xref: /openbmc/linux/sound/usb/usx2y/usb_stream.c (revision 9a8f3203)
1 /*
2  * Copyright (C) 2007, 2008 Karsten Wiese <fzu@wemgehoertderstaat.de>
3  *
4  * This program is free software; you can redistribute it and/or modify it
5  * under the terms of the GNU General Public License as published by the
6  * Free Software Foundation; either version 2 of the License, or (at your
7  * option) any later version.
8  *
9  * This program is distributed in the hope that it will be useful, but
10  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
11  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12  * for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, write to the Free Software Foundation,
16  * Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
17  */
18 
19 #include <linux/usb.h>
20 #include <linux/gfp.h>
21 
22 #include "usb_stream.h"
23 
24 
25 /*                             setup                                  */
26 
27 static unsigned usb_stream_next_packet_size(struct usb_stream_kernel *sk)
28 {
29 	struct usb_stream *s = sk->s;
30 	sk->out_phase_peeked = (sk->out_phase & 0xffff) + sk->freqn;
31 	return (sk->out_phase_peeked >> 16) * s->cfg.frame_size;
32 }
33 
34 static void playback_prep_freqn(struct usb_stream_kernel *sk, struct urb *urb)
35 {
36 	struct usb_stream *s = sk->s;
37 	int pack, lb = 0;
38 
39 	for (pack = 0; pack < sk->n_o_ps; pack++) {
40 		int l = usb_stream_next_packet_size(sk);
41 		if (s->idle_outsize + lb + l > s->period_size)
42 			goto check;
43 
44 		sk->out_phase = sk->out_phase_peeked;
45 		urb->iso_frame_desc[pack].offset = lb;
46 		urb->iso_frame_desc[pack].length = l;
47 		lb += l;
48 	}
49 	snd_printdd(KERN_DEBUG "%i\n", lb);
50 
51 check:
52 	urb->number_of_packets = pack;
53 	urb->transfer_buffer_length = lb;
54 	s->idle_outsize += lb - s->period_size;
55 	snd_printdd(KERN_DEBUG "idle=%i ul=%i ps=%i\n", s->idle_outsize,
56 		    lb, s->period_size);
57 }
58 
59 static int init_pipe_urbs(struct usb_stream_kernel *sk, unsigned use_packsize,
60 			   struct urb **urbs, char *transfer,
61 			   struct usb_device *dev, int pipe)
62 {
63 	int u, p;
64 	int maxpacket = use_packsize ?
65 		use_packsize : usb_maxpacket(dev, pipe, usb_pipeout(pipe));
66 	int transfer_length = maxpacket * sk->n_o_ps;
67 
68 	for (u = 0; u < USB_STREAM_NURBS;
69 	     ++u, transfer += transfer_length) {
70 		struct urb *urb = urbs[u];
71 		struct usb_iso_packet_descriptor *desc;
72 		urb->transfer_buffer = transfer;
73 		urb->dev = dev;
74 		urb->pipe = pipe;
75 		urb->number_of_packets = sk->n_o_ps;
76 		urb->context = sk;
77 		urb->interval = 1;
78 		if (usb_pipeout(pipe))
79 			continue;
80 		if (usb_urb_ep_type_check(urb))
81 			return -EINVAL;
82 
83 		urb->transfer_buffer_length = transfer_length;
84 		desc = urb->iso_frame_desc;
85 		desc->offset = 0;
86 		desc->length = maxpacket;
87 		for (p = 1; p < sk->n_o_ps; ++p) {
88 			desc[p].offset = desc[p - 1].offset + maxpacket;
89 			desc[p].length = maxpacket;
90 		}
91 	}
92 
93 	return 0;
94 }
95 
96 static int init_urbs(struct usb_stream_kernel *sk, unsigned use_packsize,
97 		      struct usb_device *dev, int in_pipe, int out_pipe)
98 {
99 	struct usb_stream	*s = sk->s;
100 	char			*indata = (char *)s + sizeof(*s) +
