Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 927 insertions, 0 deletions

diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
new file mode 100644
index 000000000..008a2a3e3
--- /dev/null
+++ b/drivers/media/v4l2-core/v4l2-async.c
@@ -0,0 +1,927 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * V4L2 asynchronous subdevice registration API
+ *
+ * Copyright (C) 2012-2013, Guennadi Liakhovetski <g.liakhovetski@gmx.de>
+ */
+
+#include <linux/debugfs.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include <media/v4l2-async.h>
+#include <media/v4l2-device.h>
+#include <media/v4l2-fwnode.h>
+#include <media/v4l2-subdev.h>
+
+static int v4l2_async_nf_call_bound(struct v4l2_async_notifier *n,
+				    struct v4l2_subdev *subdev,
+				    struct v4l2_async_subdev *asd)
+{
+	if (!n->ops || !n->ops->bound)
+		return 0;
+
+	return n->ops->bound(n, subdev, asd);
+}
+
+static void v4l2_async_nf_call_unbind(struct v4l2_async_notifier *n,
+				      struct v4l2_subdev *subdev,
+				      struct v4l2_async_subdev *asd)
+{
+	if (!n->ops || !n->ops->unbind)
+		return;
+
+	n->ops->unbind(n, subdev, asd);
+}
+
+static int v4l2_async_nf_call_complete(struct v4l2_async_notifier *n)
+{
+	if (!n->ops || !n->ops->complete)
+		return 0;
+
+	return n->ops->complete(n);
+}
+
+static void v4l2_async_nf_call_destroy(struct v4l2_async_notifier *n,
+				       struct v4l2_async_subdev *asd)
+{
+	if (!n->ops || !n->ops->destroy)
+		return;
+
+	n->ops->destroy(asd);
+}
+
+static bool match_i2c(struct v4l2_async_notifier *notifier,
+		      struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)
+{
+#if IS_ENABLED(CONFIG_I2C)
+	struct i2c_client *client = i2c_verify_client(sd->dev);
+
+	return client &&
+		asd->match.i2c.adapter_id == client->adapter->nr &&
+		asd->match.i2c.address == client->addr;
+#else
+	return false;
+#endif
+}
+
+static bool
+match_fwnode_one(struct v4l2_async_notifier *notifier,
+		 struct v4l2_subdev *sd, struct fwnode_handle *sd_fwnode,
+		 struct v4l2_async_subdev *asd)
+{
+	struct fwnode_handle *other_fwnode;
+	struct fwnode_handle *dev_fwnode;
+	bool asd_fwnode_is_ep;
+	bool sd_fwnode_is_ep;
+	struct device *dev;
+
+	/*
+	 * Both the subdev and the async subdev can provide either an endpoint
+	 * fwnode or a device fwnode. Start with the simple case of direct
+	 * fwnode matching.
+	 */
+	if (sd_fwnode == asd->match.fwnode)
+		return true;
+
+	/*
+	 * Otherwise, check if the sd fwnode and the asd fwnode refer to an
+	 * endpoint or a device. If they're of the same type, there's no match.
+	 * Technically speaking this checks if the nodes refer to a connected
+	 * endpoint, which is the simplest check that works for both OF and
+	 * ACPI. This won't make a difference, as drivers should not try to
+	 * match unconnected endpoints.
+	 */
+	sd_fwnode_is_ep = fwnode_graph_is_endpoint(sd_fwnode);
+	asd_fwnode_is_ep = fwnode_graph_is_endpoint(asd->match.fwnode);
+
+	if (sd_fwnode_is_ep == asd_fwnode_is_ep)
+		return false;
+
+	/*
+	 * The sd and asd fwnodes are of different types. Get the device fwnode
+	 * parent of the endpoint fwnode, and compare it with the other fwnode.
+	 */
+	if (sd_fwnode_is_ep) {
+		dev_fwnode = fwnode_graph_get_port_parent(sd_fwnode);
+		other_fwnode = asd->match.fwnode;
+	} else {
+		dev_fwnode = fwnode_graph_get_port_parent(asd->match.fwnode);
+		other_fwnode = sd_fwnode;
+	}
+
+	fwnode_handle_put(dev_fwnode);
+
+	if (dev_fwnode != other_fwnode)
+		return false;
+
+	/*
+	 * We have a heterogeneous match. Retrieve the struct device of the side
+	 * that matched on a device fwnode to print its driver name.
