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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *      uvc_video.c  --  USB Video Class driver - Video handling
  *
  *      Copyright (C) 2005-2010
  *          Laurent Pinchart (laurent.pinchart@ideasonboard.com)
  */
 
 #include <linux/dma-mapping.h>
 #include <linux/highmem.h>
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/usb.h>
 #include <linux/usb/hcd.h>
 #include <linux/videodev2.h>
 #include <linux/vmalloc.h>
 #include <linux/wait.h>
 #include <linux/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;
 
     pipe = (query & 0x80) ? usb_rcvctrlpipe(dev->udev, 0)
                   : usb_sndctrlpipe(dev->udev, 0);
     type |= (query & 0x80) ? USB_DIR_IN : USB_DIR_OUT;
 
     return usb_control_msg(dev->udev, pipe, query, type, cs << 8,
             unit << 8 | intfnum, data, size, timeout);
 }
 
 static const char *uvc_query_name(u8 query)
 {
     switch (query) {
     case UVC_SET_CUR:
         return "SET_CUR";
     case UVC_GET_CUR:
         return "GET_CUR";
     case UVC_GET_MIN:
         return "GET_MIN";
     case UVC_GET_MAX:
         return "GET_MAX";
     case UVC_GET_RES:
         return "GET_RES";
     case UVC_GET_LEN:
         return "GET_LEN";
     case UVC_GET_INFO:
         return "GET_INFO";
     case UVC_GET_DEF:
         return "GET_DEF";
     default:
         return "<invalid>";
     }
 }
 
 int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
             u8 intfnum, u8 cs, void *data, u16 size)
 {
     int ret;
     u8 error;
     u8 tmp;
 
     ret = __uvc_query_ctrl(dev, query, unit, intfnum, cs, data, size,
                 UVC_CTRL_CONTROL_TIMEOUT);
     if (likely(ret == size))
         return 0;
 
     dev_err(&dev->udev->dev,
         "Failed to query (%s) UVC control %u on unit %u: %d (exp. %u).\n",
         uvc_query_name(query), cs, unit, ret, size);
 
     if (ret != -EPIPE)
         return ret;
 
     tmp = *(u8 *)data;
 
     ret = __uvc_query_ctrl(dev, UVC_GET_CUR, 0, intfnum,
                    UVC_VC_REQUEST_ERROR_CODE_CONTROL, data, 1,
                    UVC_CTRL_CONTROL_TIMEOUT);
 
     error = *(u8 *)data;
     *(u8 *)data = tmp;
 
     if (ret != 1)
         return ret < 0 ? ret : -EPIPE;
 
     uvc_dbg(dev, CONTROL, "Control error %u\n", error);
 
     switch (error) {
     case 0:
         /* Cannot happen - we received a STALL */
         return -EPIPE;
     case 1: /* Not ready */
         return -EBUSY;
     case 2: /* Wrong state */
         return -EILSEQ;
     case 3: /* Power */
         return -EREMOTE;
     case 4: /* Out of range */
         return -ERANGE;
     case 5: /* Invalid unit */
     case 6: /* Invalid control */
     case 7: /* Invalid Request */
         /*
          * The firmware has not properly implemented
          * the control or there has been a HW error.
          */
         return -EIO;
     case 8: /* Invalid value within range */
         return -EINVAL;
     default: /* reserved or unknown */
         break;
     }
 
     return -EPIPE;
 }
 
 static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
     struct uvc_streaming_control *ctrl)
 {
     static const struct usb_device_id elgato_cam_link_4k = {
         USB_DEVICE(0x0fd9, 0x0066)
     };
     struct uvc_format *format = NULL;
     struct uvc_frame *frame = NULL;
     unsigned int i;
 
     /*
      * The response of the Elgato Cam Link 4K is incorrect: The second byte
      * contains bFormatIndex (instead of being the second byte of bmHint).
      * The first byte is always zero. The third byte is always 1.
      *
      * The UVC 1.5 class specification defines the first five bits in the
      * bmHint bitfield. The remaining bits are reserved and should be zero.
      * Therefore a valid bmHint will be less than 32.
      *
      * Latest Elgato Cam Link 4K firmware as of 2021-03-23 needs this fix.
      * MCU: 20.02.19, FPGA: 67
      */
     if (usb_match_one_id(stream->dev->intf, &elgato_cam_link_4k) &&
         ctrl->bmHint > 255) {
         u8 corrected_format_index = ctrl->bmHint >> 8;
 
         uvc_dbg(stream->dev, VIDEO,
             "Correct USB video probe response from {bmHint: 0x%04x, bFormatIndex: %u} to {bmHint: 0x%04x, bFormatIndex: %u}\n",
             ctrl->bmHint, ctrl->bFormatIndex,
             1, corrected_format_index);
         ctrl->bmHint = 1;
         ctrl->bFormatIndex = corrected_format_index;
     }
 
     for (i = 0; i < stream->nformats; ++i) {
         if (stream->format[i].index == ctrl->bFormatIndex) {
             format = &stream->format[i];
             break;
         }
     }
 
     if (format == NULL)
         return;
 
     for (i = 0; i < format->nframes; ++i) {
         if (format->frame[i].bFrameIndex == ctrl->bFrameIndex) {
             frame = &format->frame[i];
             break;
         }
     }
 
     if (frame == NULL)
         return;
 
     if (!(format->flags & UVC_FMT_FLAG_COMPRESSED) ||
          (ctrl->dwMaxVideoFrameSize == 0 &&
           stream->dev->uvc_version < 0x0110))
         ctrl->dwMaxVideoFrameSize =
             frame->dwMaxVideoFrameBufferSize;
 
     /*
      * The "TOSHIBA Web Camera - 5M" Chicony device (04f2:b50b) seems to
      * compute the bandwidth on 16 bits and erroneously sign-extend it to
      * 32 bits, resulting in a huge bandwidth value. Detect and fix that
      * condition by setting the 16 MSBs to 0 when they're all equal to 1.
      */
     if ((ctrl->dwMaxPayloadTransferSize & 0xffff0000) == 0xffff0000)
         ctrl->dwMaxPayloadTransferSize &= ~0xffff0000;
 
     if (!(format->flags & UVC_FMT_FLAG_COMPRESSED) &&
         stream->dev->quirks & UVC_QUIRK_FIX_BANDWIDTH &&
         stream->intf->num_altsetting > 1) {
         u32 interval;
         u32 bandwidth;
 
         interval = (ctrl->dwFrameInterval > 100000)
              ? ctrl->dwFrameInterval
              : frame->dwFrameInterval[0];
 
         /*
          * Compute a bandwidth estimation by multiplying the frame
          * size by the number of video frames per second, divide the
          * result by the number of USB frames (or micro-frames for
          * high-speed devices) per second and add the UVC header size
          * (assumed to be 12 bytes long).
          */
         bandwidth = frame->wWidth * frame->wHeight / 8 * format->bpp;
         bandwidth *= 10000000 / interval + 1;
         bandwidth /= 1000;
         if (stream->dev->udev->speed == USB_SPEED_HIGH)
             bandwidth /= 8;
         bandwidth += 12;
 
         /*
          * The bandwidth estimate is too low for many cameras. Don't use
          * maximum packet sizes lower than 1024 bytes to try and work
          * around the problem. According to measurements done on two
          * different camera models, the value is high enough to get most
          * resolutions working while not preventing two simultaneous
          * VGA streams at 15 fps.
          */
         bandwidth = max_t(u32, bandwidth, 1024);
 
         ctrl->dwMaxPayloadTransferSize = bandwidth;
     }
 }
 
 static size_t uvc_video_ctrl_size(struct uvc_streaming *stream)
 {
     /*
      * Return the size of the video probe and commit controls, which depends
      * on the protocol version.
      */
     if (stream->dev->uvc_version < 0x0110)
         return 26;
     else if (stream->dev->uvc_version < 0x0150)
         return 34;
     else
         return 48;
 }
 
 static int uvc_get_video_ctrl(struct uvc_streaming *stream,
     struct uvc_streaming_control *ctrl, int probe, u8 query)
 {
     u16 size = uvc_video_ctrl_size(stream);
     u8 *data;
     int ret;
 
     if ((stream->dev->quirks & UVC_QUIRK_PROBE_DEF) &&
             query == UVC_GET_DEF)
         return -EIO;
 
     data = kmalloc(size, GFP_KERNEL);
     if (data == NULL)
         return -ENOMEM;
 
     ret = __uvc_query_ctrl(stream->dev, query, 0, stream->intfnum,
         probe ? UVC_VS_PROBE_CONTROL : UVC_VS_COMMIT_CONTROL, data,
         size, uvc_timeout_param);
 
     if ((query == UVC_GET_MIN || query == UVC_GET_MAX) && ret == 2) {
         /*
          * Some cameras, mostly based on Bison Electronics chipsets,
          * answer a GET_MIN or GET_MAX request with the wCompQuality
          * field only.
          */
         uvc_warn_once(stream->dev, UVC_WARN_MINMAX, "UVC non "
             "compliance - GET_MIN/MAX(PROBE) incorrectly "
             "supported. Enabling workaround.\n");
         memset(ctrl, 0, sizeof(*ctrl));
         ctrl->wCompQuality = le16_to_cpup((__le16 *)data);
         ret = 0;
         goto out;
     } else if (query == UVC_GET_DEF && probe == 1 && ret != size) {
         /*
          * Many cameras don't support the GET_DEF request on their
          * video probe control. Warn once and return, the caller will
          * fall back to GET_CUR.
          */
         uvc_warn_once(stream->dev, UVC_WARN_PROBE_DEF, "UVC non "
             "compliance - GET_DEF(PROBE) not supported. "
             "Enabling workaround.\n");
         ret = -EIO;
         goto out;
     } else if (ret != size) {
         dev_err(&stream->intf->dev,
             "Failed to query (%u) UVC %s control : %d (exp. %u).\n",
             query, probe ? "probe" : "commit", ret, size);
         ret = -EIO;
         goto out;
     }
 
