7 files changed, 682 insertions, 5 deletions

diff --git a/drivers/base/base.h b/drivers/base/base.h
index e05db388bd1c..e19b1008e5fb 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -107,6 +107,9 @@ extern void bus_remove_device(struct device *dev);
 
 extern int bus_add_driver(struct device_driver *drv);
 extern void bus_remove_driver(struct device_driver *drv);
+extern void device_release_driver_internal(struct device *dev,
+					   struct device_driver *drv,
+					   struct device *parent);
 
 extern void driver_detach(struct device_driver *drv);
 extern int driver_probe_device(struct device_driver *drv, struct device *dev);
@@ -152,3 +155,13 @@ extern int devtmpfs_init(void);
 #else
 static inline int devtmpfs_init(void) { return 0; }
 #endif
+
+/* Device links support */
+extern int device_links_read_lock(void);
+extern void device_links_read_unlock(int idx);
+extern int device_links_check_suppliers(struct device *dev);
+extern void device_links_driver_bound(struct device *dev);
+extern void device_links_driver_cleanup(struct device *dev);
+extern void device_links_no_driver(struct device *dev);
+extern bool device_links_busy(struct device *dev);
+extern void device_links_unbind_consumers(struct device *dev);
diff --git a/drivers/base/core.c b/drivers/base/core.c
index ce057a568673..3c5ff17f578f 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -44,6 +44,541 @@ static int __init sysfs_deprecated_setup(char *arg)
 early_param("sysfs.deprecated", sysfs_deprecated_setup);
 #endif
 
