Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
/*
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 */

/* USX2Y "rawusb" aka hwdep_pcm implementation

 Its usb's unableness to atomically handle power of 2 period sized data chuncs
 at standard samplerates,
 what led to this part of the usx2y module: 
 It provides the alsa kernel half of the usx2y-alsa-jack driver pair.
 The pair uses a hardware dependent alsa-device for mmaped pcm transport.
 Advantage achieved:
         The usb_hc moves pcm data from/into memory via DMA.
         That memory is mmaped by jack's usx2y driver.
         Jack's usx2y driver is the first/last to read/write pcm data.
         Read/write is a combination of power of 2 period shaping and
         float/int conversation.
         Compared to mainline alsa/jack we leave out power of 2 period shaping inside
         snd-usb-usx2y which needs memcpy() and additional buffers.
         As a side effect possible unwanted pcm-data coruption resulting of
         standard alsa's snd-usb-usx2y period shaping scheme falls away.
         Result is sane jack operation at buffering schemes down to 128frames,
         2 periods.
         plain usx2y alsa mode is able to achieve 64frames, 4periods, but only at the
         cost of easier triggered i.e. aeolus xruns (128 or 256frames,
         2periods works but is useless cause of crackling).

 This is a first "proof of concept" implementation.
 Later, functionalities should migrate to more appropriate places:
 Userland:
 - The jackd could mmap its float-pcm buffers directly from alsa-lib.
 - alsa-lib could provide power of 2 period sized shaping combined with int/float
   conversation.
   Currently the usx2y jack driver provides above 2 services.
 Kernel:
 - rawusb dma pcm buffer transport should go to snd-usb-lib, so also snd-usb-audio
   devices can use it.
   Currently rawusb dma pcm buffer transport (this file) is only available to snd-usb-usx2y. 
*/

#include <linux/delay.h>
#include <linux/gfp.h>
#include "usbusx2yaudio.c"

#if defined(USX2Y_NRPACKS_VARIABLE) || USX2Y_NRPACKS == 1

#include <sound/hwdep.h>


static int usX2Y_usbpcm_urb_capt_retire(struct snd_usX2Y_substream *subs)
{
	struct urb	*urb = subs->completed_urb;
	struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
	int 		i, lens = 0, hwptr_done = subs->hwptr_done;
	struct usX2Ydev	*usX2Y = subs->usX2Y;
	if (0 > usX2Y->hwdep_pcm_shm->capture_iso_start) { //FIXME
		int head = usX2Y->hwdep_pcm_shm->captured_iso_head + 1;
		if (head >= ARRAY_SIZE(usX2Y->hwdep_pcm_shm->captured_iso))
			head = 0;
		usX2Y->hwdep_pcm_shm->capture_iso_start = head;
		snd_printdd("cap start %i\n", head);
	}
	for (i = 0; i < nr_of_packs(); i++) {
		if (urb->iso_frame_desc[i].status) { /* active? hmm, skip this */
			snd_printk(KERN_ERR "active frame status %i. Most probably some hardware problem.\n", urb->iso_frame_desc[i].status);
			return urb->iso_frame_desc[i].status;
		}
		lens += urb->iso_frame_desc[i].actual_length / usX2Y->stride;
	}
	if ((hwptr_done += lens) >= runtime->buffer_size)
		hwptr_done -= runtime->buffer_size;
	subs->hwptr_done = hwptr_done;
	subs->transfer_done += lens;
	/* update the pointer, call callback if necessary */
	if (subs->transfer_done >= runtime->period_size) {
		subs->transfer_done -= runtime->period_size;
		snd_pcm_period_elapsed(subs->pcm_substream);
	}
	return 0;
}

static inline int usX2Y_iso_frames_per_buffer(struct snd_pcm_runtime *runtime,
					      struct usX2Ydev * usX2Y)
{
	return (runtime->buffer_size * 1000) / usX2Y->rate + 1;	//FIXME: so far only correct period_size == 2^x ?
}

