V4L/DVB (8145a): USB Video Class driver

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / drivers / media / video / uvc / uvc_video.c

/*
 *      uvc_video.c  --  USB Video Class driver - Video handling
 *
 *      Copyright (C) 2005-2008
 *          Laurent Pinchart (laurent.pinchart@skynet.be)
 *
 *      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/version.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/videodev2.h>
#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <asm/atomic.h>
#include <asm/unaligned.h>

#include <media/v4l2-common.h>

#include "uvcvideo.h"

/* ------------------------------------------------------------------------
 * UVC Controls
 */

static int __uvc_query_ctrl(struct uvc_device *dev, __u8 query, __u8 unit,
                        __u8 intfnum, __u8 cs, void *data, __u16 size,
                        int timeout)
{
        __u8 type = USB_TYPE_CLASS | USB_RECIP_INTERFACE;
        unsigned int pipe;
        int ret;

        pipe = (query & 0x80) ? usb_rcvctrlpipe(dev->udev, 0)
                              : usb_sndctrlpipe(dev->udev, 0);
        type |= (query & 0x80) ? USB_DIR_IN : USB_DIR_OUT;

        ret = usb_control_msg(dev->udev, pipe, query, type, cs << 8,
                        unit << 8 | intfnum, data, size, timeout);

        if (ret != size) {
                uvc_printk(KERN_ERR, "Failed to query (%u) UVC control %u "
                        "(unit %u) : %d (exp. %u).\n", query, cs, unit, ret,
                        size);
                return -EIO;
        }

        return 0;
}

int uvc_query_ctrl(struct uvc_device *dev, __u8 query, __u8 unit,
                        __u8 intfnum, __u8 cs, void *data, __u16 size)
{
        return __uvc_query_ctrl(dev, query, unit, intfnum, cs, data, size,
                                UVC_CTRL_CONTROL_TIMEOUT);
}

static void uvc_fixup_buffer_size(struct uvc_video_device *video,
        struct uvc_streaming_control *ctrl)
{
        struct uvc_format *format;
        struct uvc_frame *frame;

        if (ctrl->bFormatIndex <= 0 ||
            ctrl->bFormatIndex > video->streaming->nformats)
                return;

        format = &video->streaming->format[ctrl->bFormatIndex - 1];

        if (ctrl->bFrameIndex <= 0 ||
            ctrl->bFrameIndex > format->nframes)
                return;

        frame = &format->frame[ctrl->bFrameIndex - 1];

        if (!(format->flags & UVC_FMT_FLAG_COMPRESSED) ||
             (ctrl->dwMaxVideoFrameSize == 0 &&
              video->dev->uvc_version < 0x0110))
                ctrl->dwMaxVideoFrameSize =
                        frame->dwMaxVideoFrameBufferSize;
}

static int uvc_get_video_ctrl(struct uvc_video_device *video,
        struct uvc_streaming_control *ctrl, int probe, __u8 query)
{
        __u8 data[34];
        __u8 size;
        int ret;

        size = video->dev->uvc_version >= 0x0110 ? 34 : 26;
        ret = __uvc_query_ctrl(video->dev, query, 0, video->streaming->intfnum,
                probe ? VS_PROBE_CONTROL : VS_COMMIT_CONTROL, &data, size,
                UVC_CTRL_STREAMING_TIMEOUT);

        if (ret < 0)
                return ret;

        ctrl->bmHint = le16_to_cpup((__le16 *)&data[0]);
        ctrl->bFormatIndex = data[2];
        ctrl->bFrameIndex = data[3];
        ctrl->dwFrameInterval = le32_to_cpup((__le32 *)&data[4]);
        ctrl->wKeyFrameRate = le16_to_cpup((__le16 *)&data[8]);
        ctrl->wPFrameRate = le16_to_cpup((__le16 *)&data[10]);
        ctrl->wCompQuality = le16_to_cpup((__le16 *)&data[12]);
        ctrl->wCompWindowSize = le16_to_cpup((__le16 *)&data[14]);
        ctrl->wDelay = le16_to_cpup((__le16 *)&data[16]);
        ctrl->dwMaxVideoFrameSize =
                le32_to_cpu(get_unaligned((__le32 *)&data[18]));
        ctrl->dwMaxPayloadTransferSize =
                le32_to_cpu(get_unaligned((__le32 *)&data[22]));

