// 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>

#include "v4l2-subdev-priv.h"

static int v4l2_async_nf_call_bound(struct v4l2_async_notifier *n,
                                    struct v4l2_subdev *subdev,
                                    struct v4l2_async_connection *asc)
{
        if (!n->ops || !n->ops->bound)
                return 0;

        return n->ops->bound(n, subdev, asc);
}

static void v4l2_async_nf_call_unbind(struct v4l2_async_notifier *n,
                                      struct v4l2_subdev *subdev,
                                      struct v4l2_async_connection *asc)
{
        if (!n->ops || !n->ops->unbind)
                return;

        n->ops->unbind(n, subdev, asc);
}

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_connection *asc)
{
        if (!n->ops || !n->ops->destroy)
                return;

        n->ops->destroy(asc);
}

static bool match_i2c(struct v4l2_async_notifier *notifier,
                      struct v4l2_subdev *sd,
                      struct v4l2_async_match_desc *match)
{
#if IS_ENABLED(CONFIG_I2C)
        struct i2c_client *client = i2c_verify_client(sd->dev);

        return client &&
                match->i2c.adapter_id == client->adapter->nr &&
                match->i2c.address == client->addr;
#else
        return false;
#endif
}

static struct device *notifier_dev(struct v4l2_async_notifier *notifier)
{
        if (notifier->sd)
                return notifier->sd->dev;

        if (notifier->v4l2_dev)
                return notifier->v4l2_dev->dev;

        return NULL;
}

static bool
match_fwnode_one(struct v4l2_async_notifier *notifier,
                 struct v4l2_subdev *sd, struct fwnode_handle *sd_fwnode,
                 struct v4l2_async_match_desc *match)
{
        struct fwnode_handle *asd_dev_fwnode;
        bool ret;

        dev_dbg(notifier_dev(notifier),
                "v4l2-async: fwnode match: need %pfw, trying %pfw\n",
                sd_fwnode, match->fwnode);

        if (sd_fwnode == match->fwnode) {
                dev_dbg(notifier_dev(notifier),
                        "v4l2-async: direct match found\n");
                return true;
        }

        if (!fwnode_graph_is_endpoint(match->fwnode)) {
                dev_dbg(notifier_dev(notifier),
                        "v4l2-async: direct match not found\n");
                return false;
        }

        asd_dev_fwnode = fwnode_graph_get_port_parent(match->fwnode);

        ret = sd_fwnode == asd_dev_fwnode;

        fwnode_handle_put(asd_dev_fwnode);

        dev_dbg(notifier_dev(notifier),
                "v4l2-async: device--endpoint match %sfound\n",
                ret ? "" : "not ");

        return ret;
}

static bool match_fwnode(struct v4l2_async_notifier *notifier,
                         struct v4l2_subdev *sd,
                         struct v4l2_async_match_desc *match)
{
        dev_dbg(notifier_dev(notifier),
                "v4l2-async: matching for notifier %pfw, sd fwnode %pfw\n",
                dev_fwnode(notifier_dev(notifier)), sd->fwnode);

        if (!list_empty(&sd->async_subdev_endpoint_list)) {
                struct v4l2_async_subdev_endpoint *ase;

                dev_dbg(sd->dev,
                        "v4l2-async: endpoint fwnode list available, looking for %pfw\n",
                        match->fwnode);

                list_for_each_entry(ase, &sd->async_subdev_endpoint_list,
                                    async_subdev_endpoint_entry) {
                        bool matched = ase->endpoint == match->fwnode;

                        dev_dbg(sd->dev,
                                "v4l2-async: endpoint-endpoint match %sfound with %pfw\n",
                                matched ? "" : "not ", ase->endpoint);

                        if (matched)
                                return true;
                }

                dev_dbg(sd->dev, "async: no endpoint matched\n");

                return false;
        }

        if (match_fwnode_one(notifier, sd, sd->fwnode, match))
                return true;

