text: // 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_notifier_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_notifier_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_notifier_call_complete(struct v4l2_async_notifier *n)
  {
  	if (!n->ops || !n->ops->complete)
  		return 0;
  
  	return n->ops->complete(n);
  }
  
  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(struct v4l2_async_notifier *notifier,
  			 struct v4l2_subdev *sd, 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;
  
  	/*
  	 * Check the same situation for any possible secondary assigned to the
  	 * subdev's fwnode
  	 */
  	if (!IS_ERR_OR_NULL(sd->fwnode->secondary) &&
  	    sd->fwnode->secondary == 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 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_notifier_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_notifier_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_notifier_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_notifier_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_notifier_can_complete(notifier))
  		return 0;
  
  	return v4l2_async_notifier_call_complete(notifier);
  }
  
  static int
  v4l2_async_notifier_try_all_subdevs(struct v4l2_async_notifier *notifier);
  
  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_notifier_call_bound(notifier, sd, asd);
  	if (ret < 0) {
  		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_notifier_try_all_subdevs(subdev_notifier);
  }
  
  /* Test all async sub-devices in a notifier for a match. */
  static int
  v4l2_async_notifier_try_all_subdevs(struct v4l2_async_notifier *notifier)
  {
  	struct v4l2_device *v4l2_dev =
  		v4l2_async_notifier_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_notifier_unbind_all_subdevs(struct v4l2_async_notifier *notifier)
  {
  	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_notifier_unbind_all_subdevs(subdev_notifier);
  
  		v4l2_async_notifier_call_unbind(notifier, sd, sd->asd);
  		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_notifier_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_notifier_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_notifier_has_async_subdev(notifier, asd))
  			return true;
  
  	return false;
  }
  
  static int v4l2_async_notifier_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_notifier_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_notifier_init(struct v4l2_async_notifier *notifier)
  {
  	INIT_LIST_HEAD(&notifier->asd_list);
  }
  EXPORT_SYMBOL(v4l2_async_notifier_init);
  
  static int __v4l2_async_notifier_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_notifier_asd_valid(notifier, asd, i++);
  		if (ret)
  			goto err_unlock;
  
  		list_add_tail(&asd->list, &notifier->waiting);
  	}
  
  	ret = v4l2_async_notifier_try_all_subdevs(notifier);
  	if (ret < 0)
  		goto err_unbind;
  
  	ret = v4l2_async_notifier_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_notifier_unbind_all_subdevs(notifier);
  
  err_unlock:
  	mutex_unlock(&list_lock);
  
  	return ret;
  }
  
  int v4l2_async_notifier_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_notifier_register(notifier);
  	if (ret)
  		notifier->v4l2_dev = NULL;
  
  	return ret;
  }
  EXPORT_SYMBOL(v4l2_async_notifier_register);
  
  int v4l2_async_subdev_notifier_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_notifier_register(notifier);
  	if (ret)
  		notifier->sd = NULL;
  
  	return ret;
  }
  EXPORT_SYMBOL(v4l2_async_subdev_notifier_register);
  
  static void
  __v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
  {
  	if (!notifier || (!notifier->v4l2_dev && !notifier->sd))
  		return;
  
  	v4l2_async_notifier_unbind_all_subdevs(notifier);
  
  	notifier->sd = NULL;
  	notifier->v4l2_dev = NULL;
  
  	list_del(&notifier->list);
  }
  
  void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
  {
  	mutex_lock(&list_lock);
  
  	__v4l2_async_notifier_unregister(notifier);
  
  	mutex_unlock(&list_lock);
  }
  EXPORT_SYMBOL(v4l2_async_notifier_unregister);
  
  static void __v4l2_async_notifier_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);
  		kfree(asd);
  	}
  }
  
  void v4l2_async_notifier_cleanup(struct v4l2_async_notifier *notifier)
  {
  	mutex_lock(&list_lock);
  
  	__v4l2_async_notifier_cleanup(notifier);
  
  	mutex_unlock(&list_lock);
  }
  EXPORT_SYMBOL_GPL(v4l2_async_notifier_cleanup);
  
  int __v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
  				   struct v4l2_async_subdev *asd)
  {
  	int ret;
  
  	mutex_lock(&list_lock);
  
  	ret = v4l2_async_notifier_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_notifier_add_subdev);
  
  struct v4l2_async_subdev *
  __v4l2_async_notifier_add_fwnode_subdev(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_notifier_add_subdev(notifier, asd);
  	if (ret) {
  		fwnode_handle_put(fwnode);
  		kfree(asd);
  		return ERR_PTR(ret);
  	}
  
  	return asd;
  }
  EXPORT_SYMBOL_GPL(__v4l2_async_notifier_add_fwnode_subdev);
  
  struct v4l2_async_subdev *
  __v4l2_async_notifier_add_fwnode_remote_subdev(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_port_parent(endpoint);
  	if (!remote)
  		return ERR_PTR(-ENOTCONN);
  
  	asd = __v4l2_async_notifier_add_fwnode_subdev(notif, remote,
  						      asd_struct_size);
  	/*
  	 * Calling __v4l2_async_notifier_add_fwnode_subdev 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_notifier_add_fwnode_remote_subdev);
  
  struct v4l2_async_subdev *
  __v4l2_async_notifier_add_i2c_subdev(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_notifier_add_subdev(notifier, asd);
  	if (ret) {
  		kfree(asd);
  		return ERR_PTR(ret);
  	}
  
  	return asd;
  }
  EXPORT_SYMBOL_GPL(__v4l2_async_notifier_add_i2c_subdev);
  
  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_notifier_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_notifier_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_notifier_unbind_all_subdevs(subdev_notifier);
  
  	if (sd->asd)
  		v4l2_async_notifier_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_notifier_unregister(sd->subdev_notifier);
  	__v4l2_async_notifier_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_notifier_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_notifier_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_notifier_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");
  