// SPDX-License-Identifier: GPL-2.0
/*
 * Media device request objects
 *
 * Copyright 2018 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
 * Copyright (C) 2018 Intel Corporation
 * Copyright (C) 2018 Google, Inc.
 *
 * Author: Hans Verkuil <hans.verkuil@cisco.com>
 * Author: Sakari Ailus <sakari.ailus@linux.intel.com>
 */

#include <linux/anon_inodes.h>
#include <linux/file.h>
#include <linux/refcount.h>

#include <media/media-device.h>
#include <media/media-request.h>

static const char * const request_state[] = {
        [MEDIA_REQUEST_STATE_IDLE]       = "idle",
        [MEDIA_REQUEST_STATE_VALIDATING] = "validating",
        [MEDIA_REQUEST_STATE_QUEUED]     = "queued",
        [MEDIA_REQUEST_STATE_COMPLETE]   = "complete",
        [MEDIA_REQUEST_STATE_CLEANING]   = "cleaning",
        [MEDIA_REQUEST_STATE_UPDATING]   = "updating",
};

static const char *
media_request_state_str(enum media_request_state state)
{
        BUILD_BUG_ON(ARRAY_SIZE(request_state) != NR_OF_MEDIA_REQUEST_STATE);

        if (WARN_ON(state >= ARRAY_SIZE(request_state)))
                return "invalid";
        return request_state[state];
}

static void media_request_clean(struct media_request *req)
{
        struct media_request_object *obj, *obj_safe;

        /* Just a sanity check. No other code path is allowed to change this. */
        WARN_ON(req->state != MEDIA_REQUEST_STATE_CLEANING);
        WARN_ON(req->updating_count);
        WARN_ON(req->access_count);

        list_for_each_entry_safe(obj, obj_safe, &req->objects, list) {
                media_request_object_unbind(obj);
                media_request_object_put(obj);
        }

        req->updating_count = 0;
        req->access_count = 0;
        WARN_ON(req->num_incomplete_objects);
        req->num_incomplete_objects = 0;
        wake_up_interruptible_all(&req->poll_wait);
}

static void media_request_release(struct kref *kref)
{
        struct media_request *req =
                container_of(kref, struct media_request, kref);
        struct media_device *mdev = req->mdev;

        dev_dbg(mdev->dev, "request: release %s\n", req->debug_str);

        /* No other users, no need for a spinlock */
        req->state = MEDIA_REQUEST_STATE_CLEANING;

        media_request_clean(req);

        if (mdev->ops->req_free)
                mdev->ops->req_free(req);
        else
                kfree(req);
}

void media_request_put(struct media_request *req)
{
        kref_put(&req->kref, media_request_release);
}
EXPORT_SYMBOL_GPL(media_request_put);

static int media_request_close(struct inode *inode, struct file *filp)
{
        struct media_request *req = filp->private_data;

        media_request_put(req);
        return 0;
}

static __poll_t media_request_poll(struct file *filp,
                                   struct poll_table_struct *wait)
{
        struct media_request *req = filp->private_data;
        unsigned long flags;
        __poll_t ret = 0;

        if (!(poll_requested_events(wait) & EPOLLPRI))
                return 0;

        poll_wait(filp, &req->poll_wait, wait);
        spin_lock_irqsave(&req->lock, flags);
        if (req->state == MEDIA_REQUEST_STATE_COMPLETE) {
                ret = EPOLLPRI;
                goto unlock;
        }
        if (req->state != MEDIA_REQUEST_STATE_QUEUED) {
                ret = EPOLLERR;
                goto unlock;
        }

unlock:
        spin_unlock_irqrestore(&req->lock, flags);
        return ret;
}

static long media_request_ioctl_queue(struct media_request *req)
{
        struct media_device *mdev = req->mdev;
        enum media_request_state state;
        unsigned long flags;
        int ret;

        dev_dbg(mdev->dev, "request: queue %s\n", req->debug_str);