/*
 * prepare urb for playback data pipe
 *
 * we copy the data directly from the pcm buffer.
 * the current position to be copied is held in hwptr field.
 * since a urb can handle only a single linear buffer, if the total
 * transferred area overflows the buffer boundary, we cannot send
 * it directly from the buffer.  thus the data is once copied to
 * a temporary buffer and urb points to that.
 */
static int usX2Y_hwdep_urb_play_prepare(struct snd_usX2Y_substream *subs,
					struct urb *urb)
{
	int count, counts, pack;
	struct usX2Ydev *usX2Y = subs->usX2Y;
	struct snd_usX2Y_hwdep_pcm_shm *shm = usX2Y->hwdep_pcm_shm;
	struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;

	if (0 > shm->playback_iso_start) {
		shm->playback_iso_start = shm->captured_iso_head -
			usX2Y_iso_frames_per_buffer(runtime, usX2Y);
		if (0 > shm->playback_iso_start)
			shm->playback_iso_start += ARRAY_SIZE(shm->captured_iso);
		shm->playback_iso_head = shm->playback_iso_start;
	}

	count = 0;
	for (pack = 0; pack < nr_of_packs(); pack++) {
		/* calculate the size of a packet */
		counts = shm->captured_iso[shm->playback_iso_head].length / usX2Y->stride;
		if (counts < 43 || counts > 50) {
			snd_printk(KERN_ERR "should not be here with counts=%i\n", counts);
			return -EPIPE;
		}
		/* set up descriptor */
		urb->iso_frame_desc[pack].offset = shm->captured_iso[shm->playback_iso_head].offset;
		urb->iso_frame_desc[pack].length = shm->captured_iso[shm->playback_iso_head].length;
		if (atomic_read(&subs->state) != state_RUNNING)
			memset((char *)urb->transfer_buffer + urb->iso_frame_desc[pack].offset, 0,
			       urb->iso_frame_desc[pack].length);
		if (++shm->playback_iso_head >= ARRAY_SIZE(shm->captured_iso))
			shm->playback_iso_head = 0;
		count += counts;
	}
	urb->transfer_buffer_length = count * usX2Y->stride;
	return 0;
}


static inline void usX2Y_usbpcm_urb_capt_iso_advance(struct snd_usX2Y_substream *subs,
						     struct urb *urb)
{
	int pack;
	for (pack = 0; pack < nr_of_packs(); ++pack) {
		struct usb_iso_packet_descriptor *desc = urb->iso_frame_desc + pack;
		if (NULL != subs) {
			struct snd_usX2Y_hwdep_pcm_shm *shm = subs->usX2Y->hwdep_pcm_shm;
			int head = shm->captured_iso_head + 1;
			if (head >= ARRAY_SIZE(shm->captured_iso))
				head = 0;
			shm->captured_iso[head].frame = urb->start_frame + pack;
			shm->captured_iso[head].offset = desc->offset;
			shm->captured_iso[head].length = desc->actual_length;
			shm->captured_iso_head = head;
			shm->captured_iso_frames++;
		}
		if ((desc->offset += desc->length * NRURBS*nr_of_packs()) +
		    desc->length >= SSS)
			desc->offset -= (SSS - desc->length);
	}
}

static inline int usX2Y_usbpcm_usbframe_complete(struct snd_usX2Y_substream *capsubs,
						 struct snd_usX2Y_substream *capsubs2,
						 struct snd_usX2Y_substream *playbacksubs,
						 int frame)
{
	int err, state;
	struct urb *urb = playbacksubs->completed_urb;

	state = atomic_read(&playbacksubs->state);
	if (NULL != urb) {
		if (state == state_RUNNING)
			usX2Y_urb_play_retire(playbacksubs, urb);
		else if (state >= state_PRERUNNING)
			atomic_inc(&playbacksubs->state);
	} else {
		switch (state) {
		case state_STARTING1:
			urb = playbacksubs->urb[0];
			atomic_inc(&playbacksubs->state);
			break;
		case state_STARTING2:
			urb = playbacksubs->urb[1];
			atomic_inc(&playbacksubs->state);
			break;
		}
	}
	if (urb) {
		if ((err = usX2Y_hwdep_urb_play_prepare(playbacksubs, urb)) ||
		    (err = usX2Y_urb_submit(playbacksubs, urb, frame))) {
			return err;
		}
	}
	
