xref: /openbmc/linux/drivers/media/usb/uvc/uvc_video.c (revision 6774def6)
1 /*
2  *      uvc_video.c  --  USB Video Class driver - Video handling
3  *
4  *      Copyright (C) 2005-2010
5  *          Laurent Pinchart (laurent.pinchart@ideasonboard.com)
6  *
7  *      This program is free software; you can redistribute it and/or modify
8  *      it under the terms of the GNU General Public License as published by
9  *      the Free Software Foundation; either version 2 of the License, or
10  *      (at your option) any later version.
11  *
12  */
13 
14 #include <linux/kernel.h>
15 #include <linux/list.h>
16 #include <linux/module.h>
17 #include <linux/slab.h>
18 #include <linux/usb.h>
19 #include <linux/videodev2.h>
20 #include <linux/vmalloc.h>
21 #include <linux/wait.h>
22 #include <linux/atomic.h>
23 #include <asm/unaligned.h>
24 
25 #include <media/v4l2-common.h>
26 
27 #include "uvcvideo.h"
28 
29 /* ------------------------------------------------------------------------
30  * UVC Controls
31  */
32 
33 static int __uvc_query_ctrl(struct uvc_device *dev, __u8 query, __u8 unit,
34 			__u8 intfnum, __u8 cs, void *data, __u16 size,
35 			int timeout)
36 {
37 	__u8 type = USB_TYPE_CLASS | USB_RECIP_INTERFACE;
38 	unsigned int pipe;
39 
40 	pipe = (query & 0x80) ? usb_rcvctrlpipe(dev->udev, 0)
41 			      : usb_sndctrlpipe(dev->udev, 0);
42 	type |= (query & 0x80) ? USB_DIR_IN : USB_DIR_OUT;
43 
44 	return usb_control_msg(dev->udev, pipe, query, type, cs << 8,
45 			unit << 8 | intfnum, data, size, timeout);
46 }
47 
48 static const char *uvc_query_name(__u8 query)
49 {
50 	switch (query) {
51 	case UVC_SET_CUR:
52 		return "SET_CUR";
53 	case UVC_GET_CUR:
54 		return "GET_CUR";
55 	case UVC_GET_MIN:
56 		return "GET_MIN";
57 	case UVC_GET_MAX:
58 		return "GET_MAX";
59 	case UVC_GET_RES:
60 		return "GET_RES";
61 	case UVC_GET_LEN:
62 		return "GET_LEN";
63 	case UVC_GET_INFO:
64 		return "GET_INFO";
65 	case UVC_GET_DEF:
66 		return "GET_DEF";
67 	default:
68 		return "<invalid>";
69 	}
70 }
71 
72 int uvc_query_ctrl(struct uvc_device *dev, __u8 query, __u8 unit,
73 			__u8 intfnum, __u8 cs, void *data, __u16 size)
74 {
75 	int ret;
76 
77 	ret = __uvc_query_ctrl(dev, query, unit, intfnum, cs, data, size,
78 				UVC_CTRL_CONTROL_TIMEOUT);
79 	if (ret != size) {
80 		uvc_printk(KERN_ERR, "Failed to query (%s) UVC control %u on "
81 			"unit %u: %d (exp. %u).\n", uvc_query_name(query), cs,
82 			unit, ret, size);
83 		return -EIO;
84 	}
85 
86 	return 0;
87 }
88 
89 static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
90 	struct uvc_streaming_control *ctrl)
91 {
92 	struct uvc_format *format = NULL;
93 	struct uvc_frame *frame = NULL;
94 	unsigned int i;
95 
96 	for (i = 0; i < stream->nformats; ++i) {
97 		if (stream->format[i].index == ctrl->bFormatIndex) {
98 			format = &stream->format[i];
99 			break;
100 		}
101 	}
102 
103 	if (format == NULL)
104 		return;
105 
106 	for (i = 0; i < format->nframes; ++i) {
107 		if (format->frame[i].bFrameIndex == ctrl->bFrameIndex) {
108 			frame = &format->frame[i];
109 			break;
110 		}
111 	}
112 
113 	if (frame == NULL)
114 		return;
115 
116 	if (!(format->flags & UVC_FMT_FLAG_COMPRESSED) ||
117 	     (ctrl->dwMaxVideoFrameSize == 0 &&
118 	      stream->dev->uvc_version < 0x0110))
119 		ctrl->dwMaxVideoFrameSize =
120 			frame->dwMaxVideoFrameBufferSize;
121 
122 	if (!(format->flags & UVC_FMT_FLAG_COMPRESSED) &&
123 	    stream->dev->quirks & UVC_QUIRK_FIX_BANDWIDTH &&
124 	    stream->intf->num_altsetting > 1) {
125 		u32 interval;
126 		u32 bandwidth;
127 
128 		interval = (ctrl->dwFrameInterval > 100000)
129 			 ? ctrl->dwFrameInterval
130 			 : frame->dwFrameInterval[0];
131 
132 		/* Compute a bandwidth estimation by multiplying the frame
133 		 * size by the number of video frames per second, divide the
134 		 * result by the number of USB frames (or micro-frames for
135 		 * high-speed devices) per second and add the UVC header size
136 		 * (assumed to be 12 bytes long).
137 		 */
138 		bandwidth = frame->wWidth * frame->wHeight / 8 * format->bpp;
139 		bandwidth *= 10000000 / interval + 1;
140 		bandwidth /= 1000;
141 		if (stream->dev->udev->speed == USB_SPEED_HIGH)
142 			bandwidth /= 8;
143 		bandwidth += 12;
144 
145 		/* The bandwidth estimate is too low for many cameras. Don't use
146 		 * maximum packet sizes lower than 1024 bytes to try and work
147 		 * around the problem. According to measurements done on two
148 		 * different camera models, the value is high enough to get most
149 		 * resolutions working while not preventing two simultaneous
150 		 * VGA streams at 15 fps.
151 		 */
152 		bandwidth = max_t(u32, bandwidth, 1024);
153 
154 		ctrl->dwMaxPayloadTransferSize = bandwidth;
155 	}
156 }
157 
158 static int uvc_get_video_ctrl(struct uvc_streaming *stream,
159 	struct uvc_streaming_control *ctrl, int probe, __u8 query)
160 {
161 	__u8 *data;
162 	__u16 size;
163 	int ret;
164 
165 	size = stream->dev->uvc_version >= 0x0110 ? 34 : 26;
166 	if ((stream->dev->quirks & UVC_QUIRK_PROBE_DEF) &&
167 			query == UVC_GET_DEF)
168 		return -EIO;
169 
170 	data = kmalloc(size, GFP_KERNEL);
171 	if (data == NULL)
172 		return -ENOMEM;
173 
174 	ret = __uvc_query_ctrl(stream->dev, query, 0, stream->intfnum,
175 		probe ? UVC_VS_PROBE_CONTROL : UVC_VS_COMMIT_CONTROL, data,
176 		size, uvc_timeout_param);
177 
178 	if ((query == UVC_GET_MIN || query == UVC_GET_MAX) && ret == 2) {
179 		/* Some cameras, mostly based on Bison Electronics chipsets,
180 		 * answer a GET_MIN or GET_MAX request with the wCompQuality
181 		 * field only.
182 		 */
183 		uvc_warn_once(stream->dev, UVC_WARN_MINMAX, "UVC non "
184 			"compliance - GET_MIN/MAX(PROBE) incorrectly "
185 			"supported. Enabling workaround.\n");
186 		memset(ctrl, 0, sizeof *ctrl);
187 		ctrl->wCompQuality = le16_to_cpup((__le16 *)data);
188 		ret = 0;
189 		goto out;
190 	} else if (query == UVC_GET_DEF && probe == 1 && ret != size) {
191 		/* Many cameras don't support the GET_DEF request on their
192 		 * video probe control. Warn once and return, the caller will
193 		 * fall back to GET_CUR.
194 		 */
195 		uvc_warn_once(stream->dev, UVC_WARN_PROBE_DEF, "UVC non "
196 			"compliance - GET_DEF(PROBE) not supported. "
197 			"Enabling workaround.\n");
198 		ret = -EIO;
199 		goto out;
200 	} else if (ret != size) {
201 		uvc_printk(KERN_ERR, "Failed to query (%u) UVC %s control : "
202 			"%d (exp. %u).\n", query, probe ? "probe" : "commit",
203 			ret, size);
204 		ret = -EIO;
205 		goto out;
206 	}
207 
208 	ctrl->bmHint = le16_to_cpup((__le16 *)&data[0]);
209 	ctrl->bFormatIndex = data[2];
210 	ctrl->bFrameIndex = data[3];
211 	ctrl->dwFrameInterval = le32_to_cpup((__le32 *)&data[4]);
212 	ctrl->wKeyFrameRate = le16_to_cpup((__le16 *)&data[8]);
213 	ctrl->wPFrameRate = le16_to_cpup((__le16 *)&data[10]);
214 	ctrl->wCompQuality = le16_to_cpup((__le16 *)&data[12]);
215 	ctrl->wCompWindowSize = le16_to_cpup((__le16 *)&data[14]);
216 	ctrl->wDelay = le16_to_cpup((__le16 *)&data[16]);
217 	ctrl->dwMaxVideoFrameSize = get_unaligned_le32(&data[18]);
218 	ctrl->dwMaxPayloadTransferSize = get_unaligned_le32(&data[22]);
219 
220 	if (size == 34) {
221 		ctrl->dwClockFrequency = get_unaligned_le32(&data[26]);
222 		ctrl->bmFramingInfo = data[30];
223 		ctrl->bPreferedVersion = data[31];
224 		ctrl->bMinVersion = data[32];
225 		ctrl->bMaxVersion = data[33];
226 	} else {
227 		ctrl->dwClockFrequency = stream->dev->clock_frequency;
228 		ctrl->bmFramingInfo = 0;
229 		ctrl->bPreferedVersion = 0;
230 		ctrl->bMinVersion = 0;
231 		ctrl->bMaxVersion = 0;
232 	}
233 
234 	/* Some broken devices return null or wrong dwMaxVideoFrameSize and
235 	 * dwMaxPayloadTransferSize fields. Try to get the value from the
236 	 * format and frame descriptors.