        /*
         * Ensure the request that is validated will be the one that gets queued
         * next by serialising the queueing process. This mutex is also used
         * to serialize with canceling a vb2 queue and with setting values such
         * as controls in a request.
         */
        mutex_lock(&mdev->req_queue_mutex);

        media_request_get(req);

        spin_lock_irqsave(&req->lock, flags);
        if (req->state == MEDIA_REQUEST_STATE_IDLE)
                req->state = MEDIA_REQUEST_STATE_VALIDATING;
        state = req->state;
        spin_unlock_irqrestore(&req->lock, flags);
        if (state != MEDIA_REQUEST_STATE_VALIDATING) {
                dev_dbg(mdev->dev,
                        "request: unable to queue %s, request in state %s\n",
                        req->debug_str, media_request_state_str(state));
                media_request_put(req);
                mutex_unlock(&mdev->req_queue_mutex);
                return -EBUSY;
        }

        ret = mdev->ops->req_validate(req);

        /*
         * If the req_validate was successful, then we mark the state as QUEUED
         * and call req_queue. The reason we set the state first is that this
         * allows req_queue to unbind or complete the queued objects in case
         * they are immediately 'consumed'. State changes from QUEUED to another
         * state can only happen if either the driver changes the state or if
         * the user cancels the vb2 queue. The driver can only change the state
         * after each object is queued through the req_queue op (and note that
         * that op cannot fail), so setting the state to QUEUED up front is
         * safe.
         *
         * The other reason for changing the state is if the vb2 queue is
         * canceled, and that uses the req_queue_mutex which is still locked
         * while req_queue is called, so that's safe as well.
         */
        spin_lock_irqsave(&req->lock, flags);
        req->state = ret ? MEDIA_REQUEST_STATE_IDLE
                         : MEDIA_REQUEST_STATE_QUEUED;
        spin_unlock_irqrestore(&req->lock, flags);

        if (!ret)
                mdev->ops->req_queue(req);

        mutex_unlock(&mdev->req_queue_mutex);

        if (ret) {
                dev_dbg(mdev->dev, "request: can't queue %s (%d)\n",
                        req->debug_str, ret);
                media_request_put(req);
        }

        return ret;
}

static long media_request_ioctl_reinit(struct media_request *req)
{
        struct media_device *mdev = req->mdev;
        unsigned long flags;

        spin_lock_irqsave(&req->lock, flags);
        if (req->state != MEDIA_REQUEST_STATE_IDLE &&
            req->state != MEDIA_REQUEST_STATE_COMPLETE) {
                dev_dbg(mdev->dev,
                        "request: %s not in idle or complete state, cannot reinit\n",
                        req->debug_str);
                spin_unlock_irqrestore(&req->lock, flags);
                return -EBUSY;
        }
        if (req->access_count) {
                dev_dbg(mdev->dev,
                        "request: %s is being accessed, cannot reinit\n",
                        req->debug_str);
                spin_unlock_irqrestore(&req->lock, flags);
                return -EBUSY;
        }
        req->state = MEDIA_REQUEST_STATE_CLEANING;
        spin_unlock_irqrestore(&req->lock, flags);

        media_request_clean(req);

        spin_lock_irqsave(&req->lock, flags);
        req->state = MEDIA_REQUEST_STATE_IDLE;
        spin_unlock_irqrestore(&req->lock, flags);

        return 0;
}

static long media_request_ioctl(struct file *filp, unsigned int cmd,
                                unsigned long arg)
{
        struct media_request *req = filp->private_data;

        switch (cmd) {
        case MEDIA_REQUEST_IOC_QUEUE:
                return media_request_ioctl_queue(req);
        case MEDIA_REQUEST_IOC_REINIT:
                return media_request_ioctl_reinit(req);
        default:
                return -ENOIOCTLCMD;
        }
}

