OpenHarmony-v6.0-Release/s

// SPDX-License-Identifier: GPL-2.0-only
/*
 * V4L2 asynchronous subdevice registration API
 *
 * Copyright (C) 2012-2013, Guennadi Liakhovetski <g.liakhovetski@gmx.de>
 */

#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/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_devname(struct v4l2_async_notifier *notifier, struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)
{
    return !strcmp(asd->match.device_name, dev_name(sd->dev));
}

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;
    }

    /*
     * 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_custom(struct v4l2_async_notifier *notifier, struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)
{
    if (!asd->match.custom.match) {
        /* Match always */
        return true;
    }

    return asd->match.custom.match(sd->dev, 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_CUSTOM:
                match = match_custom;
                break;
            case V4L2_ASYNC_MATCH_DEVNAME:
                match = match_devname;
                break;
            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_DEVNAME:
            return strcmp(asd_x->match.device_name, asd_y->match.device_name) == 0;
        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_ext(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_ext(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_CUSTOM:
        case V4L2_ASYNC_MATCH_DEVNAME:
        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_ext(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_ext(notifier);
    if (ret) {
        notifier->v4l2_dev = NULL;
    }

    return ret;
}
EXPORT_SYMBOL(v4l2_async_notifier_register);

#if IS_ENABLED(CONFIG_NO_GKI)
static int v4l2_async_notifier_clr_unready_dev_ext(struct v4l2_async_notifier *notifier)
{
    struct v4l2_subdev *sd, *tmp;
    int clr_num = 0;

    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) {
            clr_num += v4l2_async_notifier_clr_unready_dev_ext(subdev_notifier);
        }
    }

    list_for_each_entry_safe(sd, tmp, &notifier->waiting, async_list)
    {
        list_del_init(&sd->async_list);
        sd->asd = NULL;
        sd->dev = NULL;
        clr_num++;
    }

    return clr_num;
}

int v4l2_async_notifier_clr_unready_dev(struct v4l2_async_notifier *notifier)
{
    int ret = 0;
    int clr_num = 0;

    mutex_lock(&list_lock);

    while (notifier->parent) {
        notifier = notifier->parent;
    }

    if (!notifier->v4l2_dev) {
        goto out;
    }

    clr_num = v4l2_async_notifier_clr_unready_dev_ext(notifier);
    dev_info(notifier->v4l2_dev->dev, "clear unready subdev num: %d\n", clr_num);

    if (clr_num > 0) {
        ret = v4l2_async_notifier_try_complete(notifier);
    }

out:
    mutex_unlock(&list_lock);

    return ret;
}
EXPORT_SYMBOL(v4l2_async_notifier_clr_unready_dev);
#endif

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_ext(notifier);
    if (ret) {
        notifier->sd = NULL;
    }

    return ret;
}
EXPORT_SYMBOL(v4l2_async_subdev_notifier_register);

static void v4l2_async_notifier_unregister_ext(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_ext(notifier);

    mutex_unlock(&list_lock);
}
EXPORT_SYMBOL(v4l2_async_notifier_unregister);

static void v4l2_async_notifier_cleanup_ext(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_ext(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);

struct v4l2_async_subdev *v4l2_async_notifier_add_devname_subdev(struct v4l2_async_notifier *notifier,
                                                                 const char *device_name, 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_DEVNAME;
    asd->match.device_name = device_name;

    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_devname_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)
{
    mutex_lock(&list_lock);

    v4l2_async_notifier_unregister_ext(sd->subdev_notifier);
    v4l2_async_notifier_cleanup_ext(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);