101 					sizeof(struct usb_stream_packet) *
102 					s->inpackets;
103 	int			u;
104 
105 	for (u = 0; u < USB_STREAM_NURBS; ++u) {
106 		sk->inurb[u] = usb_alloc_urb(sk->n_o_ps, GFP_KERNEL);
107 		if (!sk->inurb[u])
108 			return -ENOMEM;
109 
110 		sk->outurb[u] = usb_alloc_urb(sk->n_o_ps, GFP_KERNEL);
111 		if (!sk->outurb[u])
112 			return -ENOMEM;
113 	}
114 
115 	if (init_pipe_urbs(sk, use_packsize, sk->inurb, indata, dev, in_pipe) ||
116 	    init_pipe_urbs(sk, use_packsize, sk->outurb, sk->write_page, dev,
117 			   out_pipe))
118 		return -EINVAL;
119 
120 	return 0;
121 }
122 
123 
124 /*
125  * convert a sampling rate into our full speed format (fs/1000 in Q16.16)
126  * this will overflow at approx 524 kHz
127  */
128 static inline unsigned get_usb_full_speed_rate(unsigned rate)
129 {
130 	return ((rate << 13) + 62) / 125;
131 }
132 
133 /*
134  * convert a sampling rate into USB high speed format (fs/8000 in Q16.16)
135  * this will overflow at approx 4 MHz
136  */
137 static inline unsigned get_usb_high_speed_rate(unsigned rate)
138 {
139 	return ((rate << 10) + 62) / 125;
140 }
141 
142 void usb_stream_free(struct usb_stream_kernel *sk)
143 {
144 	struct usb_stream *s;
145 	unsigned u;
146 
147 	for (u = 0; u < USB_STREAM_NURBS; ++u) {
148 		usb_free_urb(sk->inurb[u]);
149 		sk->inurb[u] = NULL;
150 		usb_free_urb(sk->outurb[u]);
151 		sk->outurb[u] = NULL;
152 	}
153 
154 	s = sk->s;
155 	if (!s)
156 		return;
157 
158 	free_pages((unsigned long)sk->write_page, get_order(s->write_size));
159 	sk->write_page = NULL;
160 	free_pages((unsigned long)s, get_order(s->read_size));
161 	sk->s = NULL;
162 }
163 
164 struct usb_stream *usb_stream_new(struct usb_stream_kernel *sk,
165 				  struct usb_device *dev,
166 				  unsigned in_endpoint, unsigned out_endpoint,
167 				  unsigned sample_rate, unsigned use_packsize,
168 				  unsigned period_frames, unsigned frame_size)
169 {
170 	int packets, max_packsize;
171 	int in_pipe, out_pipe;
172 	int read_size = sizeof(struct usb_stream);
173 	int write_size;
174 	int usb_frames = dev->speed == USB_SPEED_HIGH ? 8000 : 1000;
175 	int pg;
176 
177 	in_pipe = usb_rcvisocpipe(dev, in_endpoint);
178 	out_pipe = usb_sndisocpipe(dev, out_endpoint);
179 
180 	max_packsize = use_packsize ?
181 		use_packsize : usb_maxpacket(dev, in_pipe, 0);
182 
183 	/*
184 		t_period = period_frames / sample_rate
185 		iso_packs = t_period / t_iso_frame
186 			= (period_frames / sample_rate) * (1 / t_iso_frame)
187 	*/
188 
189 	packets = period_frames * usb_frames / sample_rate + 1;
190 
191 	if (dev->speed == USB_SPEED_HIGH)
192 		packets = (packets + 7) & ~7;
193 
194 	read_size += packets * USB_STREAM_URBDEPTH *
195 		(max_packsize + sizeof(struct usb_stream_packet));
196 
197 	max_packsize = usb_maxpacket(dev, out_pipe, 1);
198 	write_size = max_packsize * packets * USB_STREAM_URBDEPTH;
199 
200 	if (read_size >= 256*PAGE_SIZE || write_size >= 256*PAGE_SIZE) {
201 		snd_printk(KERN_WARNING "a size exceeds 128*PAGE_SIZE\n");
202 		goto out;
203 	}
204 
205 	pg = get_order(read_size);
206 	sk->s = (void *) __get_free_pages(GFP_KERNEL|__GFP_COMP|__GFP_ZERO|
207 					  __GFP_NOWARN, pg);
208 	if (!sk->s) {
209 		snd_printk(KERN_WARNING "couldn't __get_free_pages()\n");