        if (size == 34) {
                ctrl->dwClockFrequency =
                        le32_to_cpu(get_unaligned((__le32 *)&data[26]));
                ctrl->bmFramingInfo = data[30];
                ctrl->bPreferedVersion = data[31];
                ctrl->bMinVersion = data[32];
                ctrl->bMaxVersion = data[33];
        } else {
                ctrl->dwClockFrequency = video->dev->clock_frequency;
                ctrl->bmFramingInfo = 0;
                ctrl->bPreferedVersion = 0;
                ctrl->bMinVersion = 0;
                ctrl->bMaxVersion = 0;
        }

        /* Some broken devices return a null or wrong dwMaxVideoFrameSize.
         * Try to get the value from the format and frame descriptor.
         */
        uvc_fixup_buffer_size(video, ctrl);

        return 0;
}

int uvc_set_video_ctrl(struct uvc_video_device *video,
        struct uvc_streaming_control *ctrl, int probe)
{
        __u8 data[34];
        __u8 size;

        size = video->dev->uvc_version >= 0x0110 ? 34 : 26;
        memset(data, 0, sizeof data);

        *(__le16 *)&data[0] = cpu_to_le16(ctrl->bmHint);
        data[2] = ctrl->bFormatIndex;
        data[3] = ctrl->bFrameIndex;
        *(__le32 *)&data[4] = cpu_to_le32(ctrl->dwFrameInterval);
        *(__le16 *)&data[8] = cpu_to_le16(ctrl->wKeyFrameRate);
        *(__le16 *)&data[10] = cpu_to_le16(ctrl->wPFrameRate);
        *(__le16 *)&data[12] = cpu_to_le16(ctrl->wCompQuality);
        *(__le16 *)&data[14] = cpu_to_le16(ctrl->wCompWindowSize);
        *(__le16 *)&data[16] = cpu_to_le16(ctrl->wDelay);
        /* Note: Some of the fields below are not required for IN devices (see
         * UVC spec, 4.3.1.1), but we still copy them in case support for OUT
         * devices is added in the future. */
        put_unaligned(cpu_to_le32(ctrl->dwMaxVideoFrameSize),
                (__le32 *)&data[18]);
        put_unaligned(cpu_to_le32(ctrl->dwMaxPayloadTransferSize),
                (__le32 *)&data[22]);

        if (size == 34) {
                put_unaligned(cpu_to_le32(ctrl->dwClockFrequency),
                        (__le32 *)&data[26]);
                data[30] = ctrl->bmFramingInfo;
                data[31] = ctrl->bPreferedVersion;
                data[32] = ctrl->bMinVersion;
                data[33] = ctrl->bMaxVersion;
        }

        return __uvc_query_ctrl(video->dev, SET_CUR, 0,
                video->streaming->intfnum,
                probe ? VS_PROBE_CONTROL : VS_COMMIT_CONTROL, &data, size,
                UVC_CTRL_STREAMING_TIMEOUT);
}

int uvc_probe_video(struct uvc_video_device *video,
        struct uvc_streaming_control *probe)
{
        struct uvc_streaming_control probe_min, probe_max;
        __u16 bandwidth;
        unsigned int i;
        int ret;

        mutex_lock(&video->streaming->mutex);

        /* Perform probing. The device should adjust the requested values
         * according to its capabilities. However, some devices, namely the
         * first generation UVC Logitech webcams, don't implement the Video
         * Probe control properly, and just return the needed bandwidth. For
         * that reason, if the needed bandwidth exceeds the maximum available
         * bandwidth, try to lower the quality.
         */
        if ((ret = uvc_set_video_ctrl(video, probe, 1)) < 0)
                goto done;