237 	 */
238 	uvc_fixup_video_ctrl(stream, ctrl);
239 	ret = 0;
240 
241 out:
242 	kfree(data);
243 	return ret;
244 }
245 
246 static int uvc_set_video_ctrl(struct uvc_streaming *stream,
247 	struct uvc_streaming_control *ctrl, int probe)
248 {
249 	__u8 *data;
250 	__u16 size;
251 	int ret;
252 
253 	size = stream->dev->uvc_version >= 0x0110 ? 34 : 26;
254 	data = kzalloc(size, GFP_KERNEL);
255 	if (data == NULL)
256 		return -ENOMEM;
257 
258 	*(__le16 *)&data[0] = cpu_to_le16(ctrl->bmHint);
259 	data[2] = ctrl->bFormatIndex;
260 	data[3] = ctrl->bFrameIndex;
261 	*(__le32 *)&data[4] = cpu_to_le32(ctrl->dwFrameInterval);
262 	*(__le16 *)&data[8] = cpu_to_le16(ctrl->wKeyFrameRate);
263 	*(__le16 *)&data[10] = cpu_to_le16(ctrl->wPFrameRate);
264 	*(__le16 *)&data[12] = cpu_to_le16(ctrl->wCompQuality);
265 	*(__le16 *)&data[14] = cpu_to_le16(ctrl->wCompWindowSize);
266 	*(__le16 *)&data[16] = cpu_to_le16(ctrl->wDelay);
267 	put_unaligned_le32(ctrl->dwMaxVideoFrameSize, &data[18]);
268 	put_unaligned_le32(ctrl->dwMaxPayloadTransferSize, &data[22]);
269 
270 	if (size == 34) {
271 		put_unaligned_le32(ctrl->dwClockFrequency, &data[26]);
272 		data[30] = ctrl->bmFramingInfo;
273 		data[31] = ctrl->bPreferedVersion;
274 		data[32] = ctrl->bMinVersion;
275 		data[33] = ctrl->bMaxVersion;
276 	}
277 
278 	ret = __uvc_query_ctrl(stream->dev, UVC_SET_CUR, 0, stream->intfnum,
279 		probe ? UVC_VS_PROBE_CONTROL : UVC_VS_COMMIT_CONTROL, data,
280 		size, uvc_timeout_param);
281 	if (ret != size) {
282 		uvc_printk(KERN_ERR, "Failed to set UVC %s control : "
283 			"%d (exp. %u).\n", probe ? "probe" : "commit",
284 			ret, size);
285 		ret = -EIO;
286 	}
287 
288 	kfree(data);
289 	return ret;
290 }
291 
292 int uvc_probe_video(struct uvc_streaming *stream,
293 	struct uvc_streaming_control *probe)
294 {
295 	struct uvc_streaming_control probe_min, probe_max;
296 	__u16 bandwidth;
297 	unsigned int i;
298 	int ret;
299 
300 	/* Perform probing. The device should adjust the requested values
301 	 * according to its capabilities. However, some devices, namely the
302 	 * first generation UVC Logitech webcams, don't implement the Video
303 	 * Probe control properly, and just return the needed bandwidth. For
304 	 * that reason, if the needed bandwidth exceeds the maximum available
305 	 * bandwidth, try to lower the quality.
306 	 */
307 	ret = uvc_set_video_ctrl(stream, probe, 1);
308 	if (ret < 0)
309 		goto done;
310 
311 	/* Get the minimum and maximum values for compression settings. */
312 	if (!(stream->dev->quirks & UVC_QUIRK_PROBE_MINMAX)) {
313 		ret = uvc_get_video_ctrl(stream, &probe_min, 1, UVC_GET_MIN);
314 		if (ret < 0)
315 			goto done;
316 		ret = uvc_get_video_ctrl(stream, &probe_max, 1, UVC_GET_MAX);
317 		if (ret < 0)
318 			goto done;
319 
320 		probe->wCompQuality = probe_max.wCompQuality;
321 	}
322 
323 	for (i = 0; i < 2; ++i) {
324 		ret = uvc_set_video_ctrl(stream, probe, 1);
325 		if (ret < 0)
326 			goto done;
327 		ret = uvc_get_video_ctrl(stream, probe, 1, UVC_GET_CUR);
328 		if (ret < 0)
329 			goto done;
330 
331 		if (stream->intf->num_altsetting == 1)
332 			break;
333 
334 		bandwidth = probe->dwMaxPayloadTransferSize;
335 		if (bandwidth <= stream->maxpsize)
336 			break;
337 
338 		if (stream->dev->quirks & UVC_QUIRK_PROBE_MINMAX) {
339 			ret = -ENOSPC;
340 			goto done;
341 		}
342 
343 		/* TODO: negotiate compression parameters */
344 		probe->wKeyFrameRate = probe_min.wKeyFrameRate;
345 		probe->wPFrameRate = probe_min.wPFrameRate;
346 		probe->wCompQuality = probe_max.wCompQuality;
347 		probe->wCompWindowSize = probe_min.wCompWindowSize;
348 	}
349 
350 done:
351 	return ret;
352 }
353 
354 static int uvc_commit_video(struct uvc_streaming *stream,
355 			    struct uvc_streaming_control *probe)
356 {
357 	return uvc_set_video_ctrl(stream, probe, 0);
358 }
359 
360 /* -----------------------------------------------------------------------------
361  * Clocks and timestamps
362  */
363 
364 static inline void uvc_video_get_ts(struct timespec *ts)
365 {
366 	if (uvc_clock_param == CLOCK_MONOTONIC)
367 		ktime_get_ts(ts);
368 	else
369 		ktime_get_real_ts(ts);
370 }
371 
372 static void
373 uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
374 		       const __u8 *data, int len)
375 {
376 	struct uvc_clock_sample *sample;
377 	unsigned int header_size;
378 	bool has_pts = false;
379 	bool has_scr = false;
380 	unsigned long flags;
381 	struct timespec ts;
382 	u16 host_sof;
383 	u16 dev_sof;
384 
385 	switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
386 	case UVC_STREAM_PTS | UVC_STREAM_SCR:
387 		header_size = 12;
388 		has_pts = true;
389 		has_scr = true;
390 		break;
391 	case UVC_STREAM_PTS:
392 		header_size = 6;
393 		has_pts = true;
394 		break;
395 	case UVC_STREAM_SCR:
396 		header_size = 8;
397 		has_scr = true;
398 		break;
399 	default:
400 		header_size = 2;
401 		break;
402 	}
403 
404 	/* Check for invalid headers. */
405 	if (len < header_size)
406 		return;
407 
408 	/* Extract the timestamps:
409 	 *
410 	 * - store the frame PTS in the buffer structure
411 	 * - if the SCR field is present, retrieve the host SOF counter and
412 	 *   kernel timestamps and store them with the SCR STC and SOF fields
413 	 *   in the ring buffer
414 	 */
415 	if (has_pts && buf != NULL)
416 		buf->pts = get_unaligned_le32(&data[2]);
417 
418 	if (!has_scr)
419 		return;
420 
421 	/* To limit the amount of data, drop SCRs with an SOF identical to the
422 	 * previous one.
423 	 */
424 	dev_sof = get_unaligned_le16(&data[header_size - 2]);
425 	if (dev_sof == stream->clock.last_sof)
426 		return;
427 
428 	stream->clock.last_sof = dev_sof;
429 
430 	host_sof = usb_get_current_frame_number(stream->dev->udev);
431 	uvc_video_get_ts(&ts);
432 
433 	/* The UVC specification allows device implementations that can't obtain
434 	 * the USB frame number to keep their own frame counters as long as they
435 	 * match the size and frequency of the frame number associated with USB
436 	 * SOF tokens. The SOF values sent by such devices differ from the USB
437 	 * SOF tokens by a fixed offset that needs to be estimated and accounted
438 	 * for to make timestamp recovery as accurate as possible.
439 	 *
440 	 * The offset is estimated the first time a device SOF value is received
441 	 * as the difference between the host and device SOF values. As the two
442 	 * SOF values can differ slightly due to transmission delays, consider
443 	 * that the offset is null if the difference is not higher than 10 ms
444 	 * (negative differences can not happen and are thus considered as an
445 	 * offset). The video commit control wDelay field should be used to
446 	 * compute a dynamic threshold instead of using a fixed 10 ms value, but
447 	 * devices don't report reliable wDelay values.
448 	 *
449 	 * See uvc_video_clock_host_sof() for an explanation regarding why only
450 	 * the 8 LSBs of the delta are kept.
451 	 */
452 	if (stream->clock.sof_offset == (u16)-1) {
453 		u16 delta_sof = (host_sof - dev_sof) & 255;
454 		if (delta_sof >= 10)
455 			stream->clock.sof_offset = delta_sof;
456 		else
457 			stream->clock.sof_offset = 0;
458 	}
459 
460 	dev_sof = (dev_sof + stream->clock.sof_offset) & 2047;
461 
462 	spin_lock_irqsave(&stream->clock.lock, flags);
463 
464 	sample = &stream->clock.samples[stream->clock.head];
465 	sample->dev_stc = get_unaligned_le32(&data[header_size - 6]);
466 	sample->dev_sof = dev_sof;
467 	sample->host_sof = host_sof;
468 	sample->host_ts = ts;
469 
470 	/* Update the sliding window head and count. */
471 	stream->clock.head = (stream->clock.head + 1) % stream->clock.size;
472 
473 	if (stream->clock.count < stream->clock.size)
474 		stream->clock.count++;
475 
476 	spin_unlock_irqrestore(&stream->clock.lock, flags);
477 }
478 
479 static void uvc_video_clock_reset(struct uvc_streaming *stream)
480 {
481 	struct uvc_clock *clock = &stream->clock;
482 
483 	clock->head = 0;
484 	clock->count = 0;
485 	clock->last_sof = -1;
486 	clock->sof_offset = -1;
487 }
488 
489 static int uvc_video_clock_init(struct uvc_streaming *stream)
490 {
491 	struct uvc_clock *clock = &stream->clock;
492 
493 	spin_lock_init(&clock->lock);
494 	clock->size = 32;
495 
496 	clock->samples = kmalloc(clock->size * sizeof(*clock->samples),
497 				 GFP_KERNEL);
498 	if (clock->samples == NULL)
499 		return -ENOMEM;
500 
501 	uvc_video_clock_reset(stream);
502 
503 	return 0;
504 }
505 
506 static void uvc_video_clock_cleanup(struct uvc_streaming *stream)
507 {
508 	kfree(stream->clock.samples);
509 	stream->clock.samples = NULL;
510 }
511 
512 /*
513  * uvc_video_clock_host_sof - Return the host SOF value for a clock sample
514  *
515  * Host SOF counters reported by usb_get_current_frame_number() usually don't
516  * cover the whole 11-bits SOF range (0-2047) but are limited to the HCI frame
517  * schedule window. They can be limited to 8, 9 or 10 bits depending on the host
518  * controller and its configuration.