210 		goto out;
211 	}
212 	sk->s->cfg.version = USB_STREAM_INTERFACE_VERSION;
213 
214 	sk->s->read_size = read_size;
215 
216 	sk->s->cfg.sample_rate = sample_rate;
217 	sk->s->cfg.frame_size = frame_size;
218 	sk->n_o_ps = packets;
219 	sk->s->inpackets = packets * USB_STREAM_URBDEPTH;
220 	sk->s->cfg.period_frames = period_frames;
221 	sk->s->period_size = frame_size * period_frames;
222 
223 	sk->s->write_size = write_size;
224 	pg = get_order(write_size);
225 
226 	sk->write_page =
227 		(void *)__get_free_pages(GFP_KERNEL|__GFP_COMP|__GFP_ZERO|
228 					 __GFP_NOWARN, pg);
229 	if (!sk->write_page) {
230 		snd_printk(KERN_WARNING "couldn't __get_free_pages()\n");
231 		usb_stream_free(sk);
232 		return NULL;
233 	}
234 
235 	/* calculate the frequency in 16.16 format */
236 	if (dev->speed == USB_SPEED_FULL)
237 		sk->freqn = get_usb_full_speed_rate(sample_rate);
238 	else
239 		sk->freqn = get_usb_high_speed_rate(sample_rate);
240 
241 	if (init_urbs(sk, use_packsize, dev, in_pipe, out_pipe) < 0) {
242 		usb_stream_free(sk);
243 		return NULL;
244 	}
245 
246 	sk->s->state = usb_stream_stopped;
247 out:
248 	return sk->s;
249 }
250 
251 
252 /*                             start                                  */
253 
254 static bool balance_check(struct usb_stream_kernel *sk, struct urb *urb)
255 {
256 	bool r;
257 	if (unlikely(urb->status)) {
258 		if (urb->status != -ESHUTDOWN && urb->status != -ENOENT)
259 			snd_printk(KERN_WARNING "status=%i\n", urb->status);
260 		sk->iso_frame_balance = 0x7FFFFFFF;
261 		return false;
262 	}
263 	r = sk->iso_frame_balance == 0;
264 	if (!r)
265 		sk->i_urb = urb;
266 	return r;
267 }
268 
269 static bool balance_playback(struct usb_stream_kernel *sk, struct urb *urb)
270 {
271 	sk->iso_frame_balance += urb->number_of_packets;
272 	return balance_check(sk, urb);
273 }
274 
275 static bool balance_capture(struct usb_stream_kernel *sk, struct urb *urb)
276 {
277 	sk->iso_frame_balance -= urb->number_of_packets;
278 	return balance_check(sk, urb);
279 }
280 
281 static void subs_set_complete(struct urb **urbs, void (*complete)(struct urb *))
282 {
283 	int u;
284 
285 	for (u = 0; u < USB_STREAM_NURBS; u++) {
286 		struct urb *urb = urbs[u];
287 		urb->complete = complete;
288 	}
289 }
290 
291 static int usb_stream_prepare_playback(struct usb_stream_kernel *sk,
292 		struct urb *inurb)
293 {
294 	struct usb_stream *s = sk->s;
295 	struct urb *io;
296 	struct usb_iso_packet_descriptor *id, *od;
297 	int p = 0, lb = 0, l = 0;
298 
299 	io = sk->idle_outurb;
300 	od = io->iso_frame_desc;
301 
302 	for (; s->sync_packet < 0; ++p, ++s->sync_packet) {
303 		struct urb *ii = sk->completed_inurb;
304 		id = ii->iso_frame_desc +
305 			ii->number_of_packets + s->sync_packet;
306 		l = id->actual_length;
307 
308 		od[p].length = l;
309 		od[p].offset = lb;
310 		lb += l;
311 	}
312 
313 	for (;
314 	     s->sync_packet < inurb->number_of_packets && p < sk->n_o_ps;
315 	     ++p, ++s->sync_packet) {
316 		l = inurb->iso_frame_desc[s->sync_packet].actual_length;
317 
318 		if (s->idle_outsize + lb + l > s->period_size)
319 			goto check_ok;
320 
321 		od[p].length = l;
322 		od[p].offset = lb;
323 		lb += l;
324 	}
325 