     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 = get_unaligned_le32(&data[18]);
     ctrl->dwMaxPayloadTransferSize = get_unaligned_le32(&data[22]);
 
     if (size >= 34) {
         ctrl->dwClockFrequency = get_unaligned_le32(&data[26]);
         ctrl->bmFramingInfo = data[30];
         ctrl->bPreferedVersion = data[31];
         ctrl->bMinVersion = data[32];
         ctrl->bMaxVersion = data[33];
     } else {
         ctrl->dwClockFrequency = stream->dev->clock_frequency;
         ctrl->bmFramingInfo = 0;
         ctrl->bPreferedVersion = 0;
         ctrl->bMinVersion = 0;
         ctrl->bMaxVersion = 0;
     }
 
     /*
      * Some broken devices return null or wrong dwMaxVideoFrameSize and
      * dwMaxPayloadTransferSize fields. Try to get the value from the
      * format and frame descriptors.
      */
     uvc_fixup_video_ctrl(stream, ctrl);
     ret = 0;
 
 out:
     kfree(data);
     return ret;
 }
 
 static int uvc_set_video_ctrl(struct uvc_streaming *stream,
     struct uvc_streaming_control *ctrl, int probe)
 {
     u16 size = uvc_video_ctrl_size(stream);
     u8 *data;
     int ret;
 
     data = kzalloc(size, GFP_KERNEL);
     if (data == NULL)
         return -ENOMEM;
 
     *(__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);
     put_unaligned_le32(ctrl->dwMaxVideoFrameSize, &data[18]);
     put_unaligned_le32(ctrl->dwMaxPayloadTransferSize, &data[22]);
 
     if (size >= 34) {
         put_unaligned_le32(ctrl->dwClockFrequency, &data[26]);
         data[30] = ctrl->bmFramingInfo;
         data[31] = ctrl->bPreferedVersion;
         data[32] = ctrl->bMinVersion;
         data[33] = ctrl->bMaxVersion;
     }
 
     ret = __uvc_query_ctrl(stream->dev, UVC_SET_CUR, 0, stream->intfnum,
         probe ? UVC_VS_PROBE_CONTROL : UVC_VS_COMMIT_CONTROL, data,
         size, uvc_timeout_param);
     if (ret != size) {
         dev_err(&stream->intf->dev,
             "Failed to set UVC %s control : %d (exp. %u).\n",
             probe ? "probe" : "commit", ret, size);
         ret = -EIO;
     }
 
     kfree(data);
     return ret;
 }
 
 int uvc_probe_video(struct uvc_streaming *stream,
     struct uvc_streaming_control *probe)
 {
     struct uvc_streaming_control probe_min, probe_max;
     unsigned int i;
     int ret;
 
     /*
      * 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.
      */
     ret = uvc_set_video_ctrl(stream, probe, 1);
     if (ret < 0)
         goto done;
 
     /* Get the minimum and maximum values for compression settings. */
     if (!(stream->dev->quirks & UVC_QUIRK_PROBE_MINMAX)) {
         ret = uvc_get_video_ctrl(stream, &probe_min, 1, UVC_GET_MIN);
         if (ret < 0)
             goto done;
         ret = uvc_get_video_ctrl(stream, &probe_max, 1, UVC_GET_MAX);
         if (ret < 0)
             goto done;
 
         probe->wCompQuality = probe_max.wCompQuality;
     }
 
     for (i = 0; i < 2; ++i) {
         ret = uvc_set_video_ctrl(stream, probe, 1);
         if (ret < 0)
             goto done;
         ret = uvc_get_video_ctrl(stream, probe, 1, UVC_GET_CUR);
         if (ret < 0)
             goto done;
 
         if (stream->intf->num_altsetting == 1)
             break;
 
         if (probe->dwMaxPayloadTransferSize <= stream->maxpsize)
             break;
 
         if (stream->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:
     return ret;
 }
 
 static int uvc_commit_video(struct uvc_streaming *stream,
                 struct uvc_streaming_control *probe)
 {
     return uvc_set_video_ctrl(stream, probe, 0);
 }
 
 /* -----------------------------------------------------------------------------
  * Clocks and timestamps
  */
 
 static inline ktime_t uvc_video_get_time(void)
 {
     if (uvc_clock_param == CLOCK_MONOTONIC)
         return ktime_get();
     else
         return ktime_get_real();
 }
 
 static void
 uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
                const u8 *data, int len)
 {
     struct uvc_clock_sample *sample;
     unsigned int header_size;
     bool has_pts = false;
     bool has_scr = false;
     unsigned long flags;
     ktime_t time;
     u16 host_sof;
     u16 dev_sof;
 
     switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
     case UVC_STREAM_PTS | UVC_STREAM_SCR:
         header_size = 12;
         has_pts = true;
         has_scr = true;
         break;
     case UVC_STREAM_PTS:
         header_size = 6;
         has_pts = true;
         break;
     case UVC_STREAM_SCR:
         header_size = 8;
         has_scr = true;
         break;
     default:
         header_size = 2;
         break;
     }
 
     /* Check for invalid headers. */
     if (len < header_size)
         return;
 
     /*
      * Extract the timestamps:
      *
      * - store the frame PTS in the buffer structure
      * - if the SCR field is present, retrieve the host SOF counter and
      *   kernel timestamps and store them with the SCR STC and SOF fields
      *   in the ring buffer
      */
     if (has_pts && buf != NULL)
         buf->pts = get_unaligned_le32(&data[2]);
 
     if (!has_scr)
         return;
 
     /*
      * To limit the amount of data, drop SCRs with an SOF identical to the
      * previous one.
      */
     dev_sof = get_unaligned_le16(&data[header_size - 2]);
     if (dev_sof == stream->clock.last_sof)
         return;
 
     stream->clock.last_sof = dev_sof;
 
     host_sof = usb_get_current_frame_number(stream->dev->udev);
     time = uvc_video_get_time();
 
     /*
      * The UVC specification allows device implementations that can't obtain
      * the USB frame number to keep their own frame counters as long as they
      * match the size and frequency of the frame number associated with USB
      * SOF tokens. The SOF values sent by such devices differ from the USB
      * SOF tokens by a fixed offset that needs to be estimated and accounted
      * for to make timestamp recovery as accurate as possible.
      *
      * The offset is estimated the first time a device SOF value is received
      * as the difference between the host and device SOF values. As the two
      * SOF values can differ slightly due to transmission delays, consider
      * that the offset is null if the difference is not higher than 10 ms
      * (negative differences can not happen and are thus considered as an
      * offset). The video commit control wDelay field should be used to
      * compute a dynamic threshold instead of using a fixed 10 ms value, but
      * devices don't report reliable wDelay values.
      *
      * See uvc_video_clock_host_sof() for an explanation regarding why only
      * the 8 LSBs of the delta are kept.
      */
     if (stream->clock.sof_offset == (u16)-1) {
         u16 delta_sof = (host_sof - dev_sof) & 255;
         if (delta_sof >= 10)
             stream->clock.sof_offset = delta_sof;
         else
             stream->clock.sof_offset = 0;
     }
 
     dev_sof = (dev_sof + stream->clock.sof_offset) & 2047;
 
     spin_lock_irqsave(&stream->clock.lock, flags);
 
     sample = &stream->clock.samples[stream->clock.head];
     sample->dev_stc = get_unaligned_le32(&data[header_size - 6]);
     sample->dev_sof = dev_sof;
     sample->host_sof = host_sof;
     sample->host_time = time;
 