+	 */
+	if (sd_fwnode_is_ep)
+		dev = notifier->v4l2_dev ? notifier->v4l2_dev->dev
+		    : notifier->sd->dev;
+	else
+		dev = sd->dev;
+
+	if (dev && dev->driver) {
+		if (sd_fwnode_is_ep)
+			dev_warn(dev, "Driver %s uses device fwnode, incorrect match may occur\n",
+				 dev->driver->name);
+		dev_notice(dev, "Consider updating driver %s to match on endpoints\n",
+			   dev->driver->name);
+	}
+
+	return true;
+}
+
+static bool match_fwnode(struct v4l2_async_notifier *notifier,
+			 struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)
+{
+	if (match_fwnode_one(notifier, sd, sd->fwnode, asd))
+		return true;
+
+	/* Also check the secondary fwnode. */
+	if (IS_ERR_OR_NULL(sd->fwnode->secondary))
+		return false;
+
+	return match_fwnode_one(notifier, sd, sd->fwnode->secondary, asd);
+}
+
+static LIST_HEAD(subdev_list);
+static LIST_HEAD(notifier_list);
+static DEFINE_MUTEX(list_lock);
+
+static struct v4l2_async_subdev *
+v4l2_async_find_match(struct v4l2_async_notifier *notifier,
+		      struct v4l2_subdev *sd)
+{
+	bool (*match)(struct v4l2_async_notifier *notifier,
+		      struct v4l2_subdev *sd, struct v4l2_async_subdev *asd);
+	struct v4l2_async_subdev *asd;
+
+	list_for_each_entry(asd, &notifier->waiting, list) {
+		/* bus_type has been verified valid before */
+		switch (asd->match_type) {
+		case V4L2_ASYNC_MATCH_I2C:
+			match = match_i2c;
+			break;
+		case V4L2_ASYNC_MATCH_FWNODE:
+			match = match_fwnode;
+			break;
+		default:
+			/* Cannot happen, unless someone breaks us */
+			WARN_ON(true);
+			return NULL;
+		}
+
+		/* match cannot be NULL here */
+		if (match(notifier, sd, asd))
+			return asd;
+	}
+
+	return NULL;
+}
+
+/* Compare two async sub-device descriptors for equivalence */
+static bool asd_equal(struct v4l2_async_subdev *asd_x,
+		      struct v4l2_async_subdev *asd_y)
+{
+	if (asd_x->match_type != asd_y->match_type)
+		return false;
+
+	switch (asd_x->match_type) {
+	case V4L2_ASYNC_MATCH_I2C:
+		return asd_x->match.i2c.adapter_id ==
+			asd_y->match.i2c.adapter_id &&
+			asd_x->match.i2c.address ==
+			asd_y->match.i2c.address;
+	case V4L2_ASYNC_MATCH_FWNODE:
+		return asd_x->match.fwnode == asd_y->match.fwnode;
+	default:
+		break;
+	}
+
+	return false;
+}
+
+/* Find the sub-device notifier registered by a sub-device driver. */
+static struct v4l2_async_notifier *
+v4l2_async_find_subdev_notifier(struct v4l2_subdev *sd)
+{
+	struct v4l2_async_notifier *n;
+
+	list_for_each_entry(n, &notifier_list, list)
+		if (n->sd == sd)
+			return n;
+
+	return NULL;
+}
+
+/* Get v4l2_device related to the notifier if one can be found. */
+static struct v4l2_device *
+v4l2_async_nf_find_v4l2_dev(struct v4l2_async_notifier *notifier)
+{
+	while (notifier->parent)
+		notifier = notifier->parent;
+
+	return notifier->v4l2_dev;
+}
+
+/*
+ * Return true if all child sub-device notifiers are complete, false otherwise.
+ */
+static bool
+v4l2_async_nf_can_complete(struct v4l2_async_notifier *notifier)
+{
+	struct v4l2_subdev *sd;
+
+	if (!list_empty(&notifier->waiting))
+		return false;
+
+	list_for_each_entry(sd, &notifier->done, async_list) {
+		struct v4l2_async_notifier *subdev_notifier =
+			v4l2_async_find_subdev_notifier(sd);
+
+		if (subdev_notifier &&
+		    !v4l2_async_nf_can_complete(subdev_notifier))
+			return false;
+	}
+
+	return true;
+}
+
+/*
+ * Complete the master notifier if possible. This is done when all async
+ * sub-devices have been bound; v4l2_device is also available then.