326 check_ok:
327 	s->sync_packet -= inurb->number_of_packets;
328 	if (unlikely(s->sync_packet < -2 || s->sync_packet > 0)) {
329 		snd_printk(KERN_WARNING "invalid sync_packet = %i;"
330 			   " p=%i nop=%i %i %x %x %x > %x\n",
331 			   s->sync_packet, p, inurb->number_of_packets,
332 			   s->idle_outsize + lb + l,
333 			   s->idle_outsize, lb,  l,
334 			   s->period_size);
335 		return -1;
336 	}
337 	if (unlikely(lb % s->cfg.frame_size)) {
338 		snd_printk(KERN_WARNING"invalid outsize = %i\n",
339 			   lb);
340 		return -1;
341 	}
342 	s->idle_outsize += lb - s->period_size;
343 	io->number_of_packets = p;
344 	io->transfer_buffer_length = lb;
345 	if (s->idle_outsize <= 0)
346 		return 0;
347 
348 	snd_printk(KERN_WARNING "idle=%i\n", s->idle_outsize);
349 	return -1;
350 }
351 
352 static void prepare_inurb(int number_of_packets, struct urb *iu)
353 {
354 	struct usb_iso_packet_descriptor *id;
355 	int p;
356 
357 	iu->number_of_packets = number_of_packets;
358 	id = iu->iso_frame_desc;
359 	id->offset = 0;
360 	for (p = 0; p < iu->number_of_packets - 1; ++p)
361 		id[p + 1].offset = id[p].offset + id[p].length;
362 
363 	iu->transfer_buffer_length =
364 		id[0].length * iu->number_of_packets;
365 }
366 
367 static int submit_urbs(struct usb_stream_kernel *sk,
368 		       struct urb *inurb, struct urb *outurb)
369 {
370 	int err;
371 	prepare_inurb(sk->idle_outurb->number_of_packets, sk->idle_inurb);
372 	err = usb_submit_urb(sk->idle_inurb, GFP_ATOMIC);
373 	if (err < 0)
374 		goto report_failure;
375 
376 	sk->idle_inurb = sk->completed_inurb;
377 	sk->completed_inurb = inurb;
378 	err = usb_submit_urb(sk->idle_outurb, GFP_ATOMIC);
379 	if (err < 0)
380 		goto report_failure;
381 
382 	sk->idle_outurb = sk->completed_outurb;
383 	sk->completed_outurb = outurb;
384 	return 0;
385 
386 report_failure:
387 	snd_printk(KERN_ERR "%i\n", err);
388 	return err;
389 }
390 
391 #ifdef DEBUG_LOOP_BACK
392 /*
393   This loop_back() shows how to read/write the period data.
394  */
395 static void loop_back(struct usb_stream *s)
396 {
397 	char *i, *o;
398 	int il, ol, l, p;
399 	struct urb *iu;
400 	struct usb_iso_packet_descriptor *id;
401 
402 	o = s->playback1st_to;
403 	ol = s->playback1st_size;
404 	l = 0;
405 
406 	if (s->insplit_pack >= 0) {
407 		iu = sk->idle_inurb;
408 		id = iu->iso_frame_desc;
409 		p = s->insplit_pack;
410 	} else
411 		goto second;
412 loop:
413 	for (; p < iu->number_of_packets && l < s->period_size; ++p) {
414 		i = iu->transfer_buffer + id[p].offset;
415 		il = id[p].actual_length;
416 		if (l + il > s->period_size)
417 			il = s->period_size - l;
418 		if (il <= ol) {
419 			memcpy(o, i, il);
420 			o += il;
421 			ol -= il;
422 		} else {
423 			memcpy(o, i, ol);
424 			singen_6pack(o, ol);
425 			o = s->playback_to;
426 			memcpy(o, i + ol, il - ol);
427 			o += il - ol;
428 			ol = s->period_size - s->playback1st_size;
429 		}
430 		l += il;
431 	}
432 	if (iu == sk->completed_inurb) {
433 		if (l != s->period_size)
434 			printk(KERN_DEBUG"%s:%i %i\n", __func__, __LINE__,
435 			       l/(int)s->cfg.frame_size);
436 
437 		return;
438 	}
439 second:
440 	iu = sk->completed_inurb;
441 	id = iu->iso_frame_desc;
442 	p = 0;
443 	goto loop;
444 
445 }