     /* Update the sliding window head and count. */
     stream->clock.head = (stream->clock.head + 1) % stream->clock.size;
 
     if (stream->clock.count < stream->clock.size)
         stream->clock.count++;
 
     spin_unlock_irqrestore(&stream->clock.lock, flags);
 }
 
 static void uvc_video_clock_reset(struct uvc_streaming *stream)
 {
     struct uvc_clock *clock = &stream->clock;
 
     clock->head = 0;
     clock->count = 0;
     clock->last_sof = -1;
     clock->sof_offset = -1;
 }
 
 static int uvc_video_clock_init(struct uvc_streaming *stream)
 {
     struct uvc_clock *clock = &stream->clock;
 
     spin_lock_init(&clock->lock);
     clock->size = 32;
 
     clock->samples = kmalloc_array(clock->size, sizeof(*clock->samples),
                        GFP_KERNEL);
     if (clock->samples == NULL)
         return -ENOMEM;
 
     uvc_video_clock_reset(stream);
 
     return 0;
 }
 
 static void uvc_video_clock_cleanup(struct uvc_streaming *stream)
 {
     kfree(stream->clock.samples);
     stream->clock.samples = NULL;
 }
 
 /*
  * uvc_video_clock_host_sof - Return the host SOF value for a clock sample
  *
  * Host SOF counters reported by usb_get_current_frame_number() usually don't
  * cover the whole 11-bits SOF range (0-2047) but are limited to the HCI frame
  * schedule window. They can be limited to 8, 9 or 10 bits depending on the host
  * controller and its configuration.
  *
  * We thus need to recover the SOF value corresponding to the host frame number.
  * As the device and host frame numbers are sampled in a short interval, the
  * difference between their values should be equal to a small delta plus an
  * integer multiple of 256 caused by the host frame number limited precision.
  *
  * To obtain the recovered host SOF value, compute the small delta by masking
  * the high bits of the host frame counter and device SOF difference and add it
  * to the device SOF value.
  */
 static u16 uvc_video_clock_host_sof(const struct uvc_clock_sample *sample)
 {
     /* The delta value can be negative. */
     s8 delta_sof;
 
     delta_sof = (sample->host_sof - sample->dev_sof) & 255;
 
     return (sample->dev_sof + delta_sof) & 2047;
 }
 
 /*
  * uvc_video_clock_update - Update the buffer timestamp
  *
  * This function converts the buffer PTS timestamp to the host clock domain by
  * going through the USB SOF clock domain and stores the result in the V4L2
  * buffer timestamp field.
  *
  * The relationship between the device clock and the host clock isn't known.
  * However, the device and the host share the common USB SOF clock which can be
  * used to recover that relationship.
  *
  * The relationship between the device clock and the USB SOF clock is considered
  * to be linear over the clock samples sliding window and is given by
  *
  * SOF = m * PTS + p
  *
  * Several methods to compute the slope (m) and intercept (p) can be used. As
  * the clock drift should be small compared to the sliding window size, we
  * assume that the line that goes through the points at both ends of the window
  * is a good approximation. Naming those points P1 and P2, we get
  *
  * SOF = (SOF2 - SOF1) / (STC2 - STC1) * PTS
  *     + (SOF1 * STC2 - SOF2 * STC1) / (STC2 - STC1)
  *
  * or
  *
  * SOF = ((SOF2 - SOF1) * PTS + SOF1 * STC2 - SOF2 * STC1) / (STC2 - STC1)   (1)
  *
  * to avoid losing precision in the division. Similarly, the host timestamp is
  * computed with
  *
  * TS = ((TS2 - TS1) * SOF + TS1 * SOF2 - TS2 * SOF1) / (SOF2 - SOF1)        (2)
  *
  * SOF values are coded on 11 bits by USB. We extend their precision with 16
  * decimal bits, leading to a 11.16 coding.
  *
  * TODO: To avoid surprises with device clock values, PTS/STC timestamps should
  * be normalized using the nominal device clock frequency reported through the
  * UVC descriptors.
  *
  * Both the PTS/STC and SOF counters roll over, after a fixed but device
  * specific amount of time for PTS/STC and after 2048ms for SOF. As long as the
  * sliding window size is smaller than the rollover period, differences computed
  * on unsigned integers will produce the correct result. However, the p term in
  * the linear relations will be miscomputed.
  *
  * To fix the issue, we subtract a constant from the PTS and STC values to bring
  * PTS to half the 32 bit STC range. The sliding window STC values then fit into
  * the 32 bit range without any rollover.
  *
  * Similarly, we add 2048 to the device SOF values to make sure that the SOF
  * computed by (1) will never be smaller than 0. This offset is then compensated
  * by adding 2048 to the SOF values used in (2). However, this doesn't prevent
  * rollovers between (1) and (2): the SOF value computed by (1) can be slightly
  * lower than 4096, and the host SOF counters can have rolled over to 2048. This
  * case is handled by subtracting 2048 from the SOF value if it exceeds the host
  * SOF value at the end of the sliding window.
  *
  * Finally we subtract a constant from the host timestamps to bring the first
  * timestamp of the sliding window to 1s.
  */
 void uvc_video_clock_update(struct uvc_streaming *stream,
                 struct vb2_v4l2_buffer *vbuf,
                 struct uvc_buffer *buf)
 {
     struct uvc_clock *clock = &stream->clock;
     struct uvc_clock_sample *first;
     struct uvc_clock_sample *last;
     unsigned long flags;
     u64 timestamp;
     u32 delta_stc;
     u32 y1, y2;
     u32 x1, x2;
     u32 mean;
     u32 sof;
     u64 y;
 
     if (!uvc_hw_timestamps_param)
         return;
 
     /*
      * We will get called from __vb2_queue_cancel() if there are buffers
      * done but not dequeued by the user, but the sample array has already
      * been released at that time. Just bail out in that case.
      */
     if (!clock->samples)
         return;
 
     spin_lock_irqsave(&clock->lock, flags);
 
     if (clock->count < clock->size)
         goto done;
 
     first = &clock->samples[clock->head];
     last = &clock->samples[(clock->head - 1) % clock->size];
 
     /* First step, PTS to SOF conversion. */
     delta_stc = buf->pts - (1UL << 31);
     x1 = first->dev_stc - delta_stc;
     x2 = last->dev_stc - delta_stc;
     if (x1 == x2)
         goto done;
 
     y1 = (first->dev_sof + 2048) << 16;
     y2 = (last->dev_sof + 2048) << 16;
     if (y2 < y1)
         y2 += 2048 << 16;
 
     y = (u64)(y2 - y1) * (1ULL << 31) + (u64)y1 * (u64)x2
       - (u64)y2 * (u64)x1;
     y = div_u64(y, x2 - x1);
 
     sof = y;
 
     uvc_dbg(stream->dev, CLOCK,
         "%s: PTS %u y %llu.%06llu SOF %u.%06llu (x1 %u x2 %u y1 %u y2 %u SOF offset %u)\n",
         stream->dev->name, buf->pts,
         y >> 16, div_u64((y & 0xffff) * 1000000, 65536),
         sof >> 16, div_u64(((u64)sof & 0xffff) * 1000000LLU, 65536),
         x1, x2, y1, y2, clock->sof_offset);
 
     /* Second step, SOF to host clock conversion. */
     x1 = (uvc_video_clock_host_sof(first) + 2048) << 16;
     x2 = (uvc_video_clock_host_sof(last) + 2048) << 16;
     if (x2 < x1)
         x2 += 2048 << 16;
     if (x1 == x2)
         goto done;
 
     y1 = NSEC_PER_SEC;
     y2 = (u32)ktime_to_ns(ktime_sub(last->host_time, first->host_time)) + y1;
 
     /*
      * Interpolated and host SOF timestamps can wrap around at slightly
      * different times. Handle this by adding or removing 2048 to or from
      * the computed SOF value to keep it close to the SOF samples mean
      * value.
      */
     mean = (x1 + x2) / 2;
     if (mean - (1024 << 16) > sof)
         sof += 2048 << 16;
     else if (sof > mean + (1024 << 16))
         sof -= 2048 << 16;
 
     y = (u64)(y2 - y1) * (u64)sof + (u64)y1 * (u64)x2
       - (u64)y2 * (u64)x1;
     y = div_u64(y, x2 - x1);
 
     timestamp = ktime_to_ns(first->host_time) + y - y1;
 
     uvc_dbg(stream->dev, CLOCK,
         "%s: SOF %u.%06llu y %llu ts %llu buf ts %llu (x1 %u/%u/%u x2 %u/%u/%u y1 %u y2 %u)\n",
         stream->dev->name,
         sof >> 16, div_u64(((u64)sof & 0xffff) * 1000000LLU, 65536),
         y, timestamp, vbuf->vb2_buf.timestamp,
         x1, first->host_sof, first->dev_sof,
         x2, last->host_sof, last->dev_sof, y1, y2);
 