519  *
520  * We thus need to recover the SOF value corresponding to the host frame number.
521  * As the device and host frame numbers are sampled in a short interval, the
522  * difference between their values should be equal to a small delta plus an
523  * integer multiple of 256 caused by the host frame number limited precision.
524  *
525  * To obtain the recovered host SOF value, compute the small delta by masking
526  * the high bits of the host frame counter and device SOF difference and add it
527  * to the device SOF value.
528  */
529 static u16 uvc_video_clock_host_sof(const struct uvc_clock_sample *sample)
530 {
531 	/* The delta value can be negative. */
532 	s8 delta_sof;
533 
534 	delta_sof = (sample->host_sof - sample->dev_sof) & 255;
535 
536 	return (sample->dev_sof + delta_sof) & 2047;
537 }
538 
539 /*
540  * uvc_video_clock_update - Update the buffer timestamp
541  *
542  * This function converts the buffer PTS timestamp to the host clock domain by
543  * going through the USB SOF clock domain and stores the result in the V4L2
544  * buffer timestamp field.
545  *
546  * The relationship between the device clock and the host clock isn't known.
547  * However, the device and the host share the common USB SOF clock which can be
548  * used to recover that relationship.
549  *
550  * The relationship between the device clock and the USB SOF clock is considered
551  * to be linear over the clock samples sliding window and is given by
552  *
553  * SOF = m * PTS + p
554  *
555  * Several methods to compute the slope (m) and intercept (p) can be used. As
556  * the clock drift should be small compared to the sliding window size, we
557  * assume that the line that goes through the points at both ends of the window
558  * is a good approximation. Naming those points P1 and P2, we get
559  *
560  * SOF = (SOF2 - SOF1) / (STC2 - STC1) * PTS
561  *     + (SOF1 * STC2 - SOF2 * STC1) / (STC2 - STC1)
562  *
563  * or
564  *
565  * SOF = ((SOF2 - SOF1) * PTS + SOF1 * STC2 - SOF2 * STC1) / (STC2 - STC1)   (1)
566  *
567  * to avoid losing precision in the division. Similarly, the host timestamp is
568  * computed with
569  *
570  * TS = ((TS2 - TS1) * PTS + TS1 * SOF2 - TS2 * SOF1) / (SOF2 - SOF1)	     (2)
571  *
572  * SOF values are coded on 11 bits by USB. We extend their precision with 16
573  * decimal bits, leading to a 11.16 coding.
574  *
575  * TODO: To avoid surprises with device clock values, PTS/STC timestamps should
576  * be normalized using the nominal device clock frequency reported through the
577  * UVC descriptors.
578  *
579  * Both the PTS/STC and SOF counters roll over, after a fixed but device
580  * specific amount of time for PTS/STC and after 2048ms for SOF. As long as the
581  * sliding window size is smaller than the rollover period, differences computed
582  * on unsigned integers will produce the correct result. However, the p term in
583  * the linear relations will be miscomputed.
584  *
585  * To fix the issue, we subtract a constant from the PTS and STC values to bring
586  * PTS to half the 32 bit STC range. The sliding window STC values then fit into
587  * the 32 bit range without any rollover.
588  *
589  * Similarly, we add 2048 to the device SOF values to make sure that the SOF
590  * computed by (1) will never be smaller than 0. This offset is then compensated
591  * by adding 2048 to the SOF values used in (2). However, this doesn't prevent
592  * rollovers between (1) and (2): the SOF value computed by (1) can be slightly
593  * lower than 4096, and the host SOF counters can have rolled over to 2048. This
594  * case is handled by subtracting 2048 from the SOF value if it exceeds the host
595  * SOF value at the end of the sliding window.
596  *
597  * Finally we subtract a constant from the host timestamps to bring the first
598  * timestamp of the sliding window to 1s.
599  */
600 void uvc_video_clock_update(struct uvc_streaming *stream,
601 			    struct v4l2_buffer *v4l2_buf,
602 			    struct uvc_buffer *buf)
603 {
604 	struct uvc_clock *clock = &stream->clock;
605 	struct uvc_clock_sample *first;
606 	struct uvc_clock_sample *last;
607 	unsigned long flags;
608 	struct timespec ts;
609 	u32 delta_stc;
610 	u32 y1, y2;
611 	u32 x1, x2;
612 	u32 mean;
613 	u32 sof;
614 	u32 div;
615 	u32 rem;
616 	u64 y;
617 
618 	spin_lock_irqsave(&clock->lock, flags);
619 
620 	if (clock->count < clock->size)
621 		goto done;
622 
623 	first = &clock->samples[clock->head];
624 	last = &clock->samples[(clock->head - 1) % clock->size];
625 
626 	/* First step, PTS to SOF conversion. */
627 	delta_stc = buf->pts - (1UL << 31);
628 	x1 = first->dev_stc - delta_stc;
629 	x2 = last->dev_stc - delta_stc;
630 	if (x1 == x2)
631 		goto done;
632 
633 	y1 = (first->dev_sof + 2048) << 16;
634 	y2 = (last->dev_sof + 2048) << 16;
635 	if (y2 < y1)
636 		y2 += 2048 << 16;
637 
638 	y = (u64)(y2 - y1) * (1ULL << 31) + (u64)y1 * (u64)x2
639 	  - (u64)y2 * (u64)x1;
640 	y = div_u64(y, x2 - x1);
641 
642 	sof = y;
643 
644 	uvc_trace(UVC_TRACE_CLOCK, "%s: PTS %u y %llu.%06llu SOF %u.%06llu "
645 		  "(x1 %u x2 %u y1 %u y2 %u SOF offset %u)\n",
646 		  stream->dev->name, buf->pts,
647 		  y >> 16, div_u64((y & 0xffff) * 1000000, 65536),
648 		  sof >> 16, div_u64(((u64)sof & 0xffff) * 1000000LLU, 65536),
649 		  x1, x2, y1, y2, clock->sof_offset);
650 
651 	/* Second step, SOF to host clock conversion. */
652 	x1 = (uvc_video_clock_host_sof(first) + 2048) << 16;
653 	x2 = (uvc_video_clock_host_sof(last) + 2048) << 16;
654 	if (x2 < x1)
655 		x2 += 2048 << 16;
656 	if (x1 == x2)
657 		goto done;
658 
659 	ts = timespec_sub(last->host_ts, first->host_ts);
660 	y1 = NSEC_PER_SEC;
661 	y2 = (ts.tv_sec + 1) * NSEC_PER_SEC + ts.tv_nsec;
662 
663 	/* Interpolated and host SOF timestamps can wrap around at slightly
664 	 * different times. Handle this by adding or removing 2048 to or from
665 	 * the computed SOF value to keep it close to the SOF samples mean
666 	 * value.