+/* Device links support. */
+
+#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)
+{
+	return srcu_read_lock(&device_links_srcu);
+}
+
+void device_links_read_unlock(int idx)
+{
+	srcu_read_unlock(&device_links_srcu, idx);
+}
+#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);
+}
+#endif /* !CONFIG_SRCU */
+
+/**
+ * device_is_dependent - Check if one device depends on another one
+ * @dev: Device to check dependencies for.
+ * @target: Device to check against.
+ *
+ * Check if @target depends on @dev or any device dependent on it (its child or
+ * its consumer etc).  Return 1 if that is the case or 0 otherwise.
+ */
+static int device_is_dependent(struct device *dev, void *target)
+{
+	struct device_link *link;
+	int ret;
+
+	if (WARN_ON(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 (WARN_ON(link->consumer == target))
+			return 1;
+
+		ret = device_is_dependent(link->consumer, target);
+		if (ret)
+			break;
+	}
+	return ret;
+}
+
+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)
+		device_reorder_to_tail(link->consumer, NULL);
+
+	return 0;
+}
+
+/**
+ * device_link_add - Create a link between two devices.
+ * @consumer: Consumer end of the link.
+ * @supplier: Supplier end of the link.
+ * @flags: Link flags.
+ *
+ * If the DL_FLAG_AUTOREMOVE is set, the link will be removed automatically
+ * when the consumer device driver unbinds from it.  The combination of both
+ * DL_FLAG_AUTOREMOVE and DL_FLAG_STATELESS set is invalid and will cause NULL
+ * to be returned.
+ *
+ * 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 registerd, however.
+ */
+struct device_link *device_link_add(struct device *consumer,
+				    struct device *supplier, u32 flags)
+{
+	struct device_link *link;
+
+	if (!consumer || !supplier ||
+	    ((flags & DL_FLAG_STATELESS) && (flags & DL_FLAG_AUTOREMOVE)))
+		return NULL;
+
+	device_links_write_lock();
+	device_pm_lock();
+
+	/*
+	 * If the supplier has not been fully registered yet or there is a
+	 * reverse dependency between the consumer and the supplier already in
+	 * the graph, return NULL.
+	 */
+	if (!device_pm_initialized(supplier)
+	    || device_is_dependent(consumer, supplier)) {
+		link = NULL;
+		goto out;
+	}
+
+	list_for_each_entry(link, &supplier->links.consumers, s_node)
+		if (link->consumer == consumer)
+			goto out;
+
+	link = kmalloc(sizeof(*link), GFP_KERNEL);
+	if (!link)
+		goto out;
+
+	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;
+
+	/* Deterine the initial link state. */
+	if (flags & DL_FLAG_STATELESS) {
+		link->status = DL_STATE_NONE;
+	} else {
+		switch (supplier->links.status) {
+		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;
+		}
+	}
+
+	/*
+	 * 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);
+
+	list_add_tail_rcu(&link->s_node, &supplier->links.consumers);
+	list_add_tail_rcu(&link->c_node, &consumer->links.suppliers);
+
+	dev_info(consumer, "Linked as a consumer to %s\n", dev_name(supplier));
+
+ out:
+	device_pm_unlock();
+	device_links_write_unlock();
+	return link;
+}
+EXPORT_SYMBOL_GPL(device_link_add);
+
+static void device_link_free(struct device_link *link)
+{
+	put_device(link->consumer);
+	put_device(link->supplier);
+	kfree(link);
+}
+
+#ifdef CONFIG_SRCU
+static void __device_link_free_srcu(struct rcu_head *rhead)
+{
+	device_link_free(container_of(rhead, struct device_link, rcu_head));
+}
+
+static void __device_link_del(struct device_link *link)
+{
+	dev_info(link->consumer, "Dropping the link to %s\n",
+		 dev_name(link->supplier));
+
+	list_del_rcu(&link->s_node);
+	list_del_rcu(&link->c_node);
+	call_srcu(&device_links_srcu, &link->rcu_head, __device_link_free_srcu);
+}
+#else /* !CONFIG_SRCU */
+static void __device_link_del(struct device_link *link)
+{
+	dev_info(link->consumer, "Dropping the link to %s\n",
+		 dev_name(link->supplier));
+
+	list_del(&link->s_node);
+	list_del(&link->c_node);
+	device_link_free(link);
+}
+#endif /* !CONFIG_SRCU */
+
+/**
+ * device_link_del - Delete a link between two devices.
+ * @link: Device link to delete.
+ *
+ * The caller must ensure proper synchronization of this function with runtime
+ * PM.
+ */
+void device_link_del(struct device_link *link)
+{
+	device_links_write_lock();
+	device_pm_lock();
+	__device_link_del(link);
+	device_pm_unlock();
+	device_links_write_unlock();
+}
+EXPORT_SYMBOL_GPL(device_link_del);
+
+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)
+			WRITE_ONCE(link->status, DL_STATE_AVAILABLE);
+}
+
+/**
+ * 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 with the DL_FLAG_STATELESS flag set are ignored.
+ */
+int device_links_check_suppliers(struct device *dev)
+{
+	struct device_link *link;
+	int ret = 0;
+
+	device_links_write_lock();
+
+	list_for_each_entry(link, &dev->links.suppliers, c_node) {
+		if (link->flags & DL_FLAG_STATELESS)
+			continue;
+
+		if (link->status != DL_STATE_AVAILABLE) {
+			device_links_missing_supplier(dev);
+			ret = -EPROBE_DEFER;
+			break;
+		}
+		WRITE_ONCE(link->status, DL_STATE_CONSUMER_PROBE);
+	}
+	dev->links.status = DL_DEV_PROBING;
+
+	device_links_write_unlock();
+	return ret;
+}
+
+/**
+ * device_links_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 with the DL_FLAG_STATELESS flag set are ignored.
+ */
+void device_links_driver_bound(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_STATELESS)
+			continue;
+
+		WARN_ON(link->status != DL_STATE_DORMANT);
+		WRITE_ONCE(link->status, DL_STATE_AVAILABLE);
+	}
+
+	list_for_each_entry(link, &dev->links.suppliers, c_node) {
+		if (link->flags & DL_FLAG_STATELESS)
+			continue;
+
+		WARN_ON(link->status != DL_STATE_CONSUMER_PROBE);
+		WRITE_ONCE(link->status, DL_STATE_ACTIVE);
+	}
+
+	dev->links.status = DL_DEV_DRIVER_BOUND;
+
+	device_links_write_unlock();
+}
+
+/**
+ * __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 with the DL_FLAG_STATELESS 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_STATELESS)
+			continue;
+
+		if (link->flags & DL_FLAG_AUTOREMOVE)
+			__device_link_del(link);
+		else if (link->status != DL_STATE_SUPPLIER_UNBIND)
+			WRITE_ONCE(link->status, DL_STATE_AVAILABLE);
+	}
+
+	dev->links.status = DL_DEV_NO_DRIVER;
+}
+
+void device_links_no_driver(struct device *dev)
+{
+	device_links_write_lock();
+	__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 with the DL_FLAG_STATELESS flag set are ignored.
+ */
+void device_links_driver_cleanup(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_STATELESS)
+			continue;
+
+		WARN_ON(link->flags & DL_FLAG_AUTOREMOVE);
+		WARN_ON(link->status != DL_STATE_SUPPLIER_UNBIND);
+		WRITE_ONCE(link->status, DL_STATE_DORMANT);
+	}
+
+	__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 with the DL_FLAG_STATELESS 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_STATELESS)
+			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 with the DL_FLAG_STATELESS 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_STATELESS)
+			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;
+
+	/*
+	 * 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);
+	}
+
+	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);
+	}
+
+	device_links_write_unlock();
+}
+
+/* Device links support end. */
+
 int (*platform_notify)(struct device *dev) = NULL;
 int (*platform_notify_remove)(struct device *dev) = NULL;
 static struct kobject *dev_kobj;
@@ -711,6 +1246,9 @@ void device_initialize(struct device *dev)
 #ifdef CONFIG_GENERIC_MSI_IRQ
 	INIT_LIST_HEAD(&dev->msi_list);
 #endif
+	INIT_LIST_HEAD(&dev->links.consumers);
+	INIT_LIST_HEAD(&dev->links.suppliers);
+	dev->links.status = DL_DEV_NO_DRIVER;
 }
 EXPORT_SYMBOL_GPL(device_initialize);
 