     /* Update the V4L2 buffer. */
     vbuf->vb2_buf.timestamp = timestamp;
 
 done:
     spin_unlock_irqrestore(&clock->lock, flags);
 }
 
 /* ------------------------------------------------------------------------
  * Stream statistics
  */
 
 static void uvc_video_stats_decode(struct uvc_streaming *stream,
         const u8 *data, int len)
 {
     unsigned int header_size;
     bool has_pts = false;
     bool has_scr = false;
     u16 scr_sof;
     u32 scr_stc;
     u32 pts;
 
     if (stream->stats.stream.nb_frames == 0 &&
         stream->stats.frame.nb_packets == 0)
         stream->stats.stream.start_ts = ktime_get();
 
     switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
     case UVC_STREAM_PTS | UVC_STREAM_SCR:
         header_size = 12;
         has_pts = true;
         has_scr = true;
         break;
     case UVC_STREAM_PTS:
         header_size = 6;
         has_pts = true;
         break;
     case UVC_STREAM_SCR:
         header_size = 8;
         has_scr = true;
         break;
     default:
         header_size = 2;
         break;
     }
 
     /* Check for invalid headers. */
     if (len < header_size || data[0] < header_size) {
         stream->stats.frame.nb_invalid++;
         return;
     }
 
     /* Extract the timestamps. */
     if (has_pts)
         pts = get_unaligned_le32(&data[2]);
 
     if (has_scr) {
         scr_stc = get_unaligned_le32(&data[header_size - 6]);
         scr_sof = get_unaligned_le16(&data[header_size - 2]);
     }
 
     /* Is PTS constant through the whole frame ? */
     if (has_pts && stream->stats.frame.nb_pts) {
         if (stream->stats.frame.pts != pts) {
             stream->stats.frame.nb_pts_diffs++;
             stream->stats.frame.last_pts_diff =
                 stream->stats.frame.nb_packets;
         }
     }
 
     if (has_pts) {
         stream->stats.frame.nb_pts++;
         stream->stats.frame.pts = pts;
     }
 
     /*
      * Do all frames have a PTS in their first non-empty packet, or before
      * their first empty packet ?
      */
     if (stream->stats.frame.size == 0) {
         if (len > header_size)
             stream->stats.frame.has_initial_pts = has_pts;
         if (len == header_size && has_pts)
             stream->stats.frame.has_early_pts = true;
     }
 
     /* Do the SCR.STC and SCR.SOF fields vary through the frame ? */
     if (has_scr && stream->stats.frame.nb_scr) {
         if (stream->stats.frame.scr_stc != scr_stc)
             stream->stats.frame.nb_scr_diffs++;
     }
 
     if (has_scr) {
         /* Expand the SOF counter to 32 bits and store its value. */
         if (stream->stats.stream.nb_frames > 0 ||
             stream->stats.frame.nb_scr > 0)
             stream->stats.stream.scr_sof_count +=
                 (scr_sof - stream->stats.stream.scr_sof) % 2048;
         stream->stats.stream.scr_sof = scr_sof;
 
         stream->stats.frame.nb_scr++;
         stream->stats.frame.scr_stc = scr_stc;
         stream->stats.frame.scr_sof = scr_sof;
 
         if (scr_sof < stream->stats.stream.min_sof)
             stream->stats.stream.min_sof = scr_sof;
         if (scr_sof > stream->stats.stream.max_sof)
             stream->stats.stream.max_sof = scr_sof;
     }
 
     /* Record the first non-empty packet number. */
     if (stream->stats.frame.size == 0 && len > header_size)
         stream->stats.frame.first_data = stream->stats.frame.nb_packets;
 
     /* Update the frame size. */
     stream->stats.frame.size += len - header_size;
 
     /* Update the packets counters. */
     stream->stats.frame.nb_packets++;
     if (len <= header_size)
         stream->stats.frame.nb_empty++;
 
     if (data[1] & UVC_STREAM_ERR)
         stream->stats.frame.nb_errors++;
 }
 
 static void uvc_video_stats_update(struct uvc_streaming *stream)
 {
     struct uvc_stats_frame *frame = &stream->stats.frame;
 
     uvc_dbg(stream->dev, STATS,
         "frame %u stats: %u/%u/%u packets, %u/%u/%u pts (%searly %sinitial), %u/%u scr, last pts/stc/sof %u/%u/%u\n",
         stream->sequence, frame->first_data,
         frame->nb_packets - frame->nb_empty, frame->nb_packets,
         frame->nb_pts_diffs, frame->last_pts_diff, frame->nb_pts,
         frame->has_early_pts ? "" : "!",
         frame->has_initial_pts ? "" : "!",
         frame->nb_scr_diffs, frame->nb_scr,
         frame->pts, frame->scr_stc, frame->scr_sof);
 
     stream->stats.stream.nb_frames++;
     stream->stats.stream.nb_packets += stream->stats.frame.nb_packets;
     stream->stats.stream.nb_empty += stream->stats.frame.nb_empty;
     stream->stats.stream.nb_errors += stream->stats.frame.nb_errors;
     stream->stats.stream.nb_invalid += stream->stats.frame.nb_invalid;
 
     if (frame->has_early_pts)
         stream->stats.stream.nb_pts_early++;
     if (frame->has_initial_pts)
         stream->stats.stream.nb_pts_initial++;
     if (frame->last_pts_diff <= frame->first_data)
         stream->stats.stream.nb_pts_constant++;
     if (frame->nb_scr >= frame->nb_packets - frame->nb_empty)
         stream->stats.stream.nb_scr_count_ok++;
     if (frame->nb_scr_diffs + 1 == frame->nb_scr)
         stream->stats.stream.nb_scr_diffs_ok++;
 
     memset(&stream->stats.frame, 0, sizeof(stream->stats.frame));
 }
 
 size_t uvc_video_stats_dump(struct uvc_streaming *stream, char *buf,
                 size_t size)
 {
     unsigned int scr_sof_freq;
     unsigned int duration;
     size_t count = 0;
 
     /*
      * Compute the SCR.SOF frequency estimate. At the nominal 1kHz SOF
      * frequency this will not overflow before more than 1h.
      */
     duration = ktime_ms_delta(stream->stats.stream.stop_ts,
                   stream->stats.stream.start_ts);
     if (duration != 0)
         scr_sof_freq = stream->stats.stream.scr_sof_count * 1000
                  / duration;
     else
         scr_sof_freq = 0;
 
     count += scnprintf(buf + count, size - count,
                "frames:  %u\npackets: %u\nempty:   %u\n"
                "errors:  %u\ninvalid: %u\n",
                stream->stats.stream.nb_frames,
                stream->stats.stream.nb_packets,
                stream->stats.stream.nb_empty,
                stream->stats.stream.nb_errors,
                stream->stats.stream.nb_invalid);
     count += scnprintf(buf + count, size - count,
                "pts: %u early, %u initial, %u ok\n",
                stream->stats.stream.nb_pts_early,
                stream->stats.stream.nb_pts_initial,
                stream->stats.stream.nb_pts_constant);
     count += scnprintf(buf + count, size - count,
                "scr: %u count ok, %u diff ok\n",
                stream->stats.stream.nb_scr_count_ok,
                stream->stats.stream.nb_scr_diffs_ok);
     count += scnprintf(buf + count, size - count,
                "sof: %u <= sof <= %u, freq %u.%03u kHz\n",
                stream->stats.stream.min_sof,
                stream->stats.stream.max_sof,
                scr_sof_freq / 1000, scr_sof_freq % 1000);
 
     return count;
 }
 
 static void uvc_video_stats_start(struct uvc_streaming *stream)
 {
     memset(&stream->stats, 0, sizeof(stream->stats));
     stream->stats.stream.min_sof = 2048;
 }
 
 static void uvc_video_stats_stop(struct uvc_streaming *stream)
 {
     stream->stats.stream.stop_ts = ktime_get();
 }
 
 /* ------------------------------------------------------------------------
  * Video codecs
  */
 
 /*
  * 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 occurred. 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 transferred 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_streaming *stream,
         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) {
         stream->stats.frame.nb_invalid++;
         return -EINVAL;
     }
 
     fid = data[1] & UVC_STREAM_FID;
 
     /*
      * Increase the sequence number regardless of any buffer states, so
      * that discontinuous sequence numbers always indicate lost frames.
      */
     if (stream->last_fid != fid) {
         stream->sequence++;
         if (stream->sequence)
             uvc_video_stats_update(stream);
     }
 
     uvc_video_clock_decode(stream, buf, data, len);
     uvc_video_stats_decode(stream, data, len);
 
     /*
      * Store the payload FID bit and return immediately when the buffer is
      * NULL.
      */
     if (buf == NULL) {
         stream->last_fid = fid;
         return -ENODATA;
     }
 
     /* Mark the buffer as bad if the error bit is set. */
     if (data[1] & UVC_STREAM_ERR) {
         uvc_dbg(stream->dev, FRAME,
             "Marking buffer as bad (error bit set)\n");
         buf->error = 1;
     }
 
     /*
      * 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.
      * stream->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 stream->last_fid
      * when the EOF bit is set to force synchronisation on the next packet.
      */
     if (buf->state != UVC_BUF_STATE_ACTIVE) {
         if (fid == stream->last_fid) {
             uvc_dbg(stream->dev, FRAME,
                 "Dropping payload (out of sync)\n");
             if ((stream->dev->quirks & UVC_QUIRK_STREAM_NO_FID) &&
                 (data[1] & UVC_STREAM_EOF))
                 stream->last_fid ^= UVC_STREAM_FID;
             return -ENODATA;
         }
 
         buf->buf.field = V4L2_FIELD_NONE;
         buf->buf.sequence = stream->sequence;
         buf->buf.vb2_buf.timestamp = ktime_to_ns(uvc_video_get_time());
 