+ */
+static int
+v4l2_async_nf_try_complete(struct v4l2_async_notifier *notifier)
+{
+	/* Quick check whether there are still more sub-devices here. */
+	if (!list_empty(&notifier->waiting))
+		return 0;
+
+	/* Check the entire notifier tree; find the root notifier first. */
+	while (notifier->parent)
+		notifier = notifier->parent;
+
+	/* This is root if it has v4l2_dev. */
+	if (!notifier->v4l2_dev)
+		return 0;
+
+	/* Is everything ready? */
+	if (!v4l2_async_nf_can_complete(notifier))
+		return 0;
+
+	return v4l2_async_nf_call_complete(notifier);
+}
+
+static int
+v4l2_async_nf_try_all_subdevs(struct v4l2_async_notifier *notifier);
+
+static int v4l2_async_create_ancillary_links(struct v4l2_async_notifier *n,
+					     struct v4l2_subdev *sd)
+{
+	struct media_link *link = NULL;
+
+#if IS_ENABLED(CONFIG_MEDIA_CONTROLLER)
+
+	if (sd->entity.function != MEDIA_ENT_F_LENS &&
+	    sd->entity.function != MEDIA_ENT_F_FLASH)
+		return 0;
+
+	link = media_create_ancillary_link(&n->sd->entity, &sd->entity);
+
+#endif
+
+	return IS_ERR(link) ? PTR_ERR(link) : 0;
+}
+
+static int v4l2_async_match_notify(struct v4l2_async_notifier *notifier,
+				   struct v4l2_device *v4l2_dev,
+				   struct v4l2_subdev *sd,
+				   struct v4l2_async_subdev *asd)
+{
+	struct v4l2_async_notifier *subdev_notifier;
+	int ret;
+
+	ret = v4l2_device_register_subdev(v4l2_dev, sd);
+	if (ret < 0)
+		return ret;
+
+	ret = v4l2_async_nf_call_bound(notifier, sd, asd);
+	if (ret < 0) {
+		v4l2_device_unregister_subdev(sd);
+		return ret;
+	}
+
+	/*
+	 * Depending of the function of the entities involved, we may want to
+	 * create links between them (for example between a sensor and its lens
+	 * or between a sensor's source pad and the connected device's sink
+	 * pad).
+	 */
+	ret = v4l2_async_create_ancillary_links(notifier, sd);
+	if (ret) {
+		v4l2_async_nf_call_unbind(notifier, sd, asd);
+		v4l2_device_unregister_subdev(sd);
+		return ret;
+	}
+
+	/* Remove from the waiting list */
+	list_del(&asd->list);
+	sd->asd = asd;
+	sd->notifier = notifier;
+
+	/* Move from the global subdevice list to notifier's done */
+	list_move(&sd->async_list, &notifier->done);
+
+	/*
+	 * See if the sub-device has a notifier. If not, return here.
+	 */
+	subdev_notifier = v4l2_async_find_subdev_notifier(sd);
+	if (!subdev_notifier || subdev_notifier->parent)
+		return 0;
+
+	/*
+	 * Proceed with checking for the sub-device notifier's async
+	 * sub-devices, and return the result. The error will be handled by the
+	 * caller.
+	 */
+	subdev_notifier->parent = notifier;
+
+	return v4l2_async_nf_try_all_subdevs(subdev_notifier);
+}
+
+/* Test all async sub-devices in a notifier for a match. */
+static int
+v4l2_async_nf_try_all_subdevs(struct v4l2_async_notifier *notifier)
+{
+	struct v4l2_device *v4l2_dev =
+		v4l2_async_nf_find_v4l2_dev(notifier);
+	struct v4l2_subdev *sd;
+
+	if (!v4l2_dev)
+		return 0;
+
+again:
+	list_for_each_entry(sd, &subdev_list, async_list) {
+		struct v4l2_async_subdev *asd;
+		int ret;
+
+		asd = v4l2_async_find_match(notifier, sd);
+		if (!asd)
+			continue;
+
+		ret = v4l2_async_match_notify(notifier, v4l2_dev, sd, asd);
+		if (ret < 0)
+			return ret;
+
+		/*
+		 * v4l2_async_match_notify() may lead to registering a
+		 * new notifier and thus changing the async subdevs
+		 * list. In order to proceed safely from here, restart
+		 * parsing the list from the beginning.
