// SPDX-License-Identifier: GPL-2.0+
/*
 *      uvc_video.c  --  USB Video Class Gadget driver
 *
 *      Copyright (C) 2009-2010
 *          Laurent Pinchart (laurent.pinchart@ideasonboard.com)
 */

#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/usb/ch9.h>
#include <linux/usb/gadget.h>
#include <linux/usb/video.h>
#include <linux/unaligned.h>

#include <media/v4l2-dev.h>

#include "uvc.h"
#include "uvc_queue.h"
#include "uvc_video.h"
#include "uvc_trace.h"

/* --------------------------------------------------------------------------
 * Video codecs
 */

static int
uvc_video_encode_header(struct uvc_video *video, struct uvc_buffer *buf,
                u8 *data, int len)
{
        struct uvc_device *uvc = container_of(video, struct uvc_device, video);
        struct usb_composite_dev *cdev = uvc->func.config->cdev;
        struct timespec64 ts = ns_to_timespec64(buf->buf.vb2_buf.timestamp);
        int pos = 2;

        data[1] = UVC_STREAM_EOH | video->fid;

        if (video->queue.flags & UVC_QUEUE_DROP_INCOMPLETE)
                data[1] |= UVC_STREAM_ERR;

        if (video->queue.buf_used == 0 && ts.tv_sec) {
                /* dwClockFrequency is 48 MHz */
                u32 pts = ((u64)ts.tv_sec * USEC_PER_SEC + ts.tv_nsec / NSEC_PER_USEC) * 48;

                data[1] |= UVC_STREAM_PTS;
                put_unaligned_le32(pts, &data[pos]);
                pos += 4;
        }

        if (cdev->gadget->ops->get_frame) {
                u32 sof, stc;

                sof = usb_gadget_frame_number(cdev->gadget);
                ktime_get_ts64(&ts);
                stc = ((u64)ts.tv_sec * USEC_PER_SEC + ts.tv_nsec / NSEC_PER_USEC) * 48;

                data[1] |= UVC_STREAM_SCR;
                put_unaligned_le32(stc, &data[pos]);
                put_unaligned_le16(sof, &data[pos+4]);
                pos += 6;
        }

        data[0] = pos;

        if (buf->bytesused - video->queue.buf_used <= len - pos)
                data[1] |= UVC_STREAM_EOF;

        return pos;
}

static int
uvc_video_encode_data(struct uvc_video *video, struct uvc_buffer *buf,
                u8 *data, int len)
{
        struct uvc_video_queue *queue = &video->queue;
        unsigned int nbytes;
        void *mem;

        /* Copy video data to the USB buffer. */
        mem = buf->mem + queue->buf_used;
        nbytes = min_t(unsigned int, len, buf->bytesused - queue->buf_used);

        memcpy(data, mem, nbytes);
        queue->buf_used += nbytes;

        return nbytes;
}

static void
uvc_video_encode_bulk(struct usb_request *req, struct uvc_video *video,
                struct uvc_buffer *buf)
{
        void *mem = req->buf;
        struct uvc_request *ureq = req->context;
        int len = video->req_size;
        int ret;

        /* Add a header at the beginning of the payload. */
        if (video->payload_size == 0) {
                ret = uvc_video_encode_header(video, buf, mem, len);
                video->payload_size += ret;
                mem += ret;
                len -= ret;
        }

        /* Process video data. */
        len = min_t(int, video->max_payload_size - video->payload_size, len);
        ret = uvc_video_encode_data(video, buf, mem, len);

        video->payload_size += ret;
        len -= ret;

        req->length = video->req_size - len;
        req->zero = video->payload_size == video->max_payload_size;

        if (buf->bytesused == video->queue.buf_used) {
                video->queue.buf_used = 0;
                buf->state = UVC_BUF_STATE_DONE;
                list_del(&buf->queue);
                video->fid ^= UVC_STREAM_FID;
                ureq->last_buf = buf;

                video->payload_size = 0;
        }

        if (video->payload_size == video->max_payload_size ||
            video->queue.flags & UVC_QUEUE_DROP_INCOMPLETE ||
            buf->bytesused == video->queue.buf_used)
                video->payload_size = 0;
}

static void
uvc_video_encode_isoc_sg(struct usb_request *req, struct uvc_video *video,
                struct uvc_buffer *buf)
{
        unsigned int pending = buf->bytesused - video->queue.buf_used;
        struct uvc_request *ureq = req->context;
        struct scatterlist *sg, *iter;
        unsigned int len = buf->req_payload_size;
        unsigned int sg_left, part = 0;
        unsigned int i;
        int header_len;

        sg = ureq->sgt.sgl;
        sg_init_table(sg, ureq->sgt.nents);