         /* 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.
      *
      * stream->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 end of frame conditions at FID toggling if the
      * previous payload had the EOF bit set.
      */
     if (fid != stream->last_fid && buf->bytesused != 0) {
         uvc_dbg(stream->dev, FRAME,
             "Frame complete (FID bit toggled)\n");
         buf->state = UVC_BUF_STATE_READY;
         return -EAGAIN;
     }
 
     stream->last_fid = fid;
 
     return data[0];
 }
 
 static inline enum dma_data_direction uvc_stream_dir(
                 struct uvc_streaming *stream)
 {
     if (stream->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
         return DMA_FROM_DEVICE;
     else
         return DMA_TO_DEVICE;
 }
 
 static inline struct device *uvc_stream_to_dmadev(struct uvc_streaming *stream)
 {
     return bus_to_hcd(stream->dev->udev->bus)->self.sysdev;
 }
 
 static int uvc_submit_urb(struct uvc_urb *uvc_urb, gfp_t mem_flags)
 {
     /* Sync DMA. */
     dma_sync_sgtable_for_device(uvc_stream_to_dmadev(uvc_urb->stream),
                     uvc_urb->sgt,
                     uvc_stream_dir(uvc_urb->stream));
     return usb_submit_urb(uvc_urb->urb, mem_flags);
 }
 
 /*
  * uvc_video_decode_data_work: Asynchronous memcpy processing
  *
  * Copy URB data to video buffers in process context, releasing buffer
  * references and requeuing the URB when done.
  */
 static void uvc_video_copy_data_work(struct work_struct *work)
 {
     struct uvc_urb *uvc_urb = container_of(work, struct uvc_urb, work);
     unsigned int i;
     int ret;
 
     for (i = 0; i < uvc_urb->async_operations; i++) {
         struct uvc_copy_op *op = &uvc_urb->copy_operations[i];
 
         memcpy(op->dst, op->src, op->len);
 
         /* Release reference taken on this buffer. */
         uvc_queue_buffer_release(op->buf);
     }
 
     ret = uvc_submit_urb(uvc_urb, GFP_KERNEL);
     if (ret < 0)
         dev_err(&uvc_urb->stream->intf->dev,
             "Failed to resubmit video URB (%d).\n", ret);
 }
 
 static void uvc_video_decode_data(struct uvc_urb *uvc_urb,
         struct uvc_buffer *buf, const u8 *data, int len)
 {
     unsigned int active_op = uvc_urb->async_operations;
     struct uvc_copy_op *op = &uvc_urb->copy_operations[active_op];
     unsigned int maxlen;
 
     if (len <= 0)
         return;
 
     maxlen = buf->length - buf->bytesused;
 
     /* Take a buffer reference for async work. */
     kref_get(&buf->ref);
 
     op->buf = buf;
     op->src = data;
     op->dst = buf->mem + buf->bytesused;
     op->len = min_t(unsigned int, len, maxlen);
 
     buf->bytesused += op->len;
 
     /* Complete the current frame if the buffer size was exceeded. */
     if (len > maxlen) {
         uvc_dbg(uvc_urb->stream->dev, FRAME,
             "Frame complete (overflow)\n");
         buf->error = 1;
         buf->state = UVC_BUF_STATE_READY;
     }
 
     uvc_urb->async_operations++;
 }
 
 static void uvc_video_decode_end(struct uvc_streaming *stream,
         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->bytesused != 0) {
         uvc_dbg(stream->dev, FRAME, "Frame complete (EOF found)\n");
         if (data[0] == len)
             uvc_dbg(stream->dev, FRAME, "EOF in empty payload\n");
         buf->state = UVC_BUF_STATE_READY;
         if (stream->dev->quirks & UVC_QUIRK_STREAM_NO_FID)
             stream->last_fid ^= UVC_STREAM_FID;
     }
 }
 
 /*
  * Video payload encoding is handled by uvc_video_encode_header() and
  * uvc_video_encode_data(). Only bulk transfers are currently supported.
  *
  * uvc_video_encode_header is called at the start of a payload. It adds header
  * data to the transfer buffer and returns the header size. As the only known
  * UVC output device transfers a whole frame in a single payload, the EOF bit
  * is always set in the header.
  *
  * uvc_video_encode_data is called for every URB and copies the data from the
  * video buffer to the transfer buffer.
  */
 static int uvc_video_encode_header(struct uvc_streaming *stream,
         struct uvc_buffer *buf, u8 *data, int len)
 {
     data[0] = 2;    /* Header length */
     data[1] = UVC_STREAM_EOH | UVC_STREAM_EOF
         | (stream->last_fid & UVC_STREAM_FID);
     return 2;
 }
 
 static int uvc_video_encode_data(struct uvc_streaming *stream,
         struct uvc_buffer *buf, u8 *data, int len)
 {
     struct uvc_video_queue *queue = &stream->queue;
     unsigned int nbytes;
     void *mem;
 
     /* Copy video data to the URB buffer. */
     mem = buf->mem + queue->buf_used;
     nbytes = min((unsigned int)len, buf->bytesused - queue->buf_used);
     nbytes = min(stream->bulk.max_payload_size - stream->bulk.payload_size,
             nbytes);
     memcpy(data, mem, nbytes);
 
     queue->buf_used += nbytes;
 
     return nbytes;
 }
 
 /* ------------------------------------------------------------------------
  * Metadata
  */
 
 /*
  * Additionally to the payload headers we also want to provide the user with USB
  * Frame Numbers and system time values. The resulting buffer is thus composed
  * of blocks, containing a 64-bit timestamp in  nanoseconds, a 16-bit USB Frame
  * Number, and a copy of the payload header.
  *
  * Ideally we want to capture all payload headers for each frame. However, their
  * number is unknown and unbound. We thus drop headers that contain no vendor
  * data and that either contain no SCR value or an SCR value identical to the
  * previous header.
  */
 static void uvc_video_decode_meta(struct uvc_streaming *stream,
                   struct uvc_buffer *meta_buf,
                   const u8 *mem, unsigned int length)
 {
     struct uvc_meta_buf *meta;
     size_t len_std = 2;
     bool has_pts, has_scr;
     unsigned long flags;
     unsigned int sof;
     ktime_t time;
     const u8 *scr;
 
     if (!meta_buf || length == 2)
         return;
 
     if (meta_buf->length - meta_buf->bytesused <
         length + sizeof(meta->ns) + sizeof(meta->sof)) {
         meta_buf->error = 1;
         return;
     }
 
     has_pts = mem[1] & UVC_STREAM_PTS;
     has_scr = mem[1] & UVC_STREAM_SCR;
 
     if (has_pts) {
         len_std += 4;
         scr = mem + 6;
     } else {
         scr = mem + 2;
     }
 
     if (has_scr)
         len_std += 6;
 
     if (stream->meta.format == V4L2_META_FMT_UVC)
         length = len_std;
 
     if (length == len_std && (!has_scr ||
                   !memcmp(scr, stream->clock.last_scr, 6)))
         return;
 
     meta = (struct uvc_meta_buf *)((u8 *)meta_buf->mem + meta_buf->bytesused);
     local_irq_save(flags);
     time = uvc_video_get_time();
     sof = usb_get_current_frame_number(stream->dev->udev);
     local_irq_restore(flags);
     put_unaligned(ktime_to_ns(time), &meta->ns);
     put_unaligned(sof, &meta->sof);
 
     if (has_scr)
         memcpy(stream->clock.last_scr, scr, 6);
 
     memcpy(&meta->length, mem, length);
     meta_buf->bytesused += length + sizeof(meta->ns) + sizeof(meta->sof);
 
     uvc_dbg(stream->dev, FRAME,
         "%s(): t-sys %lluns, SOF %u, len %u, flags 0x%x, PTS %u, STC %u frame SOF %u\n",
         __func__, ktime_to_ns(time), meta->sof, meta->length,
         meta->flags,
         has_pts ? *(u32 *)meta->buf : 0,
         has_scr ? *(u32 *)scr : 0,
         has_scr ? *(u32 *)(scr + 4) & 0x7ff : 0);
 }
 
 /* ------------------------------------------------------------------------
  * URB handling
  */
 
 /*
  * Set error flag for incomplete buffer.
  */
 static void uvc_video_validate_buffer(const struct uvc_streaming *stream,
                       struct uvc_buffer *buf)
 {
     if (stream->ctrl.dwMaxVideoFrameSize != buf->bytesused &&
         !(stream->cur_format->flags & UVC_FMT_FLAG_COMPRESSED))
         buf->error = 1;
 }
 