	playbacksubs->completed_urb = NULL;

	state = atomic_read(&capsubs->state);
	if (state >= state_PREPARED) {
		if (state == state_RUNNING) {
			if ((err = usX2Y_usbpcm_urb_capt_retire(capsubs)))
				return err;
		} else if (state >= state_PRERUNNING)
			atomic_inc(&capsubs->state);
		usX2Y_usbpcm_urb_capt_iso_advance(capsubs, capsubs->completed_urb);
		if (NULL != capsubs2)
			usX2Y_usbpcm_urb_capt_iso_advance(NULL, capsubs2->completed_urb);
		if ((err = usX2Y_urb_submit(capsubs, capsubs->completed_urb, frame)))
			return err;
		if (NULL != capsubs2)
			if ((err = usX2Y_urb_submit(capsubs2, capsubs2->completed_urb, frame)))
				return err;
	}
	capsubs->completed_urb = NULL;
	if (NULL != capsubs2)
		capsubs2->completed_urb = NULL;
	return 0;
}


static void i_usX2Y_usbpcm_urb_complete(struct urb *urb)
{
	struct snd_usX2Y_substream *subs = urb->context;
	struct usX2Ydev *usX2Y = subs->usX2Y;
	struct snd_usX2Y_substream *capsubs, *capsubs2, *playbacksubs;

	if (unlikely(atomic_read(&subs->state) < state_PREPARED)) {
		snd_printdd("hcd_frame=%i ep=%i%s status=%i start_frame=%i\n",
			    usb_get_current_frame_number(usX2Y->dev),
			    subs->endpoint, usb_pipein(urb->pipe) ? "in" : "out",
			    urb->status, urb->start_frame);
		return;
	}
	if (unlikely(urb->status)) {
		usX2Y_error_urb_status(usX2Y, subs, urb);
		return;
	}
	if (likely((urb->start_frame & 0xFFFF) == (usX2Y->wait_iso_frame & 0xFFFF)))
		subs->completed_urb = urb;
	else {
		usX2Y_error_sequence(usX2Y, subs, urb);
		return;
	}

	capsubs = usX2Y->subs[SNDRV_PCM_STREAM_CAPTURE];
	capsubs2 = usX2Y->subs[SNDRV_PCM_STREAM_CAPTURE + 2];
	playbacksubs = usX2Y->subs[SNDRV_PCM_STREAM_PLAYBACK];
	if (capsubs->completed_urb && atomic_read(&capsubs->state) >= state_PREPARED &&
	    (NULL == capsubs2 || capsubs2->completed_urb) &&
	    (playbacksubs->completed_urb || atomic_read(&playbacksubs->state) < state_PREPARED)) {
		if (!usX2Y_usbpcm_usbframe_complete(capsubs, capsubs2, playbacksubs, urb->start_frame))
			usX2Y->wait_iso_frame += nr_of_packs();
		else {
			snd_printdd("\n");
			usX2Y_clients_stop(usX2Y);
		}
	}
}


static void usX2Y_hwdep_urb_release(struct urb **urb)
{
	usb_kill_urb(*urb);
	usb_free_urb(*urb);
	*urb = NULL;
}

/*
 * release a substream
 */
static void usX2Y_usbpcm_urbs_release(struct snd_usX2Y_substream *subs)
{
	int i;
	snd_printdd("snd_usX2Y_urbs_release() %i\n", subs->endpoint);
	for (i = 0; i < NRURBS; i++)
		usX2Y_hwdep_urb_release(subs->urb + i);
}

static void usX2Y_usbpcm_subs_startup_finish(struct usX2Ydev * usX2Y)
{
	usX2Y_urbs_set_complete(usX2Y, i_usX2Y_usbpcm_urb_complete);
	usX2Y->prepare_subs = NULL;
}