static const struct file_operations request_fops = {
        .owner = THIS_MODULE,
        .poll = media_request_poll,
        .unlocked_ioctl = media_request_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = media_request_ioctl,
#endif /* CONFIG_COMPAT */
        .release = media_request_close,
};

struct media_request *
media_request_get_by_fd(struct media_device *mdev, int request_fd)
{
        struct fd f;
        struct media_request *req;

        if (!mdev || !mdev->ops ||
            !mdev->ops->req_validate || !mdev->ops->req_queue)
                return ERR_PTR(-EBADR);

        f = fdget(request_fd);
        if (!f.file)
                goto err_no_req_fd;

        if (f.file->f_op != &request_fops)
                goto err_fput;
        req = f.file->private_data;
        if (req->mdev != mdev)
                goto err_fput;

        /*
         * Note: as long as someone has an open filehandle of the request,
         * the request can never be released. The fdget() above ensures that
         * even if userspace closes the request filehandle, the release()
         * fop won't be called, so the media_request_get() always succeeds
         * and there is no race condition where the request was released
         * before media_request_get() is called.
         */
        media_request_get(req);
        fdput(f);

        return req;

err_fput:
        fdput(f);

err_no_req_fd:
        dev_dbg(mdev->dev, "cannot find request_fd %d\n", request_fd);
        return ERR_PTR(-EINVAL);
}
EXPORT_SYMBOL_GPL(media_request_get_by_fd);

int media_request_alloc(struct media_device *mdev, int *alloc_fd)
{
        struct media_request *req;
        struct file *filp;
        int fd;
        int ret;

        /* Either both are NULL or both are non-NULL */
        if (WARN_ON(!mdev->ops->req_alloc ^ !mdev->ops->req_free))
                return -ENOMEM;

        fd = get_unused_fd_flags(O_CLOEXEC);
        if (fd < 0)
                return fd;

        filp = anon_inode_getfile("request", &request_fops, NULL, O_CLOEXEC);
        if (IS_ERR(filp)) {
                ret = PTR_ERR(filp);
                goto err_put_fd;
        }

        if (mdev->ops->req_alloc)
                req = mdev->ops->req_alloc(mdev);
        else
                req = kzalloc(sizeof(*req), GFP_KERNEL);
        if (!req) {
                ret = -ENOMEM;
                goto err_fput;
        }

        filp->private_data = req;
        req->mdev = mdev;
        req->state = MEDIA_REQUEST_STATE_IDLE;
        req->num_incomplete_objects = 0;
        kref_init(&req->kref);
        INIT_LIST_HEAD(&req->objects);
        spin_lock_init(&req->lock);
        init_waitqueue_head(&req->poll_wait);
        req->updating_count = 0;
        req->access_count = 0;

        *alloc_fd = fd;

        snprintf(req->debug_str, sizeof(req->debug_str), "%u:%d",
                 atomic_inc_return(&mdev->request_id), fd);
        dev_dbg(mdev->dev, "request: allocated %s\n", req->debug_str);

        fd_install(fd, filp);

        return 0;

err_fput:
        fput(filp);

err_put_fd:
        put_unused_fd(fd);

        return ret;
}

static void media_request_object_release(struct kref *kref)
{
        struct media_request_object *obj =
                container_of(kref, struct media_request_object, kref);
        struct media_request *req = obj->req;

        if (WARN_ON(req))
                media_request_object_unbind(obj);
        obj->ops->release(obj);
}

struct media_request_object *
media_request_object_find(struct media_request *req,
                          const struct media_request_object_ops *ops,
                          void *priv)
{
        struct media_request_object *obj;
        struct media_request_object *found = NULL;
        unsigned long flags;

        if (WARN_ON(!ops || !priv))
                return NULL;