        /* Init the header. */
        header_len = uvc_video_encode_header(video, buf, ureq->header,
                                             buf->req_payload_size);
        sg_set_buf(sg, ureq->header, header_len);
        len -= header_len;

        if (pending <= len)
                len = pending;

        req->length = (len == pending) ? len + header_len :
                buf->req_payload_size;

        /* Init the pending sgs with payload */
        sg = sg_next(sg);

        for_each_sg(sg, iter, ureq->sgt.nents - 1, i) {
                if (!len || !buf->sg || !buf->sg->length)
                        break;

                sg_left = buf->sg->length - buf->offset;
                part = min_t(unsigned int, len, sg_left);

                sg_set_page(iter, sg_page(buf->sg), part, buf->offset);

                if (part == sg_left) {
                        buf->offset = 0;
                        buf->sg = sg_next(buf->sg);
                } else {
                        buf->offset += part;
                }
                len -= part;
        }

        /* Assign the video data with header. */
        req->buf = NULL;
        req->sg = ureq->sgt.sgl;
        req->num_sgs = i + 1;

        req->length -= len;
        video->queue.buf_used += req->length - header_len;

        if (buf->bytesused == video->queue.buf_used || !buf->sg ||
                        video->queue.flags & UVC_QUEUE_DROP_INCOMPLETE) {
                video->queue.buf_used = 0;
                buf->state = UVC_BUF_STATE_DONE;
                buf->offset = 0;
                list_del(&buf->queue);
                video->fid ^= UVC_STREAM_FID;
                ureq->last_buf = buf;
        }
}

static void
uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
                struct uvc_buffer *buf)
{
        void *mem = req->buf;
        struct uvc_request *ureq = req->context;
        int len = buf->req_payload_size;
        int ret;

        /* Add the header. */
        ret = uvc_video_encode_header(video, buf, mem, len);
        mem += ret;
        len -= ret;

        /* Process video data. */
        ret = uvc_video_encode_data(video, buf, mem, len);
        len -= ret;

        req->length = buf->req_payload_size - len;

        if (buf->bytesused == video->queue.buf_used ||
                        video->queue.flags & UVC_QUEUE_DROP_INCOMPLETE) {
                video->queue.buf_used = 0;
                buf->state = UVC_BUF_STATE_DONE;
                list_del(&buf->queue);
                video->fid ^= UVC_STREAM_FID;
                ureq->last_buf = buf;
        }
}

/* --------------------------------------------------------------------------
 * Request handling
 */

/*
 * Callers must take care to hold req_lock when this function may be called
 * from multiple threads. For example, when frames are streaming to the host.
 */
static void
uvc_video_free_request(struct uvc_request *ureq, struct usb_ep *ep)
{
        sg_free_table(&ureq->sgt);
        if (ureq->req && ep) {
                usb_ep_free_request(ep, ureq->req);
                ureq->req = NULL;
        }

        kfree(ureq->req_buffer);
        ureq->req_buffer = NULL;

        if (!list_empty(&ureq->list))
                list_del_init(&ureq->list);

        kfree(ureq);
}

static int uvcg_video_ep_queue(struct uvc_video *video, struct usb_request *req)
{
        int ret;

        ret = usb_ep_queue(video->ep, req, GFP_ATOMIC);
        if (ret < 0) {
                uvcg_err(&video->uvc->func, "Failed to queue request (%d).\n",
                         ret);

                /* If the endpoint is disabled the descriptor may be NULL. */
                if (video->ep->desc) {
                        /* Isochronous endpoints can't be halted. */
                        if (usb_endpoint_xfer_bulk(video->ep->desc))
                                usb_ep_set_halt(video->ep);
                }
        }

        atomic_inc(&video->queued);

        trace_uvcg_video_queue(req, atomic_read(&video->queued));

        return ret;
}

/* This function must be called with video->req_lock held. */
static int uvcg_video_usb_req_queue(struct uvc_video *video,
        struct usb_request *req, bool queue_to_ep)
{
        bool is_bulk = video->max_payload_size;
        struct list_head *list = NULL;

        if (!video->is_enabled)
                return -ENODEV;

