// 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");