static void i_usX2Y_usbpcm_subs_startup(struct urb *urb)
{
	struct snd_usX2Y_substream *subs = urb->context;
	struct usX2Ydev *usX2Y = subs->usX2Y;
	struct snd_usX2Y_substream *prepare_subs = usX2Y->prepare_subs;
	if (NULL != prepare_subs &&
	    urb->start_frame == prepare_subs->urb[0]->start_frame) {
		atomic_inc(&prepare_subs->state);
		if (prepare_subs == usX2Y->subs[SNDRV_PCM_STREAM_CAPTURE]) {
			struct snd_usX2Y_substream *cap_subs2 = usX2Y->subs[SNDRV_PCM_STREAM_CAPTURE + 2];
			if (cap_subs2 != NULL)
				atomic_inc(&cap_subs2->state);
		}
		usX2Y_usbpcm_subs_startup_finish(usX2Y);
		wake_up(&usX2Y->prepare_wait_queue);
	}

	i_usX2Y_usbpcm_urb_complete(urb);
}

/*
 * initialize a substream's urbs
 */
static int usX2Y_usbpcm_urbs_allocate(struct snd_usX2Y_substream *subs)
{
	int i;
	unsigned int pipe;
	int is_playback = subs == subs->usX2Y->subs[SNDRV_PCM_STREAM_PLAYBACK];
	struct usb_device *dev = subs->usX2Y->dev;

	pipe = is_playback ? usb_sndisocpipe(dev, subs->endpoint) :
			usb_rcvisocpipe(dev, subs->endpoint);
	subs->maxpacksize = usb_maxpacket(dev, pipe, is_playback);
	if (!subs->maxpacksize)
		return -EINVAL;

	/* allocate and initialize data urbs */
	for (i = 0; i < NRURBS; i++) {
		struct urb **purb = subs->urb + i;
		if (*purb) {
			usb_kill_urb(*purb);
			continue;
		}
		*purb = usb_alloc_urb(nr_of_packs(), GFP_KERNEL);
		if (NULL == *purb) {
			usX2Y_usbpcm_urbs_release(subs);
			return -ENOMEM;
		}
		(*purb)->transfer_buffer = is_playback ?
			subs->usX2Y->hwdep_pcm_shm->playback : (
				subs->endpoint == 0x8 ?
				subs->usX2Y->hwdep_pcm_shm->capture0x8 :
				subs->usX2Y->hwdep_pcm_shm->capture0xA);

		(*purb)->dev = dev;
		(*purb)->pipe = pipe;
		(*purb)->number_of_packets = nr_of_packs();
		(*purb)->context = subs;
		(*purb)->interval = 1;
		(*purb)->complete = i_usX2Y_usbpcm_subs_startup;
	}
	return 0;
}

/*
 * free the buffer
 */
static int snd_usX2Y_usbpcm_hw_free(struct snd_pcm_substream *substream)
{
	struct snd_pcm_runtime *runtime = substream->runtime;
	struct snd_usX2Y_substream *subs = runtime->private_data,
		*cap_subs2 = subs->usX2Y->subs[SNDRV_PCM_STREAM_CAPTURE + 2];
	mutex_lock(&subs->usX2Y->prepare_mutex);
	snd_printdd("snd_usX2Y_usbpcm_hw_free(%p)\n", substream);

	if (SNDRV_PCM_STREAM_PLAYBACK == substream->stream) {
		struct snd_usX2Y_substream *cap_subs = subs->usX2Y->subs[SNDRV_PCM_STREAM_CAPTURE];
		atomic_set(&subs->state, state_STOPPED);
		usX2Y_usbpcm_urbs_release(subs);
		if (!cap_subs->pcm_substream ||
		    !cap_subs->pcm_substream->runtime ||
		    !cap_subs->pcm_substream->runtime->status ||
		    cap_subs->pcm_substream->runtime->status->state < SNDRV_PCM_STATE_PREPARED) {
			atomic_set(&cap_subs->state, state_STOPPED);
			if (NULL != cap_subs2)
				atomic_set(&cap_subs2->state, state_STOPPED);
			usX2Y_usbpcm_urbs_release(cap_subs);
			if (NULL != cap_subs2)
				usX2Y_usbpcm_urbs_release(cap_subs2);
		}
	} else {
		struct snd_usX2Y_substream *playback_subs = subs->usX2Y->subs[SNDRV_PCM_STREAM_PLAYBACK];
		if (atomic_read(&playback_subs->state) < state_PREPARED) {
			atomic_set(&subs->state, state_STOPPED);
			if (NULL != cap_subs2)
				atomic_set(&cap_subs2->state, state_STOPPED);
			usX2Y_usbpcm_urbs_release(subs);
			if (NULL != cap_subs2)
				usX2Y_usbpcm_urbs_release(cap_subs2);
		}
	}
	mutex_unlock(&subs->usX2Y->prepare_mutex);
	return snd_pcm_lib_free_pages(substream);
}