        /* Also check the secondary fwnode. */
        if (IS_ERR_OR_NULL(sd->fwnode->secondary))
                return false;

        dev_dbg(notifier_dev(notifier),
                "v4l2-async: trying secondary fwnode match\n");

        return match_fwnode_one(notifier, sd, sd->fwnode->secondary, match);
}

static LIST_HEAD(subdev_list);
static LIST_HEAD(notifier_list);
static DEFINE_MUTEX(list_lock);

static struct v4l2_async_connection *
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_match_desc *match);
        struct v4l2_async_connection *asc;

        list_for_each_entry(asc, &notifier->waiting_list, asc_entry) {
                /* bus_type has been verified valid before */
                switch (asc->match.type) {
                case V4L2_ASYNC_MATCH_TYPE_I2C:
                        match = match_i2c;
                        break;
                case V4L2_ASYNC_MATCH_TYPE_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, &asc->match))
                        return asc;
        }

        return NULL;
}

/* Compare two async match descriptors for equivalence */
static bool v4l2_async_match_equal(struct v4l2_async_match_desc *match1,
                                   struct v4l2_async_match_desc *match2)
{
        if (match1->type != match2->type)
                return false;

        switch (match1->type) {
        case V4L2_ASYNC_MATCH_TYPE_I2C:
                return match1->i2c.adapter_id == match2->i2c.adapter_id &&
                        match1->i2c.address == match2->i2c.address;
        case V4L2_ASYNC_MATCH_TYPE_FWNODE:
                return match1->fwnode == match2->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, notifier_entry)
                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_async_connection *asc;

        if (!list_empty(&notifier->waiting_list))
                return false;

        list_for_each_entry(asc, &notifier->done_list, asc_entry) {
                struct v4l2_async_notifier *subdev_notifier =
                        v4l2_async_find_subdev_notifier(asc->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)
{
        struct v4l2_async_notifier *__notifier = notifier;

        /* Quick check whether there are still more sub-devices here. */
        if (!list_empty(&notifier->waiting_list))
                return 0;

        if (notifier->sd)
                dev_dbg(notifier_dev(notifier),
                        "v4l2-async: trying to complete\n");

        /* 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) {
                dev_dbg(notifier_dev(__notifier),
                        "v4l2-async: V4L2 device not available\n");
                return 0;
        }

        /* Is everything ready? */
        if (!v4l2_async_nf_can_complete(notifier))
                return 0;

        dev_dbg(notifier_dev(__notifier), "v4l2-async: complete\n");

        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)
{
#if IS_ENABLED(CONFIG_MEDIA_CONTROLLER)
        struct media_link *link;

        if (sd->entity.function != MEDIA_ENT_F_LENS &&
            sd->entity.function != MEDIA_ENT_F_FLASH)
                return 0;

        if (!n->sd) {
                dev_warn(notifier_dev(n),
                         "not a sub-device notifier, not creating an ancillary link for %s!\n",
                         dev_name(sd->dev));
                return 0;
        }

        link = media_create_ancillary_link(&n->sd->entity, &sd->entity);

        return IS_ERR(link) ? PTR_ERR(link) : 0;
#else
        return 0;
#endif
}

static int v4l2_async_match_notify(struct v4l2_async_notifier *notifier,
                                   struct v4l2_device *v4l2_dev,
                                   struct v4l2_subdev *sd,
                                   struct v4l2_async_connection *asc)
{
        bool registered = false;
        int ret;

        if (list_empty(&sd->asc_list)) {
                ret = __v4l2_device_register_subdev(v4l2_dev, sd, sd->owner);
                if (ret < 0)
                        return ret;
                registered = true;
        }

        ret = v4l2_async_nf_call_bound(notifier, sd, asc);
        if (ret < 0) {
                if (asc->match.type == V4L2_ASYNC_MATCH_TYPE_FWNODE)
                        dev_dbg(notifier_dev(notifier),
                                "failed binding %pfw (%d)\n",
                                asc->match.fwnode, ret);
                goto err_unregister_subdev;
        }

        if (registered) {
                /*
                 * 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) {
                        if (asc->match.type == V4L2_ASYNC_MATCH_TYPE_FWNODE)
                                dev_dbg(notifier_dev(notifier),
                                        "failed creating links for %pfw (%d)\n",
                                        asc->match.fwnode, ret);
                        goto err_call_unbind;
                }
        }

        list_add(&asc->asc_subdev_entry, &sd->asc_list);
        asc->sd = sd;

        /* Move from the waiting list to notifier's done */
        list_move(&asc->asc_entry, &notifier->done_list);

        dev_dbg(notifier_dev(notifier), "v4l2-async: %s bound (ret %d)\n",
                dev_name(sd->dev), ret);

        return 0;

err_call_unbind:
        v4l2_async_nf_call_unbind(notifier, sd, asc);
        list_del(&asc->asc_subdev_entry);

err_unregister_subdev:
        if (registered)
                v4l2_device_unregister_subdev(sd);

        return ret;
}

static int
v4l2_async_nf_try_subdev_notifier(struct v4l2_async_notifier *notifier,
                                  struct v4l2_subdev *sd)
{
        struct v4l2_async_notifier *subdev_notifier;