        /* Get the minimum and maximum values for compression settings. */
        if (!(video->dev->quirks & UVC_QUIRK_PROBE_MINMAX)) {
                ret = uvc_get_video_ctrl(video, &probe_min, 1, GET_MIN);
                if (ret < 0)
                        goto done;
                ret = uvc_get_video_ctrl(video, &probe_max, 1, GET_MAX);
                if (ret < 0)
                        goto done;

                probe->wCompQuality = probe_max.wCompQuality;
        }

        for (i = 0; i < 2; ++i) {
                if ((ret = uvc_set_video_ctrl(video, probe, 1)) < 0 ||
                    (ret = uvc_get_video_ctrl(video, probe, 1, GET_CUR)) < 0)
                        goto done;

                if (video->streaming->intf->num_altsetting == 1)
                        break;

                bandwidth = probe->dwMaxPayloadTransferSize;
                if (bandwidth <= video->streaming->maxpsize)
                        break;

                if (video->dev->quirks & UVC_QUIRK_PROBE_MINMAX) {
                        ret = -ENOSPC;
                        goto done;
                }

                /* TODO: negotiate compression parameters */
                probe->wKeyFrameRate = probe_min.wKeyFrameRate;
                probe->wPFrameRate = probe_min.wPFrameRate;
                probe->wCompQuality = probe_max.wCompQuality;
                probe->wCompWindowSize = probe_min.wCompWindowSize;
        }

done:
        mutex_unlock(&video->streaming->mutex);
        return ret;
}

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

/* Values for bmHeaderInfo (Video and Still Image Payload Headers, 2.4.3.3) */
#define UVC_STREAM_EOH  (1 << 7)
#define UVC_STREAM_ERR  (1 << 6)
#define UVC_STREAM_STI  (1 << 5)
#define UVC_STREAM_RES  (1 << 4)
#define UVC_STREAM_SCR  (1 << 3)
#define UVC_STREAM_PTS  (1 << 2)
#define UVC_STREAM_EOF  (1 << 1)
#define UVC_STREAM_FID  (1 << 0)

/* Video payload decoding is handled by uvc_video_decode_start(),
 * uvc_video_decode_data() and uvc_video_decode_end().
 *
 * uvc_video_decode_start is called with URB data at the start of a bulk or
 * isochronous payload. It processes header data and returns the header size
 * in bytes if successful. If an error occurs, it returns a negative error
 * code. The following error codes have special meanings.
 *
 * - EAGAIN informs the caller that the current video buffer should be marked
 *   as done, and that the function should be called again with the same data
 *   and a new video buffer. This is used when end of frame conditions can be
 *   reliably detected at the beginning of the next frame only.
 *
 * If an error other than -EAGAIN is returned, the caller will drop the current
 * payload. No call to uvc_video_decode_data and uvc_video_decode_end will be
 * made until the next payload. -ENODATA can be used to drop the current
 * payload if no other error code is appropriate.
 *
 * uvc_video_decode_data is called for every URB with URB data. It copies the
 * data to the video buffer.
 *
 * uvc_video_decode_end is called with header data at the end of a bulk or
 * isochronous payload. It performs any additional header data processing and
 * returns 0 or a negative error code if an error occured. As header data have
 * already been processed by uvc_video_decode_start, this functions isn't
 * required to perform sanity checks a second time.
 *
 * For isochronous transfers where a payload is always transfered in a single
 * URB, the three functions will be called in a row.
 *
 * To let the decoder process header data and update its internal state even
 * when no video buffer is available, uvc_video_decode_start must be prepared
 * to be called with a NULL buf parameter. uvc_video_decode_data and
 * uvc_video_decode_end will never be called with a NULL buffer.
 */
static int uvc_video_decode_start(struct uvc_video_device *video,
                struct uvc_buffer *buf, const __u8 *data, int len)
{
        __u8 fid;

        /* Sanity checks:
         * - packet must be at least 2 bytes long
         * - bHeaderLength value must be at least 2 bytes (see above)
         * - bHeaderLength value can't be larger than the packet size.
         */
        if (len < 2 || data[0] < 2 || data[0] > len)
                return -EINVAL;

        /* Skip payloads marked with the error bit ("error frames"). */
        if (data[1] & UVC_STREAM_ERR) {
                uvc_trace(UVC_TRACE_FRAME, "Dropping payload (error bit "
                          "set).\n");
                return -ENODATA;
        }

        fid = data[1] & UVC_STREAM_FID;