 /*
  * Completion handler for video URBs.
  */
 
 static void uvc_video_next_buffers(struct uvc_streaming *stream,
         struct uvc_buffer **video_buf, struct uvc_buffer **meta_buf)
 {
     uvc_video_validate_buffer(stream, *video_buf);
 
     if (*meta_buf) {
         struct vb2_v4l2_buffer *vb2_meta = &(*meta_buf)->buf;
         const struct vb2_v4l2_buffer *vb2_video = &(*video_buf)->buf;
 
         vb2_meta->sequence = vb2_video->sequence;
         vb2_meta->field = vb2_video->field;
         vb2_meta->vb2_buf.timestamp = vb2_video->vb2_buf.timestamp;
 
         (*meta_buf)->state = UVC_BUF_STATE_READY;
         if (!(*meta_buf)->error)
             (*meta_buf)->error = (*video_buf)->error;
         *meta_buf = uvc_queue_next_buffer(&stream->meta.queue,
                           *meta_buf);
     }
     *video_buf = uvc_queue_next_buffer(&stream->queue, *video_buf);
 }
 
 static void uvc_video_decode_isoc(struct uvc_urb *uvc_urb,
             struct uvc_buffer *buf, struct uvc_buffer *meta_buf)
 {
     struct urb *urb = uvc_urb->urb;
     struct uvc_streaming *stream = uvc_urb->stream;
     u8 *mem;
     int ret, i;
 
     for (i = 0; i < urb->number_of_packets; ++i) {
         if (urb->iso_frame_desc[i].status < 0) {
             uvc_dbg(stream->dev, FRAME,
                 "USB isochronous frame lost (%d)\n",
                 urb->iso_frame_desc[i].status);
             /* Mark the buffer as faulty. */
             if (buf != NULL)
                 buf->error = 1;
             continue;
         }
 
         /* Decode the payload header. */
         mem = urb->transfer_buffer + urb->iso_frame_desc[i].offset;
         do {
             ret = uvc_video_decode_start(stream, buf, mem,
                 urb->iso_frame_desc[i].actual_length);
             if (ret == -EAGAIN)
                 uvc_video_next_buffers(stream, &buf, &meta_buf);
         } while (ret == -EAGAIN);
 
         if (ret < 0)
             continue;
 
         uvc_video_decode_meta(stream, meta_buf, mem, ret);
 
         /* Decode the payload data. */
         uvc_video_decode_data(uvc_urb, buf, mem + ret,
             urb->iso_frame_desc[i].actual_length - ret);
 
         /* Process the header again. */
         uvc_video_decode_end(stream, buf, mem,
             urb->iso_frame_desc[i].actual_length);
 
         if (buf->state == UVC_BUF_STATE_READY)
             uvc_video_next_buffers(stream, &buf, &meta_buf);
     }
 }
 
 static void uvc_video_decode_bulk(struct uvc_urb *uvc_urb,
             struct uvc_buffer *buf, struct uvc_buffer *meta_buf)
 {
     struct urb *urb = uvc_urb->urb;
     struct uvc_streaming *stream = uvc_urb->stream;
     u8 *mem;
     int len, ret;
 
     /*
      * Ignore ZLPs if they're not part of a frame, otherwise process them
      * to trigger the end of payload detection.
      */
     if (urb->actual_length == 0 && stream->bulk.header_size == 0)
         return;
 
     mem = urb->transfer_buffer;
     len = urb->actual_length;
     stream->bulk.payload_size += len;
 
     /*
      * If the URB is the first of its payload, decode and save the
      * header.
      */
     if (stream->bulk.header_size == 0 && !stream->bulk.skip_payload) {
         do {
             ret = uvc_video_decode_start(stream, buf, mem, len);
             if (ret == -EAGAIN)
                 uvc_video_next_buffers(stream, &buf, &meta_buf);
         } while (ret == -EAGAIN);
 
         /* If an error occurred skip the rest of the payload. */
         if (ret < 0 || buf == NULL) {
             stream->bulk.skip_payload = 1;
         } else {
             memcpy(stream->bulk.header, mem, ret);
             stream->bulk.header_size = ret;
 
             uvc_video_decode_meta(stream, meta_buf, mem, ret);
 
             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.
      */
 
     /* Prepare video data for processing. */
     if (!stream->bulk.skip_payload && buf != NULL)
         uvc_video_decode_data(uvc_urb, 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 ||
         stream->bulk.payload_size >= stream->bulk.max_payload_size) {
         if (!stream->bulk.skip_payload && buf != NULL) {
             uvc_video_decode_end(stream, buf, stream->bulk.header,
                 stream->bulk.payload_size);
             if (buf->state == UVC_BUF_STATE_READY)
                 uvc_video_next_buffers(stream, &buf, &meta_buf);
         }
 
         stream->bulk.header_size = 0;
         stream->bulk.skip_payload = 0;
         stream->bulk.payload_size = 0;
     }
 }
 
 static void uvc_video_encode_bulk(struct uvc_urb *uvc_urb,
     struct uvc_buffer *buf, struct uvc_buffer *meta_buf)
 {
     struct urb *urb = uvc_urb->urb;
     struct uvc_streaming *stream = uvc_urb->stream;
 
     u8 *mem = urb->transfer_buffer;
     int len = stream->urb_size, ret;
 
     if (buf == NULL) {
         urb->transfer_buffer_length = 0;
         return;
     }
 
     /* If the URB is the first of its payload, add the header. */
     if (stream->bulk.header_size == 0) {
         ret = uvc_video_encode_header(stream, buf, mem, len);
         stream->bulk.header_size = ret;
         stream->bulk.payload_size += ret;
         mem += ret;
         len -= ret;
     }
 
     /* Process video data. */
     ret = uvc_video_encode_data(stream, buf, mem, len);
 
     stream->bulk.payload_size += ret;
     len -= ret;
 
     if (buf->bytesused == stream->queue.buf_used ||
         stream->bulk.payload_size == stream->bulk.max_payload_size) {
         if (buf->bytesused == stream->queue.buf_used) {
             stream->queue.buf_used = 0;
             buf->state = UVC_BUF_STATE_READY;
             buf->buf.sequence = ++stream->sequence;
             uvc_queue_next_buffer(&stream->queue, buf);
             stream->last_fid ^= UVC_STREAM_FID;
         }
 
         stream->bulk.header_size = 0;
         stream->bulk.payload_size = 0;
     }
 
     urb->transfer_buffer_length = stream->urb_size - len;
 }
 
 static void uvc_video_complete(struct urb *urb)
 {
     struct uvc_urb *uvc_urb = urb->context;
     struct uvc_streaming *stream = uvc_urb->stream;
     struct uvc_video_queue *queue = &stream->queue;
     struct uvc_video_queue *qmeta = &stream->meta.queue;
     struct vb2_queue *vb2_qmeta = stream->meta.vdev.queue;
     struct uvc_buffer *buf = NULL;
     struct uvc_buffer *buf_meta = NULL;
     unsigned long flags;
     int ret;
 
     switch (urb->status) {
     case 0:
         break;
 
     default:
         dev_warn(&stream->intf->dev,
              "Non-zero status (%d) in video completion handler.\n",
              urb->status);
         fallthrough;
     case -ENOENT:       /* usb_poison_urb() called. */
         if (stream->frozen)
             return;
         fallthrough;
     case -ECONNRESET:   /* usb_unlink_urb() called. */
     case -ESHUTDOWN:    /* The endpoint is being disabled. */
         uvc_queue_cancel(queue, urb->status == -ESHUTDOWN);
         if (vb2_qmeta)
             uvc_queue_cancel(qmeta, urb->status == -ESHUTDOWN);
         return;
     }
 
     buf = uvc_queue_get_current_buffer(queue);
 
     if (vb2_qmeta) {
         spin_lock_irqsave(&qmeta->irqlock, flags);
         if (!list_empty(&qmeta->irqqueue))
             buf_meta = list_first_entry(&qmeta->irqqueue,
                             struct uvc_buffer, queue);
         spin_unlock_irqrestore(&qmeta->irqlock, flags);
     }
 
     /* Re-initialise the URB async work. */
     uvc_urb->async_operations = 0;
 
     /* Sync DMA and invalidate vmap range. */
     dma_sync_sgtable_for_cpu(uvc_stream_to_dmadev(uvc_urb->stream),
                  uvc_urb->sgt, uvc_stream_dir(stream));
     invalidate_kernel_vmap_range(uvc_urb->buffer,
                      uvc_urb->stream->urb_size);
 
     /*
      * Process the URB headers, and optionally queue expensive memcpy tasks
      * to be deferred to a work queue.
      */
     stream->decode(uvc_urb, buf, buf_meta);
 