@@ -1258,6 +1796,8 @@ void device_del(struct device *dev)
 	if (dev->bus)
 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 					     BUS_NOTIFY_DEL_DEVICE, dev);
+
+	device_links_purge(dev);
 	dpm_sysfs_remove(dev);
 	if (parent)
 		klist_del(&dev->p->knode_parent);
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index df4ab5509c04..b2bca3cf0dd2 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -244,6 +244,7 @@ static void driver_bound(struct device *dev)
 		 __func__, dev_name(dev));
 
 	klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
+	device_links_driver_bound(dev);
 
 	device_pm_check_callbacks(dev);
 
@@ -337,6 +338,10 @@ static int really_probe(struct device *dev, struct device_driver *drv)
 		return ret;
 	}
 
+	ret = device_links_check_suppliers(dev);
+	if (ret)
+		return ret;
+
 	atomic_inc(&probe_count);
 	pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 		 drv->bus->name, __func__, drv->name, dev_name(dev));
@@ -415,6 +420,7 @@ probe_failed:
 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 					     BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 pinctrl_bind_failed:
+	device_links_no_driver(dev);
 	devres_release_all(dev);
 	driver_sysfs_remove(dev);
 	dev->driver = NULL;
@@ -771,7 +777,7 @@ EXPORT_SYMBOL_GPL(driver_attach);
  * __device_release_driver() must be called with @dev lock held.
  * When called for a USB interface, @dev->parent lock must be held as well.
  */
-static void __device_release_driver(struct device *dev)
+static void __device_release_driver(struct device *dev, struct device *parent)
 {
 	struct device_driver *drv;
 
@@ -780,6 +786,25 @@ static void __device_release_driver(struct device *dev)
 		if (driver_allows_async_probing(drv))
 			async_synchronize_full();
 