static void usX2Y_usbpcm_subs_startup(struct snd_usX2Y_substream *subs)
{
	struct usX2Ydev * usX2Y = subs->usX2Y;
	usX2Y->prepare_subs = subs;
	subs->urb[0]->start_frame = -1;
	smp_wmb();	// Make sure above modifications are seen by i_usX2Y_subs_startup()
	usX2Y_urbs_set_complete(usX2Y, i_usX2Y_usbpcm_subs_startup);
}

static int usX2Y_usbpcm_urbs_start(struct snd_usX2Y_substream *subs)
{
	int	p, u, err,
		stream = subs->pcm_substream->stream;
	struct usX2Ydev *usX2Y = subs->usX2Y;

	if (SNDRV_PCM_STREAM_CAPTURE == stream) {
		usX2Y->hwdep_pcm_shm->captured_iso_head = -1;
		usX2Y->hwdep_pcm_shm->captured_iso_frames = 0;
	}

	for (p = 0; 3 >= (stream + p); p += 2) {
		struct snd_usX2Y_substream *subs = usX2Y->subs[stream + p];
		if (subs != NULL) {
			if ((err = usX2Y_usbpcm_urbs_allocate(subs)) < 0)
				return err;
			subs->completed_urb = NULL;
		}
	}

	for (p = 0; p < 4; p++) {
		struct snd_usX2Y_substream *subs = usX2Y->subs[p];
		if (subs != NULL && atomic_read(&subs->state) >= state_PREPARED)
			goto start;
	}

 start:
	usX2Y_usbpcm_subs_startup(subs);
	for (u = 0; u < NRURBS; u++) {
		for (p = 0; 3 >= (stream + p); p += 2) {
			struct snd_usX2Y_substream *subs = usX2Y->subs[stream + p];
			if (subs != NULL) {
				struct urb *urb = subs->urb[u];
				if (usb_pipein(urb->pipe)) {
					unsigned long pack;
					if (0 == u)
						atomic_set(&subs->state, state_STARTING3);
					urb->dev = usX2Y->dev;
					urb->transfer_flags = URB_ISO_ASAP;
					for (pack = 0; pack < nr_of_packs(); pack++) {
						urb->iso_frame_desc[pack].offset = subs->maxpacksize * (pack + u * nr_of_packs());
						urb->iso_frame_desc[pack].length = subs->maxpacksize;
					}
					urb->transfer_buffer_length = subs->maxpacksize * nr_of_packs(); 
					if ((err = usb_submit_urb(urb, GFP_KERNEL)) < 0) {
						snd_printk (KERN_ERR "cannot usb_submit_urb() for urb %d, err = %d\n", u, err);
						err = -EPIPE;
						goto cleanup;
					}  else {
						snd_printdd("%i\n", urb->start_frame);
						if (u == 0)
							usX2Y->wait_iso_frame = urb->start_frame;
					}
					urb->transfer_flags = 0;
				} else {
					atomic_set(&subs->state, state_STARTING1);
					break;
				}			
			}
		}
	}
	err = 0;
	wait_event(usX2Y->prepare_wait_queue, NULL == usX2Y->prepare_subs);
	if (atomic_read(&subs->state) != state_PREPARED)
		err = -EPIPE;
		
 cleanup:
	if (err) {
		usX2Y_subs_startup_finish(usX2Y);	// Call it now
		usX2Y_clients_stop(usX2Y);		// something is completely wroong > stop evrything			
	}
	return err;
}

