aboutsummaryrefslogtreecommitdiffstats
path: root/sound/usb/stream.c
blob: badd1d6d175dee658bc6fd3ddf72268523492910 (plain) (blame)
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
/*
 *   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
 */


#include <linux/init.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include <linux/usb/audio.h>
#include <linux/usb/audio-v2.h>

#include <sound/core.h>
#include <sound/pcm.h>
#include <sound/control.h>
#include <sound/tlv.h>

#include "usbaudio.h"
#include "card.h"
#include "proc.h"
#include "quirks.h"
#include "endpoint.h"
#include "pcm.h"
#include "helper.h"
#include "format.h"
#include "clock.h"
#include "stream.h"

/*
 * free a substream
 */
static void free_substream(struct snd_usb_substream *subs)
{
	struct audioformat *fp, *n;

	if (!subs->num_formats)
		return; /* not initialized */
	list_for_each_entry_safe(fp, n, &subs->fmt_list, list) {
		kfree(fp->rate_table);
		kfree(fp->chmap);
		kfree(fp);
	}
	kfree(subs->rate_list.list);
}


/*
 * free a usb stream instance
 */
static void snd_usb_audio_stream_free(struct snd_usb_stream *stream)
{
	free_substream(&stream->substream[0]);
	free_substream(&stream->substream[1]);
	list_del(&stream->list);
	kfree(stream);
}

static void snd_usb_audio_pcm_free(struct snd_pcm *pcm)
{
	struct snd_usb_stream *stream = pcm->private_data;
	if (stream) {
		stream->pcm = NULL;
		snd_usb_audio_stream_free(stream);
	}
}

/*
 * initialize the substream instance.
 */

static void snd_usb_init_substream(struct snd_usb_stream *as,
				   int stream,
				   struct audioformat *fp)
{
	struct snd_usb_substream *subs = &as->substream[stream];

	INIT_LIST_HEAD(&subs->fmt_list);
	spin_lock_init(&subs->lock);

	subs->stream = as;
	subs->direction = stream;
	subs->dev = as->chip->dev;
	subs->txfr_quirk = as->chip->txfr_quirk;
	subs->speed = snd_usb_get_speed(subs->dev);
	subs->pkt_offset_adj = 0;

	snd_usb_set_pcm_ops(as->pcm, stream);

	list_add_tail(&fp->list, &subs->fmt_list);
	subs->formats |= fp->formats;
	subs->num_formats++;
	subs->fmt_type = fp->fmt_type;
	subs->ep_num = fp->endpoint;
	if (fp->channels > subs->channels_max)
		subs->channels_max = fp->channels;
}

/* kctl callbacks for usb-audio channel maps */
static int usb_chmap_ctl_info(struct snd_kcontrol *kcontrol,
			      struct snd_ctl_elem_info *uinfo)
{
	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
	struct snd_usb_substream *subs = info->private_data;

	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
	uinfo->count = subs->channels_max;
	uinfo->value.integer.min = 0;
	uinfo->value.integer.max = SNDRV_CHMAP_LAST;
	return 0;
}

/* check whether a duplicated entry exists in the audiofmt list */
static bool have_dup_chmap(struct snd_usb_substream *subs,
			   struct audioformat *fp)
{
	struct list_head *p;

	for (p = fp->list.prev; p != &subs->fmt_list; p = p->prev) {
		struct audioformat *prev;
		prev = list_entry(p, struct audioformat, list);
		if (prev->chmap &&
		    !memcmp(prev->chmap, fp->chmap, sizeof(*fp->chmap)))
			return true;
	}
	return false;
}

static int usb_chmap_ctl_tlv(struct snd_kcontrol *kcontrol, int op_flag,
			     unsigned int size, unsigned int __user *tlv)
{
	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
	struct snd_usb_substream *subs = info->private_data;
	struct audioformat *fp;
	unsigned int __user *dst;
	int count = 0;

	if (size < 8)
		return -ENOMEM;
	if (put_user(SNDRV_CTL_TLVT_CONTAINER, tlv))
		return -EFAULT;
	size -= 8;
	dst = tlv + 2;
	list_for_each_entry(fp, &subs->fmt_list, list) {
		int i, ch_bytes;