446 #else
447 static void loop_back(struct usb_stream *s)
448 {
449 }
450 #endif
451 
452 static void stream_idle(struct usb_stream_kernel *sk,
453 			struct urb *inurb, struct urb *outurb)
454 {
455 	struct usb_stream *s = sk->s;
456 	int l, p;
457 	int insize = s->idle_insize;
458 	int urb_size = 0;
459 
460 	s->inpacket_split = s->next_inpacket_split;
461 	s->inpacket_split_at = s->next_inpacket_split_at;
462 	s->next_inpacket_split = -1;
463 	s->next_inpacket_split_at = 0;
464 
465 	for (p = 0; p < inurb->number_of_packets; ++p) {
466 		struct usb_iso_packet_descriptor *id = inurb->iso_frame_desc;
467 		l = id[p].actual_length;
468 		if (unlikely(l == 0 || id[p].status)) {
469 			snd_printk(KERN_WARNING "underrun, status=%u\n",
470 				   id[p].status);
471 			goto err_out;
472 		}
473 		s->inpacket_head++;
474 		s->inpacket_head %= s->inpackets;
475 		if (s->inpacket_split == -1)
476 			s->inpacket_split = s->inpacket_head;
477 
478 		s->inpacket[s->inpacket_head].offset =
479 			id[p].offset + (inurb->transfer_buffer - (void *)s);
480 		s->inpacket[s->inpacket_head].length = l;
481 		if (insize + l > s->period_size &&
482 		    s->next_inpacket_split == -1) {
483 			s->next_inpacket_split = s->inpacket_head;
484 			s->next_inpacket_split_at = s->period_size - insize;
485 		}
486 		insize += l;
487 		urb_size += l;
488 	}
489 	s->idle_insize += urb_size - s->period_size;
490 	if (s->idle_insize < 0) {
491 		snd_printk(KERN_WARNING "%i\n",
492 			   (s->idle_insize)/(int)s->cfg.frame_size);
493 		goto err_out;
494 	}
495 	s->insize_done += urb_size;
496 
497 	l = s->idle_outsize;
498 	s->outpacket[0].offset = (sk->idle_outurb->transfer_buffer -
499 				  sk->write_page) - l;
500 
501 	if (usb_stream_prepare_playback(sk, inurb) < 0)
502 		goto err_out;
503 
504 	s->outpacket[0].length = sk->idle_outurb->transfer_buffer_length + l;
505 	s->outpacket[1].offset = sk->completed_outurb->transfer_buffer -
506 		sk->write_page;
507 
508 	if (submit_urbs(sk, inurb, outurb) < 0)
509 		goto err_out;
510 
511 	loop_back(s);
512 	s->periods_done++;
513 	wake_up_all(&sk->sleep);
514 	return;
515 err_out:
516 	s->state = usb_stream_xrun;
517 	wake_up_all(&sk->sleep);
518 }
519 
520 static void i_capture_idle(struct urb *urb)
521 {
522 	struct usb_stream_kernel *sk = urb->context;
523 	if (balance_capture(sk, urb))
524 		stream_idle(sk, urb, sk->i_urb);
525 }
526 
527 static void i_playback_idle(struct urb *urb)
528 {
529 	struct usb_stream_kernel *sk = urb->context;
530 	if (balance_playback(sk, urb))
531 		stream_idle(sk, sk->i_urb, urb);
532 }
533 
534 static void stream_start(struct usb_stream_kernel *sk,
535 			 struct urb *inurb, struct urb *outurb)
536 {
537 	struct usb_stream *s = sk->s;
538 	if (s->state >= usb_stream_sync1) {
539 		int l, p, max_diff, max_diff_0;
540 		int urb_size = 0;
541 		unsigned frames_per_packet, min_frames = 0;
542 		frames_per_packet = (s->period_size - s->idle_insize);
543 		frames_per_packet <<= 8;
544 		frames_per_packet /=
545 			s->cfg.frame_size * inurb->number_of_packets;
546 		frames_per_packet++;
547 
548 		max_diff_0 = s->cfg.frame_size;
549 		if (s->cfg.period_frames >= 256)
550 			max_diff_0 <<= 1;
551 		if (s->cfg.period_frames >= 1024)