        if (queue_to_ep) {
                struct uvc_request *ureq = req->context;
                /*
                 * With USB3 handling more requests at a higher speed, we can't
                 * afford to generate an interrupt for every request. Decide to
                 * interrupt:
                 *
                 * - When no more requests are available in the free queue, as
                 *   this may be our last chance to refill the endpoint's
                 *   request queue.
                 *
                 * - When this is request is the last request for the video
                 *   buffer, as we want to start sending the next video buffer
                 *   ASAP in case it doesn't get started already in the next
                 *   iteration of this loop.
                 *
                 * - Four times over the length of the requests queue (as
                 *   indicated by video->uvc_num_requests), as a trade-off
                 *   between latency and interrupt load.
                 */
                if (list_empty(&video->req_free) || ureq->last_buf ||
                        !(video->req_int_count %
                        min(DIV_ROUND_UP(video->uvc_num_requests, 4), UVCG_REQ_MAX_INT_COUNT))) {
                        video->req_int_count = 0;
                        req->no_interrupt = 0;
                } else {
                        req->no_interrupt = 1;
                }
                video->req_int_count++;
                return uvcg_video_ep_queue(video, req);
        }
        /*
         * If we're not queuing to the ep, for isoc we're queuing
         * to the req_ready list, otherwise req_free.
         */
        list = is_bulk ? &video->req_free : &video->req_ready;
        list_add_tail(&req->list, list);
        return 0;
}

static void
uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct uvc_request *ureq = req->context;
        struct uvc_video *video = ureq->video;
        struct uvc_video_queue *queue = &video->queue;
        struct uvc_buffer *last_buf;
        unsigned long flags;

        spin_lock_irqsave(&video->req_lock, flags);
        atomic_dec(&video->queued);
        if (!video->is_enabled) {
                /*
                 * When is_enabled is false, uvcg_video_disable() ensures
                 * that in-flight uvc_buffers are returned, so we can
                 * safely call free_request without worrying about
                 * last_buf.
                 */
                uvc_video_free_request(ureq, ep);
                spin_unlock_irqrestore(&video->req_lock, flags);
                return;
        }

        last_buf = ureq->last_buf;
        ureq->last_buf = NULL;
        spin_unlock_irqrestore(&video->req_lock, flags);

        switch (req->status) {
        case 0:
                break;

        case -EXDEV:
                uvcg_dbg(&video->uvc->func, "VS request missed xfer.\n");
                if (req->length != 0)
                        queue->flags |= UVC_QUEUE_DROP_INCOMPLETE;
                break;

        case -ESHUTDOWN:        /* disconnect from host. */
                uvcg_dbg(&video->uvc->func, "VS request cancelled.\n");
                uvcg_queue_cancel(queue, 1);
                break;

        default:
                uvcg_warn(&video->uvc->func,
                          "VS request completed with status %d.\n",
                          req->status);
                uvcg_queue_cancel(queue, 0);
        }

        if (last_buf) {
                spin_lock_irqsave(&queue->irqlock, flags);
                uvcg_complete_buffer(queue, last_buf);
                spin_unlock_irqrestore(&queue->irqlock, flags);
        }

        spin_lock_irqsave(&video->req_lock, flags);
        /*
         * Video stream might have been disabled while we were
         * processing the current usb_request. So make sure
         * we're still streaming before queueing the usb_request
         * back to req_free
         */
        if (!video->is_enabled) {
                uvc_video_free_request(ureq, ep);
                spin_unlock_irqrestore(&video->req_lock, flags);
                uvcg_queue_cancel(queue, 0);

                return;
        }

        list_add_tail(&req->list, &video->req_free);
        /*
         * Queue work to the wq as well since it is possible that a
         * buffer may not have been completely encoded with the set of
         * in-flight usb requests for whih the complete callbacks are
         * firing.
         * In that case, if we do not queue work to the worker thread,
         * the buffer will never be marked as complete - and therefore
         * not be returned to userpsace. As a result,
         * dequeue -> queue -> dequeue flow of uvc buffers will not
         * happen. Since there are is a new free request wake up the pump.
         */
        queue_work(video->async_wq, &video->pump);

        trace_uvcg_video_complete(req, atomic_read(&video->queued));

        spin_unlock_irqrestore(&video->req_lock, flags);

        kthread_queue_work(video->kworker, &video->hw_submit);
}

static void uvcg_video_hw_submit(struct kthread_work *work)
{
        struct uvc_video *video = container_of(work, struct uvc_video, hw_submit);
        bool is_bulk = video->max_payload_size;
        unsigned long flags;
        struct usb_request *req;
        int ret = 0;