+		while (device_links_busy(dev)) {
+			device_unlock(dev);
+			if (parent)
+				device_unlock(parent);
+
+			device_links_unbind_consumers(dev);
+			if (parent)
+				device_lock(parent);
+
+			device_lock(dev);
+			/*
+			 * A concurrent invocation of the same function might
+			 * have released the driver successfully while this one
+			 * was waiting, so check for that.
+			 */
+			if (dev->driver != drv)
+				return;
+		}
+
 		pm_runtime_get_sync(dev);
 
 		driver_sysfs_remove(dev);
@@ -795,6 +820,8 @@ static void __device_release_driver(struct device *dev)
 			dev->bus->remove(dev);
 		else if (drv->remove)
 			drv->remove(dev);
+
+		device_links_driver_cleanup(dev);
 		devres_release_all(dev);
 		dev->driver = NULL;
 		dev_set_drvdata(dev, NULL);
@@ -811,16 +838,16 @@ static void __device_release_driver(struct device *dev)
 	}
 }
 
-static void device_release_driver_internal(struct device *dev,
-					   struct device_driver *drv,
-					   struct device *parent)
+void device_release_driver_internal(struct device *dev,
+				    struct device_driver *drv,
+				    struct device *parent)
 {
 	if (parent)
 		device_lock(parent);
 
 	device_lock(dev);
 	if (!drv || drv == dev->driver)
-		__device_release_driver(dev);
+		__device_release_driver(dev, parent);
 
 	device_unlock(dev);
 	if (parent)
@@ -833,6 +860,10 @@ static void device_release_driver_internal(struct device *dev,
  *
  * Manually detach device from driver.
  * When called for a USB interface, @dev->parent lock must be held.
+ *
+ * If this function is to be called with @dev->parent lock held, ensure that
+ * the device's consumers are unbound in advance or that their locks can be
+ * acquired under the @dev->parent lock.
  */
 void device_release_driver(struct device *dev)
 {
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index e44944f4be77..420914061405 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -131,6 +131,7 @@ void device_pm_add(struct device *dev)
 		dev_warn(dev, "parent %s should not be sleeping\n",
 			dev_name(dev->parent));
 	list_add_tail(&dev->power.entry, &dpm_list);
+	dev->power.in_dpm_list = true;
 	mutex_unlock(&dpm_list_mtx);
 }
 
@@ -145,6 +146,7 @@ void device_pm_remove(struct device *dev)
 	complete_all(&dev->power.completion);
 	mutex_lock(&dpm_list_mtx);
 	list_del_init(&dev->power.entry);
+	dev->power.in_dpm_list = false;
 	mutex_unlock(&dpm_list_mtx);
 	device_wakeup_disable(dev);
 	pm_runtime_remove(dev);
diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h
index 50e30e7b059d..0ba7842d665b 100644
--- a/drivers/base/power/power.h
+++ b/drivers/base/power/power.h
@@ -127,6 +127,11 @@ extern void device_pm_move_after(struct device *, struct device *);
 extern void device_pm_move_last(struct device *);
 extern void device_pm_check_callbacks(struct device *dev);
 
+static inline bool device_pm_initialized(struct device *dev)
+{
+	return dev->power.in_dpm_list;
+}
+
 #else /* !CONFIG_PM_SLEEP */
 
 static inline void device_pm_sleep_init(struct device *dev) {}
@@ -146,6 +151,11 @@ static inline void device_pm_move_last(struct device *dev) {}
 
 static inline void device_pm_check_callbacks(struct device *dev) {}
 
+static inline bool device_pm_initialized(struct device *dev)
+{
+	return device_is_registered(dev);
+}
+
 #endif /* !CONFIG_PM_SLEEP */
 
 static inline void device_pm_init(struct device *dev)
diff --git a/include/linux/device.h b/include/linux/device.h
index bc41e87a969b..9cae2feaf5cb 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -708,6 +708,81 @@ struct device_dma_parameters {
 };
 