552 			max_diff_0 <<= 1;
553 		max_diff = max_diff_0;
554 		for (p = 0; p < inurb->number_of_packets; ++p) {
555 			int diff;
556 			l = inurb->iso_frame_desc[p].actual_length;
557 			urb_size += l;
558 
559 			min_frames += frames_per_packet;
560 			diff = urb_size -
561 				(min_frames >> 8) * s->cfg.frame_size;
562 			if (diff < max_diff) {
563 				snd_printdd(KERN_DEBUG "%i %i %i %i\n",
564 					    s->insize_done,
565 					    urb_size / (int)s->cfg.frame_size,
566 					    inurb->number_of_packets, diff);
567 				max_diff = diff;
568 			}
569 		}
570 		s->idle_insize -= max_diff - max_diff_0;
571 		s->idle_insize += urb_size - s->period_size;
572 		if (s->idle_insize < 0) {
573 			snd_printk(KERN_WARNING "%i %i %i\n",
574 				   s->idle_insize, urb_size, s->period_size);
575 			return;
576 		} else if (s->idle_insize == 0) {
577 			s->next_inpacket_split =
578 				(s->inpacket_head + 1) % s->inpackets;
579 			s->next_inpacket_split_at = 0;
580 		} else {
581 			unsigned split = s->inpacket_head;
582 			l = s->idle_insize;
583 			while (l > s->inpacket[split].length) {
584 				l -= s->inpacket[split].length;
585 				if (split == 0)
586 					split = s->inpackets - 1;
587 				else
588 					split--;
589 			}
590 			s->next_inpacket_split = split;
591 			s->next_inpacket_split_at =
592 				s->inpacket[split].length - l;
593 		}
594 
595 		s->insize_done += urb_size;
596 
597 		if (usb_stream_prepare_playback(sk, inurb) < 0)
598 			return;
599 
600 	} else
601 		playback_prep_freqn(sk, sk->idle_outurb);
602 
603 	if (submit_urbs(sk, inurb, outurb) < 0)
604 		return;
605 
606 	if (s->state == usb_stream_sync1 && s->insize_done > 360000) {
607 		/* just guesswork                            ^^^^^^ */
608 		s->state = usb_stream_ready;
609 		subs_set_complete(sk->inurb, i_capture_idle);
610 		subs_set_complete(sk->outurb, i_playback_idle);
611 	}
612 }
613 
614 static void i_capture_start(struct urb *urb)
615 {
616 	struct usb_iso_packet_descriptor *id = urb->iso_frame_desc;
617 	struct usb_stream_kernel *sk = urb->context;
618 	struct usb_stream *s = sk->s;
619 	int p;
620 	int empty = 0;
621 
622 	if (urb->status) {
623 		snd_printk(KERN_WARNING "status=%i\n", urb->status);
624 		return;
625 	}
626 
627 	for (p = 0; p < urb->number_of_packets; ++p) {
628 		int l = id[p].actual_length;
629 		if (l < s->cfg.frame_size) {
630 			++empty;
631 			if (s->state >= usb_stream_sync0) {
632 				snd_printk(KERN_WARNING "%i\n", l);
633 				return;
634 			}
635 		}
636 		s->inpacket_head++;
637 		s->inpacket_head %= s->inpackets;
638 		s->inpacket[s->inpacket_head].offset =
639 			id[p].offset + (urb->transfer_buffer - (void *)s);
640 		s->inpacket[s->inpacket_head].length = l;
641 	}
642 #ifdef SHOW_EMPTY
643 	if (empty) {
644 		printk(KERN_DEBUG"%s:%i: %i", __func__, __LINE__,
645 		       urb->iso_frame_desc[0].actual_length);
646 		for (pack = 1; pack < urb->number_of_packets; ++pack) {
647 			int l = urb->iso_frame_desc[pack].actual_length;
648 			printk(KERN_CONT " %i", l);
649 		}
650 		printk(KERN_CONT "\n");
651 	}
652 #endif
653 	if (!empty && s->state < usb_stream_sync1)
654 		++s->state;
655 
656 	if (balance_capture(sk, urb))
657 		stream_start(sk, urb, sk->i_urb);
658 }
659 