/*
 * prepare callback
 *
 * set format and initialize urbs
 */
static int snd_usX2Y_usbpcm_prepare(struct snd_pcm_substream *substream)
{
	struct snd_pcm_runtime *runtime = substream->runtime;
	struct snd_usX2Y_substream *subs = runtime->private_data;
	struct usX2Ydev *usX2Y = subs->usX2Y;
	struct snd_usX2Y_substream *capsubs = subs->usX2Y->subs[SNDRV_PCM_STREAM_CAPTURE];
	int err = 0;
	snd_printdd("snd_usX2Y_pcm_prepare(%p)\n", substream);

	if (NULL == usX2Y->hwdep_pcm_shm) {
		if (NULL == (usX2Y->hwdep_pcm_shm = snd_malloc_pages(sizeof(struct snd_usX2Y_hwdep_pcm_shm), GFP_KERNEL)))
			return -ENOMEM;
		memset(usX2Y->hwdep_pcm_shm, 0, sizeof(struct snd_usX2Y_hwdep_pcm_shm));
	}

	mutex_lock(&usX2Y->prepare_mutex);
	usX2Y_subs_prepare(subs);
// Start hardware streams
// SyncStream first....
	if (atomic_read(&capsubs->state) < state_PREPARED) {
		if (usX2Y->format != runtime->format)
			if ((err = usX2Y_format_set(usX2Y, runtime->format)) < 0)
				goto up_prepare_mutex;
		if (usX2Y->rate != runtime->rate)
			if ((err = usX2Y_rate_set(usX2Y, runtime->rate)) < 0)
				goto up_prepare_mutex;
		snd_printdd("starting capture pipe for %s\n", subs == capsubs ?
			    "self" : "playpipe");
		if (0 > (err = usX2Y_usbpcm_urbs_start(capsubs)))
			goto up_prepare_mutex;
	}

	if (subs != capsubs) {
		usX2Y->hwdep_pcm_shm->playback_iso_start = -1;
		if (atomic_read(&subs->state) < state_PREPARED) {
			while (usX2Y_iso_frames_per_buffer(runtime, usX2Y) >
			       usX2Y->hwdep_pcm_shm->captured_iso_frames) {
				snd_printdd("Wait: iso_frames_per_buffer=%i,"
					    "captured_iso_frames=%i\n",
					    usX2Y_iso_frames_per_buffer(runtime, usX2Y),
					    usX2Y->hwdep_pcm_shm->captured_iso_frames);
				if (msleep_interruptible(10)) {
					err = -ERESTARTSYS;
					goto up_prepare_mutex;
				}
			} 
			if (0 > (err = usX2Y_usbpcm_urbs_start(subs)))
				goto up_prepare_mutex;
		}
		snd_printdd("Ready: iso_frames_per_buffer=%i,captured_iso_frames=%i\n",
			    usX2Y_iso_frames_per_buffer(runtime, usX2Y),
			    usX2Y->hwdep_pcm_shm->captured_iso_frames);
	} else
		usX2Y->hwdep_pcm_shm->capture_iso_start = -1;

 up_prepare_mutex:
	mutex_unlock(&usX2Y->prepare_mutex);
	return err;
}

static struct snd_pcm_hardware snd_usX2Y_4c =
{
	.info =			(SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_INTERLEAVED |
				 SNDRV_PCM_INFO_BLOCK_TRANSFER |
				 SNDRV_PCM_INFO_MMAP_VALID),
	.formats =                 SNDRV_PCM_FMTBIT_S16_LE | SNDRV_PCM_FMTBIT_S24_3LE,
	.rates =                   SNDRV_PCM_RATE_44100 | SNDRV_PCM_RATE_48000,
	.rate_min =                44100,
	.rate_max =                48000,
	.channels_min =            2,
	.channels_max =            4,
	.buffer_bytes_max =	(2*128*1024),
	.period_bytes_min =	64,
	.period_bytes_max =	(128*1024),
	.periods_min =		2,
	.periods_max =		1024,
	.fifo_size =              0
};



static int snd_usX2Y_usbpcm_open(struct snd_pcm_substream *substream)
{
	struct snd_usX2Y_substream	*subs = ((struct snd_usX2Y_substream **)
					 snd_pcm_substream_chip(substream))[substream->stream];
	struct snd_pcm_runtime	*runtime = substream->runtime;

