/*
 *      uvc_video.c  --  USB Video Class Gadget driver
 *
 *      Copyright (C) 2009-2010
 *          Laurent Pinchart (laurent.pinchart@ideasonboard.com)
 *
 *      This program is free software; you can redistribute it and/or modify
 *      it under the terms of the GNU General Public License as published by
 *      the Free Software Foundation; either version 2 of the License, or
 *      (at your option) any later version.
 */

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

#include <media/v4l2-dev.h>

#include "uvc.h"
#include "uvc_queue.h"

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

static int
uvc_video_encode_header(struct uvc_video *video, struct uvc_buffer *buf,
                u8 *data, int len)
{
        data[0] = 2;
        data[1] = UVC_STREAM_EOH | video->fid;

        if (buf->buf.bytesused - video->queue.buf_used <= len - 2)
                data[1] |= UVC_STREAM_EOF;

        return 2;
}

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 = queue->mem + buf->buf.m.offset + queue->buf_used;
        nbytes = min((unsigned int)len, buf->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;
        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((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->buf.bytesused == video->queue.buf_used) {
                video->queue.buf_used = 0;
                buf->state = UVC_BUF_STATE_DONE;
                uvc_queue_next_buffer(&video->queue, buf);
                video->fid ^= UVC_STREAM_FID;

                video->payload_size = 0;
        }

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

static void
uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
                struct uvc_buffer *buf)
{
        void *mem = req->buf;
        int len = video->req_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 = video->req_size - len;

        if (buf->buf.bytesused == video->queue.buf_used) {
                video->queue.buf_used = 0;
                buf->state = UVC_BUF_STATE_DONE;
                uvc_queue_next_buffer(&video->queue, buf);
                video->fid ^= UVC_STREAM_FID;
        }
}

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

/*
 * I somehow feel that synchronisation won't be easy to achieve here. We have
 * three events that control USB requests submission:
 *
 * - USB request completion: the completion handler will resubmit the request
 *   if a video buffer is available.
 *
 * - USB interface setting selection: in response to a SET_INTERFACE request,
 *   the handler will start streaming if a video buffer is available and if
 *   video is not currently streaming.
 *
 * - V4L2 buffer queueing: the driver will start streaming if video is not
 *   currently streaming.
 *
 * Race conditions between those 3 events might lead to deadlocks or other
 * nasty side effects.
 *
 * The "video currently streaming" condition can't be detected by the irqqueue
 * being empty, as a request can still be in flight. A separate "queue paused"
 * flag is thus needed.
 *
 * The paused flag will be set when we try to retrieve the irqqueue head if the
 * queue is empty, and cleared when we queue a buffer.
 *
 * The USB request completion handler will get the buffer at the irqqueue head
 * under protection of the queue spinlock. If the queue is empty, the streaming
 * paused flag will be set. Right after releasing the spinlock a userspace
 * application can queue a buffer. The flag will then cleared, and the ioctl
 * handler will restart the video stream.
 */
static void
uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct uvc_video *video = req->context;
        struct uvc_buffer *buf;
        unsigned long flags;
        int ret;

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

        case -ESHUTDOWN:
                printk(KERN_INFO "VS request cancelled.\n");
                goto requeue;

        default:
                printk(KERN_INFO "VS request completed with status %d.\n",
                        req->status);
                goto requeue;
        }

        spin_lock_irqsave(&video->queue.irqlock, flags);
        buf = uvc_queue_head(&video->queue);
        if (buf == NULL) {
                spin_unlock_irqrestore(&video->queue.irqlock, flags);
                goto requeue;
        }