        while (true) {
                if (!video->ep->enabled)
                        return;
                spin_lock_irqsave(&video->req_lock, flags);
                /*
                 * Here we check whether any request is available in the ready
                 * list. If it is, queue it to the ep and add the current
                 * usb_request to the req_free list - for video_pump to fill in.
                 * Otherwise, just use the current usb_request to queue a 0
                 * length request to the ep. Since we always add to the req_free
                 * list if we dequeue from the ready list, there will never
                 * be a situation where the req_free list is completely out of
                 * requests and cannot recover.
                 */
                if (!list_empty(&video->req_ready)) {
                        req = list_first_entry(&video->req_ready,
                                               struct usb_request, list);
                } else {
                        if (list_empty(&video->req_free) ||
                            (atomic_read(&video->queued) > UVCG_REQ_MAX_ZERO_COUNT)) {
                                spin_unlock_irqrestore(&video->req_lock, flags);

                                return;
                        }
                        req = list_first_entry(&video->req_free, struct usb_request,
                                               list);
                        req->length = 0;
                }
                list_del(&req->list);

                /*
                 * Queue to the endpoint. The actual queueing to ep will
                 * only happen on one thread - the async_wq for bulk endpoints
                 * and this thread for isoc endpoints.
                 */
                ret = uvcg_video_usb_req_queue(video, req, !is_bulk);
                if (ret < 0) {
                        /*
                         * Endpoint error, but the stream is still enabled.
                         * Put request back in req_free for it to be cleaned
                         * up later.
                         */
                        list_add_tail(&req->list, &video->req_free);
                        /*
                         * There is a new free request - wake up the pump.
                         */
                        queue_work(video->async_wq, &video->pump);

                }

                spin_unlock_irqrestore(&video->req_lock, flags);
        }
}

static int
uvc_video_free_requests(struct uvc_video *video)
{
        struct uvc_request *ureq, *temp;

        list_for_each_entry_safe(ureq, temp, &video->ureqs, list)
                uvc_video_free_request(ureq, video->ep);

        INIT_LIST_HEAD(&video->ureqs);
        INIT_LIST_HEAD(&video->req_free);
        INIT_LIST_HEAD(&video->req_ready);
        return 0;
}

static void
uvc_video_prep_requests(struct uvc_video *video)
{
        struct uvc_device *uvc = container_of(video, struct uvc_device, video);
        struct usb_composite_dev *cdev = uvc->func.config->cdev;
        unsigned int interval_duration;
        unsigned int max_req_size, req_size, header_size;
        unsigned int nreq;

        max_req_size = video->max_req_size;

        if (!usb_endpoint_xfer_isoc(video->ep->desc)) {
                video->req_size = max_req_size;
                video->reqs_per_frame = video->uvc_num_requests =
                        DIV_ROUND_UP(video->imagesize, max_req_size);

                return;
        }

        interval_duration = 1 << (video->ep->desc->bInterval - 1);
        if (cdev->gadget->speed < USB_SPEED_HIGH)
                interval_duration *= 10000;
        else
                interval_duration *= 1250;

        nreq = DIV_ROUND_UP(video->interval, interval_duration);

        header_size = nreq * UVCG_REQUEST_HEADER_LEN;

        req_size = DIV_ROUND_UP(video->imagesize + header_size, nreq);

        if (req_size > max_req_size) {
                /* The prepared interval length and expected buffer size
                 * is not possible to stream with the currently configured
                 * isoc bandwidth. Fallback to the maximum.
                 */
                req_size = max_req_size;
        }
        video->req_size = req_size;

        /* We need to compensate the amount of requests to be
         * allocated with the maximum amount of zero length requests.
         * Since it is possible that hw_submit will initially
         * enqueue some zero length requests and we then will not be
         * able to fully encode one frame.
         */
        video->uvc_num_requests = nreq + UVCG_REQ_MAX_ZERO_COUNT;
        video->reqs_per_frame = nreq;
}

static int
uvc_video_alloc_requests(struct uvc_video *video)
{
        struct uvc_request *ureq;
        unsigned int i;
        int ret = -ENOMEM;

        /*
         * calculate in uvc_video_prep_requests
         * - video->uvc_num_requests
         * - video->req_size
         */
        uvc_video_prep_requests(video);

        for (i = 0; i < video->uvc_num_requests; i++) {
                ureq = kzalloc_obj(struct uvc_request);
                if (ureq == NULL)
                        goto error;