		if (!fp->chmap)
			continue;
		if (have_dup_chmap(subs, fp))
			continue;
		/* copy the entry */
		ch_bytes = fp->chmap->channels * 4;
		if (size < 8 + ch_bytes)
			return -ENOMEM;
		if (put_user(SNDRV_CTL_TLVT_CHMAP_FIXED, dst) ||
		    put_user(ch_bytes, dst + 1))
			return -EFAULT;
		dst += 2;
		for (i = 0; i < fp->chmap->channels; i++, dst++) {
			if (put_user(fp->chmap->map[i], dst))
				return -EFAULT;
		}

		count += 8 + ch_bytes;
		size -= 8 + ch_bytes;
	}
	if (put_user(count, tlv + 1))
		return -EFAULT;
	return 0;
}

static int usb_chmap_ctl_get(struct snd_kcontrol *kcontrol,
			     struct snd_ctl_elem_value *ucontrol)
{
	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
	struct snd_usb_substream *subs = info->private_data;
	struct snd_pcm_chmap_elem *chmap = NULL;
	int i;

	memset(ucontrol->value.integer.value, 0,
	       sizeof(ucontrol->value.integer.value));
	if (subs->cur_audiofmt)
		chmap = subs->cur_audiofmt->chmap;
	if (chmap) {
		for (i = 0; i < chmap->channels; i++)
			ucontrol->value.integer.value[i] = chmap->map[i];
	}
	return 0;
}

/* create a chmap kctl assigned to the given USB substream */
static int add_chmap(struct snd_pcm *pcm, int stream,
		     struct snd_usb_substream *subs)
{
	struct audioformat *fp;
	struct snd_pcm_chmap *chmap;
	struct snd_kcontrol *kctl;
	int err;

	list_for_each_entry(fp, &subs->fmt_list, list)
		if (fp->chmap)
			goto ok;
	/* no chmap is found */
	return 0;

 ok:
	err = snd_pcm_add_chmap_ctls(pcm, stream, NULL, 0, 0, &chmap);
	if (err < 0)
		return err;

	/* override handlers */
	chmap->private_data = subs;
	kctl = chmap->kctl;
	kctl->info = usb_chmap_ctl_info;
	kctl->get = usb_chmap_ctl_get;
	kctl->tlv.c = usb_chmap_ctl_tlv;

	return 0;
}

/* convert from USB ChannelConfig bits to ALSA chmap element */
static struct snd_pcm_chmap_elem *convert_chmap(int channels, unsigned int bits,
						int protocol)
{
	static unsigned int uac1_maps[] = {
		SNDRV_CHMAP_FL,		/* left front */
		SNDRV_CHMAP_FR,		/* right front */
		SNDRV_CHMAP_FC,		/* center front */
		SNDRV_CHMAP_LFE,	/* LFE */
		SNDRV_CHMAP_SL,		/* left surround */
		SNDRV_CHMAP_SR,		/* right surround */
		SNDRV_CHMAP_FLC,	/* left of center */
		SNDRV_CHMAP_FRC,	/* right of center */
		SNDRV_CHMAP_RC,		/* surround */
		SNDRV_CHMAP_SL,		/* side left */
		SNDRV_CHMAP_SR,		/* side right */
		SNDRV_CHMAP_TC,		/* top */
		0 /* terminator */
	};
	static unsigned int uac2_maps[] = {
		SNDRV_CHMAP_FL,		/* front left */
		SNDRV_CHMAP_FR,		/* front right */
		SNDRV_CHMAP_FC,		/* front center */
		SNDRV_CHMAP_LFE,	/* LFE */
		SNDRV_CHMAP_RL,		/* back left */
		SNDRV_CHMAP_RR,		/* back right */
		SNDRV_CHMAP_FLC,	/* front left of center */
		SNDRV_CHMAP_FRC,	/* front right of center */
		SNDRV_CHMAP_RC,		/* back center */
		SNDRV_CHMAP_SL,		/* side left */
		SNDRV_CHMAP_SR,		/* side right */
		SNDRV_CHMAP_TC,		/* top center */
		SNDRV_CHMAP_TFL,	/* top front left */
		SNDRV_CHMAP_TFC,	/* top front center */
		SNDRV_CHMAP_TFR,	/* top front right */
		SNDRV_CHMAP_TRL,	/* top back left */
		SNDRV_CHMAP_TRC,	/* top back center */
		SNDRV_CHMAP_TRR,	/* top back right */
		SNDRV_CHMAP_TFLC,	/* top front left of center */
		SNDRV_CHMAP_TFRC,	/* top front right of center */
		SNDRV_CHMAP_LLFE,	/* left LFE */
		SNDRV_CHMAP_RLFE,	/* right LFE */
		SNDRV_CHMAP_TSL,	/* top side left */
		SNDRV_CHMAP_TSR,	/* top side right */
		SNDRV_CHMAP_BC,		/* bottom center */
		SNDRV_CHMAP_BLC,	/* bottom left center */
		SNDRV_CHMAP_BRC,	/* bottom right center */
		0 /* terminator */
	};
	struct snd_pcm_chmap_elem *chmap;
	const unsigned int *maps;
	int c;