        /* Store the payload FID bit and return immediately when the buffer is
         * NULL.
         */
        if (buf == NULL) {
                video->last_fid = fid;
                return -ENODATA;
        }

        /* Synchronize to the input stream by waiting for the FID bit to be
         * toggled when the the buffer state is not UVC_BUF_STATE_ACTIVE.
         * queue->last_fid is initialized to -1, so the first isochronous
         * frame will always be in sync.
         *
         * If the device doesn't toggle the FID bit, invert video->last_fid
         * when the EOF bit is set to force synchronisation on the next packet.
         */
        if (buf->state != UVC_BUF_STATE_ACTIVE) {
                if (fid == video->last_fid) {
                        uvc_trace(UVC_TRACE_FRAME, "Dropping payload (out of "
                                "sync).\n");
                        if ((video->dev->quirks & UVC_QUIRK_STREAM_NO_FID) &&
                            (data[1] & UVC_STREAM_EOF))
                                video->last_fid ^= UVC_STREAM_FID;
                        return -ENODATA;
                }

                /* TODO: Handle PTS and SCR. */
                buf->state = UVC_BUF_STATE_ACTIVE;
        }

        /* Mark the buffer as done if we're at the beginning of a new frame.
         * End of frame detection is better implemented by checking the EOF
         * bit (FID bit toggling is delayed by one frame compared to the EOF
         * bit), but some devices don't set the bit at end of frame (and the
         * last payload can be lost anyway). We thus must check if the FID has
         * been toggled.
         *
         * queue->last_fid is initialized to -1, so the first isochronous
         * frame will never trigger an end of frame detection.
         *
         * Empty buffers (bytesused == 0) don't trigger end of frame detection
         * as it doesn't make sense to return an empty buffer. This also
         * avoids detecting and of frame conditions at FID toggling if the
         * previous payload had the EOF bit set.
         */
        if (fid != video->last_fid && buf->buf.bytesused != 0) {
                uvc_trace(UVC_TRACE_FRAME, "Frame complete (FID bit "
                                "toggled).\n");
                buf->state = UVC_BUF_STATE_DONE;
                return -EAGAIN;
        }

        video->last_fid = fid;

        return data[0];
}

static void uvc_video_decode_data(struct uvc_video_device *video,
                struct uvc_buffer *buf, const __u8 *data, int len)
{
        struct uvc_video_queue *queue = &video->queue;
        unsigned int maxlen, nbytes;
        void *mem;

        if (len <= 0)
                return;

        /* Copy the video data to the buffer. */
        maxlen = buf->buf.length - buf->buf.bytesused;
        mem = queue->mem + buf->buf.m.offset + buf->buf.bytesused;
        nbytes = min((unsigned int)len, maxlen);
        memcpy(mem, data, nbytes);
        buf->buf.bytesused += nbytes;

        /* Complete the current frame if the buffer size was exceeded. */
        if (len > maxlen) {
                uvc_trace(UVC_TRACE_FRAME, "Frame complete (overflow).\n");
                buf->state = UVC_BUF_STATE_DONE;
        }
}

static void uvc_video_decode_end(struct uvc_video_device *video,
                struct uvc_buffer *buf, const __u8 *data, int len)
{
        /* Mark the buffer as done if the EOF marker is set. */
        if (data[1] & UVC_STREAM_EOF && buf->buf.bytesused != 0) {
                uvc_trace(UVC_TRACE_FRAME, "Frame complete (EOF found).\n");
                if (data[0] == len)
                        uvc_trace(UVC_TRACE_FRAME, "EOF in empty payload.\n");
                buf->state = UVC_BUF_STATE_DONE;
                if (video->dev->quirks & UVC_QUIRK_STREAM_NO_FID)
                        video->last_fid ^= UVC_STREAM_FID;
        }
}

/* ------------------------------------------------------------------------
 * URB handling
 */