+		 */
+		goto again;
+	}
+
+	return 0;
+}
+
+static void v4l2_async_cleanup(struct v4l2_subdev *sd)
+{
+	v4l2_device_unregister_subdev(sd);
+	/*
+	 * Subdevice driver will reprobe and put the subdev back
+	 * onto the list
+	 */
+	list_del_init(&sd->async_list);
+	sd->asd = NULL;
+}
+
+/* Unbind all sub-devices in the notifier tree. */
+static void
+v4l2_async_nf_unbind_all_subdevs(struct v4l2_async_notifier *notifier,
+				 bool readd)
+{
+	struct v4l2_subdev *sd, *tmp;
+
+	list_for_each_entry_safe(sd, tmp, &notifier->done, async_list) {
+		struct v4l2_async_notifier *subdev_notifier =
+			v4l2_async_find_subdev_notifier(sd);
+
+		if (subdev_notifier)
+			v4l2_async_nf_unbind_all_subdevs(subdev_notifier, true);
+
+		v4l2_async_nf_call_unbind(notifier, sd, sd->asd);
+		if (readd)
+			list_add_tail(&sd->asd->list, &notifier->waiting);
+		v4l2_async_cleanup(sd);
+
+		list_move(&sd->async_list, &subdev_list);
+	}
+
+	notifier->parent = NULL;
+}
+
+/* See if an async sub-device can be found in a notifier's lists. */
+static bool
+__v4l2_async_nf_has_async_subdev(struct v4l2_async_notifier *notifier,
+				 struct v4l2_async_subdev *asd)
+{
+	struct v4l2_async_subdev *asd_y;
+	struct v4l2_subdev *sd;
+
+	list_for_each_entry(asd_y, &notifier->waiting, list)
+		if (asd_equal(asd, asd_y))
+			return true;
+
+	list_for_each_entry(sd, &notifier->done, async_list) {
+		if (WARN_ON(!sd->asd))
+			continue;
+
+		if (asd_equal(asd, sd->asd))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Find out whether an async sub-device was set up already or
+ * whether it exists in a given notifier before @this_index.
+ * If @this_index < 0, search the notifier's entire @asd_list.
+ */
+static bool
+v4l2_async_nf_has_async_subdev(struct v4l2_async_notifier *notifier,
+			       struct v4l2_async_subdev *asd, int this_index)
+{
+	struct v4l2_async_subdev *asd_y;
+	int j = 0;
+
+	lockdep_assert_held(&list_lock);
+
+	/* Check that an asd is not being added more than once. */
+	list_for_each_entry(asd_y, &notifier->asd_list, asd_list) {
+		if (this_index >= 0 && j++ >= this_index)
+			break;
+		if (asd_equal(asd, asd_y))
+			return true;
+	}
+
+	/* Check that an asd does not exist in other notifiers. */
+	list_for_each_entry(notifier, &notifier_list, list)
+		if (__v4l2_async_nf_has_async_subdev(notifier, asd))
+			return true;
+
+	return false;
+}
+
+static int v4l2_async_nf_asd_valid(struct v4l2_async_notifier *notifier,
+				   struct v4l2_async_subdev *asd,
+				   int this_index)
+{
+	struct device *dev =
+		notifier->v4l2_dev ? notifier->v4l2_dev->dev : NULL;
+
+	if (!asd)
+		return -EINVAL;
+
+	switch (asd->match_type) {
+	case V4L2_ASYNC_MATCH_I2C:
+	case V4L2_ASYNC_MATCH_FWNODE:
+		if (v4l2_async_nf_has_async_subdev(notifier, asd, this_index)) {
+			dev_dbg(dev, "subdev descriptor already listed in this or other notifiers\n");
+			return -EEXIST;
+		}
+		break;
+	default:
+		dev_err(dev, "Invalid match type %u on %p\n",
+			asd->match_type, asd);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+void v4l2_async_nf_init(struct v4l2_async_notifier *notifier)
+{
+	INIT_LIST_HEAD(&notifier->asd_list);
+}
+EXPORT_SYMBOL(v4l2_async_nf_init);
+
+static int __v4l2_async_nf_register(struct v4l2_async_notifier *notifier)
+{
+	struct v4l2_async_subdev *asd;
+	int ret, i = 0;
+
+	INIT_LIST_HEAD(&notifier->waiting);
+	INIT_LIST_HEAD(&notifier->done);
+
+	mutex_lock(&list_lock);
+
+	list_for_each_entry(asd, &notifier->asd_list, asd_list) {
+		ret = v4l2_async_nf_asd_valid(notifier, asd, i++);
+		if (ret)
+			goto err_unlock;
+
+		list_add_tail(&asd->list, &notifier->waiting);
+	}
+
+	ret = v4l2_async_nf_try_all_subdevs(notifier);
+	if (ret < 0)
+		goto err_unbind;
+
+	ret = v4l2_async_nf_try_complete(notifier);
+	if (ret < 0)
+		goto err_unbind;
+
+	/* Keep also completed notifiers on the list */
+	list_add(&notifier->list, &notifier_list);
+
+	mutex_unlock(&list_lock);
+
+	return 0;
+
+err_unbind:
+	/*
+	 * On failure, unbind all sub-devices registered through this notifier.