	if (channels > ARRAY_SIZE(chmap->map))
		return NULL;

	chmap = kzalloc(sizeof(*chmap), GFP_KERNEL);
	if (!chmap)
		return NULL;

	maps = protocol == UAC_VERSION_2 ? uac2_maps : uac1_maps;
	chmap->channels = channels;
	c = 0;

	if (bits) {
		for (; bits && *maps; maps++, bits >>= 1)
			if (bits & 1)
				chmap->map[c++] = *maps;
	} else {
		/* If we're missing wChannelConfig, then guess something
		    to make sure the channel map is not skipped entirely */
		if (channels == 1)
			chmap->map[c++] = SNDRV_CHMAP_MONO;
		else
			for (; c < channels && *maps; maps++)
				chmap->map[c++] = *maps;
	}

	for (; c < channels; c++)
		chmap->map[c] = SNDRV_CHMAP_UNKNOWN;

	return chmap;
}

/*
 * add this endpoint to the chip instance.
 * if a stream with the same endpoint already exists, append to it.
 * if not, create a new pcm stream.
 */
int snd_usb_add_audio_stream(struct snd_usb_audio *chip,
			     int stream,
			     struct audioformat *fp)
{
	struct snd_usb_stream *as;
	struct snd_usb_substream *subs;
	struct snd_pcm *pcm;
	int err;

	list_for_each_entry(as, &chip->pcm_list, list) {
		if (as->fmt_type != fp->fmt_type)
			continue;
		subs = &as->substream[stream];
		if (subs->ep_num == fp->endpoint) {
			list_add_tail(&fp->list, &subs->fmt_list);
			subs->num_formats++;
			subs->formats |= fp->formats;
			return 0;
		}
	}
	/* look for an empty stream */
	list_for_each_entry(as, &chip->pcm_list, list) {
		if (as->fmt_type != fp->fmt_type)
			continue;
		subs = &as->substream[stream];
		if (subs->ep_num)
			continue;
		err = snd_pcm_new_stream(as->pcm, stream, 1);
		if (err < 0)
			return err;
		snd_usb_init_substream(as, stream, fp);
		return add_chmap(as->pcm, stream, subs);
	}

	/* create a new pcm */
	as = kzalloc(sizeof(*as), GFP_KERNEL);
	if (!as)
		return -ENOMEM;
	as->pcm_index = chip->pcm_devs;
	as->chip = chip;
	as->fmt_type = fp->fmt_type;
	err = snd_pcm_new(chip->card, "USB Audio", chip->pcm_devs,
			  stream == SNDRV_PCM_STREAM_PLAYBACK ? 1 : 0,
			  stream == SNDRV_PCM_STREAM_PLAYBACK ? 0 : 1,
			  &pcm);
	if (err < 0) {
		kfree(as);
		return err;
	}
	as->pcm = pcm;
	pcm->private_data = as;
	pcm->private_free = snd_usb_audio_pcm_free;
	pcm->info_flags = 0;
	if (chip->pcm_devs > 0)
		sprintf(pcm->name, "USB Audio #%d", chip->pcm_devs);
	else
		strcpy(pcm->name, "USB Audio");

	snd_usb_init_substream(as, stream, fp);

	list_add(&as->list, &chip->pcm_list);
	chip->pcm_devs++;

	snd_usb_proc_pcm_format_add(as);

	return add_chmap(pcm, stream, &as->substream[stream]);
}

static int parse_uac_endpoint_attributes(struct snd_usb_audio *chip,
					 struct usb_host_interface *alts,
					 int protocol, int iface_no)
{
	/* parsed with a v1 header here. that's ok as we only look at the
	 * header first which is the same for both versions */
	struct uac_iso_endpoint_descriptor *csep;
	struct usb_interface_descriptor *altsd = get_iface_desc(alts);
	int attributes = 0;

	csep = snd_usb_find_desc(alts->endpoint[0].extra, alts->endpoint[0].extralen, NULL, USB_DT_CS_ENDPOINT);