     /* If no async work is needed, resubmit the URB immediately. */
     if (!uvc_urb->async_operations) {
         ret = uvc_submit_urb(uvc_urb, GFP_ATOMIC);
         if (ret < 0)
             dev_err(&stream->intf->dev,
                 "Failed to resubmit video URB (%d).\n", ret);
         return;
     }
 
     queue_work(stream->async_wq, &uvc_urb->work);
 }
 
 /*
  * Free transfer buffers.
  */
 static void uvc_free_urb_buffers(struct uvc_streaming *stream)
 {
     struct device *dma_dev = uvc_stream_to_dmadev(stream);
     struct uvc_urb *uvc_urb;
 
     for_each_uvc_urb(uvc_urb, stream) {
         if (!uvc_urb->buffer)
             continue;
 
         dma_vunmap_noncontiguous(dma_dev, uvc_urb->buffer);
         dma_free_noncontiguous(dma_dev, stream->urb_size, uvc_urb->sgt,
                        uvc_stream_dir(stream));
 
         uvc_urb->buffer = NULL;
         uvc_urb->sgt = NULL;
     }
 
     stream->urb_size = 0;
 }
 
 static bool uvc_alloc_urb_buffer(struct uvc_streaming *stream,
                  struct uvc_urb *uvc_urb, gfp_t gfp_flags)
 {
     struct device *dma_dev = uvc_stream_to_dmadev(stream);
 
     uvc_urb->sgt = dma_alloc_noncontiguous(dma_dev, stream->urb_size,
                            uvc_stream_dir(stream),
                            gfp_flags, 0);
     if (!uvc_urb->sgt)
         return false;
     uvc_urb->dma = uvc_urb->sgt->sgl->dma_address;
 
     uvc_urb->buffer = dma_vmap_noncontiguous(dma_dev, stream->urb_size,
                          uvc_urb->sgt);
     if (!uvc_urb->buffer) {
         dma_free_noncontiguous(dma_dev, stream->urb_size,
                        uvc_urb->sgt,
                        uvc_stream_dir(stream));
         uvc_urb->sgt = NULL;
         return false;
     }
 
     return true;
 }
 
 /*
  * Allocate transfer buffers. This function can be called with buffers
  * already allocated when resuming from suspend, in which case it will
  * return without touching the buffers.
  *
  * Limit the buffer size to UVC_MAX_PACKETS bulk/isochronous packets. If the
  * system is too low on memory try successively smaller numbers of packets
  * until allocation succeeds.
  *
  * Return the number of allocated packets on success or 0 when out of memory.
  */
 static int uvc_alloc_urb_buffers(struct uvc_streaming *stream,
     unsigned int size, unsigned int psize, gfp_t gfp_flags)
 {
     unsigned int npackets;
     unsigned int i;
 
     /* Buffers are already allocated, bail out. */
     if (stream->urb_size)
         return stream->urb_size / psize;
 
     /*
      * Compute the number of packets. Bulk endpoints might transfer UVC
      * payloads across multiple URBs.
      */
     npackets = DIV_ROUND_UP(size, psize);
     if (npackets > UVC_MAX_PACKETS)
         npackets = UVC_MAX_PACKETS;
 
     /* Retry allocations until one succeed. */
     for (; npackets > 1; npackets /= 2) {
         stream->urb_size = psize * npackets;
 
         for (i = 0; i < UVC_URBS; ++i) {
             struct uvc_urb *uvc_urb = &stream->uvc_urb[i];
 
             if (!uvc_alloc_urb_buffer(stream, uvc_urb, gfp_flags)) {
                 uvc_free_urb_buffers(stream);
                 break;
             }
 
             uvc_urb->stream = stream;
         }
 
         if (i == UVC_URBS) {
             uvc_dbg(stream->dev, VIDEO,
                 "Allocated %u URB buffers of %ux%u bytes each\n",
                 UVC_URBS, npackets, psize);
             return npackets;
         }
     }
 
     uvc_dbg(stream->dev, VIDEO,
         "Failed to allocate URB buffers (%u bytes per packet)\n",
         psize);
     return 0;
 }
 
 /*
  * Uninitialize isochronous/bulk URBs and free transfer buffers.
  */
 static void uvc_video_stop_transfer(struct uvc_streaming *stream,
                     int free_buffers)
 {
     struct uvc_urb *uvc_urb;
 
     uvc_video_stats_stop(stream);
 
     /*
      * We must poison the URBs rather than kill them to ensure that even
      * after the completion handler returns, any asynchronous workqueues
      * will be prevented from resubmitting the URBs.
      */
     for_each_uvc_urb(uvc_urb, stream)
         usb_poison_urb(uvc_urb->urb);
 
     flush_workqueue(stream->async_wq);
 
     for_each_uvc_urb(uvc_urb, stream) {
         usb_free_urb(uvc_urb->urb);
         uvc_urb->urb = NULL;
     }
 
     if (free_buffers)
         uvc_free_urb_buffers(stream);
 }
 
 /*
  * Compute the maximum number of bytes per interval for an endpoint.
  */
 u16 uvc_endpoint_max_bpi(struct usb_device *dev, struct usb_host_endpoint *ep)
 {
     u16 psize;
 
     switch (dev->speed) {
     case USB_SPEED_SUPER:
     case USB_SPEED_SUPER_PLUS:
         return le16_to_cpu(ep->ss_ep_comp.wBytesPerInterval);
     default:
         psize = usb_endpoint_maxp(&ep->desc);
         psize *= usb_endpoint_maxp_mult(&ep->desc);
         return psize;
     }
 }
 
 /*
  * Initialize isochronous URBs and allocate transfer buffers. The packet size
  * is given by the endpoint.
  */
 static int uvc_init_video_isoc(struct uvc_streaming *stream,
     struct usb_host_endpoint *ep, gfp_t gfp_flags)
 {
     struct urb *urb;
     struct uvc_urb *uvc_urb;
     unsigned int npackets, i;
     u16 psize;
     u32 size;
 
     psize = uvc_endpoint_max_bpi(stream->dev->udev, ep);
     size = stream->ctrl.dwMaxVideoFrameSize;
 
     npackets = uvc_alloc_urb_buffers(stream, size, psize, gfp_flags);
     if (npackets == 0)
         return -ENOMEM;
 
     size = npackets * psize;
 
     for_each_uvc_urb(uvc_urb, stream) {
         urb = usb_alloc_urb(npackets, gfp_flags);
         if (urb == NULL) {
             uvc_video_stop_transfer(stream, 1);
             return -ENOMEM;
         }
 
         urb->dev = stream->dev->udev;
         urb->context = uvc_urb;
         urb->pipe = usb_rcvisocpipe(stream->dev->udev,
                 ep->desc.bEndpointAddress);
         urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
         urb->transfer_dma = uvc_urb->dma;
         urb->interval = ep->desc.bInterval;
         urb->transfer_buffer = uvc_urb->buffer;
         urb->complete = uvc_video_complete;
         urb->number_of_packets = npackets;
         urb->transfer_buffer_length = size;
 
         for (i = 0; i < npackets; ++i) {
             urb->iso_frame_desc[i].offset = i * psize;
             urb->iso_frame_desc[i].length = psize;
         }
 
         uvc_urb->urb = 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_streaming *stream,
     struct usb_host_endpoint *ep, gfp_t gfp_flags)
 {
     struct urb *urb;
     struct uvc_urb *uvc_urb;
     unsigned int npackets, pipe;
     u16 psize;
     u32 size;
 
     psize = usb_endpoint_maxp(&ep->desc);
     size = stream->ctrl.dwMaxPayloadTransferSize;
     stream->bulk.max_payload_size = size;
 
     npackets = uvc_alloc_urb_buffers(stream, size, psize, gfp_flags);
     if (npackets == 0)
         return -ENOMEM;
 
     size = npackets * psize;
 
     if (usb_endpoint_dir_in(&ep->desc))
         pipe = usb_rcvbulkpipe(stream->dev->udev,
                        ep->desc.bEndpointAddress);
     else
         pipe = usb_sndbulkpipe(stream->dev->udev,
                        ep->desc.bEndpointAddress);
 
     if (stream->type == V4L2_BUF_TYPE_VIDEO_OUTPUT)
         size = 0;
 
     for_each_uvc_urb(uvc_urb, stream) {
         urb = usb_alloc_urb(0, gfp_flags);
         if (urb == NULL) {
             uvc_video_stop_transfer(stream, 1);
             return -ENOMEM;
         }
 
         usb_fill_bulk_urb(urb, stream->dev->udev, pipe, uvc_urb->buffer,
                   size, uvc_video_complete, uvc_urb);
         urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
         urb->transfer_dma = uvc_urb->dma;
 
         uvc_urb->urb = urb;
     }
 
     return 0;
 }
 
 /*
  * Initialize isochronous/bulk URBs and allocate transfer buffers.
  */
 static int uvc_video_start_transfer(struct uvc_streaming *stream,
                     gfp_t gfp_flags)
 {
     struct usb_interface *intf = stream->intf;
     struct usb_host_endpoint *ep;
     struct uvc_urb *uvc_urb;
     unsigned int i;
     int ret;
 
     stream->sequence = -1;
     stream->last_fid = -1;
     stream->bulk.header_size = 0;
     stream->bulk.skip_payload = 0;
     stream->bulk.payload_size = 0;
 
     uvc_video_stats_start(stream);
 
     if (intf->num_altsetting > 1) {
         struct usb_host_endpoint *best_ep = NULL;
         unsigned int best_psize = UINT_MAX;
         unsigned int bandwidth;
         unsigned int altsetting;
         int intfnum = stream->intfnum;
 