+	 */
+	v4l2_async_nf_unbind_all_subdevs(notifier, false);
+
+err_unlock:
+	mutex_unlock(&list_lock);
+
+	return ret;
+}
+
+int v4l2_async_nf_register(struct v4l2_device *v4l2_dev,
+			   struct v4l2_async_notifier *notifier)
+{
+	int ret;
+
+	if (WARN_ON(!v4l2_dev || notifier->sd))
+		return -EINVAL;
+
+	notifier->v4l2_dev = v4l2_dev;
+
+	ret = __v4l2_async_nf_register(notifier);
+	if (ret)
+		notifier->v4l2_dev = NULL;
+
+	return ret;
+}
+EXPORT_SYMBOL(v4l2_async_nf_register);
+
+int v4l2_async_subdev_nf_register(struct v4l2_subdev *sd,
+				  struct v4l2_async_notifier *notifier)
+{
+	int ret;
+
+	if (WARN_ON(!sd || notifier->v4l2_dev))
+		return -EINVAL;
+
+	notifier->sd = sd;
+
+	ret = __v4l2_async_nf_register(notifier);
+	if (ret)
+		notifier->sd = NULL;
+
+	return ret;
+}
+EXPORT_SYMBOL(v4l2_async_subdev_nf_register);
+
+static void
+__v4l2_async_nf_unregister(struct v4l2_async_notifier *notifier)
+{
+	if (!notifier || (!notifier->v4l2_dev && !notifier->sd))
+		return;
+
+	v4l2_async_nf_unbind_all_subdevs(notifier, false);
+
+	notifier->sd = NULL;
+	notifier->v4l2_dev = NULL;
+
+	list_del(&notifier->list);
+}
+
+void v4l2_async_nf_unregister(struct v4l2_async_notifier *notifier)
+{
+	mutex_lock(&list_lock);
+
+	__v4l2_async_nf_unregister(notifier);
+
+	mutex_unlock(&list_lock);
+}
+EXPORT_SYMBOL(v4l2_async_nf_unregister);
+
+static void __v4l2_async_nf_cleanup(struct v4l2_async_notifier *notifier)
+{
+	struct v4l2_async_subdev *asd, *tmp;
+
+	if (!notifier || !notifier->asd_list.next)
+		return;
+
+	list_for_each_entry_safe(asd, tmp, &notifier->asd_list, asd_list) {
+		switch (asd->match_type) {
+		case V4L2_ASYNC_MATCH_FWNODE:
+			fwnode_handle_put(asd->match.fwnode);
+			break;
+		default:
+			break;
+		}
+
+		list_del(&asd->asd_list);
+		v4l2_async_nf_call_destroy(notifier, asd);
+		kfree(asd);
+	}
+}
+
+void v4l2_async_nf_cleanup(struct v4l2_async_notifier *notifier)
+{
+	mutex_lock(&list_lock);
+
+	__v4l2_async_nf_cleanup(notifier);
+
+	mutex_unlock(&list_lock);
+}
+EXPORT_SYMBOL_GPL(v4l2_async_nf_cleanup);
+
+int __v4l2_async_nf_add_subdev(struct v4l2_async_notifier *notifier,
+			       struct v4l2_async_subdev *asd)
+{
+	int ret;
+
+	mutex_lock(&list_lock);
+
+	ret = v4l2_async_nf_asd_valid(notifier, asd, -1);
+	if (ret)
+		goto unlock;
+
+	list_add_tail(&asd->asd_list, &notifier->asd_list);
+
+unlock:
+	mutex_unlock(&list_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__v4l2_async_nf_add_subdev);
+
+struct v4l2_async_subdev *
+__v4l2_async_nf_add_fwnode(struct v4l2_async_notifier *notifier,
+			   struct fwnode_handle *fwnode,
+			   unsigned int asd_struct_size)
+{
+	struct v4l2_async_subdev *asd;
+	int ret;
+
+	asd = kzalloc(asd_struct_size, GFP_KERNEL);
+	if (!asd)
+		return ERR_PTR(-ENOMEM);
+