	/* Creamware Noah has this descriptor after the 2nd endpoint */
	if (!csep && altsd->bNumEndpoints >= 2)
		csep = snd_usb_find_desc(alts->endpoint[1].extra, alts->endpoint[1].extralen, NULL, USB_DT_CS_ENDPOINT);

	/*
	 * If we can't locate the USB_DT_CS_ENDPOINT descriptor in the extra
	 * bytes after the first endpoint, go search the entire interface.
	 * Some devices have it directly *before* the standard endpoint.
	 */
	if (!csep)
		csep = snd_usb_find_desc(alts->extra, alts->extralen, NULL, USB_DT_CS_ENDPOINT);

	if (!csep || csep->bLength < 7 ||
	    csep->bDescriptorSubtype != UAC_EP_GENERAL) {
		snd_printk(KERN_WARNING "%d:%u:%d : no or invalid"
			   " class specific endpoint descriptor\n",
			   chip->dev->devnum, iface_no,
			   altsd->bAlternateSetting);
		return 0;
	}

	if (protocol == UAC_VERSION_1) {
		attributes = csep->bmAttributes;
	} else {
		struct uac2_iso_endpoint_descriptor *csep2 =
			(struct uac2_iso_endpoint_descriptor *) csep;

		attributes = csep->bmAttributes & UAC_EP_CS_ATTR_FILL_MAX;

		/* emulate the endpoint attributes of a v1 device */
		if (csep2->bmControls & UAC2_CONTROL_PITCH)
			attributes |= UAC_EP_CS_ATTR_PITCH_CONTROL;
	}

	return attributes;
}

/* find an input terminal descriptor (either UAC1 or UAC2) with the given
 * terminal id
 */
static void *
snd_usb_find_input_terminal_descriptor(struct usb_host_interface *ctrl_iface,
					       int terminal_id)
{
	struct uac2_input_terminal_descriptor *term = NULL;

	while ((term = snd_usb_find_csint_desc(ctrl_iface->extra,
					       ctrl_iface->extralen,
					       term, UAC_INPUT_TERMINAL))) {
		if (term->bTerminalID == terminal_id)
			return term;
	}

	return NULL;
}

static struct uac2_output_terminal_descriptor *
	snd_usb_find_output_terminal_descriptor(struct usb_host_interface *ctrl_iface,
						int terminal_id)
{
	struct uac2_output_terminal_descriptor *term = NULL;

	while ((term = snd_usb_find_csint_desc(ctrl_iface->extra,
					       ctrl_iface->extralen,
					       term, UAC_OUTPUT_TERMINAL))) {
		if (term->bTerminalID == terminal_id)
			return term;
	}

	return NULL;
}

int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no)
{
	struct usb_device *dev;
	struct usb_interface *iface;
	struct usb_host_interface *alts;
	struct usb_interface_descriptor *altsd;
	int i, altno, err, stream;
	unsigned int format = 0, num_channels = 0;
	struct audioformat *fp = NULL;
	int num, protocol, clock = 0;
	struct uac_format_type_i_continuous_descriptor *fmt;
	unsigned int chconfig;

	dev = chip->dev;

	/* parse the interface's altsettings */
	iface = usb_ifnum_to_if(dev, iface_no);

	num = iface->num_altsetting;

	/*
	 * Dallas DS4201 workaround: It presents 5 altsettings, but the last
	 * one misses syncpipe, and does not produce any sound.
	 */
	if (chip->usb_id == USB_ID(0x04fa, 0x4201))
		num = 4;

	for (i = 0; i < num; i++) {
		alts = &iface->altsetting[i];
		altsd = get_iface_desc(alts);
		protocol = altsd->bInterfaceProtocol;
		/* skip invalid one */
		if (((altsd->bInterfaceClass != USB_CLASS_AUDIO ||
		      (altsd->bInterfaceSubClass != USB_SUBCLASS_AUDIOSTREAMING &&
		       altsd->bInterfaceSubClass != USB_SUBCLASS_VENDOR_SPEC)) &&
		     altsd->bInterfaceClass != USB_CLASS_VENDOR_SPEC) ||
		    altsd->bNumEndpoints < 1 ||
		    le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize) == 0)
			continue;
		/* must be isochronous */
		if ((get_endpoint(alts, 0)->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) !=
		    USB_ENDPOINT_XFER_ISOC)
			continue;
		/* check direction */
		stream = (get_endpoint(alts, 0)->bEndpointAddress & USB_DIR_IN) ?
			SNDRV_PCM_STREAM_CAPTURE : SNDRV_PCM_STREAM_PLAYBACK;
		altno = altsd->bAlternateSetting;

		if (snd_usb_apply_interface_quirk(chip, iface_no, altno))
			continue;