        /*
         * 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;

        dev_dbg(notifier_dev(notifier), "v4l2-async: trying all sub-devices\n");

again:
        list_for_each_entry(sd, &subdev_list, async_list) {
                struct v4l2_async_connection *asc;
                int ret;

                asc = v4l2_async_find_match(notifier, sd);
                if (!asc)
                        continue;

                dev_dbg(notifier_dev(notifier),
                        "v4l2-async: match found, subdev %s\n", sd->name);

                ret = v4l2_async_match_notify(notifier, v4l2_dev, sd, asc);
                if (ret < 0)
                        return ret;

                ret = v4l2_async_nf_try_subdev_notifier(notifier, sd);
                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_unbind_subdev_one(struct v4l2_async_notifier *notifier,
                                         struct v4l2_async_connection *asc)
{
        list_move_tail(&asc->asc_entry, &notifier->waiting_list);
        if (list_is_singular(&asc->asc_subdev_entry)) {
                v4l2_async_nf_call_unbind(notifier, asc->sd, asc);
                v4l2_device_unregister_subdev(asc->sd);
                asc->sd = NULL;
        }
        list_del(&asc->asc_subdev_entry);
}

/* Unbind all sub-devices in the notifier tree. */
static void
v4l2_async_nf_unbind_all_subdevs(struct v4l2_async_notifier *notifier)
{
        struct v4l2_async_connection *asc, *asc_tmp;

        list_for_each_entry_safe(asc, asc_tmp, &notifier->done_list,
                                 asc_entry) {
                struct v4l2_async_notifier *subdev_notifier =
                        v4l2_async_find_subdev_notifier(asc->sd);

                if (subdev_notifier)
                        v4l2_async_nf_unbind_all_subdevs(subdev_notifier);

                v4l2_async_unbind_subdev_one(notifier, asc);
        }

        notifier->parent = NULL;
}

/* See if an async sub-device can be found in a notifier's lists. */
static bool
v4l2_async_nf_has_async_match_entry(struct v4l2_async_notifier *notifier,
                                    struct v4l2_async_match_desc *match)
{
        struct v4l2_async_connection *asc;

        list_for_each_entry(asc, &notifier->waiting_list, asc_entry)
                if (v4l2_async_match_equal(&asc->match, match))
                        return true;

        list_for_each_entry(asc, &notifier->done_list, asc_entry)
                if (v4l2_async_match_equal(&asc->match, match))
                        return true;

        return false;
}

/*
 * Find out whether an async sub-device was set up already or whether it exists
 * in a given notifier.
 */
static bool
v4l2_async_nf_has_async_match(struct v4l2_async_notifier *notifier,
                              struct v4l2_async_match_desc *match)
{
        struct list_head *heads[] = {
                &notifier->waiting_list,
                &notifier->done_list,
        };
        unsigned int i;

        lockdep_assert_held(&list_lock);

        /* Check that an asd is not being added more than once. */
        for (i = 0; i < ARRAY_SIZE(heads); i++) {
                struct v4l2_async_connection *asc;

                list_for_each_entry(asc, heads[i], asc_entry) {
                        if (&asc->match == match)
                                continue;
                        if (v4l2_async_match_equal(&asc->match, match))
                                return true;
                }
        }

        /* Check that an asc does not exist in other notifiers. */
        list_for_each_entry(notifier, &notifier_list, notifier_entry)
                if (v4l2_async_nf_has_async_match_entry(notifier, match))
                        return true;

        return false;
}

static int v4l2_async_nf_match_valid(struct v4l2_async_notifier *notifier,
                                     struct v4l2_async_match_desc *match)
{
        struct device *dev = notifier_dev(notifier);

        switch (match->type) {
        case V4L2_ASYNC_MATCH_TYPE_I2C:
        case V4L2_ASYNC_MATCH_TYPE_FWNODE:
                if (v4l2_async_nf_has_async_match(notifier, match)) {
                        dev_dbg(dev, "v4l2-async: match descriptor already listed in a notifier\n");
                        return -EEXIST;
                }
                break;
        default:
                dev_err(dev, "v4l2-async: Invalid match type %u on %p\n",
                        match->type, match);
                return -EINVAL;
        }

        return 0;
}

void v4l2_async_nf_init(struct v4l2_async_notifier *notifier,
                        struct v4l2_device *v4l2_dev)
{
        INIT_LIST_HEAD(&notifier->waiting_list);
        INIT_LIST_HEAD(&notifier->done_list);
        INIT_LIST_HEAD(&notifier->notifier_entry);
        notifier->v4l2_dev = v4l2_dev;
}
EXPORT_SYMBOL(v4l2_async_nf_init);