                INIT_LIST_HEAD(&ureq->list);

                list_add_tail(&ureq->list, &video->ureqs);

                ureq->req_buffer = kmalloc(video->req_size, GFP_KERNEL);
                if (ureq->req_buffer == NULL)
                        goto error;

                ureq->req = usb_ep_alloc_request(video->ep, GFP_KERNEL);
                if (ureq->req == NULL)
                        goto error;

                ureq->req->buf = ureq->req_buffer;
                ureq->req->length = 0;
                ureq->req->complete = uvc_video_complete;
                ureq->req->context = ureq;
                ureq->video = video;
                ureq->last_buf = NULL;

                list_add_tail(&ureq->req->list, &video->req_free);
                /* req_size/PAGE_SIZE + 1 for overruns and + 1 for header */
                sg_alloc_table(&ureq->sgt,
                               DIV_ROUND_UP(video->req_size - UVCG_REQUEST_HEADER_LEN,
                                            PAGE_SIZE) + 2, GFP_KERNEL);
        }

        return 0;

error:
        uvc_video_free_requests(video);
        return ret;
}

/* --------------------------------------------------------------------------
 * Video streaming
 */

/*
 * uvcg_video_pump - Pump video data into the USB requests
 *
 * This function fills the available USB requests (listed in req_free) with
 * video data from the queued buffers.
 */
static void uvcg_video_pump(struct work_struct *work)
{
        struct uvc_video *video = container_of(work, struct uvc_video, pump);
        struct uvc_video_queue *queue = &video->queue;
        /* video->max_payload_size is only set when using bulk transfer */
        bool is_bulk = video->max_payload_size;
        struct usb_request *req = NULL;
        struct uvc_buffer *buf;
        unsigned long flags;
        int ret = 0;

        while (true) {
                if (!video->ep->enabled)
                        return;

                /*
                 * Check is_enabled and retrieve the first available USB
                 * request, protected by the request lock.
                 */
                spin_lock_irqsave(&video->req_lock, flags);
                if (!video->is_enabled || list_empty(&video->req_free)) {
                        spin_unlock_irqrestore(&video->req_lock, flags);
                        return;
                }
                req = list_first_entry(&video->req_free, struct usb_request,
                                        list);
                list_del(&req->list);
                spin_unlock_irqrestore(&video->req_lock, flags);

                /*
                 * Retrieve the first available video buffer and fill the
                 * request, protected by the video queue irqlock.
                 */
                spin_lock_irqsave(&queue->irqlock, flags);
                buf = uvcg_queue_head(queue);
                if (!buf) {
                        /*
                         * Either the queue has been disconnected or no video buffer
                         * available for bulk transfer. Either way, stop processing
                         * further.
                         */
                        spin_unlock_irqrestore(&queue->irqlock, flags);
                        break;
                }

                video->encode(req, video, buf);

                spin_unlock_irqrestore(&queue->irqlock, flags);

                spin_lock_irqsave(&video->req_lock, flags);
                /* For bulk end points we queue from the worker thread
                 * since we would preferably not want to wait on requests
                 * to be ready, in the uvcg_video_complete() handler.
                 * For isoc endpoints we add the request to the ready list
                 * and only queue it to the endpoint from the complete handler.
                 */
                ret = uvcg_video_usb_req_queue(video, req, is_bulk);
                spin_unlock_irqrestore(&video->req_lock, flags);

                if (ret < 0) {
                        uvcg_queue_cancel(queue, 0);
                        break;
                }
        }
        spin_lock_irqsave(&video->req_lock, flags);
        if (video->is_enabled)
                list_add_tail(&req->list, &video->req_free);
        else
                uvc_video_free_request(req->context, video->ep);
        spin_unlock_irqrestore(&video->req_lock, flags);
}

/*
 * Disable the video stream
 */
int
uvcg_video_disable(struct uvc_video *video)
{
        unsigned long flags;
        struct list_head inflight_bufs;
        struct usb_request *req, *temp;
        struct uvc_buffer *buf, *btemp;
        struct uvc_request *ureq, *utemp;

        if (video->ep == NULL) {
                uvcg_info(&video->uvc->func,
                          "Video disable failed, device is uninitialized.\n");
                return -ENODEV;
        }

        INIT_LIST_HEAD(&inflight_bufs);
        spin_lock_irqsave(&video->req_lock, flags);
        video->is_enabled = false;