		/*
		 * Roland audio streaming interfaces are marked with protocols
		 * 0/1/2, but are UAC 1 compatible.
		 */
		if (USB_ID_VENDOR(chip->usb_id) == 0x0582 &&
		    altsd->bInterfaceClass == USB_CLASS_VENDOR_SPEC &&
		    protocol <= 2)
			protocol = UAC_VERSION_1;

		chconfig = 0;
		/* get audio formats */
		switch (protocol) {
		default:
			snd_printdd(KERN_WARNING "%d:%u:%d: unknown interface protocol %#02x, assuming v1\n",
				    dev->devnum, iface_no, altno, protocol);
			protocol = UAC_VERSION_1;
			/* fall through */

		case UAC_VERSION_1: {
			struct uac1_as_header_descriptor *as =
				snd_usb_find_csint_desc(alts->extra, alts->extralen, NULL, UAC_AS_GENERAL);
			struct uac_input_terminal_descriptor *iterm;

			if (!as) {
				snd_printk(KERN_ERR "%d:%u:%d : UAC_AS_GENERAL descriptor not found\n",
					   dev->devnum, iface_no, altno);
				continue;
			}

			if (as->bLength < sizeof(*as)) {
				snd_printk(KERN_ERR "%d:%u:%d : invalid UAC_AS_GENERAL desc\n",
					   dev->devnum, iface_no, altno);
				continue;
			}

			format = le16_to_cpu(as->wFormatTag); /* remember the format value */

			iterm = snd_usb_find_input_terminal_descriptor(chip->ctrl_intf,
								       as->bTerminalLink);
			if (iterm) {
				num_channels = iterm->bNrChannels;
				chconfig = le16_to_cpu(iterm->wChannelConfig);
			}

			break;
		}

		case UAC_VERSION_2: {
			struct uac2_input_terminal_descriptor *input_term;
			struct uac2_output_terminal_descriptor *output_term;
			struct uac2_as_header_descriptor *as =
				snd_usb_find_csint_desc(alts->extra, alts->extralen, NULL, UAC_AS_GENERAL);

			if (!as) {
				snd_printk(KERN_ERR "%d:%u:%d : UAC_AS_GENERAL descriptor not found\n",
					   dev->devnum, iface_no, altno);
				continue;
			}

			if (as->bLength < sizeof(*as)) {
				snd_printk(KERN_ERR "%d:%u:%d : invalid UAC_AS_GENERAL desc\n",
					   dev->devnum, iface_no, altno);
				continue;
			}

			num_channels = as->bNrChannels;
			format = le32_to_cpu(as->bmFormats);
			chconfig = le32_to_cpu(as->bmChannelConfig);

			/* lookup the terminal associated to this interface
			 * to extract the clock */
			input_term = snd_usb_find_input_terminal_descriptor(chip->ctrl_intf,
									    as->bTerminalLink);
			if (input_term) {
				clock = input_term->bCSourceID;
				if (!chconfig && (num_channels == input_term->bNrChannels))
					chconfig = le32_to_cpu(input_term->bmChannelConfig);
				break;
			}

			output_term = snd_usb_find_output_terminal_descriptor(chip->ctrl_intf,
									      as->bTerminalLink);
			if (output_term) {
				clock = output_term->bCSourceID;
				break;
			}

			snd_printk(KERN_ERR "%d:%u:%d : bogus bTerminalLink %d\n",
				   dev->devnum, iface_no, altno, as->bTerminalLink);
			continue;
		}
		}

		/* get format type */
		fmt = snd_usb_find_csint_desc(alts->extra, alts->extralen, NULL, UAC_FORMAT_TYPE);
		if (!fmt) {
			snd_printk(KERN_ERR "%d:%u:%d : no UAC_FORMAT_TYPE desc\n",
				   dev->devnum, iface_no, altno);
			continue;
		}
		if (((protocol == UAC_VERSION_1) && (fmt->bLength < 8)) ||
		    ((protocol == UAC_VERSION_2) && (fmt->bLength < 6))) {
			snd_printk(KERN_ERR "%d:%u:%d : invalid UAC_FORMAT_TYPE desc\n",
				   dev->devnum, iface_no, altno);
			continue;
		}