+	asd->match_type = V4L2_ASYNC_MATCH_FWNODE;
+	asd->match.fwnode = fwnode_handle_get(fwnode);
+
+	ret = __v4l2_async_nf_add_subdev(notifier, asd);
+	if (ret) {
+		fwnode_handle_put(fwnode);
+		kfree(asd);
+		return ERR_PTR(ret);
+	}
+
+	return asd;
+}
+EXPORT_SYMBOL_GPL(__v4l2_async_nf_add_fwnode);
+
+struct v4l2_async_subdev *
+__v4l2_async_nf_add_fwnode_remote(struct v4l2_async_notifier *notif,
+				  struct fwnode_handle *endpoint,
+				  unsigned int asd_struct_size)
+{
+	struct v4l2_async_subdev *asd;
+	struct fwnode_handle *remote;
+
+	remote = fwnode_graph_get_remote_endpoint(endpoint);
+	if (!remote)
+		return ERR_PTR(-ENOTCONN);
+
+	asd = __v4l2_async_nf_add_fwnode(notif, remote, asd_struct_size);
+	/*
+	 * Calling __v4l2_async_nf_add_fwnode grabs a refcount,
+	 * so drop the one we got in fwnode_graph_get_remote_port_parent.
+	 */
+	fwnode_handle_put(remote);
+	return asd;
+}
+EXPORT_SYMBOL_GPL(__v4l2_async_nf_add_fwnode_remote);
+
+struct v4l2_async_subdev *
+__v4l2_async_nf_add_i2c(struct v4l2_async_notifier *notifier, int adapter_id,
+			unsigned short address, unsigned int asd_struct_size)
+{
+	struct v4l2_async_subdev *asd;
+	int ret;
+
+	asd = kzalloc(asd_struct_size, GFP_KERNEL);
+	if (!asd)
+		return ERR_PTR(-ENOMEM);
+
+	asd->match_type = V4L2_ASYNC_MATCH_I2C;
+	asd->match.i2c.adapter_id = adapter_id;
+	asd->match.i2c.address = address;
+
+	ret = __v4l2_async_nf_add_subdev(notifier, asd);
+	if (ret) {
+		kfree(asd);
+		return ERR_PTR(ret);
+	}
+
+	return asd;
+}
+EXPORT_SYMBOL_GPL(__v4l2_async_nf_add_i2c);
+
+int v4l2_async_register_subdev(struct v4l2_subdev *sd)
+{
+	struct v4l2_async_notifier *subdev_notifier;
+	struct v4l2_async_notifier *notifier;
+	int ret;
+
+	/*
+	 * No reference taken. The reference is held by the device
+	 * (struct v4l2_subdev.dev), and async sub-device does not
+	 * exist independently of the device at any point of time.
+	 */
+	if (!sd->fwnode && sd->dev)
+		sd->fwnode = dev_fwnode(sd->dev);
+
+	mutex_lock(&list_lock);
+
+	INIT_LIST_HEAD(&sd->async_list);
+
+	list_for_each_entry(notifier, &notifier_list, list) {
+		struct v4l2_device *v4l2_dev =
+			v4l2_async_nf_find_v4l2_dev(notifier);
+		struct v4l2_async_subdev *asd;
+
+		if (!v4l2_dev)
+			continue;
+
+		asd = v4l2_async_find_match(notifier, sd);
+		if (!asd)
+			continue;
+
+		ret = v4l2_async_match_notify(notifier, v4l2_dev, sd, asd);
+		if (ret)
+			goto err_unbind;
+
+		ret = v4l2_async_nf_try_complete(notifier);
+		if (ret)
+			goto err_unbind;
+
+		goto out_unlock;
+	}
+
+	/* None matched, wait for hot-plugging */
+	list_add(&sd->async_list, &subdev_list);
+
+out_unlock:
+	mutex_unlock(&list_lock);
+
+	return 0;
+
+err_unbind:
+	/*
+	 * Complete failed. Unbind the sub-devices bound through registering
+	 * this async sub-device.