/*
 * Completion handler for video URBs.
 */
static void uvc_video_decode_isoc(struct urb *urb,
        struct uvc_video_device *video, struct uvc_buffer *buf)
{
        u8 *mem;
        int ret, i;

        for (i = 0; i < urb->number_of_packets; ++i) {
                if (urb->iso_frame_desc[i].status < 0) {
                        uvc_trace(UVC_TRACE_FRAME, "USB isochronous frame "
                                "lost (%d).\n", urb->iso_frame_desc[i].status);
                        continue;
                }

                /* Decode the payload header. */
                mem = urb->transfer_buffer + urb->iso_frame_desc[i].offset;
                do {
                        ret = uvc_video_decode_start(video, buf, mem,
                                urb->iso_frame_desc[i].actual_length);
                        if (ret == -EAGAIN)
                                buf = uvc_queue_next_buffer(&video->queue, buf);
                } while (ret == -EAGAIN);

                if (ret < 0)
                        continue;

                /* Decode the payload data. */
                uvc_video_decode_data(video, buf, mem + ret,
                        urb->iso_frame_desc[i].actual_length - ret);

                /* Process the header again. */
                uvc_video_decode_end(video, buf, mem, ret);

                if (buf->state == UVC_BUF_STATE_DONE ||
                    buf->state == UVC_BUF_STATE_ERROR)
                        buf = uvc_queue_next_buffer(&video->queue, buf);
        }
}

static void uvc_video_decode_bulk(struct urb *urb,
        struct uvc_video_device *video, struct uvc_buffer *buf)
{
        u8 *mem;
        int len, ret;

        mem = urb->transfer_buffer;
        len = urb->actual_length;
        video->bulk.payload_size += len;

        /* If the URB is the first of its payload, decode and save the
         * header.
         */
        if (video->bulk.header_size == 0) {
                do {
                        ret = uvc_video_decode_start(video, buf, mem, len);
                        if (ret == -EAGAIN)
                                buf = uvc_queue_next_buffer(&video->queue, buf);
                } while (ret == -EAGAIN);

                /* If an error occured skip the rest of the payload. */
                if (ret < 0 || buf == NULL) {
                        video->bulk.skip_payload = 1;
                        return;
                }

                video->bulk.header_size = ret;
                memcpy(video->bulk.header, mem, video->bulk.header_size);

                mem += ret;
                len -= ret;
        }

        /* The buffer queue might have been cancelled while a bulk transfer
         * was in progress, so we can reach here with buf equal to NULL. Make
         * sure buf is never dereferenced if NULL.
         */

        /* Process video data. */
        if (!video->bulk.skip_payload && buf != NULL)
                uvc_video_decode_data(video, buf, mem, len);

        /* Detect the payload end by a URB smaller than the maximum size (or
         * a payload size equal to the maximum) and process the header again.
         */
        if (urb->actual_length < urb->transfer_buffer_length ||
            video->bulk.payload_size >= video->bulk.max_payload_size) {
                if (!video->bulk.skip_payload && buf != NULL) {
                        uvc_video_decode_end(video, buf, video->bulk.header,
                                video->bulk.header_size);
                        if (buf->state == UVC_BUF_STATE_DONE ||
                            buf->state == UVC_BUF_STATE_ERROR)
                                buf = uvc_queue_next_buffer(&video->queue, buf);
                }

                video->bulk.header_size = 0;
                video->bulk.skip_payload = 0;
                video->bulk.payload_size = 0;
        }
}

static void uvc_video_complete(struct urb *urb)
{
        struct uvc_video_device *video = urb->context;
        struct uvc_video_queue *queue = &video->queue;
        struct uvc_buffer *buf = NULL;
        unsigned long flags;
        int ret;

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

        default:
                uvc_printk(KERN_WARNING, "Non-zero status (%d) in video "
                        "completion handler.\n", urb->status);

        case -ENOENT:           /* usb_kill_urb() called. */
                if (video->frozen)
                        return;

        case -ECONNRESET:       /* usb_unlink_urb() called. */
        case -ESHUTDOWN:        /* The endpoint is being disabled. */
                uvc_queue_cancel(queue, urb->status == -ESHUTDOWN);
                return;
        }

        spin_lock_irqsave(&queue->irqlock, flags);
        if (!list_empty(&queue->irqqueue))
                buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
                                       queue);
        spin_unlock_irqrestore(&queue->irqlock, flags);

        video->decode(urb, video, buf);

        if ((ret = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
                uvc_printk(KERN_ERR, "Failed to resubmit video URB (%d).\n",
                        ret);
        }
}