667 	 */
668 	mean = (x1 + x2) / 2;
669 	if (mean - (1024 << 16) > sof)
670 		sof += 2048 << 16;
671 	else if (sof > mean + (1024 << 16))
672 		sof -= 2048 << 16;
673 
674 	y = (u64)(y2 - y1) * (u64)sof + (u64)y1 * (u64)x2
675 	  - (u64)y2 * (u64)x1;
676 	y = div_u64(y, x2 - x1);
677 
678 	div = div_u64_rem(y, NSEC_PER_SEC, &rem);
679 	ts.tv_sec = first->host_ts.tv_sec - 1 + div;
680 	ts.tv_nsec = first->host_ts.tv_nsec + rem;
681 	if (ts.tv_nsec >= NSEC_PER_SEC) {
682 		ts.tv_sec++;
683 		ts.tv_nsec -= NSEC_PER_SEC;
684 	}
685 
686 	uvc_trace(UVC_TRACE_CLOCK, "%s: SOF %u.%06llu y %llu ts %lu.%06lu "
687 		  "buf ts %lu.%06lu (x1 %u/%u/%u x2 %u/%u/%u y1 %u y2 %u)\n",
688 		  stream->dev->name,
689 		  sof >> 16, div_u64(((u64)sof & 0xffff) * 1000000LLU, 65536),
690 		  y, ts.tv_sec, ts.tv_nsec / NSEC_PER_USEC,
691 		  v4l2_buf->timestamp.tv_sec,
692 		  (unsigned long)v4l2_buf->timestamp.tv_usec,
693 		  x1, first->host_sof, first->dev_sof,
694 		  x2, last->host_sof, last->dev_sof, y1, y2);
695 
696 	/* Update the V4L2 buffer. */
697 	v4l2_buf->timestamp.tv_sec = ts.tv_sec;
698 	v4l2_buf->timestamp.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
699 
700 done:
701 	spin_unlock_irqrestore(&stream->clock.lock, flags);
702 }
703 
704 /* ------------------------------------------------------------------------
705  * Stream statistics
706  */
707 
708 static void uvc_video_stats_decode(struct uvc_streaming *stream,
709 		const __u8 *data, int len)
710 {
711 	unsigned int header_size;
712 	bool has_pts = false;
713 	bool has_scr = false;
714 	u16 uninitialized_var(scr_sof);
715 	u32 uninitialized_var(scr_stc);
716 	u32 uninitialized_var(pts);
717 
718 	if (stream->stats.stream.nb_frames == 0 &&
719 	    stream->stats.frame.nb_packets == 0)
720 		ktime_get_ts(&stream->stats.stream.start_ts);
721 
722 	switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
723 	case UVC_STREAM_PTS | UVC_STREAM_SCR:
724 		header_size = 12;
725 		has_pts = true;
726 		has_scr = true;
727 		break;
728 	case UVC_STREAM_PTS:
729 		header_size = 6;
730 		has_pts = true;
731 		break;
732 	case UVC_STREAM_SCR:
733 		header_size = 8;
734 		has_scr = true;
735 		break;
736 	default:
737 		header_size = 2;
738 		break;
739 	}
740 
741 	/* Check for invalid headers. */
742 	if (len < header_size || data[0] < header_size) {
743 		stream->stats.frame.nb_invalid++;
744 		return;
745 	}
746 
747 	/* Extract the timestamps. */
748 	if (has_pts)
749 		pts = get_unaligned_le32(&data[2]);
750 
751 	if (has_scr) {
752 		scr_stc = get_unaligned_le32(&data[header_size - 6]);
753 		scr_sof = get_unaligned_le16(&data[header_size - 2]);
754 	}
755 
756 	/* Is PTS constant through the whole frame ? */
757 	if (has_pts && stream->stats.frame.nb_pts) {
758 		if (stream->stats.frame.pts != pts) {
759 			stream->stats.frame.nb_pts_diffs++;
760 			stream->stats.frame.last_pts_diff =
761 				stream->stats.frame.nb_packets;
762 		}
763 	}
764 
765 	if (has_pts) {
766 		stream->stats.frame.nb_pts++;
767 		stream->stats.frame.pts = pts;
768 	}
769 
770 	/* Do all frames have a PTS in their first non-empty packet, or before
771 	 * their first empty packet ?
772 	 */
773 	if (stream->stats.frame.size == 0) {
774 		if (len > header_size)
775 			stream->stats.frame.has_initial_pts = has_pts;
776 		if (len == header_size && has_pts)
777 			stream->stats.frame.has_early_pts = true;
778 	}
779 
780 	/* Do the SCR.STC and SCR.SOF fields vary through the frame ? */
781 	if (has_scr && stream->stats.frame.nb_scr) {
782 		if (stream->stats.frame.scr_stc != scr_stc)
783 			stream->stats.frame.nb_scr_diffs++;
784 	}
785 
786 	if (has_scr) {
787 		/* Expand the SOF counter to 32 bits and store its value. */
788 		if (stream->stats.stream.nb_frames > 0 ||
789 		    stream->stats.frame.nb_scr > 0)
790 			stream->stats.stream.scr_sof_count +=
791 				(scr_sof - stream->stats.stream.scr_sof) % 2048;
792 		stream->stats.stream.scr_sof = scr_sof;
793 
794 		stream->stats.frame.nb_scr++;
795 		stream->stats.frame.scr_stc = scr_stc;
796 		stream->stats.frame.scr_sof = scr_sof;
797 
798 		if (scr_sof < stream->stats.stream.min_sof)
799 			stream->stats.stream.min_sof = scr_sof;
800 		if (scr_sof > stream->stats.stream.max_sof)
801 			stream->stats.stream.max_sof = scr_sof;
802 	}
803 
804 	/* Record the first non-empty packet number. */
805 	if (stream->stats.frame.size == 0 && len > header_size)
806 		stream->stats.frame.first_data = stream->stats.frame.nb_packets;
807 
808 	/* Update the frame size. */
809 	stream->stats.frame.size += len - header_size;
810 
811 	/* Update the packets counters. */
812 	stream->stats.frame.nb_packets++;
813 	if (len > header_size)
814 		stream->stats.frame.nb_empty++;
815 
816 	if (data[1] & UVC_STREAM_ERR)
817 		stream->stats.frame.nb_errors++;
818 }
819 
820 static void uvc_video_stats_update(struct uvc_streaming *stream)
821 {
822 	struct uvc_stats_frame *frame = &stream->stats.frame;
823 
824 	uvc_trace(UVC_TRACE_STATS, "frame %u stats: %u/%u/%u packets, "
825 		  "%u/%u/%u pts (%searly %sinitial), %u/%u scr, "
826 		  "last pts/stc/sof %u/%u/%u\n",
827 		  stream->sequence, frame->first_data,
828 		  frame->nb_packets - frame->nb_empty, frame->nb_packets,
829 		  frame->nb_pts_diffs, frame->last_pts_diff, frame->nb_pts,
830 		  frame->has_early_pts ? "" : "!",
831 		  frame->has_initial_pts ? "" : "!",
832 		  frame->nb_scr_diffs, frame->nb_scr,
833 		  frame->pts, frame->scr_stc, frame->scr_sof);
834 
835 	stream->stats.stream.nb_frames++;
836 	stream->stats.stream.nb_packets += stream->stats.frame.nb_packets;
837 	stream->stats.stream.nb_empty += stream->stats.frame.nb_empty;
838 	stream->stats.stream.nb_errors += stream->stats.frame.nb_errors;
839 	stream->stats.stream.nb_invalid += stream->stats.frame.nb_invalid;
840 
841 	if (frame->has_early_pts)
842 		stream->stats.stream.nb_pts_early++;
843 	if (frame->has_initial_pts)
844 		stream->stats.stream.nb_pts_initial++;
845 	if (frame->last_pts_diff <= frame->first_data)
846 		stream->stats.stream.nb_pts_constant++;
847 	if (frame->nb_scr >= frame->nb_packets - frame->nb_empty)
848 		stream->stats.stream.nb_scr_count_ok++;
849 	if (frame->nb_scr_diffs + 1 == frame->nb_scr)
850 		stream->stats.stream.nb_scr_diffs_ok++;
851 
852 	memset(&stream->stats.frame, 0, sizeof(stream->stats.frame));
853 }
854 
855 size_t uvc_video_stats_dump(struct uvc_streaming *stream, char *buf,
856 			    size_t size)
857 {
858 	unsigned int scr_sof_freq;
859 	unsigned int duration;
860 	struct timespec ts;
861 	size_t count = 0;
862 
863 	ts.tv_sec = stream->stats.stream.stop_ts.tv_sec
864 		  - stream->stats.stream.start_ts.tv_sec;
865 	ts.tv_nsec = stream->stats.stream.stop_ts.tv_nsec
866 		   - stream->stats.stream.start_ts.tv_nsec;
867 	if (ts.tv_nsec < 0) {
868 		ts.tv_sec--;
869 		ts.tv_nsec += 1000000000;
870 	}
871 
872 	/* Compute the SCR.SOF frequency estimate. At the nominal 1kHz SOF
873 	 * frequency this will not overflow before more than 1h.
874 	 */
875 	duration = ts.tv_sec * 1000 + ts.tv_nsec / 1000000;
876 	if (duration != 0)
877 		scr_sof_freq = stream->stats.stream.scr_sof_count * 1000
878 			     / duration;
879 	else
880 		scr_sof_freq = 0;
881 
882 	count += scnprintf(buf + count, size - count,
883 			   "frames:  %u\npackets: %u\nempty:   %u\n"
884 			   "errors:  %u\ninvalid: %u\n",
885 			   stream->stats.stream.nb_frames,
886 			   stream->stats.stream.nb_packets,
887 			   stream->stats.stream.nb_empty,
888 			   stream->stats.stream.nb_errors,
889 			   stream->stats.stream.nb_invalid);
890 	count += scnprintf(buf + count, size - count,
891 			   "pts: %u early, %u initial, %u ok\n",
892 			   stream->stats.stream.nb_pts_early,
893 			   stream->stats.stream.nb_pts_initial,
894 			   stream->stats.stream.nb_pts_constant);
895 	count += scnprintf(buf + count, size - count,
896 			   "scr: %u count ok, %u diff ok\n",
897 			   stream->stats.stream.nb_scr_count_ok,
898 			   stream->stats.stream.nb_scr_diffs_ok);
899 	count += scnprintf(buf + count, size - count,
900 			   "sof: %u <= sof <= %u, freq %u.%03u kHz\n",
901 			   stream->stats.stream.min_sof,
902 			   stream->stats.stream.max_sof,
903 			   scr_sof_freq / 1000, scr_sof_freq % 1000);
904 
905 	return count;
906 }
907 
908 static void uvc_video_stats_start(struct uvc_streaming *stream)
909 {
910 	memset(&stream->stats, 0, sizeof(stream->stats));
911 	stream->stats.stream.min_sof = 2048;
912 }
913 
914 static void uvc_video_stats_stop(struct uvc_streaming *stream)
915 {
916 	ktime_get_ts(&stream->stats.stream.stop_ts);
917 }
918 
919 /* ------------------------------------------------------------------------
920  * Video codecs
921  */
922 
923 /* Video payload decoding is handled by uvc_video_decode_start(),
924  * uvc_video_decode_data() and uvc_video_decode_end().
925  *
926  * uvc_video_decode_start is called with URB data at the start of a bulk or
927  * isochronous payload. It processes header data and returns the header size
928  * in bytes if successful. If an error occurs, it returns a negative error
929  * code. The following error codes have special meanings.
930  *
931  * - EAGAIN informs the caller that the current video buffer should be marked
932  *   as done, and that the function should be called again with the same data
933  *   and a new video buffer. This is used when end of frame conditions can be
934  *   reliably detected at the beginning of the next frame only.
935  *
936  * If an error other than -EAGAIN is returned, the caller will drop the current
937  * payload. No call to uvc_video_decode_data and uvc_video_decode_end will be
938  * made until the next payload. -ENODATA can be used to drop the current
939  * payload if no other error code is appropriate.