+	 */
+	subdev_notifier = v4l2_async_find_subdev_notifier(sd);
+	if (subdev_notifier)
+		v4l2_async_nf_unbind_all_subdevs(subdev_notifier, false);
+
+	if (sd->asd)
+		v4l2_async_nf_call_unbind(notifier, sd, sd->asd);
+	v4l2_async_cleanup(sd);
+
+	mutex_unlock(&list_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL(v4l2_async_register_subdev);
+
+void v4l2_async_unregister_subdev(struct v4l2_subdev *sd)
+{
+	if (!sd->async_list.next)
+		return;
+
+	mutex_lock(&list_lock);
+
+	__v4l2_async_nf_unregister(sd->subdev_notifier);
+	__v4l2_async_nf_cleanup(sd->subdev_notifier);
+	kfree(sd->subdev_notifier);
+	sd->subdev_notifier = NULL;
+
+	if (sd->asd) {
+		struct v4l2_async_notifier *notifier = sd->notifier;
+
+		list_add(&sd->asd->list, &notifier->waiting);
+
+		v4l2_async_nf_call_unbind(notifier, sd, sd->asd);
+	}
+
+	v4l2_async_cleanup(sd);
+
+	mutex_unlock(&list_lock);
+}
+EXPORT_SYMBOL(v4l2_async_unregister_subdev);
+
+static void print_waiting_subdev(struct seq_file *s,
+				 struct v4l2_async_subdev *asd)
+{
+	switch (asd->match_type) {
+	case V4L2_ASYNC_MATCH_I2C:
+		seq_printf(s, " [i2c] dev=%d-%04x\n", asd->match.i2c.adapter_id,
+			   asd->match.i2c.address);
+		break;
+	case V4L2_ASYNC_MATCH_FWNODE: {
+		struct fwnode_handle *devnode, *fwnode = asd->match.fwnode;
+
+		devnode = fwnode_graph_is_endpoint(fwnode) ?
+			  fwnode_graph_get_port_parent(fwnode) :
+			  fwnode_handle_get(fwnode);
+
+		seq_printf(s, " [fwnode] dev=%s, node=%pfw\n",
+			   devnode->dev ? dev_name(devnode->dev) : "nil",
+			   fwnode);
+
+		fwnode_handle_put(devnode);
+		break;
+	}
+	}
+}
+
+static const char *
+v4l2_async_nf_name(struct v4l2_async_notifier *notifier)
+{
+	if (notifier->v4l2_dev)
+		return notifier->v4l2_dev->name;
+	else if (notifier->sd)
+		return notifier->sd->name;
+	else
+		return "nil";
+}
+
+static int pending_subdevs_show(struct seq_file *s, void *data)
+{
+	struct v4l2_async_notifier *notif;
+	struct v4l2_async_subdev *asd;
+
+	mutex_lock(&list_lock);
+
+	list_for_each_entry(notif, &notifier_list, list) {
+		seq_printf(s, "%s:\n", v4l2_async_nf_name(notif));
+		list_for_each_entry(asd, &notif->waiting, list)
+			print_waiting_subdev(s, asd);
+	}
+
+	mutex_unlock(&list_lock);
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(pending_subdevs);
+
+static struct dentry *v4l2_async_debugfs_dir;
+
+static int __init v4l2_async_init(void)
+{
+	v4l2_async_debugfs_dir = debugfs_create_dir("v4l2-async", NULL);
+	debugfs_create_file("pending_async_subdevices", 0444,
+			    v4l2_async_debugfs_dir, NULL,
+			    &pending_subdevs_fops);
+
+	return 0;
+}
+
+static void __exit v4l2_async_exit(void)
+{
+	debugfs_remove_recursive(v4l2_async_debugfs_dir);
+}
+
+subsys_initcall(v4l2_async_init);
+module_exit(v4l2_async_exit);
+
+MODULE_AUTHOR("Guennadi Liakhovetski <g.liakhovetski@gmx.de>");
+MODULE_AUTHOR("Sakari Ailus <sakari.ailus@linux.intel.com>");
+MODULE_AUTHOR("Ezequiel Garcia <ezequiel@collabora.com>");
+MODULE_LICENSE("GPL");