/*
 * Uninitialize isochronous/bulk URBs and free transfer buffers.
 */
static void uvc_uninit_video(struct uvc_video_device *video)
{
        struct urb *urb;
        unsigned int i;

        for (i = 0; i < UVC_URBS; ++i) {
                if ((urb = video->urb[i]) == NULL)
                        continue;

                usb_kill_urb(urb);
                /* urb->transfer_buffer_length is not touched by USB core, so
                 * we can use it here as the buffer length.
                 */
                if (video->urb_buffer[i]) {
                        usb_buffer_free(video->dev->udev,
                                urb->transfer_buffer_length,
                                video->urb_buffer[i], urb->transfer_dma);
                        video->urb_buffer[i] = NULL;
                }

                usb_free_urb(urb);
                video->urb[i] = NULL;
        }
}

/*
 * Initialize isochronous URBs and allocate transfer buffers. The packet size
 * is given by the endpoint.
 */
static int uvc_init_video_isoc(struct uvc_video_device *video,
        struct usb_host_endpoint *ep)
{
        struct urb *urb;
        unsigned int npackets, i, j;
        __u16 psize;
        __u32 size;

        /* Compute the number of isochronous packets to allocate by dividing
         * the maximum video frame size by the packet size. Limit the result
         * to UVC_MAX_ISO_PACKETS.
         */
        psize = le16_to_cpu(ep->desc.wMaxPacketSize);
        psize = (psize & 0x07ff) * (1 + ((psize >> 11) & 3));

        size = video->streaming->ctrl.dwMaxVideoFrameSize;
        if (size > UVC_MAX_FRAME_SIZE)
                return -EINVAL;

        npackets = (size + psize - 1) / psize;
        if (npackets > UVC_MAX_ISO_PACKETS)
                npackets = UVC_MAX_ISO_PACKETS;

        size = npackets * psize;

        for (i = 0; i < UVC_URBS; ++i) {
                urb = usb_alloc_urb(npackets, GFP_KERNEL);
                if (urb == NULL) {
                        uvc_uninit_video(video);
                        return -ENOMEM;
                }

                video->urb_buffer[i] = usb_buffer_alloc(video->dev->udev,
                        size, GFP_KERNEL, &urb->transfer_dma);
                if (video->urb_buffer[i] == NULL) {
                        usb_free_urb(urb);
                        uvc_uninit_video(video);
                        return -ENOMEM;
                }

                urb->dev = video->dev->udev;
                urb->context = video;
                urb->pipe = usb_rcvisocpipe(video->dev->udev,
                                ep->desc.bEndpointAddress);
                urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
                urb->interval = ep->desc.bInterval;
                urb->transfer_buffer = video->urb_buffer[i];
                urb->complete = uvc_video_complete;
                urb->number_of_packets = npackets;
                urb->transfer_buffer_length = size;

                for (j = 0; j < npackets; ++j) {
                        urb->iso_frame_desc[j].offset = j * psize;
                        urb->iso_frame_desc[j].length = psize;
                }

                video->urb[i] = urb;
        }

        return 0;
}

/*
 * Initialize bulk URBs and allocate transfer buffers. The packet size is
 * given by the endpoint.
 */
static int uvc_init_video_bulk(struct uvc_video_device *video,
        struct usb_host_endpoint *ep)
{
        struct urb *urb;
        unsigned int pipe, i;
        __u16 psize;
        __u32 size;