940  *
941  * uvc_video_decode_data is called for every URB with URB data. It copies the
942  * data to the video buffer.
943  *
944  * uvc_video_decode_end is called with header data at the end of a bulk or
945  * isochronous payload. It performs any additional header data processing and
946  * returns 0 or a negative error code if an error occurred. As header data have
947  * already been processed by uvc_video_decode_start, this functions isn't
948  * required to perform sanity checks a second time.
949  *
950  * For isochronous transfers where a payload is always transferred in a single
951  * URB, the three functions will be called in a row.
952  *
953  * To let the decoder process header data and update its internal state even
954  * when no video buffer is available, uvc_video_decode_start must be prepared
955  * to be called with a NULL buf parameter. uvc_video_decode_data and
956  * uvc_video_decode_end will never be called with a NULL buffer.
957  */
958 static int uvc_video_decode_start(struct uvc_streaming *stream,
959 		struct uvc_buffer *buf, const __u8 *data, int len)
960 {
961 	__u8 fid;
962 
963 	/* Sanity checks:
964 	 * - packet must be at least 2 bytes long
965 	 * - bHeaderLength value must be at least 2 bytes (see above)
966 	 * - bHeaderLength value can't be larger than the packet size.
967 	 */
968 	if (len < 2 || data[0] < 2 || data[0] > len) {
969 		stream->stats.frame.nb_invalid++;
970 		return -EINVAL;
971 	}
972 
973 	fid = data[1] & UVC_STREAM_FID;
974 
975 	/* Increase the sequence number regardless of any buffer states, so
976 	 * that discontinuous sequence numbers always indicate lost frames.
977 	 */
978 	if (stream->last_fid != fid) {
979 		stream->sequence++;
980 		if (stream->sequence)
981 			uvc_video_stats_update(stream);
982 	}
983 
984 	uvc_video_clock_decode(stream, buf, data, len);
985 	uvc_video_stats_decode(stream, data, len);
986 
987 	/* Store the payload FID bit and return immediately when the buffer is
988 	 * NULL.
989 	 */
990 	if (buf == NULL) {
991 		stream->last_fid = fid;
992 		return -ENODATA;
993 	}
994 
995 	/* Mark the buffer as bad if the error bit is set. */
996 	if (data[1] & UVC_STREAM_ERR) {
997 		uvc_trace(UVC_TRACE_FRAME, "Marking buffer as bad (error bit "
998 			  "set).\n");
999 		buf->error = 1;
1000 	}
1001 
1002 	/* Synchronize to the input stream by waiting for the FID bit to be
1003 	 * toggled when the the buffer state is not UVC_BUF_STATE_ACTIVE.
1004 	 * stream->last_fid is initialized to -1, so the first isochronous
1005 	 * frame will always be in sync.
1006 	 *
1007 	 * If the device doesn't toggle the FID bit, invert stream->last_fid
1008 	 * when the EOF bit is set to force synchronisation on the next packet.
1009 	 */
1010 	if (buf->state != UVC_BUF_STATE_ACTIVE) {
1011 		struct timespec ts;
1012 
1013 		if (fid == stream->last_fid) {
1014 			uvc_trace(UVC_TRACE_FRAME, "Dropping payload (out of "
1015 				"sync).\n");
1016 			if ((stream->dev->quirks & UVC_QUIRK_STREAM_NO_FID) &&
1017 			    (data[1] & UVC_STREAM_EOF))
1018 				stream->last_fid ^= UVC_STREAM_FID;
1019 			return -ENODATA;
1020 		}
1021 
1022 		uvc_video_get_ts(&ts);
1023 
1024 		buf->buf.v4l2_buf.sequence = stream->sequence;
1025 		buf->buf.v4l2_buf.timestamp.tv_sec = ts.tv_sec;
1026 		buf->buf.v4l2_buf.timestamp.tv_usec =
1027 			ts.tv_nsec / NSEC_PER_USEC;
1028 
1029 		/* TODO: Handle PTS and SCR. */
1030 		buf->state = UVC_BUF_STATE_ACTIVE;
1031 	}
1032 
1033 	/* Mark the buffer as done if we're at the beginning of a new frame.
1034 	 * End of frame detection is better implemented by checking the EOF
1035 	 * bit (FID bit toggling is delayed by one frame compared to the EOF
1036 	 * bit), but some devices don't set the bit at end of frame (and the
1037 	 * last payload can be lost anyway). We thus must check if the FID has
1038 	 * been toggled.
1039 	 *
1040 	 * stream->last_fid is initialized to -1, so the first isochronous
1041 	 * frame will never trigger an end of frame detection.
1042 	 *
1043 	 * Empty buffers (bytesused == 0) don't trigger end of frame detection
1044 	 * as it doesn't make sense to return an empty buffer. This also
1045 	 * avoids detecting end of frame conditions at FID toggling if the
1046 	 * previous payload had the EOF bit set.
1047 	 */
1048 	if (fid != stream->last_fid && buf->bytesused != 0) {
1049 		uvc_trace(UVC_TRACE_FRAME, "Frame complete (FID bit "
1050 				"toggled).\n");
1051 		buf->state = UVC_BUF_STATE_READY;
1052 		return -EAGAIN;
1053 	}
1054 
1055 	stream->last_fid = fid;
1056 
1057 	return data[0];
1058 }
1059 
1060 static void uvc_video_decode_data(struct uvc_streaming *stream,
1061 		struct uvc_buffer *buf, const __u8 *data, int len)
1062 {
1063 	unsigned int maxlen, nbytes;
1064 	void *mem;
1065 
1066 	if (len <= 0)
1067 		return;
1068 
1069 	/* Copy the video data to the buffer. */
1070 	maxlen = buf->length - buf->bytesused;
1071 	mem = buf->mem + buf->bytesused;
1072 	nbytes = min((unsigned int)len, maxlen);
1073 	memcpy(mem, data, nbytes);
1074 	buf->bytesused += nbytes;
1075 
1076 	/* Complete the current frame if the buffer size was exceeded. */
1077 	if (len > maxlen) {
1078 		uvc_trace(UVC_TRACE_FRAME, "Frame complete (overflow).\n");
1079 		buf->state = UVC_BUF_STATE_READY;
1080 	}
1081 }
1082 
1083 static void uvc_video_decode_end(struct uvc_streaming *stream,
1084 		struct uvc_buffer *buf, const __u8 *data, int len)
1085 {
1086 	/* Mark the buffer as done if the EOF marker is set. */
1087 	if (data[1] & UVC_STREAM_EOF && buf->bytesused != 0) {
1088 		uvc_trace(UVC_TRACE_FRAME, "Frame complete (EOF found).\n");
1089 		if (data[0] == len)
1090 			uvc_trace(UVC_TRACE_FRAME, "EOF in empty payload.\n");
1091 		buf->state = UVC_BUF_STATE_READY;
1092 		if (stream->dev->quirks & UVC_QUIRK_STREAM_NO_FID)
1093 			stream->last_fid ^= UVC_STREAM_FID;
1094 	}
1095 }
1096 
1097 /* Video payload encoding is handled by uvc_video_encode_header() and
1098  * uvc_video_encode_data(). Only bulk transfers are currently supported.
1099  *
1100  * uvc_video_encode_header is called at the start of a payload. It adds header
1101  * data to the transfer buffer and returns the header size. As the only known
1102  * UVC output device transfers a whole frame in a single payload, the EOF bit
1103  * is always set in the header.
1104  *
1105  * uvc_video_encode_data is called for every URB and copies the data from the
1106  * video buffer to the transfer buffer.
1107  */
1108 static int uvc_video_encode_header(struct uvc_streaming *stream,
1109 		struct uvc_buffer *buf, __u8 *data, int len)
1110 {
1111 	data[0] = 2;	/* Header length */
1112 	data[1] = UVC_STREAM_EOH | UVC_STREAM_EOF
1113 		| (stream->last_fid & UVC_STREAM_FID);
1114 	return 2;
1115 }
1116 
1117 static int uvc_video_encode_data(struct uvc_streaming *stream,
1118 		struct uvc_buffer *buf, __u8 *data, int len)
1119 {
1120 	struct uvc_video_queue *queue = &stream->queue;
1121 	unsigned int nbytes;
1122 	void *mem;
1123 
1124 	/* Copy video data to the URB buffer. */
1125 	mem = buf->mem + queue->buf_used;
1126 	nbytes = min((unsigned int)len, buf->bytesused - queue->buf_used);
1127 	nbytes = min(stream->bulk.max_payload_size - stream->bulk.payload_size,
1128 			nbytes);
1129 	memcpy(data, mem, nbytes);
1130 
1131 	queue->buf_used += nbytes;
1132 
1133 	return nbytes;
1134 }
1135 
1136 /* ------------------------------------------------------------------------
1137  * URB handling
1138  */
1139 
1140 /*
1141  * Set error flag for incomplete buffer.
1142  */
1143 static void uvc_video_validate_buffer(const struct uvc_streaming *stream,
1144 				      struct uvc_buffer *buf)
1145 {
1146 	if (stream->ctrl.dwMaxVideoFrameSize != buf->bytesused &&
1147 	    !(stream->cur_format->flags & UVC_FMT_FLAG_COMPRESSED))
1148 		buf->error = 1;
1149 }
1150 
1151 /*
1152  * Completion handler for video URBs.