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

        if ((ret = usb_ep_queue(ep, req, GFP_ATOMIC)) < 0) {
                printk(KERN_INFO "Failed to queue request (%d).\n", ret);
                usb_ep_set_halt(ep);
                spin_unlock_irqrestore(&video->queue.irqlock, flags);
                goto requeue;
        }
        spin_unlock_irqrestore(&video->queue.irqlock, flags);

        return;

requeue:
        spin_lock_irqsave(&video->req_lock, flags);
        list_add_tail(&req->list, &video->req_free);
        spin_unlock_irqrestore(&video->req_lock, flags);
}

static int
uvc_video_free_requests(struct uvc_video *video)
{
        unsigned int i;

        for (i = 0; i < UVC_NUM_REQUESTS; ++i) {
                if (video->req[i]) {
                        usb_ep_free_request(video->ep, video->req[i]);
                        video->req[i] = NULL;
                }

                if (video->req_buffer[i]) {
                        kfree(video->req_buffer[i]);
                        video->req_buffer[i] = NULL;
                }
        }

        INIT_LIST_HEAD(&video->req_free);
        video->req_size = 0;
        return 0;
}

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

        BUG_ON(video->req_size);

        for (i = 0; i < UVC_NUM_REQUESTS; ++i) {
                video->req_buffer[i] = kmalloc(video->ep->maxpacket, GFP_KERNEL);
                if (video->req_buffer[i] == NULL)
                        goto error;

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

                video->req[i]->buf = video->req_buffer[i];
                video->req[i]->length = 0;
                video->req[i]->dma = DMA_ADDR_INVALID;
                video->req[i]->complete = uvc_video_complete;
                video->req[i]->context = video;

                list_add_tail(&video->req[i]->list, &video->req_free);
        }

        video->req_size = video->ep->maxpacket;
        return 0;

error:
        uvc_video_free_requests(video);
        return ret;
}

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

/*
 * uvc_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 int
uvc_video_pump(struct uvc_video *video)
{
        struct usb_request *req;
        struct uvc_buffer *buf;
        unsigned long flags;
        int ret;

        /* FIXME TODO Race between uvc_video_pump and requests completion
         * handler ???
         */

        while (1) {
                /* Retrieve the first available USB request, protected by the
                 * request lock.
                 */
                spin_lock_irqsave(&video->req_lock, flags);
                if (list_empty(&video->req_free)) {
                        spin_unlock_irqrestore(&video->req_lock, flags);
                        return 0;
                }
                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(&video->queue.irqlock, flags);
                buf = uvc_queue_head(&video->queue);
                if (buf == NULL) {
                        spin_unlock_irqrestore(&video->queue.irqlock, flags);
                        break;
                }

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

                /* Queue the USB request */
                if ((ret = usb_ep_queue(video->ep, req, GFP_KERNEL)) < 0) {
                        printk(KERN_INFO "Failed to queue request (%d)\n", ret);
                        usb_ep_set_halt(video->ep);
                        spin_unlock_irqrestore(&video->queue.irqlock, flags);
                        break;
                }
                spin_unlock_irqrestore(&video->queue.irqlock, flags);
        }

        spin_lock_irqsave(&video->req_lock, flags);
        list_add_tail(&req->list, &video->req_free);
        spin_unlock_irqrestore(&video->req_lock, flags);
        return 0;
}

/*
 * Enable or disable the video stream.
 */
static int
uvc_video_enable(struct uvc_video *video, int enable)
{
        unsigned int i;
        int ret;

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

        if (!enable) {
                for (i = 0; i < UVC_NUM_REQUESTS; ++i)
                        usb_ep_dequeue(video->ep, video->req[i]);

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

        if ((ret = uvc_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 = uvc_video_encode_isoc;

        return uvc_video_pump(video);
}

/*
 * Initialize the UVC video stream.
 */
static int
uvc_video_init(struct uvc_video *video)
{
        INIT_LIST_HEAD(&video->req_free);
        spin_lock_init(&video->req_lock);

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

        /* Initialize the video buffers queue. */
        uvc_queue_init(&video->queue, V4L2_BUF_TYPE_VIDEO_OUTPUT);
        return 0;
}