void v4l2_async_subdev_nf_init(struct v4l2_async_notifier *notifier,
                               struct v4l2_subdev *sd)
{
        INIT_LIST_HEAD(&notifier->waiting_list);
        INIT_LIST_HEAD(&notifier->done_list);
        INIT_LIST_HEAD(&notifier->notifier_entry);
        notifier->sd = sd;
}
EXPORT_SYMBOL_GPL(v4l2_async_subdev_nf_init);

static int __v4l2_async_nf_register(struct v4l2_async_notifier *notifier)
{
        struct v4l2_async_connection *asc;
        int ret;

        mutex_lock(&list_lock);

        list_for_each_entry(asc, &notifier->waiting_list, asc_entry) {
                ret = v4l2_async_nf_match_valid(notifier, &asc->match);
                if (ret)
                        goto err_unlock;
        }

        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->notifier_entry, &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);

err_unlock:
        mutex_unlock(&list_lock);

        return ret;
}

int v4l2_async_nf_register(struct v4l2_async_notifier *notifier)
{
        if (WARN_ON(!notifier->v4l2_dev == !notifier->sd))
                return -EINVAL;

        return __v4l2_async_nf_register(notifier);
}
EXPORT_SYMBOL(v4l2_async_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);

        list_del_init(&notifier->notifier_entry);
}

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_connection *asc, *tmp;

        if (!notifier || !notifier->waiting_list.next)
                return;

        WARN_ON(!list_empty(&notifier->done_list));

        list_for_each_entry_safe(asc, tmp, &notifier->waiting_list, asc_entry) {
                list_del(&asc->asc_entry);
                v4l2_async_nf_call_destroy(notifier, asc);

                if (asc->match.type == V4L2_ASYNC_MATCH_TYPE_FWNODE)
                        fwnode_handle_put(asc->match.fwnode);

                kfree(asc);
        }

        notifier->sd = NULL;
        notifier->v4l2_dev = NULL;
}

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);

static void __v4l2_async_nf_add_connection(struct v4l2_async_notifier *notifier,
                                           struct v4l2_async_connection *asc)
{
        mutex_lock(&list_lock);

        list_add_tail(&asc->asc_entry, &notifier->waiting_list);

        mutex_unlock(&list_lock);
}

struct v4l2_async_connection *
__v4l2_async_nf_add_fwnode(struct v4l2_async_notifier *notifier,
                           struct fwnode_handle *fwnode,
                           unsigned int asc_struct_size)
{
        struct v4l2_async_connection *asc;

        asc = kzalloc(asc_struct_size, GFP_KERNEL);
        if (!asc)
                return ERR_PTR(-ENOMEM);

        asc->notifier = notifier;
        asc->match.type = V4L2_ASYNC_MATCH_TYPE_FWNODE;
        asc->match.fwnode = fwnode_handle_get(fwnode);

        __v4l2_async_nf_add_connection(notifier, asc);

        return asc;
}
EXPORT_SYMBOL_GPL(__v4l2_async_nf_add_fwnode);

struct v4l2_async_connection *
__v4l2_async_nf_add_fwnode_remote(struct v4l2_async_notifier *notif,
                                  struct fwnode_handle *endpoint,
                                  unsigned int asc_struct_size)
{
        struct v4l2_async_connection *asc;
        struct fwnode_handle *remote;

        remote = fwnode_graph_get_remote_endpoint(endpoint);
        if (!remote)
                return ERR_PTR(-ENOTCONN);

        asc = __v4l2_async_nf_add_fwnode(notif, remote, asc_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 asc;
}
EXPORT_SYMBOL_GPL(__v4l2_async_nf_add_fwnode_remote);

struct v4l2_async_connection *
__v4l2_async_nf_add_i2c(struct v4l2_async_notifier *notifier, int adapter_id,
                        unsigned short address, unsigned int asc_struct_size)
{
        struct v4l2_async_connection *asc;

        asc = kzalloc(asc_struct_size, GFP_KERNEL);
        if (!asc)
                return ERR_PTR(-ENOMEM);

        asc->notifier = notifier;
        asc->match.type = V4L2_ASYNC_MATCH_TYPE_I2C;
        asc->match.i2c.adapter_id = adapter_id;
        asc->match.i2c.address = address;