	if (!(subs->usX2Y->chip_status & USX2Y_STAT_CHIP_MMAP_PCM_URBS))
		return -EBUSY;

	runtime->hw = SNDRV_PCM_STREAM_PLAYBACK == substream->stream ? snd_usX2Y_2c :
		(subs->usX2Y->subs[3] ? snd_usX2Y_4c : snd_usX2Y_2c);
	runtime->private_data = subs;
	subs->pcm_substream = substream;
	snd_pcm_hw_constraint_minmax(runtime, SNDRV_PCM_HW_PARAM_PERIOD_TIME, 1000, 200000);
	return 0;
}


static int snd_usX2Y_usbpcm_close(struct snd_pcm_substream *substream)
{
	struct snd_pcm_runtime *runtime = substream->runtime;
	struct snd_usX2Y_substream *subs = runtime->private_data;

	subs->pcm_substream = NULL;
	return 0;
}


static struct snd_pcm_ops snd_usX2Y_usbpcm_ops = 
{
	.open =		snd_usX2Y_usbpcm_open,
	.close =	snd_usX2Y_usbpcm_close,
	.ioctl =	snd_pcm_lib_ioctl,
	.hw_params =	snd_usX2Y_pcm_hw_params,
	.hw_free =	snd_usX2Y_usbpcm_hw_free,
	.prepare =	snd_usX2Y_usbpcm_prepare,
	.trigger =	snd_usX2Y_pcm_trigger,
	.pointer =	snd_usX2Y_pcm_pointer,
};


static int usX2Y_pcms_lock_check(struct snd_card *card)
{
	struct list_head *list;
	struct snd_device *dev;
	struct snd_pcm *pcm;
	int err = 0;
	list_for_each(list, &card->devices) {
		dev = snd_device(list);
		if (dev->type != SNDRV_DEV_PCM)
			continue;
		pcm = dev->device_data;
		mutex_lock(&pcm->open_mutex);
	}
	list_for_each(list, &card->devices) {
		int s;
		dev = snd_device(list);
		if (dev->type != SNDRV_DEV_PCM)
			continue;
		pcm = dev->device_data;
		for (s = 0; s < 2; ++s) {
			struct snd_pcm_substream *substream;
			substream = pcm->streams[s].substream;
			if (substream && SUBSTREAM_BUSY(substream))
				err = -EBUSY;
		}
	}
	return err;
}


static void usX2Y_pcms_unlock(struct snd_card *card)
{
	struct list_head *list;
	struct snd_device *dev;
	struct snd_pcm *pcm;
	list_for_each(list, &card->devices) {
		dev = snd_device(list);
		if (dev->type != SNDRV_DEV_PCM)
			continue;
		pcm = dev->device_data;
		mutex_unlock(&pcm->open_mutex);
	}
}


static int snd_usX2Y_hwdep_pcm_open(struct snd_hwdep *hw, struct file *file)
{
	// we need to be the first 
	struct snd_card *card = hw->card;
	int err = usX2Y_pcms_lock_check(card);
	if (0 == err)
		usX2Y(card)->chip_status |= USX2Y_STAT_CHIP_MMAP_PCM_URBS;
	usX2Y_pcms_unlock(card);
	return err;
}


static int snd_usX2Y_hwdep_pcm_release(struct snd_hwdep *hw, struct file *file)
{
	struct snd_card *card = hw->card;
	int err = usX2Y_pcms_lock_check(card);
	if (0 == err)
		usX2Y(hw->card)->chip_status &= ~USX2Y_STAT_CHIP_MMAP_PCM_URBS;
	usX2Y_pcms_unlock(card);
	return err;
}


static void snd_usX2Y_hwdep_pcm_vm_open(struct vm_area_struct *area)
{
}


static void snd_usX2Y_hwdep_pcm_vm_close(struct vm_area_struct *area)
{
}


static int snd_usX2Y_hwdep_pcm_vm_fault(struct vm_area_struct *area,
					struct vm_fault *vmf)
{
	unsigned long offset;
	void *vaddr;