         /* Isochronous endpoint, select the alternate setting. */
         bandwidth = stream->ctrl.dwMaxPayloadTransferSize;
 
         if (bandwidth == 0) {
             uvc_dbg(stream->dev, VIDEO,
                 "Device requested null bandwidth, defaulting to lowest\n");
             bandwidth = 1;
         } else {
             uvc_dbg(stream->dev, VIDEO,
                 "Device requested %u B/frame bandwidth\n",
                 bandwidth);
         }
 
         for (i = 0; i < intf->num_altsetting; ++i) {
             struct usb_host_interface *alts;
             unsigned int psize;
 
             alts = &intf->altsetting[i];
             ep = uvc_find_endpoint(alts,
                 stream->header.bEndpointAddress);
             if (ep == NULL)
                 continue;
 
             /* Check if the bandwidth is high enough. */
             psize = uvc_endpoint_max_bpi(stream->dev->udev, ep);
             if (psize >= bandwidth && psize <= best_psize) {
                 altsetting = alts->desc.bAlternateSetting;
                 best_psize = psize;
                 best_ep = ep;
             }
         }
 
         if (best_ep == NULL) {
             uvc_dbg(stream->dev, VIDEO,
                 "No fast enough alt setting for requested bandwidth\n");
             return -EIO;
         }
 
         uvc_dbg(stream->dev, VIDEO,
             "Selecting alternate setting %u (%u B/frame bandwidth)\n",
             altsetting, best_psize);
 
         ret = usb_set_interface(stream->dev->udev, intfnum, altsetting);
         if (ret < 0)
             return ret;
 
         ret = uvc_init_video_isoc(stream, best_ep, gfp_flags);
     } else {
         /* Bulk endpoint, proceed to URB initialization. */
         ep = uvc_find_endpoint(&intf->altsetting[0],
                 stream->header.bEndpointAddress);
         if (ep == NULL)
             return -EIO;
 
         /* Reject broken descriptors. */
         if (usb_endpoint_maxp(&ep->desc) == 0)
             return -EIO;
 
         ret = uvc_init_video_bulk(stream, ep, gfp_flags);
     }
 
     if (ret < 0)
         return ret;
 
     /* Submit the URBs. */
     for_each_uvc_urb(uvc_urb, stream) {
         ret = uvc_submit_urb(uvc_urb, gfp_flags);
         if (ret < 0) {
             dev_err(&stream->intf->dev,
                 "Failed to submit URB %u (%d).\n",
                 uvc_urb_index(uvc_urb), ret);
             uvc_video_stop_transfer(stream, 1);
             return ret;
         }
     }
 
     /*
      * The Logitech C920 temporarily forgets that it should not be adjusting
      * Exposure Absolute during init so restore controls to stored values.
      */
     if (stream->dev->quirks & UVC_QUIRK_RESTORE_CTRLS_ON_INIT)
         uvc_ctrl_restore_values(stream->dev);
 
     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_streaming *stream)
 {
     if (!uvc_queue_streaming(&stream->queue))
         return 0;
 
     stream->frozen = 1;
     uvc_video_stop_transfer(stream, 0);
     usb_set_interface(stream->dev->udev, stream->intfnum, 0);
     return 0;
 }
 
 /*
  * Reconfigure the video interface and restart streaming if it was enabled
  * 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_streaming *stream, int reset)
 {
     int ret;
 
     /*
      * If the bus has been reset on resume, set the alternate setting to 0.
      * This should be the default value, but some devices crash or otherwise
      * misbehave if they don't receive a SET_INTERFACE request before any
      * other video control request.
      */
     if (reset)
         usb_set_interface(stream->dev->udev, stream->intfnum, 0);
 
     stream->frozen = 0;
 
     uvc_video_clock_reset(stream);
 
     if (!uvc_queue_streaming(&stream->queue))
         return 0;
 
     ret = uvc_commit_video(stream, &stream->ctrl);
     if (ret < 0)
         return ret;
 
     return uvc_video_start_transfer(stream, GFP_NOIO);
 }
 
 /* ------------------------------------------------------------------------
  * Video device
  */
 
 /*
  * Initialize the UVC video device by switching to alternate setting 0 and
  * retrieve the default format.
  *
  * 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_streaming *stream)
 {
     struct uvc_streaming_control *probe = &stream->ctrl;
     struct uvc_format *format = NULL;
     struct uvc_frame *frame = NULL;
     struct uvc_urb *uvc_urb;
     unsigned int i;
     int ret;
 
     if (stream->nformats == 0) {
         dev_info(&stream->intf->dev,
              "No supported video formats found.\n");
         return -EINVAL;
     }
 
     atomic_set(&stream->active, 0);
 
     /*
      * 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(stream->dev->udev, stream->intfnum, 0);
 
     /*
      * Set the streaming probe control with default streaming parameters
      * retrieved from the device. Webcams that don't support GET_DEF
      * requests on the probe control will just keep their current streaming
      * parameters.
      */
     if (uvc_get_video_ctrl(stream, probe, 1, UVC_GET_DEF) == 0)
         uvc_set_video_ctrl(stream, probe, 1);
 
     /*
      * Initialize the streaming parameters with the probe control current
      * value. This makes sure SET_CUR requests on the streaming commit
      * control will always use values retrieved from a successful GET_CUR
      * request on the probe control, as required by the UVC specification.
      */
     ret = uvc_get_video_ctrl(stream, probe, 1, UVC_GET_CUR);
     if (ret < 0)
         return ret;
 
     /*
      * Check if the default format descriptor exists. Use the first
      * available format otherwise.
      */
     for (i = stream->nformats; i > 0; --i) {
         format = &stream->format[i-1];
         if (format->index == probe->bFormatIndex)
             break;
     }
 
     if (format->nframes == 0) {
         dev_info(&stream->intf->dev,
              "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 available frame.
      */
     for (i = format->nframes; i > 0; --i) {
         frame = &format->frame[i-1];
         if (frame->bFrameIndex == probe->bFrameIndex)
             break;
     }
 
     probe->bFormatIndex = format->index;
     probe->bFrameIndex = frame->bFrameIndex;
 
     stream->def_format = format;
     stream->cur_format = format;
     stream->cur_frame = frame;
 
     /* Select the video decoding function */
     if (stream->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
         if (stream->dev->quirks & UVC_QUIRK_BUILTIN_ISIGHT)
             stream->decode = uvc_video_decode_isight;
         else if (stream->intf->num_altsetting > 1)
             stream->decode = uvc_video_decode_isoc;
         else
             stream->decode = uvc_video_decode_bulk;
     } else {
         if (stream->intf->num_altsetting == 1)
             stream->decode = uvc_video_encode_bulk;
         else {
             dev_info(&stream->intf->dev,
                  "Isochronous endpoints are not supported for video output devices.\n");
             return -EINVAL;
         }
     }
 
     /* Prepare asynchronous work items. */
     for_each_uvc_urb(uvc_urb, stream)
         INIT_WORK(&uvc_urb->work, uvc_video_copy_data_work);
 
     return 0;
 }
 
 int uvc_video_start_streaming(struct uvc_streaming *stream)
 {
     int ret;
 
     ret = uvc_video_clock_init(stream);
     if (ret < 0)
         return ret;
 
     /* Commit the streaming parameters. */
     ret = uvc_commit_video(stream, &stream->ctrl);
     if (ret < 0)
         goto error_commit;
 
     ret = uvc_video_start_transfer(stream, GFP_KERNEL);
     if (ret < 0)
         goto error_video;
 
     return 0;
 
 error_video:
     usb_set_interface(stream->dev->udev, stream->intfnum, 0);
 error_commit:
     uvc_video_clock_cleanup(stream);
 
     return ret;
 }
 
 void uvc_video_stop_streaming(struct uvc_streaming *stream)
 {
     uvc_video_stop_transfer(stream, 1);
 
     if (stream->intf->num_altsetting > 1) {
         usb_set_interface(stream->dev->udev, stream->intfnum, 0);
     } else {
         /*
          * UVC doesn't specify how to inform a bulk-based device
          * when the video stream is stopped. Windows sends a
          * CLEAR_FEATURE(HALT) request to the video streaming
          * bulk endpoint, mimic the same behaviour.
          */
         unsigned int epnum = stream->header.bEndpointAddress
                    & USB_ENDPOINT_NUMBER_MASK;
         unsigned int dir = stream->header.bEndpointAddress
                  & USB_ENDPOINT_DIR_MASK;
         unsigned int pipe;
 
         pipe = usb_sndbulkpipe(stream->dev->udev, epnum) | dir;
         usb_clear_halt(stream->dev->udev, pipe);
     }
 
     uvc_video_clock_cleanup(stream);
 }

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