        /*
         * Remove any in-flight buffers from the uvc_requests
         * because we want to return them before cancelling the
         * queue. This ensures that we aren't stuck waiting for
         * all complete callbacks to come through before disabling
         * vb2 queue.
         */
        list_for_each_entry(ureq, &video->ureqs, list) {
                if (ureq->last_buf) {
                        list_add_tail(&ureq->last_buf->queue, &inflight_bufs);
                        ureq->last_buf = NULL;
                }
        }
        spin_unlock_irqrestore(&video->req_lock, flags);

        cancel_work_sync(&video->pump);
        uvcg_queue_cancel(&video->queue, 0);

        spin_lock_irqsave(&video->req_lock, flags);
        /*
         * Remove all uvc_requests from ureqs with list_del_init
         * This lets uvc_video_free_request correctly identify
         * if the uvc_request is attached to a list or not when freeing
         * memory.
         */
        list_for_each_entry_safe(ureq, utemp, &video->ureqs, list)
                list_del_init(&ureq->list);

        list_for_each_entry_safe(req, temp, &video->req_free, list) {
                list_del(&req->list);
                uvc_video_free_request(req->context, video->ep);
        }

        list_for_each_entry_safe(req, temp, &video->req_ready, list) {
                list_del(&req->list);
                uvc_video_free_request(req->context, video->ep);
        }

        INIT_LIST_HEAD(&video->ureqs);
        INIT_LIST_HEAD(&video->req_free);
        INIT_LIST_HEAD(&video->req_ready);
        spin_unlock_irqrestore(&video->req_lock, flags);

        /*
         * Return all the video buffers before disabling the queue.
         */
        spin_lock_irqsave(&video->queue.irqlock, flags);
        list_for_each_entry_safe(buf, btemp, &inflight_bufs, queue) {
                list_del(&buf->queue);
                uvcg_complete_buffer(&video->queue, buf);
        }
        spin_unlock_irqrestore(&video->queue.irqlock, flags);

        uvcg_queue_enable(&video->queue, 0);
        return 0;
}

/*
 * Enable the video stream.
 */
int uvcg_video_enable(struct uvc_video *video)
{
        int ret;

        if (video->ep == NULL) {
                uvcg_info(&video->uvc->func,
                          "Video enable failed, device is uninitialized.\n");
                return -ENODEV;
        }

        /*
         * Safe to access request related fields without req_lock because
         * this is the only thread currently active, and no other
         * request handling thread will become active until this function
         * returns.
         */
        video->is_enabled = true;

        if ((ret = uvcg_queue_enable(&video->queue, 1)) < 0)
                return ret;

        if ((ret = uvc_video_alloc_requests(video)) < 0)
                return ret;

        if (video->max_payload_size) {
                video->encode = uvc_video_encode_bulk;
                video->payload_size = 0;
        } else
                video->encode = video->queue.use_sg ?
                        uvc_video_encode_isoc_sg : uvc_video_encode_isoc;

        video->req_int_count = 0;

        atomic_set(&video->queued, 0);

        kthread_queue_work(video->kworker, &video->hw_submit);
        queue_work(video->async_wq, &video->pump);

        return ret;
}

/*
 * Initialize the UVC video stream.
 */
int uvcg_video_init(struct uvc_video *video, struct uvc_device *uvc)
{
        video->is_enabled = false;
        INIT_LIST_HEAD(&video->ureqs);
        INIT_LIST_HEAD(&video->req_free);
        INIT_LIST_HEAD(&video->req_ready);
        spin_lock_init(&video->req_lock);
        INIT_WORK(&video->pump, uvcg_video_pump);

        /* Allocate a work queue for asynchronous video pump handler. */
        video->async_wq = alloc_workqueue("uvcgadget", WQ_UNBOUND | WQ_HIGHPRI, 0);
        if (!video->async_wq)
                return -EINVAL;

        /* Allocate a kthread for asynchronous hw submit handler. */
        video->kworker = kthread_run_worker(0, "UVCG");
        if (IS_ERR(video->kworker)) {
                uvcg_err(&video->uvc->func, "failed to create UVCG kworker\n");
                return PTR_ERR(video->kworker);
        }

        kthread_init_work(&video->hw_submit, uvcg_video_hw_submit);

        sched_set_fifo(video->kworker->task);

        video->uvc = uvc;
        video->fcc = V4L2_PIX_FMT_YUYV;
        video->bpp = 16;
        video->width = 320;
        video->height = 240;
        video->imagesize = 320 * 240 * 2;
        video->interval = 666666;

        /* Initialize the video buffers queue. */
        return uvcg_queue_init(&video->queue, uvc->v4l2_dev.dev->parent,
                        V4L2_BUF_TYPE_VIDEO_OUTPUT, &video->mutex);
}