	offset = vmf->pgoff << PAGE_SHIFT;
	vaddr = (char*)((struct usX2Ydev *)area->vm_private_data)->hwdep_pcm_shm + offset;
	vmf->page = virt_to_page(vaddr);
	get_page(vmf->page);
	return 0;
}


static const struct vm_operations_struct snd_usX2Y_hwdep_pcm_vm_ops = {
	.open = snd_usX2Y_hwdep_pcm_vm_open,
	.close = snd_usX2Y_hwdep_pcm_vm_close,
	.fault = snd_usX2Y_hwdep_pcm_vm_fault,
};


static int snd_usX2Y_hwdep_pcm_mmap(struct snd_hwdep * hw, struct file *filp, struct vm_area_struct *area)
{
	unsigned long	size = (unsigned long)(area->vm_end - area->vm_start);
	struct usX2Ydev	*usX2Y = hw->private_data;

	if (!(usX2Y->chip_status & USX2Y_STAT_CHIP_INIT))
		return -EBUSY;

	/* if userspace tries to mmap beyond end of our buffer, fail */ 
	if (size > PAGE_ALIGN(sizeof(struct snd_usX2Y_hwdep_pcm_shm))) {
		snd_printd("%lu > %lu\n", size, (unsigned long)sizeof(struct snd_usX2Y_hwdep_pcm_shm)); 
		return -EINVAL;
	}

	if (!usX2Y->hwdep_pcm_shm) {
		return -ENODEV;
	}
	area->vm_ops = &snd_usX2Y_hwdep_pcm_vm_ops;
	area->vm_flags |= VM_RESERVED | VM_DONTEXPAND;
	area->vm_private_data = hw->private_data;
	return 0;
}


static void snd_usX2Y_hwdep_pcm_private_free(struct snd_hwdep *hwdep)
{
	struct usX2Ydev *usX2Y = hwdep->private_data;
	if (NULL != usX2Y->hwdep_pcm_shm)
		snd_free_pages(usX2Y->hwdep_pcm_shm, sizeof(struct snd_usX2Y_hwdep_pcm_shm));
}


int usX2Y_hwdep_pcm_new(struct snd_card *card)
{
	int err;
	struct snd_hwdep *hw;
	struct snd_pcm *pcm;
	struct usb_device *dev = usX2Y(card)->dev;
	if (1 != nr_of_packs())
		return 0;

	if ((err = snd_hwdep_new(card, SND_USX2Y_USBPCM_ID, 1, &hw)) < 0)
		return err;

	hw->iface = SNDRV_HWDEP_IFACE_USX2Y_PCM;
	hw->private_data = usX2Y(card);
	hw->private_free = snd_usX2Y_hwdep_pcm_private_free;
	hw->ops.open = snd_usX2Y_hwdep_pcm_open;
	hw->ops.release = snd_usX2Y_hwdep_pcm_release;
	hw->ops.mmap = snd_usX2Y_hwdep_pcm_mmap;
	hw->exclusive = 1;
	sprintf(hw->name, "/proc/bus/usb/%03d/%03d/hwdeppcm", dev->bus->busnum, dev->devnum);

	err = snd_pcm_new(card, NAME_ALLCAPS" hwdep Audio", 2, 1, 1, &pcm);
	if (err < 0) {
		return err;
	}
	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &snd_usX2Y_usbpcm_ops);
	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &snd_usX2Y_usbpcm_ops);

	pcm->private_data = usX2Y(card)->subs;
	pcm->info_flags = 0;

	sprintf(pcm->name, NAME_ALLCAPS" hwdep Audio");
	if (0 > (err = snd_pcm_lib_preallocate_pages(pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream,
						     SNDRV_DMA_TYPE_CONTINUOUS,
						     snd_dma_continuous_data(GFP_KERNEL),
						     64*1024, 128*1024)) ||
	    0 > (err = snd_pcm_lib_preallocate_pages(pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream,
	    					     SNDRV_DMA_TYPE_CONTINUOUS,
	    					     snd_dma_continuous_data(GFP_KERNEL),
						     64*1024, 128*1024))) {
		return err;
	}


	return 0;
}

#else

int usX2Y_hwdep_pcm_new(struct snd_card *card)
{
	return 0;
}

#endif