        /* Compute the bulk URB size. Some devices set the maximum payload
         * size to a value too high for memory-constrained devices. We must
         * then transfer the payload accross multiple URBs. To be consistant
         * with isochronous mode, allocate maximum UVC_MAX_ISO_PACKETS per bulk
         * URB.
         */
        psize = le16_to_cpu(ep->desc.wMaxPacketSize) & 0x07ff;
        size = video->streaming->ctrl.dwMaxPayloadTransferSize;
        video->bulk.max_payload_size = size;
        if (size > psize * UVC_MAX_ISO_PACKETS)
                size = psize * UVC_MAX_ISO_PACKETS;

        pipe = usb_rcvbulkpipe(video->dev->udev, ep->desc.bEndpointAddress);

        for (i = 0; i < UVC_URBS; ++i) {
                urb = usb_alloc_urb(0, GFP_KERNEL);
                if (urb == NULL) {
                        uvc_uninit_video(video);
                        return -ENOMEM;
                }

                video->urb_buffer[i] = usb_buffer_alloc(video->dev->udev,
                        size, GFP_KERNEL, &urb->transfer_dma);
                if (video->urb_buffer[i] == NULL) {
                        usb_free_urb(urb);
                        uvc_uninit_video(video);
                        return -ENOMEM;
                }

                usb_fill_bulk_urb(urb, video->dev->udev, pipe,
                        video->urb_buffer[i], size, uvc_video_complete,
                        video);
                urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;

                video->urb[i] = urb;
        }

        return 0;
}

/*
 * Initialize isochronous/bulk URBs and allocate transfer buffers.
 */
static int uvc_init_video(struct uvc_video_device *video)
{
        struct usb_interface *intf = video->streaming->intf;
        struct usb_host_interface *alts;
        struct usb_host_endpoint *ep = NULL;
        int intfnum = video->streaming->intfnum;
        unsigned int bandwidth, psize, i;
        int ret;

        video->last_fid = -1;
        video->bulk.header_size = 0;
        video->bulk.skip_payload = 0;
        video->bulk.payload_size = 0;

        if (intf->num_altsetting > 1) {
                /* Isochronous endpoint, select the alternate setting. */
                bandwidth = video->streaming->ctrl.dwMaxPayloadTransferSize;

                if (bandwidth == 0) {
                        uvc_printk(KERN_WARNING, "device %s requested null "
                                "bandwidth, defaulting to lowest.\n",
                                video->vdev->name);
                        bandwidth = 1;
                }

                for (i = 0; i < intf->num_altsetting; ++i) {
                        alts = &intf->altsetting[i];
                        ep = uvc_find_endpoint(alts,
                                video->streaming->header.bEndpointAddress);
                        if (ep == NULL)
                                continue;

                        /* Check if the bandwidth is high enough. */
                        psize = le16_to_cpu(ep->desc.wMaxPacketSize);
                        psize = (psize & 0x07ff) * (1 + ((psize >> 11) & 3));
                        if (psize >= bandwidth)
                                break;
                }

                if (i >= intf->num_altsetting)
                        return -EIO;

                if ((ret = usb_set_interface(video->dev->udev, intfnum, i)) < 0)
                        return ret;

                ret = uvc_init_video_isoc(video, ep);
        } else {
                /* Bulk endpoint, proceed to URB initialization. */
                ep = uvc_find_endpoint(&intf->altsetting[0],
                                video->streaming->header.bEndpointAddress);
                if (ep == NULL)
                        return -EIO;

                ret = uvc_init_video_bulk(video, ep);
        }

        if (ret < 0)
                return ret;

        /* Submit the URBs. */
        for (i = 0; i < UVC_URBS; ++i) {
                if ((ret = usb_submit_urb(video->urb[i], GFP_KERNEL)) < 0) {
                        uvc_printk(KERN_ERR, "Failed to submit URB %u "
                                        "(%d).\n", i, ret);
                        uvc_uninit_video(video);
                        return ret;
                }
        }

        return 0;
}

/* --------------------------------------------------------------------------
 * Suspend/resume
 */

/*
 * Stop streaming without disabling the video queue.
 *
 * To let userspace applications resume without trouble, we must not touch the
 * video buffers in any way. We mark the device as frozen to make sure the URB
 * completion handler won't try to cancel the queue when we kill the URBs.
 */
int uvc_video_suspend(struct uvc_video_device *video)
{
        if (!uvc_queue_streaming(&video->queue))
                return 0;

        video->frozen = 1;
        uvc_uninit_video(video);
        usb_set_interface(video->dev->udev, video->streaming->intfnum, 0);
        return 0;
}