		/*
		 * Blue Microphones workaround: The last altsetting is identical
		 * with the previous one, except for a larger packet size, but
		 * is actually a mislabeled two-channel setting; ignore it.
		 */
		if (fmt->bNrChannels == 1 &&
		    fmt->bSubframeSize == 2 &&
		    altno == 2 && num == 3 &&
		    fp && fp->altsetting == 1 && fp->channels == 1 &&
		    fp->formats == SNDRV_PCM_FMTBIT_S16_LE &&
		    protocol == UAC_VERSION_1 &&
		    le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize) ==
							fp->maxpacksize * 2)
			continue;

		fp = kzalloc(sizeof(*fp), GFP_KERNEL);
		if (! fp) {
			snd_printk(KERN_ERR "cannot malloc\n");
			return -ENOMEM;
		}

		fp->iface = iface_no;
		fp->altsetting = altno;
		fp->altset_idx = i;
		fp->endpoint = get_endpoint(alts, 0)->bEndpointAddress;
		fp->ep_attr = get_endpoint(alts, 0)->bmAttributes;
		fp->datainterval = snd_usb_parse_datainterval(chip, alts);
		fp->protocol = protocol;
		fp->maxpacksize = le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize);
		fp->channels = num_channels;
		if (snd_usb_get_speed(dev) == USB_SPEED_HIGH)
			fp->maxpacksize = (((fp->maxpacksize >> 11) & 3) + 1)
					* (fp->maxpacksize & 0x7ff);
		fp->attributes = parse_uac_endpoint_attributes(chip, alts, protocol, iface_no);
		fp->clock = clock;
		fp->chmap = convert_chmap(num_channels, chconfig, protocol);

		/* some quirks for attributes here */

		switch (chip->usb_id) {
		case USB_ID(0x0a92, 0x0053): /* AudioTrak Optoplay */
			/* Optoplay sets the sample rate attribute although
			 * it seems not supporting it in fact.
			 */
			fp->attributes &= ~UAC_EP_CS_ATTR_SAMPLE_RATE;
			break;
		case USB_ID(0x041e, 0x3020): /* Creative SB Audigy 2 NX */
		case USB_ID(0x0763, 0x2003): /* M-Audio Audiophile USB */
			/* doesn't set the sample rate attribute, but supports it */
			fp->attributes |= UAC_EP_CS_ATTR_SAMPLE_RATE;
			break;
		case USB_ID(0x0763, 0x2001):  /* M-Audio Quattro USB */
		case USB_ID(0x0763, 0x2012):  /* M-Audio Fast Track Pro USB */
		case USB_ID(0x047f, 0x0ca1): /* plantronics headset */
		case USB_ID(0x077d, 0x07af): /* Griffin iMic (note that there is
						an older model 77d:223) */
		/*
		 * plantronics headset and Griffin iMic have set adaptive-in
		 * although it's really not...
		 */
			fp->ep_attr &= ~USB_ENDPOINT_SYNCTYPE;
			if (stream == SNDRV_PCM_STREAM_PLAYBACK)
				fp->ep_attr |= USB_ENDPOINT_SYNC_ADAPTIVE;
			else
				fp->ep_attr |= USB_ENDPOINT_SYNC_SYNC;
			break;
		}

		/* ok, let's parse further... */
		if (snd_usb_parse_audio_format(chip, fp, format, fmt, stream) < 0) {
			kfree(fp->rate_table);
			kfree(fp->chmap);
			kfree(fp);
			fp = NULL;
			continue;
		}

		snd_printdd(KERN_INFO "%d:%u:%d: add audio endpoint %#x\n", dev->devnum, iface_no, altno, fp->endpoint);
		err = snd_usb_add_audio_stream(chip, stream, fp);
		if (err < 0) {
			kfree(fp->rate_table);
			kfree(fp->chmap);
			kfree(fp);
			return err;
		}
		/* try to set the interface... */
		usb_set_interface(chip->dev, iface_no, altno);
		snd_usb_init_pitch(chip, iface_no, alts, fp);
		snd_usb_init_sample_rate(chip, iface_no, alts, fp, fp->rate_max);
	}
	return 0;
}