info->subsystem, subsys, sizeof(dev_info->subsystem));
 
     /*
      * Add device identifier DEVICE=:
      *   b12:8         block dev_t
      *   c127:3        char dev_t
      *   n8            netdev ifindex
      *   +sound:card0  subsystem:devname
      */
     if (MAJOR(dev->devt)) {
         char c;
 
         if (strcmp(subsys, "block") == 0)
             c = 'b';
         else
             c = 'c';
 
         snprintf(dev_info->device, sizeof(dev_info->device),
              "%c%u:%u", c, MAJOR(dev->devt), MINOR(dev->devt));
     } else if (strcmp(subsys, "net") == 0) {
         struct net_device *net = to_net_dev(dev);
 
         snprintf(dev_info->device, sizeof(dev_info->device),
              "n%u", net->ifindex);
     } else {
         snprintf(dev_info->device, sizeof(dev_info->device),
              "+%s:%s", subsys, dev_name(dev));
     }
 }
 
 int dev_vprintk_emit(int level, const struct device *dev,
              const char *fmt, va_list args)
 {
     struct dev_printk_info dev_info;
 
     set_dev_info(dev, &dev_info);
 
     return vprintk_emit(0, level, &dev_info, fmt, args);
 }
 EXPORT_SYMBOL(dev_vprintk_emit);
 
 int dev_printk_emit(int level, const struct device *dev, const char *fmt, ...)
 {
     va_list args;
     int r;
 
     va_start(args, fmt);
 
     r = dev_vprintk_emit(level, dev, fmt, args);
 
     va_end(args);
 
     return r;
 }
 EXPORT_SYMBOL(dev_printk_emit);
 
 static void __dev_printk(const char *level, const struct device *dev,
             struct va_format *vaf)
 {
     if (dev)
         dev_printk_emit(level[1] - '0', dev, "%s %s: %pV",
                 dev_driver_string(dev), dev_name(dev), vaf);
     else
         printk("%s(NULL device *): %pV", level, vaf);
 }
 
 void _dev_printk(const char *level, const struct device *dev,
          const char *fmt, ...)
 {
     struct va_format vaf;
     va_list args;
 
     va_start(args, fmt);
 
     vaf.fmt = fmt;
     vaf.va = &args;
 
     __dev_printk(level, dev, &vaf);
 
     va_end(args);
 }
 EXPORT_SYMBOL(_dev_printk);
 
 #define define_dev_printk_level(func, kern_level)       \
 void func(const struct device *dev, const char *fmt, ...)   \
 {                               \
     struct va_format vaf;                   \
     va_list args;                       \
                                 \
     va_start(args, fmt);                    \
                                 \
     vaf.fmt = fmt;                      \
     vaf.va = &args;                     \
                                 \
     __dev_printk(kern_level, dev, &vaf);            \
                                 \
     va_end(args);                       \
 }                               \
 EXPORT_SYMBOL(func);
 
 define_dev_printk_level(_dev_emerg, KERN_EMERG);
 define_dev_printk_level(_dev_alert, KERN_ALERT);
 define_dev_printk_level(_dev_crit, KERN_CRIT);
 define_dev_printk_level(_dev_err, KERN_ERR);
 define_dev_printk_level(_dev_warn, KERN_WARNING);
 define_dev_printk_level(_dev_notice, KERN_NOTICE);
 define_dev_printk_level(_dev_info, KERN_INFO);
 
 #endif
 
 /**
  * dev_err_probe - probe error check and log helper
  * @dev: the pointer to the struct device
  * @err: error value to test
  * @fmt: printf-style format string
  * @...: arguments as specified in the format string
  *
  * This helper implements common pattern present in probe functions for error
  * checking: print debug or error message depending if the error value is
  * -EPROBE_DEFER and propagate error upwards.
  * In case of -EPROBE_DEFER it sets also defer probe reason, which can be
  * checked later by reading devices_deferred debugfs attribute.
  * It replaces code sequence::
  *
  *  if (err != -EPROBE_DEFER)
  *      dev_err(dev, ...);
  *  else
  *      dev_dbg(dev, ...);
  *  return err;
  *
  * with::
  *
  *  return dev_err_probe(dev, err, ...);
  *
  * Note that it is deemed acceptable to use this function for error
  * prints during probe even if the @err is known to never be -EPROBE_DEFER.
  * The benefit compared to a normal dev_err() is the standardized format
  * of the error code and the fact that the error code is returned.
  *
  * Returns @err.
  *
  */
 int dev_err_probe(const struct device *dev, int err, const char *fmt, ...)
 {
     struct va_format vaf;
     va_list args;
 
     va_start(args, fmt);
     vaf.fmt = fmt;
     vaf.va = &args;
 
     if (err != -EPROBE_DEFER) {
         dev_err(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
     } else {
         device_set_deferred_probe_reason(dev, &vaf);
         dev_dbg(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
     }
 
     va_end(args);
 
     return err;
 }
 EXPORT_SYMBOL_GPL(dev_err_probe);
 
 static inline bool fwnode_is_primary(struct fwnode_handle *fwnode)
 {
     return fwnode && !IS_ERR(fwnode->secondary);
 }
 