1153  */
1154 static void uvc_video_decode_isoc(struct urb *urb, struct uvc_streaming *stream,
1155 	struct uvc_buffer *buf)
1156 {
1157 	u8 *mem;
1158 	int ret, i;
1159 
1160 	for (i = 0; i < urb->number_of_packets; ++i) {
1161 		if (urb->iso_frame_desc[i].status < 0) {
1162 			uvc_trace(UVC_TRACE_FRAME, "USB isochronous frame "
1163 				"lost (%d).\n", urb->iso_frame_desc[i].status);
1164 			/* Mark the buffer as faulty. */
1165 			if (buf != NULL)
1166 				buf->error = 1;
1167 			continue;
1168 		}
1169 
1170 		/* Decode the payload header. */
1171 		mem = urb->transfer_buffer + urb->iso_frame_desc[i].offset;
1172 		do {
1173 			ret = uvc_video_decode_start(stream, buf, mem,
1174 				urb->iso_frame_desc[i].actual_length);
1175 			if (ret == -EAGAIN) {
1176 				uvc_video_validate_buffer(stream, buf);
1177 				buf = uvc_queue_next_buffer(&stream->queue,
1178 							    buf);
1179 			}
1180 		} while (ret == -EAGAIN);
1181 
1182 		if (ret < 0)
1183 			continue;
1184 
1185 		/* Decode the payload data. */
1186 		uvc_video_decode_data(stream, buf, mem + ret,
1187 			urb->iso_frame_desc[i].actual_length - ret);
1188 
1189 		/* Process the header again. */
1190 		uvc_video_decode_end(stream, buf, mem,
1191 			urb->iso_frame_desc[i].actual_length);
1192 
1193 		if (buf->state == UVC_BUF_STATE_READY) {
1194 			uvc_video_validate_buffer(stream, buf);
1195 			buf = uvc_queue_next_buffer(&stream->queue, buf);
1196 		}
1197 	}
1198 }
1199 
1200 static void uvc_video_decode_bulk(struct urb *urb, struct uvc_streaming *stream,
1201 	struct uvc_buffer *buf)
1202 {
1203 	u8 *mem;
1204 	int len, ret;
1205 
1206 	/*
1207 	 * Ignore ZLPs if they're not part of a frame, otherwise process them
1208 	 * to trigger the end of payload detection.
1209 	 */
1210 	if (urb->actual_length == 0 && stream->bulk.header_size == 0)
1211 		return;
1212 
1213 	mem = urb->transfer_buffer;
1214 	len = urb->actual_length;
1215 	stream->bulk.payload_size += len;
1216 
1217 	/* If the URB is the first of its payload, decode and save the
1218 	 * header.
1219 	 */
1220 	if (stream->bulk.header_size == 0 && !stream->bulk.skip_payload) {
1221 		do {
1222 			ret = uvc_video_decode_start(stream, buf, mem, len);
1223 			if (ret == -EAGAIN)
1224 				buf = uvc_queue_next_buffer(&stream->queue,
1225 							    buf);
1226 		} while (ret == -EAGAIN);
1227 
1228 		/* If an error occurred skip the rest of the payload. */
1229 		if (ret < 0 || buf == NULL) {
1230 			stream->bulk.skip_payload = 1;
1231 		} else {
1232 			memcpy(stream->bulk.header, mem, ret);
1233 			stream->bulk.header_size = ret;
1234 
1235 			mem += ret;
1236 			len -= ret;
1237 		}
1238 	}
1239 
1240 	/* The buffer queue might have been cancelled while a bulk transfer
1241 	 * was in progress, so we can reach here with buf equal to NULL. Make
1242 	 * sure buf is never dereferenced if NULL.
1243 	 */
1244 
1245 	/* Process video data. */
1246 	if (!stream->bulk.skip_payload && buf != NULL)
1247 		uvc_video_decode_data(stream, buf, mem, len);
1248 
1249 	/* Detect the payload end by a URB smaller than the maximum size (or
1250 	 * a payload size equal to the maximum) and process the header again.
1251 	 */
1252 	if (urb->actual_length < urb->transfer_buffer_length ||
1253 	    stream->bulk.payload_size >= stream->bulk.max_payload_size) {
1254 		if (!stream->bulk.skip_payload && buf != NULL) {
1255 			uvc_video_decode_end(stream, buf, stream->bulk.header,
1256 				stream->bulk.payload_size);
1257 			if (buf->state == UVC_BUF_STATE_READY)
1258 				buf = uvc_queue_next_buffer(&stream->queue,
1259 							    buf);
1260 		}
1261 
1262 		stream->bulk.header_size = 0;
1263 		stream->bulk.skip_payload = 0;
1264 		stream->bulk.payload_size = 0;
1265 	}
1266 }
1267 
1268 static void uvc_video_encode_bulk(struct urb *urb, struct uvc_streaming *stream,
1269 	struct uvc_buffer *buf)
1270 {
1271 	u8 *mem = urb->transfer_buffer;
1272 	int len = stream->urb_size, ret;
1273 
1274 	if (buf == NULL) {
1275 		urb->transfer_buffer_length = 0;
1276 		return;
1277 	}
1278 
1279 	/* If the URB is the first of its payload, add the header. */
1280 	if (stream->bulk.header_size == 0) {
1281 		ret = uvc_video_encode_header(stream, buf, mem, len);
1282 		stream->bulk.header_size = ret;
1283 		stream->bulk.payload_size += ret;
1284 		mem += ret;
1285 		len -= ret;
1286 	}
1287 
1288 	/* Process video data. */
1289 	ret = uvc_video_encode_data(stream, buf, mem, len);
1290 
1291 	stream->bulk.payload_size += ret;
1292 	len -= ret;
1293 
1294 	if (buf->bytesused == stream->queue.buf_used ||
1295 	    stream->bulk.payload_size == stream->bulk.max_payload_size) {
1296 		if (buf->bytesused == stream->queue.buf_used) {
1297 			stream->queue.buf_used = 0;
1298 			buf->state = UVC_BUF_STATE_READY;
1299 			buf->buf.v4l2_buf.sequence = ++stream->sequence;
1300 			uvc_queue_next_buffer(&stream->queue, buf);
1301 			stream->last_fid ^= UVC_STREAM_FID;
1302 		}
1303 
1304 		stream->bulk.header_size = 0;
1305 		stream->bulk.payload_size = 0;
1306 	}
1307 
1308 	urb->transfer_buffer_length = stream->urb_size - len;
1309 }
1310 
1311 static void uvc_video_complete(struct urb *urb)
1312 {
1313 	struct uvc_streaming *stream = urb->context;
1314 	struct uvc_video_queue *queue = &stream->queue;
1315 	struct uvc_buffer *buf = NULL;
1316 	unsigned long flags;
1317 	int ret;
1318 
1319 	switch (urb->status) {
1320 	case 0:
1321 		break;
1322 
1323 	default:
1324 		uvc_printk(KERN_WARNING, "Non-zero status (%d) in video "
1325 			"completion handler.\n", urb->status);
1326 
1327 	case -ENOENT:		/* usb_kill_urb() called. */
1328 		if (stream->frozen)
1329 			return;
1330 
1331 	case -ECONNRESET:	/* usb_unlink_urb() called. */
1332 	case -ESHUTDOWN:	/* The endpoint is being disabled. */
1333 		uvc_queue_cancel(queue, urb->status == -ESHUTDOWN);
1334 		return;
1335 	}
1336 
1337 	spin_lock_irqsave(&queue->irqlock, flags);
1338 	if (!list_empty(&queue->irqqueue))
1339 		buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
1340 				       queue);
1341 	spin_unlock_irqrestore(&queue->irqlock, flags);
1342 
1343 	stream->decode(urb, stream, buf);
1344 
1345 	if ((ret = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
1346 		uvc_printk(KERN_ERR, "Failed to resubmit video URB (%d).\n",
1347 			ret);
1348 	}
1349 }
1350 
1351 /*
1352  * Free transfer buffers.
1353  */
1354 static void uvc_free_urb_buffers(struct uvc_streaming *stream)
1355 {
1356 	unsigned int i;
1357 
1358 	for (i = 0; i < UVC_URBS; ++i) {
1359 		if (stream->urb_buffer[i]) {
1360 #ifndef CONFIG_DMA_NONCOHERENT
1361 			usb_free_coherent(stream->dev->udev, stream->urb_size,
1362 				stream->urb_buffer[i], stream->urb_dma[i]);
1363 #else
1364 			kfree(stream->urb_buffer[i]);
1365 #endif
1366 			stream->urb_buffer[i] = NULL;
1367 		}
1368 	}
1369 
1370 	stream->urb_size = 0;
1371 }
1372 
1373 /*
1374  * Allocate transfer buffers. This function can be called with buffers
1375  * already allocated when resuming from suspend, in which case it will
1376  * return without touching the buffers.
1377  *
1378  * Limit the buffer size to UVC_MAX_PACKETS bulk/isochronous packets. If the
1379  * system is too low on memory try successively smaller numbers of packets
1380  * until allocation succeeds.
1381  *
1382  * Return the number of allocated packets on success or 0 when out of memory.
1383  */
1384 static int uvc_alloc_urb_buffers(struct uvc_streaming *stream,
1385 	unsigned int size, unsigned int psize, gfp_t gfp_flags)
1386 {
1387 	unsigned int npackets;
1388 	unsigned int i;
1389 
1390 	/* Buffers are already allocated, bail out. */
1391 	if (stream->urb_size)
1392 		return stream->urb_size / psize;
1393 
1394 	/* Compute the number of packets. Bulk endpoints might transfer UVC
1395 	 * payloads across multiple URBs.
1396 	 */
1397 	npackets = DIV_ROUND_UP(size, psize);
1398 	if (npackets > UVC_MAX_PACKETS)
1399 		npackets = UVC_MAX_PACKETS;
1400 
1401 	/* Retry allocations until one succeed. */
1402 	for (; npackets > 1; npackets /= 2) {
1403 		for (i = 0; i < UVC_URBS; ++i) {
1404 			stream->urb_size = psize * npackets;
1405 #ifndef CONFIG_DMA_NONCOHERENT
1406 			stream->urb_buffer[i] = usb_alloc_coherent(
1407 				stream->dev->udev, stream->urb_size,
1408 				gfp_flags | __GFP_NOWARN, &stream->urb_dma[i]);
1409 #else
1410 			stream->urb_buffer[i] =
1411 			    kmalloc(stream->urb_size, gfp_flags | __GFP_NOWARN);
1412 #endif
1413 			if (!stream->urb_buffer[i]) {
1414 				uvc_free_urb_buffers(stream);
1415 				break;
1416 			}
1417 		}
1418 
1419 		if (i == UVC_URBS) {
1420 			uvc_trace(UVC_TRACE_VIDEO, "Allocated %u URB buffers "
1421 				"of %ux%u bytes each.\n", UVC_URBS, npackets,
1422 				psize);
1423 			return npackets;
1424 		}
1425 	}
1426 
1427 	uvc_trace(UVC_TRACE_VIDEO, "Failed to allocate URB buffers (%u bytes "
1428 		"per packet).\n", psize);
1429 	return 0;
1430 }
1431 
1432 /*
1433  * Uninitialize isochronous/bulk URBs and free transfer buffers.