 /**
+ * enum device_link_state - Device link states.
+ * @DL_STATE_NONE: The presence of the drivers is not being tracked.
+ * @DL_STATE_DORMANT: None of the supplier/consumer drivers is present.
+ * @DL_STATE_AVAILABLE: The supplier driver is present, but the consumer is not.
+ * @DL_STATE_CONSUMER_PROBE: The consumer is probing (supplier driver present).
+ * @DL_STATE_ACTIVE: Both the supplier and consumer drivers are present.
+ * @DL_STATE_SUPPLIER_UNBIND: The supplier driver is unbinding.
+ */
+enum device_link_state {
+	DL_STATE_NONE = -1,
+	DL_STATE_DORMANT = 0,
+	DL_STATE_AVAILABLE,
+	DL_STATE_CONSUMER_PROBE,
+	DL_STATE_ACTIVE,
+	DL_STATE_SUPPLIER_UNBIND,
+};
+
+/*
+ * Device link flags.
+ *
+ * STATELESS: The core won't track the presence of supplier/consumer drivers.
+ * AUTOREMOVE: Remove this link automatically on consumer driver unbind.
+ */
+#define DL_FLAG_STATELESS	BIT(0)
+#define DL_FLAG_AUTOREMOVE	BIT(1)
+
+/**
+ * struct device_link - Device link representation.
+ * @supplier: The device on the supplier end of the link.
+ * @s_node: Hook to the supplier device's list of links to consumers.
+ * @consumer: The device on the consumer end of the link.
+ * @c_node: Hook to the consumer device's list of links to suppliers.
+ * @status: The state of the link (with respect to the presence of drivers).
+ * @flags: Link flags.
+ * @rcu_head: An RCU head to use for deferred execution of SRCU callbacks.
+ */
+struct device_link {
+	struct device *supplier;
+	struct list_head s_node;
+	struct device *consumer;
+	struct list_head c_node;
+	enum device_link_state status;
+	u32 flags;
+#ifdef CONFIG_SRCU
+	struct rcu_head rcu_head;
+#endif
+};
+
+/**
+ * enum dl_dev_state - Device driver presence tracking information.
+ * @DL_DEV_NO_DRIVER: There is no driver attached to the device.
+ * @DL_DEV_PROBING: A driver is probing.
+ * @DL_DEV_DRIVER_BOUND: The driver has been bound to the device.
+ * @DL_DEV_UNBINDING: The driver is unbinding from the device.
+ */
+enum dl_dev_state {
+	DL_DEV_NO_DRIVER = 0,
+	DL_DEV_PROBING,
+	DL_DEV_DRIVER_BOUND,
+	DL_DEV_UNBINDING,
+};
+
+/**
+ * struct dev_links_info - Device data related to device links.
+ * @suppliers: List of links to supplier devices.
+ * @consumers: List of links to consumer devices.
+ * @status: Driver status information.
+ */
+struct dev_links_info {
+	struct list_head suppliers;
+	struct list_head consumers;
+	enum dl_dev_state status;
+};
+
+/**
  * struct device - The basic device structure
  * @parent:	The device's "parent" device, the device to which it is attached.
  * 		In most cases, a parent device is some sort of bus or host
@@ -799,6 +874,7 @@ struct device {
 					   core doesn't touch it */
 	void		*driver_data;	/* Driver data, set and get with
 					   dev_set/get_drvdata */
+	struct dev_links_info	links;
 	struct dev_pm_info	power;
 	struct dev_pm_domain	*pm_domain;
 
@@ -1116,6 +1192,10 @@ extern void device_shutdown(void);
 /* debugging and troubleshooting/diagnostic helpers. */
 extern const char *dev_driver_string(const struct device *dev);
 
+/* Device links interface. */
+struct device_link *device_link_add(struct device *consumer,
+				    struct device *supplier, u32 flags);
+void device_link_del(struct device_link *link);
 
 #ifdef CONFIG_PRINTK
 
diff --git a/include/linux/pm.h b/include/linux/pm.h
index 06eb353182ab..721a70241fcd 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -559,6 +559,7 @@ struct dev_pm_info {
 	pm_message_t		power_state;
 	unsigned int		can_wakeup:1;
 	unsigned int		async_suspend:1;
+	bool			in_dpm_list:1;	/* Owned by the PM core */
 	bool			is_prepared:1;	/* Owned by the PM core */
 	bool			is_suspended:1;	/* Ditto */
 	bool			is_noirq_suspended:1;