/*
 * Reconfigure the video interface and restart streaming if it was enable
 * before suspend.
 *
 * If an error occurs, disable the video queue. This will wake all pending
 * buffers, making sure userspace applications are notified of the problem
 * instead of waiting forever.
 */
int uvc_video_resume(struct uvc_video_device *video)
{
        int ret;

        video->frozen = 0;

        if ((ret = uvc_set_video_ctrl(video, &video->streaming->ctrl, 0)) < 0) {
                uvc_queue_enable(&video->queue, 0);
                return ret;
        }

        if (!uvc_queue_streaming(&video->queue))
                return 0;

        if ((ret = uvc_init_video(video)) < 0)
                uvc_queue_enable(&video->queue, 0);

        return ret;
}

/* ------------------------------------------------------------------------
 * Video device
 */

/*
 * Initialize the UVC video device by retrieving the default format and
 * committing it.
 *
 * Some cameras (namely the Fuji Finepix) set the format and frame
 * indexes to zero. The UVC standard doesn't clearly make this a spec
 * violation, so try to silently fix the values if possible.
 *
 * This function is called before registering the device with V4L.
 */
int uvc_video_init(struct uvc_video_device *video)
{
        struct uvc_streaming_control *probe = &video->streaming->ctrl;
        struct uvc_format *format = NULL;
        struct uvc_frame *frame = NULL;
        unsigned int i;
        int ret;

        if (video->streaming->nformats == 0) {
                uvc_printk(KERN_INFO, "No supported video formats found.\n");
                return -EINVAL;
        }

        /* Alternate setting 0 should be the default, yet the XBox Live Vision
         * Cam (and possibly other devices) crash or otherwise misbehave if
         * they don't receive a SET_INTERFACE request before any other video
         * control request.
         */
        usb_set_interface(video->dev->udev, video->streaming->intfnum, 0);

        /* Some webcams don't suport GET_DEF request on the probe control. We
         * fall back to GET_CUR if GET_DEF fails.
         */
        if ((ret = uvc_get_video_ctrl(video, probe, 1, GET_DEF)) < 0 &&
            (ret = uvc_get_video_ctrl(video, probe, 1, GET_CUR)) < 0)
                return ret;

        /* Check if the default format descriptor exists. Use the first
         * available format otherwise.
         */
        for (i = video->streaming->nformats; i > 0; --i) {
                format = &video->streaming->format[i-1];
                if (format->index == probe->bFormatIndex)
                        break;
        }

        if (format->nframes == 0) {
                uvc_printk(KERN_INFO, "No frame descriptor found for the "
                        "default format.\n");
                return -EINVAL;
        }

        /* Zero bFrameIndex might be correct. Stream-based formats (including
         * MPEG-2 TS and DV) do not support frames but have a dummy frame
         * descriptor with bFrameIndex set to zero. If the default frame
         * descriptor is not found, use the first avalable frame.
         */
        for (i = format->nframes; i > 0; --i) {
                frame = &format->frame[i-1];
                if (frame->bFrameIndex == probe->bFrameIndex)
                        break;
        }

        /* Commit the default settings. */
        probe->bFormatIndex = format->index;
        probe->bFrameIndex = frame->bFrameIndex;
        if ((ret = uvc_set_video_ctrl(video, probe, 0)) < 0)
                return ret;

        video->streaming->cur_format = format;
        video->streaming->cur_frame = frame;
        atomic_set(&video->active, 0);

        /* Select the video decoding function */
        if (video->dev->quirks & UVC_QUIRK_BUILTIN_ISIGHT)
                video->decode = uvc_video_decode_isight;
        else if (video->streaming->intf->num_altsetting > 1)
                video->decode = uvc_video_decode_isoc;
        else
                video->decode = uvc_video_decode_bulk;

        return 0;
}

/*
 * Enable or disable the video stream.
 */
int uvc_video_enable(struct uvc_video_device *video, int enable)
{
        int ret;

        if (!enable) {
                uvc_uninit_video(video);
                usb_set_interface(video->dev->udev,
                        video->streaming->intfnum, 0);
                uvc_queue_enable(&video->queue, 0);
                return 0;
        }

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

        return uvc_init_video(video);
}