1434  */
1435 static void uvc_uninit_video(struct uvc_streaming *stream, int free_buffers)
1436 {
1437 	struct urb *urb;
1438 	unsigned int i;
1439 
1440 	uvc_video_stats_stop(stream);
1441 
1442 	for (i = 0; i < UVC_URBS; ++i) {
1443 		urb = stream->urb[i];
1444 		if (urb == NULL)
1445 			continue;
1446 
1447 		usb_kill_urb(urb);
1448 		usb_free_urb(urb);
1449 		stream->urb[i] = NULL;
1450 	}
1451 
1452 	if (free_buffers)
1453 		uvc_free_urb_buffers(stream);
1454 }
1455 
1456 /*
1457  * Compute the maximum number of bytes per interval for an endpoint.
1458  */
1459 static unsigned int uvc_endpoint_max_bpi(struct usb_device *dev,
1460 					 struct usb_host_endpoint *ep)
1461 {
1462 	u16 psize;
1463 
1464 	switch (dev->speed) {
1465 	case USB_SPEED_SUPER:
1466 		return le16_to_cpu(ep->ss_ep_comp.wBytesPerInterval);
1467 	case USB_SPEED_HIGH:
1468 		psize = usb_endpoint_maxp(&ep->desc);
1469 		return (psize & 0x07ff) * (1 + ((psize >> 11) & 3));
1470 	case USB_SPEED_WIRELESS:
1471 		psize = usb_endpoint_maxp(&ep->desc);
1472 		return psize;
1473 	default:
1474 		psize = usb_endpoint_maxp(&ep->desc);
1475 		return psize & 0x07ff;
1476 	}
1477 }
1478 
1479 /*
1480  * Initialize isochronous URBs and allocate transfer buffers. The packet size
1481  * is given by the endpoint.
1482  */
1483 static int uvc_init_video_isoc(struct uvc_streaming *stream,
1484 	struct usb_host_endpoint *ep, gfp_t gfp_flags)
1485 {
1486 	struct urb *urb;
1487 	unsigned int npackets, i, j;
1488 	u16 psize;
1489 	u32 size;
1490 
1491 	psize = uvc_endpoint_max_bpi(stream->dev->udev, ep);
1492 	size = stream->ctrl.dwMaxVideoFrameSize;
1493 
1494 	npackets = uvc_alloc_urb_buffers(stream, size, psize, gfp_flags);
1495 	if (npackets == 0)
1496 		return -ENOMEM;
1497 
1498 	size = npackets * psize;
1499 
1500 	for (i = 0; i < UVC_URBS; ++i) {
1501 		urb = usb_alloc_urb(npackets, gfp_flags);
1502 		if (urb == NULL) {
1503 			uvc_uninit_video(stream, 1);
1504 			return -ENOMEM;
1505 		}
1506 
1507 		urb->dev = stream->dev->udev;
1508 		urb->context = stream;
1509 		urb->pipe = usb_rcvisocpipe(stream->dev->udev,
1510 				ep->desc.bEndpointAddress);
1511 #ifndef CONFIG_DMA_NONCOHERENT
1512 		urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
1513 		urb->transfer_dma = stream->urb_dma[i];
1514 #else
1515 		urb->transfer_flags = URB_ISO_ASAP;
1516 #endif
1517 		urb->interval = ep->desc.bInterval;
1518 		urb->transfer_buffer = stream->urb_buffer[i];
1519 		urb->complete = uvc_video_complete;
1520 		urb->number_of_packets = npackets;
1521 		urb->transfer_buffer_length = size;
1522 
1523 		for (j = 0; j < npackets; ++j) {
1524 			urb->iso_frame_desc[j].offset = j * psize;
1525 			urb->iso_frame_desc[j].length = psize;
1526 		}
1527 
1528 		stream->urb[i] = urb;
1529 	}
1530 
1531 	return 0;
1532 }
1533 
1534 /*
1535  * Initialize bulk URBs and allocate transfer buffers. The packet size is
1536  * given by the endpoint.
1537  */
1538 static int uvc_init_video_bulk(struct uvc_streaming *stream,
1539 	struct usb_host_endpoint *ep, gfp_t gfp_flags)
1540 {
1541 	struct urb *urb;
1542 	unsigned int npackets, pipe, i;
1543 	u16 psize;
1544 	u32 size;
1545 
1546 	psize = usb_endpoint_maxp(&ep->desc) & 0x7ff;
1547 	size = stream->ctrl.dwMaxPayloadTransferSize;
1548 	stream->bulk.max_payload_size = size;
1549 
1550 	npackets = uvc_alloc_urb_buffers(stream, size, psize, gfp_flags);
1551 	if (npackets == 0)
1552 		return -ENOMEM;
1553 
1554 	size = npackets * psize;
1555 
1556 	if (usb_endpoint_dir_in(&ep->desc))
1557 		pipe = usb_rcvbulkpipe(stream->dev->udev,
1558 				       ep->desc.bEndpointAddress);
1559 	else
1560 		pipe = usb_sndbulkpipe(stream->dev->udev,
1561 				       ep->desc.bEndpointAddress);
1562 
1563 	if (stream->type == V4L2_BUF_TYPE_VIDEO_OUTPUT)
1564 		size = 0;
1565 
1566 	for (i = 0; i < UVC_URBS; ++i) {
1567 		urb = usb_alloc_urb(0, gfp_flags);
1568 		if (urb == NULL) {
1569 			uvc_uninit_video(stream, 1);
1570 			return -ENOMEM;
1571 		}
1572 
1573 		usb_fill_bulk_urb(urb, stream->dev->udev, pipe,
1574 			stream->urb_buffer[i], size, uvc_video_complete,
1575 			stream);
1576 #ifndef CONFIG_DMA_NONCOHERENT
1577 		urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
1578 		urb->transfer_dma = stream->urb_dma[i];
1579 #endif
1580 
1581 		stream->urb[i] = urb;
1582 	}
1583 
1584 	return 0;
1585 }
1586 
1587 /*
1588  * Initialize isochronous/bulk URBs and allocate transfer buffers.
1589  */
1590 static int uvc_init_video(struct uvc_streaming *stream, gfp_t gfp_flags)
1591 {
1592 	struct usb_interface *intf = stream->intf;
1593 	struct usb_host_endpoint *ep;
1594 	unsigned int i;
1595 	int ret;
1596 
1597 	stream->sequence = -1;
1598 	stream->last_fid = -1;
1599 	stream->bulk.header_size = 0;
1600 	stream->bulk.skip_payload = 0;
1601 	stream->bulk.payload_size = 0;
1602 
1603 	uvc_video_stats_start(stream);
1604 
1605 	if (intf->num_altsetting > 1) {
1606 		struct usb_host_endpoint *best_ep = NULL;
1607 		unsigned int best_psize = UINT_MAX;
1608 		unsigned int bandwidth;
1609 		unsigned int uninitialized_var(altsetting);
1610 		int intfnum = stream->intfnum;
1611 
1612 		/* Isochronous endpoint, select the alternate setting. */
1613 		bandwidth = stream->ctrl.dwMaxPayloadTransferSize;
1614 
1615 		if (bandwidth == 0) {
1616 			uvc_trace(UVC_TRACE_VIDEO, "Device requested null "
1617 				"bandwidth, defaulting to lowest.\n");
1618 			bandwidth = 1;
1619 		} else {
1620 			uvc_trace(UVC_TRACE_VIDEO, "Device requested %u "
1621 				"B/frame bandwidth.\n", bandwidth);
1622 		}
1623 
1624 		for (i = 0; i < intf->num_altsetting; ++i) {
1625 			struct usb_host_interface *alts;
1626 			unsigned int psize;
1627 
1628 			alts = &intf->altsetting[i];
1629 			ep = uvc_find_endpoint(alts,
1630 				stream->header.bEndpointAddress);
1631 			if (ep == NULL)
1632 				continue;
1633 
1634 			/* Check if the bandwidth is high enough. */
1635 			psize = uvc_endpoint_max_bpi(stream->dev->udev, ep);
1636 			if (psize >= bandwidth && psize <= best_psize) {
1637 				altsetting = alts->desc.bAlternateSetting;
1638 				best_psize = psize;
1639 				best_ep = ep;
1640 			}
1641 		}
1642 
1643 		if (best_ep == NULL) {
1644 			uvc_trace(UVC_TRACE_VIDEO, "No fast enough alt setting "
1645 				"for requested bandwidth.\n");
1646 			return -EIO;
1647 		}
1648 
1649 		uvc_trace(UVC_TRACE_VIDEO, "Selecting alternate setting %u "
1650 			"(%u B/frame bandwidth).\n", altsetting, best_psize);
1651 
1652 		ret = usb_set_interface(stream->dev->udev, intfnum, altsetting);
1653 		if (ret < 0)
1654 			return ret;
1655 
1656 		ret = uvc_init_video_isoc(stream, best_ep, gfp_flags);
1657 	} else {
1658 		/* Bulk endpoint, proceed to URB initialization. */
1659 		ep = uvc_find_endpoint(&intf->altsetting[0],
1660 				stream->header.bEndpointAddress);
1661 		if (ep == NULL)
1662 			return -EIO;
1663 
1664 		ret = uvc_init_video_bulk(stream, ep, gfp_flags);
1665 	}
1666 
1667 	if (ret < 0)
1668 		return ret;
1669 
1670 	/* Submit the URBs. */
1671 	for (i = 0; i < UVC_URBS; ++i) {
1672 		ret = usb_submit_urb(stream->urb[i], gfp_flags);
1673 		if (ret < 0) {
1674 			uvc_printk(KERN_ERR, "Failed to submit URB %u "
1675 					"(%d).\n", i, ret);
1676 			uvc_uninit_video(stream, 1);
1677 			return ret;
1678 		}
1679 	}
1680 
1681 	/* The Logitech C920 temporarily forgets that it should not be adjusting
1682 	 * Exposure Absolute during init so restore controls to stored values.