        __v4l2_async_nf_add_connection(notifier, asc);

        return asc;
}
EXPORT_SYMBOL_GPL(__v4l2_async_nf_add_i2c);

int v4l2_async_subdev_endpoint_add(struct v4l2_subdev *sd,
                                   struct fwnode_handle *fwnode)
{
        struct v4l2_async_subdev_endpoint *ase;

        ase = kmalloc_obj(*ase);
        if (!ase)
                return -ENOMEM;

        ase->endpoint = fwnode;
        list_add(&ase->async_subdev_endpoint_entry,
                 &sd->async_subdev_endpoint_list);

        return 0;
}
EXPORT_SYMBOL_GPL(v4l2_async_subdev_endpoint_add);

struct v4l2_async_connection *
v4l2_async_connection_unique(struct v4l2_subdev *sd)
{
        if (!list_is_singular(&sd->asc_list))
                return NULL;

        return list_first_entry(&sd->asc_list,
                                struct v4l2_async_connection, asc_subdev_entry);
}
EXPORT_SYMBOL_GPL(v4l2_async_connection_unique);

int __v4l2_async_register_subdev(struct v4l2_subdev *sd, struct module *module)
{
        struct v4l2_async_notifier *subdev_notifier;
        struct v4l2_async_notifier *notifier;
        struct v4l2_async_connection *asc;
        int ret;

        INIT_LIST_HEAD(&sd->asc_list);

        /*
         * 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.
         *
         * The async sub-device shall always be registered for its device node,
         * not the endpoint node.
         */
        if (!sd->fwnode && sd->dev) {
                sd->fwnode = dev_fwnode(sd->dev);
        } else if (fwnode_graph_is_endpoint(sd->fwnode)) {
                dev_warn(sd->dev, "sub-device fwnode is an endpoint!\n");
                return -EINVAL;
        }

        sd->owner = module;

        mutex_lock(&list_lock);

        list_for_each_entry(notifier, &notifier_list, notifier_entry) {
                struct v4l2_device *v4l2_dev =
                        v4l2_async_nf_find_v4l2_dev(notifier);

                if (!v4l2_dev)
                        continue;

                while ((asc = v4l2_async_find_match(notifier, sd))) {
                        ret = v4l2_async_match_notify(notifier, v4l2_dev, sd,
                                                      asc);
                        if (ret)
                                goto err_unlock;

                        ret = v4l2_async_nf_try_subdev_notifier(notifier, sd);
                        if (ret)
                                goto err_unbind_one;

                        ret = v4l2_async_nf_try_complete(notifier);
                        if (ret)
                                goto err_unbind;
                }
        }

        /* None matched, wait for hot-plugging */
        list_add(&sd->async_list, &subdev_list);

        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);

err_unbind_one:
        v4l2_async_unbind_subdev_one(notifier, asc);

err_unlock:
        mutex_unlock(&list_lock);

        sd->owner = NULL;

        return ret;
}
EXPORT_SYMBOL(__v4l2_async_register_subdev);

void v4l2_async_unregister_subdev(struct v4l2_subdev *sd)
{
        struct v4l2_async_connection *asc, *asc_tmp;

        if (!sd->async_list.next)
                return;

        v4l2_subdev_put_privacy_led(sd);

        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->asc_list.next) {
                list_for_each_entry_safe(asc, asc_tmp, &sd->asc_list,
                                         asc_subdev_entry) {
                        v4l2_async_unbind_subdev_one(asc->notifier, asc);
                }
        }

        list_del(&sd->async_list);
        sd->async_list.next = NULL;

        mutex_unlock(&list_lock);
}
EXPORT_SYMBOL(v4l2_async_unregister_subdev);

static void print_waiting_match(struct seq_file *s,
                                struct v4l2_async_match_desc *match)
{
        switch (match->type) {
        case V4L2_ASYNC_MATCH_TYPE_I2C:
                seq_printf(s, " [i2c] dev=%d-%04x\n", match->i2c.adapter_id,
                           match->i2c.address);
                break;
        case V4L2_ASYNC_MATCH_TYPE_FWNODE: {
                struct fwnode_handle *devnode, *fwnode = 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_connection *asc;

        mutex_lock(&list_lock);

        list_for_each_entry(notif, &notifier_list, notifier_entry) {
                seq_printf(s, "%s:\n", v4l2_async_nf_name(notif));
                list_for_each_entry(asc, &notif->waiting_list, asc_entry)
                        print_waiting_match(s, &asc->match);
        }

        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_DESCRIPTION("V4L2 asynchronous subdevice registration API");
MODULE_LICENSE("GPL");