660 static void i_playback_start(struct urb *urb)
661 {
662 	struct usb_stream_kernel *sk = urb->context;
663 	if (balance_playback(sk, urb))
664 		stream_start(sk, sk->i_urb, urb);
665 }
666 
667 int usb_stream_start(struct usb_stream_kernel *sk)
668 {
669 	struct usb_stream *s = sk->s;
670 	int frame = 0, iters = 0;
671 	int u, err;
672 	int try = 0;
673 
674 	if (s->state != usb_stream_stopped)
675 		return -EAGAIN;
676 
677 	subs_set_complete(sk->inurb, i_capture_start);
678 	subs_set_complete(sk->outurb, i_playback_start);
679 	memset(sk->write_page, 0, s->write_size);
680 dotry:
681 	s->insize_done = 0;
682 	s->idle_insize = 0;
683 	s->idle_outsize = 0;
684 	s->sync_packet = -1;
685 	s->inpacket_head = -1;
686 	sk->iso_frame_balance = 0;
687 	++try;
688 	for (u = 0; u < 2; u++) {
689 		struct urb *inurb = sk->inurb[u];
690 		struct urb *outurb = sk->outurb[u];
691 		playback_prep_freqn(sk, outurb);
692 		inurb->number_of_packets = outurb->number_of_packets;
693 		inurb->transfer_buffer_length =
694 			inurb->number_of_packets *
695 			inurb->iso_frame_desc[0].length;
696 
697 		if (u == 0) {
698 			int now;
699 			struct usb_device *dev = inurb->dev;
700 			frame = usb_get_current_frame_number(dev);
701 			do {
702 				now = usb_get_current_frame_number(dev);
703 				++iters;
704 			} while (now > -1 && now == frame);
705 		}
706 		err = usb_submit_urb(inurb, GFP_ATOMIC);
707 		if (err < 0) {
708 			snd_printk(KERN_ERR"usb_submit_urb(sk->inurb[%i])"
709 				   " returned %i\n", u, err);
710 			return err;
711 		}
712 		err = usb_submit_urb(outurb, GFP_ATOMIC);
713 		if (err < 0) {
714 			snd_printk(KERN_ERR"usb_submit_urb(sk->outurb[%i])"
715 				   " returned %i\n", u, err);
716 			return err;
717 		}
718 
719 		if (inurb->start_frame != outurb->start_frame) {
720 			snd_printd(KERN_DEBUG
721 				   "u[%i] start_frames differ in:%u out:%u\n",
722 				   u, inurb->start_frame, outurb->start_frame);
723 			goto check_retry;
724 		}
725 	}
726 	snd_printdd(KERN_DEBUG "%i %i\n", frame, iters);
727 	try = 0;
728 check_retry:
729 	if (try) {
730 		usb_stream_stop(sk);
731 		if (try < 5) {
732 			msleep(1500);
733 			snd_printd(KERN_DEBUG "goto dotry;\n");
734 			goto dotry;
735 		}
736 		snd_printk(KERN_WARNING"couldn't start"
737 			   " all urbs on the same start_frame.\n");
738 		return -EFAULT;
739 	}
740 
741 	sk->idle_inurb = sk->inurb[USB_STREAM_NURBS - 2];
742 	sk->idle_outurb = sk->outurb[USB_STREAM_NURBS - 2];
743 	sk->completed_inurb = sk->inurb[USB_STREAM_NURBS - 1];
744 	sk->completed_outurb = sk->outurb[USB_STREAM_NURBS - 1];
745 
746 /* wait, check */
747 	{
748 		int wait_ms = 3000;
749 		while (s->state != usb_stream_ready && wait_ms > 0) {
750 			snd_printdd(KERN_DEBUG "%i\n", s->state);
751 			msleep(200);
752 			wait_ms -= 200;
753 		}
754 	}
755 
756 	return s->state == usb_stream_ready ? 0 : -EFAULT;
757 }
758 
759 
760 /*                             stop                                   */
761 
762 void usb_stream_stop(struct usb_stream_kernel *sk)
763 {
764 	int u;
765 	if (!sk->s)
766 		return;
767 	for (u = 0; u < USB_STREAM_NURBS; ++u) {
768 		usb_kill_urb(sk->inurb[u]);
769 		usb_kill_urb(sk->outurb[u]);
770 	}
771 	sk->s->state = usb_stream_stopped;
772 	msleep(400);
773 }
774