uvc_video.c

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/*
 *  uvc_video.c  --  USB Video Class Gadget driver
 *
 *  Copyright (C) 2009-2010
 *      Laurent Pinchart ([email protected])
 *
 *  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;
}