1683 	 */
1684 	if (stream->dev->quirks & UVC_QUIRK_RESTORE_CTRLS_ON_INIT)
1685 		uvc_ctrl_restore_values(stream->dev);
1686 
1687 	return 0;
1688 }
1689 
1690 /* --------------------------------------------------------------------------
1691  * Suspend/resume
1692  */
1693 
1694 /*
1695  * Stop streaming without disabling the video queue.
1696  *
1697  * To let userspace applications resume without trouble, we must not touch the
1698  * video buffers in any way. We mark the device as frozen to make sure the URB
1699  * completion handler won't try to cancel the queue when we kill the URBs.
1700  */
1701 int uvc_video_suspend(struct uvc_streaming *stream)
1702 {
1703 	if (!uvc_queue_streaming(&stream->queue))
1704 		return 0;
1705 
1706 	stream->frozen = 1;
1707 	uvc_uninit_video(stream, 0);
1708 	usb_set_interface(stream->dev->udev, stream->intfnum, 0);
1709 	return 0;
1710 }
1711 
1712 /*
1713  * Reconfigure the video interface and restart streaming if it was enabled
1714  * before suspend.
1715  *
1716  * If an error occurs, disable the video queue. This will wake all pending
1717  * buffers, making sure userspace applications are notified of the problem
1718  * instead of waiting forever.
1719  */
1720 int uvc_video_resume(struct uvc_streaming *stream, int reset)
1721 {
1722 	int ret;
1723 
1724 	/* If the bus has been reset on resume, set the alternate setting to 0.
1725 	 * This should be the default value, but some devices crash or otherwise
1726 	 * misbehave if they don't receive a SET_INTERFACE request before any
1727 	 * other video control request.
1728 	 */
1729 	if (reset)
1730 		usb_set_interface(stream->dev->udev, stream->intfnum, 0);
1731 
1732 	stream->frozen = 0;
1733 
1734 	uvc_video_clock_reset(stream);
1735 
1736 	ret = uvc_commit_video(stream, &stream->ctrl);
1737 	if (ret < 0) {
1738 		uvc_queue_enable(&stream->queue, 0);
1739 		return ret;
1740 	}
1741 
1742 	if (!uvc_queue_streaming(&stream->queue))
1743 		return 0;
1744 
1745 	ret = uvc_init_video(stream, GFP_NOIO);
1746 	if (ret < 0)
1747 		uvc_queue_enable(&stream->queue, 0);
1748 
1749 	return ret;
1750 }
1751 
1752 /* ------------------------------------------------------------------------
1753  * Video device
1754  */
1755 
1756 /*
1757  * Initialize the UVC video device by switching to alternate setting 0 and
1758  * retrieve the default format.
1759  *
1760  * Some cameras (namely the Fuji Finepix) set the format and frame
1761  * indexes to zero. The UVC standard doesn't clearly make this a spec
1762  * violation, so try to silently fix the values if possible.
1763  *
1764  * This function is called before registering the device with V4L.
1765  */
1766 int uvc_video_init(struct uvc_streaming *stream)
1767 {
1768 	struct uvc_streaming_control *probe = &stream->ctrl;
1769 	struct uvc_format *format = NULL;
1770 	struct uvc_frame *frame = NULL;
1771 	unsigned int i;
1772 	int ret;
1773 
1774 	if (stream->nformats == 0) {
1775 		uvc_printk(KERN_INFO, "No supported video formats found.\n");
1776 		return -EINVAL;
1777 	}
1778 
1779 	atomic_set(&stream->active, 0);
1780 
1781 	/* Initialize the video buffers queue. */
1782 	ret = uvc_queue_init(&stream->queue, stream->type, !uvc_no_drop_param);
1783 	if (ret)
1784 		return ret;
1785 
1786 	/* Alternate setting 0 should be the default, yet the XBox Live Vision
1787 	 * Cam (and possibly other devices) crash or otherwise misbehave if
1788 	 * they don't receive a SET_INTERFACE request before any other video
1789 	 * control request.
1790 	 */
1791 	usb_set_interface(stream->dev->udev, stream->intfnum, 0);
1792 
1793 	/* Set the streaming probe control with default streaming parameters
1794 	 * retrieved from the device. Webcams that don't suport GET_DEF
1795 	 * requests on the probe control will just keep their current streaming
1796 	 * parameters.
1797 	 */
1798 	if (uvc_get_video_ctrl(stream, probe, 1, UVC_GET_DEF) == 0)
1799 		uvc_set_video_ctrl(stream, probe, 1);
1800 
1801 	/* Initialize the streaming parameters with the probe control current
1802 	 * value. This makes sure SET_CUR requests on the streaming commit
1803 	 * control will always use values retrieved from a successful GET_CUR
1804 	 * request on the probe control, as required by the UVC specification.
1805 	 */
1806 	ret = uvc_get_video_ctrl(stream, probe, 1, UVC_GET_CUR);
1807 	if (ret < 0)
1808 		return ret;
1809 
1810 	/* Check if the default format descriptor exists. Use the first
1811 	 * available format otherwise.
1812 	 */
1813 	for (i = stream->nformats; i > 0; --i) {
1814 		format = &stream->format[i-1];
1815 		if (format->index == probe->bFormatIndex)
1816 			break;
1817 	}
1818 
1819 	if (format->nframes == 0) {
1820 		uvc_printk(KERN_INFO, "No frame descriptor found for the "
1821 			"default format.\n");
1822 		return -EINVAL;
1823 	}
1824 
1825 	/* Zero bFrameIndex might be correct. Stream-based formats (including
1826 	 * MPEG-2 TS and DV) do not support frames but have a dummy frame
1827 	 * descriptor with bFrameIndex set to zero. If the default frame
1828 	 * descriptor is not found, use the first available frame.
1829 	 */
1830 	for (i = format->nframes; i > 0; --i) {
1831 		frame = &format->frame[i-1];
1832 		if (frame->bFrameIndex == probe->bFrameIndex)
1833 			break;
1834 	}
1835 
1836 	probe->bFormatIndex = format->index;
1837 	probe->bFrameIndex = frame->bFrameIndex;
1838 
1839 	stream->def_format = format;
1840 	stream->cur_format = format;
1841 	stream->cur_frame = frame;
1842 
1843 	/* Select the video decoding function */
1844 	if (stream->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
1845 		if (stream->dev->quirks & UVC_QUIRK_BUILTIN_ISIGHT)
1846 			stream->decode = uvc_video_decode_isight;
1847 		else if (stream->intf->num_altsetting > 1)
1848 			stream->decode = uvc_video_decode_isoc;
1849 		else
1850 			stream->decode = uvc_video_decode_bulk;
1851 	} else {
1852 		if (stream->intf->num_altsetting == 1)
1853 			stream->decode = uvc_video_encode_bulk;
1854 		else {
1855 			uvc_printk(KERN_INFO, "Isochronous endpoints are not "
1856 				"supported for video output devices.\n");
1857 			return -EINVAL;
1858 		}
1859 	}
1860 
1861 	return 0;
1862 }
1863 
1864 /*
1865  * Enable or disable the video stream.
1866  */
1867 int uvc_video_enable(struct uvc_streaming *stream, int enable)
1868 {
1869 	int ret;
1870 
1871 	if (!enable) {
1872 		uvc_uninit_video(stream, 1);
1873 		if (stream->intf->num_altsetting > 1) {
1874 			usb_set_interface(stream->dev->udev,
1875 					  stream->intfnum, 0);
1876 		} else {
1877 			/* UVC doesn't specify how to inform a bulk-based device
1878 			 * when the video stream is stopped. Windows sends a
1879 			 * CLEAR_FEATURE(HALT) request to the video streaming
1880 			 * bulk endpoint, mimic the same behaviour.
1881 			 */
1882 			unsigned int epnum = stream->header.bEndpointAddress
1883 					   & USB_ENDPOINT_NUMBER_MASK;
1884 			unsigned int dir = stream->header.bEndpointAddress
1885 					 & USB_ENDPOINT_DIR_MASK;
1886 			unsigned int pipe;
1887 
1888 			pipe = usb_sndbulkpipe(stream->dev->udev, epnum) | dir;
1889 			usb_clear_halt(stream->dev->udev, pipe);
1890 		}
1891 
1892 		uvc_queue_enable(&stream->queue, 0);
1893 		uvc_video_clock_cleanup(stream);
1894 		return 0;
1895 	}
1896 
1897 	ret = uvc_video_clock_init(stream);
1898 	if (ret < 0)
1899 		return ret;
1900 
1901 	ret = uvc_queue_enable(&stream->queue, 1);
1902 	if (ret < 0)
1903 		goto error_queue;
1904 
1905 	/* Commit the streaming parameters. */
1906 	ret = uvc_commit_video(stream, &stream->ctrl);
1907 	if (ret < 0)
1908 		goto error_commit;
1909 
1910 	ret = uvc_init_video(stream, GFP_KERNEL);
1911 	if (ret < 0)
1912 		goto error_video;
1913 
1914 	return 0;
1915 
1916 error_video:
1917 	usb_set_interface(stream->dev->udev, stream->intfnum, 0);
1918 error_commit:
1919 	uvc_queue_enable(&stream->queue, 0);
1920 error_queue:
1921 	uvc_video_clock_cleanup(stream);
1922 
1923 	return ret;
1924 }
1925