 /**
  * set_primary_fwnode - Change the primary firmware node of a given device.
  * @dev: Device to handle.
  * @fwnode: New primary firmware node of the device.
  *
  * Set the device's firmware node pointer to @fwnode, but if a secondary
  * firmware node of the device is present, preserve it.
  *
  * Valid fwnode cases are:
  *  - primary --> secondary --> -ENODEV
  *  - primary --> NULL
  *  - secondary --> -ENODEV
  *  - NULL
  */
 void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
 {
     struct device *parent = dev->parent;
     struct fwnode_handle *fn = dev->fwnode;
 
     if (fwnode) {
         if (fwnode_is_primary(fn))
             fn = fn->secondary;
 
         if (fn) {
             WARN_ON(fwnode->secondary);
             fwnode->secondary = fn;
         }
         dev->fwnode = fwnode;
     } else {
         if (fwnode_is_primary(fn)) {
             dev->fwnode = fn->secondary;
             /* Set fn->secondary = NULL, so fn remains the primary fwnode */
             if (!(parent && fn == parent->fwnode))
                 fn->secondary = NULL;
         } else {
             dev->fwnode = NULL;
         }
     }
 }
 EXPORT_SYMBOL_GPL(set_primary_fwnode);
 
 /**
  * set_secondary_fwnode - Change the secondary firmware node of a given device.
  * @dev: Device to handle.
  * @fwnode: New secondary firmware node of the device.
  *
  * If a primary firmware node of the device is present, set its secondary
  * pointer to @fwnode.  Otherwise, set the device's firmware node pointer to
  * @fwnode.
  */
 void set_secondary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
 {
     if (fwnode)
         fwnode->secondary = ERR_PTR(-ENODEV);
 
     if (fwnode_is_primary(dev->fwnode))
         dev->fwnode->secondary = fwnode;
     else
         dev->fwnode = fwnode;
 }
 EXPORT_SYMBOL_GPL(set_secondary_fwnode);
 
 /**
  * device_set_of_node_from_dev - reuse device-tree node of another device
  * @dev: device whose device-tree node is being set
  * @dev2: device whose device-tree node is being reused
  *
  * Takes another reference to the new device-tree node after first dropping
  * any reference held to the old node.
  */
 void device_set_of_node_from_dev(struct device *dev, const struct device *dev2)
 {
     of_node_put(dev->of_node);
     dev->of_node = of_node_get(dev2->of_node);
     dev->of_node_reused = true;
 }
 EXPORT_SYMBOL_GPL(device_set_of_node_from_dev);
 
 void device_set_node(struct device *dev, struct fwnode_handle *fwnode)
 {
     dev->fwnode = fwnode;
     dev->of_node = to_of_node(fwnode);
 }
 EXPORT_SYMBOL_GPL(device_set_node);
 
 int device_match_name(struct device *dev, const void *name)
 {
     return sysfs_streq(dev_name(dev), name);
 }
 EXPORT_SYMBOL_GPL(device_match_name);
 
 int device_match_of_node(struct device *dev, const void *np)
 {
     return dev->of_node == np;
 }
 EXPORT_SYMBOL_GPL(device_match_of_node);
 
 int device_match_fwnode(struct device *dev, const void *fwnode)
 {
     return dev_fwnode(dev) == fwnode;
 }
 EXPORT_SYMBOL_GPL(device_match_fwnode);
 
 int device_match_devt(struct device *dev, const void *pdevt)
 {
     return dev->devt == *(dev_t *)pdevt;
 }
 EXPORT_SYMBOL_GPL(device_match_devt);
 
 int device_match_acpi_dev(struct device *dev, const void *adev)
 {
     return ACPI_COMPANION(dev) == adev;
 }
 EXPORT_SYMBOL(device_match_acpi_dev);
 
 int device_match_acpi_handle(struct device *dev, const void *handle)
 {
     return ACPI_HANDLE(dev) == handle;
 }
 EXPORT_SYMBOL(device_match_acpi_handle);
 
 int device_match_any(struct device *dev, const void *unused)
 {
     return 1;
 }
 EXPORT_SYMBOL_GPL(device_match_any);