        spin_lock_irqsave(&req->lock, flags);
        list_for_each_entry(obj, &req->objects, list) {
                if (obj->ops == ops && obj->priv == priv) {
                        media_request_object_get(obj);
                        found = obj;
                        break;
                }
        }
        spin_unlock_irqrestore(&req->lock, flags);
        return found;
}
EXPORT_SYMBOL_GPL(media_request_object_find);

void media_request_object_put(struct media_request_object *obj)
{
        kref_put(&obj->kref, media_request_object_release);
}
EXPORT_SYMBOL_GPL(media_request_object_put);

void media_request_object_init(struct media_request_object *obj)
{
        obj->ops = NULL;
        obj->req = NULL;
        obj->priv = NULL;
        obj->completed = false;
        INIT_LIST_HEAD(&obj->list);
        kref_init(&obj->kref);
}
EXPORT_SYMBOL_GPL(media_request_object_init);

int media_request_object_bind(struct media_request *req,
                              const struct media_request_object_ops *ops,
                              void *priv, bool is_buffer,
                              struct media_request_object *obj)
{
        unsigned long flags;
        int ret = -EBUSY;

        if (WARN_ON(!ops->release))
                return -EBADR;

        spin_lock_irqsave(&req->lock, flags);

        if (WARN_ON(req->state != MEDIA_REQUEST_STATE_UPDATING))
                goto unlock;

        obj->req = req;
        obj->ops = ops;
        obj->priv = priv;

        if (is_buffer)
                list_add_tail(&obj->list, &req->objects);
        else
                list_add(&obj->list, &req->objects);
        req->num_incomplete_objects++;
        ret = 0;

unlock:
        spin_unlock_irqrestore(&req->lock, flags);
        return ret;
}
EXPORT_SYMBOL_GPL(media_request_object_bind);

void media_request_object_unbind(struct media_request_object *obj)
{
        struct media_request *req = obj->req;
        unsigned long flags;
        bool completed = false;

        if (WARN_ON(!req))
                return;

        spin_lock_irqsave(&req->lock, flags);
        list_del(&obj->list);
        obj->req = NULL;

        if (req->state == MEDIA_REQUEST_STATE_COMPLETE)
                goto unlock;

        if (WARN_ON(req->state == MEDIA_REQUEST_STATE_VALIDATING))
                goto unlock;

        if (req->state == MEDIA_REQUEST_STATE_CLEANING) {
                if (!obj->completed)
                        req->num_incomplete_objects--;
                goto unlock;
        }

        if (WARN_ON(!req->num_incomplete_objects))
                goto unlock;

        req->num_incomplete_objects--;
        if (req->state == MEDIA_REQUEST_STATE_QUEUED &&
            !req->num_incomplete_objects) {
                req->state = MEDIA_REQUEST_STATE_COMPLETE;
                completed = true;
                wake_up_interruptible_all(&req->poll_wait);
        }

unlock:
        spin_unlock_irqrestore(&req->lock, flags);
        if (obj->ops->unbind)
                obj->ops->unbind(obj);
        if (completed)
                media_request_put(req);
}
EXPORT_SYMBOL_GPL(media_request_object_unbind);

void media_request_object_complete(struct media_request_object *obj)
{
        struct media_request *req = obj->req;
        unsigned long flags;
        bool completed = false;

        spin_lock_irqsave(&req->lock, flags);
        if (obj->completed)
                goto unlock;
        obj->completed = true;
        if (WARN_ON(!req->num_incomplete_objects) ||
            WARN_ON(req->state != MEDIA_REQUEST_STATE_QUEUED))
                goto unlock;

        if (!--req->num_incomplete_objects) {
                req->state = MEDIA_REQUEST_STATE_COMPLETE;
                wake_up_interruptible_all(&req->poll_wait);
                completed = true;
        }
unlock:
        spin_unlock_irqrestore(&req->lock, flags);
        if (completed)
                media_request_put(req);
}
EXPORT_SYMBOL_GPL(media_request_object_complete);