aboutsummaryrefslogtreecommitdiff
path: root/drivers/usb/gadget/f_audio.c
blob: 43bf44514c417d0431b52604569bef796871248b (plain)
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
795
796
797
798
799
800
/*
 * f_audio.c -- USB Audio class function driver
  *
 * Copyright (C) 2008 Bryan Wu <cooloney@kernel.org>
 * Copyright (C) 2008 Analog Devices, Inc
 *
 * Enter bugs at http://blackfin.uclinux.org/
 *
 * Licensed under the GPL-2 or later.
 */

#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <asm/atomic.h>

#include "u_audio.h"

#define OUT_EP_MAX_PACKET_SIZE	200
static int req_buf_size = OUT_EP_MAX_PACKET_SIZE;
module_param(req_buf_size, int, S_IRUGO);
MODULE_PARM_DESC(req_buf_size, "ISO OUT endpoint request buffer size");

static int req_count = 256;
module_param(req_count, int, S_IRUGO);
MODULE_PARM_DESC(req_count, "ISO OUT endpoint request count");

static int audio_buf_size = 48000;
module_param(audio_buf_size, int, S_IRUGO);
MODULE_PARM_DESC(audio_buf_size, "Audio buffer size");

static int generic_set_cmd(struct usb_audio_control *con, u8 cmd, int value);
static int generic_get_cmd(struct usb_audio_control *con, u8 cmd);

/*
 * DESCRIPTORS ... most are static, but strings and full
 * configuration descriptors are built on demand.
 */

/*
 * We have two interfaces- AudioControl and AudioStreaming
 * TODO: only supcard playback currently
 */
#define F_AUDIO_AC_INTERFACE	0
#define F_AUDIO_AS_INTERFACE	1
#define F_AUDIO_NUM_INTERFACES	2

/* B.3.1  Standard AC Interface Descriptor */
static struct usb_interface_descriptor ac_interface_desc __initdata = {
	.bLength =		USB_DT_INTERFACE_SIZE,
	.bDescriptorType =	USB_DT_INTERFACE,
	.bNumEndpoints =	0,
	.bInterfaceClass =	USB_CLASS_AUDIO,
	.bInterfaceSubClass =	USB_SUBCLASS_AUDIOCONTROL,
};

DECLARE_UAC_AC_HEADER_DESCRIPTOR(2);

#define UAC_DT_AC_HEADER_LENGTH	UAC_DT_AC_HEADER_SIZE(F_AUDIO_NUM_INTERFACES)
/* 1 input terminal, 1 output terminal and 1 feature unit */
#define UAC_DT_TOTAL_LENGTH (UAC_DT_AC_HEADER_LENGTH + UAC_DT_INPUT_TERMINAL_SIZE \
	+ UAC_DT_OUTPUT_TERMINAL_SIZE + UAC_DT_FEATURE_UNIT_SIZE(0))
/* B.3.2  Class-Specific AC Interface Descriptor */
static struct uac_ac_header_descriptor_v1_2 ac_header_desc = {
	.bLength =		UAC_DT_AC_HEADER_LENGTH,
	.bDescriptorType =	USB_DT_CS_INTERFACE,
	.bDescriptorSubtype =	UAC_HEADER,
	.bcdADC =		__constant_cpu_to_le16(0x0100),
	.wTotalLength =		__constant_cpu_to_le16(UAC_DT_TOTAL_LENGTH),
	.bInCollection =	F_AUDIO_NUM_INTERFACES,
	.baInterfaceNr = {
		[0] =		F_AUDIO_AC_INTERFACE,
		[1] =		F_AUDIO_AS_INTERFACE,
	}
};

#define INPUT_TERMINAL_ID	1
static struct uac_input_terminal_descriptor input_terminal_desc = {
	.bLength =		UAC_DT_INPUT_TERMINAL_SIZE,
	.bDescriptorType =	USB_DT_CS_INTERFACE,
	.bDescriptorSubtype =	UAC_INPUT_TERMINAL,
	.bTerminalID =		INPUT_TERMINAL_ID,
	.wTerminalType =	UAC_TERMINAL_STREAMING,
	.bAssocTerminal =	0,
	.wChannelConfig =	0x3,
};

DECLARE_UAC_FEATURE_UNIT_DESCRIPTOR(0);

#define FEATURE_UNIT_ID		2
static struct uac_feature_unit_descriptor_0 feature_unit_desc = {
	.bLength		= UAC_DT_FEATURE_UNIT_SIZE(0),
	.bDescriptorType	= USB_DT_CS_INTERFACE,
	.bDescriptorSubtype	= UAC_FEATURE_UNIT,
	.bUnitID		= FEATURE_UNIT_ID,
	.bSourceID		= INPUT_TERMINAL_ID,
	.bControlSize		= 2,
	.bmaControls[0]		= (UAC_FU_MUTE | UAC_FU_VOLUME),
};

static struct usb_audio_control mute_control = {
	.list = LIST_HEAD_INIT(mute_control.list),
	.name = "Mute Control",
	.type = UAC_MUTE_CONTROL,
	/* Todo: add real Mute control code */
	.set = generic_set_cmd,
	.get = generic_get_cmd,
};

static struct usb_audio_control volume_control = {
	.list = LIST_HEAD_INIT(volume_control.list),
	.name = "Volume Control",
	.type = UAC_VOLUME_CONTROL,
	/* Todo: add real Volume control code */
	.set = generic_set_cmd,
	.get = generic_get_cmd,
};

static struct usb_audio_control_selector feature_unit = {
	.list = LIST_HEAD_INIT(feature_unit.list),
	.id = FEATURE_UNIT_ID,
	.name = "Mute & Volume Control",
	.type = UAC_FEATURE_UNIT,
	.desc = (struct usb_descriptor_header *)&feature_unit_desc,
};

#define OUTPUT_TERMINAL_ID	3
static struct uac_output_terminal_descriptor_v1 output_terminal_desc = {
	.bLength		= UAC_DT_OUTPUT_TERMINAL_SIZE,
	.bDescriptorType	= USB_DT_CS_INTERFACE,
	.bDescriptorSubtype	= UAC_OUTPUT_TERMINAL,
	.bTerminalID		= OUTPUT_TERMINAL_ID,
	.wTerminalType		= UAC_OUTPUT_TERMINAL_SPEAKER,
	.bAssocTerminal		= FEATURE_UNIT_ID,
	.bSourceID		= FEATURE_UNIT_ID,
};

/* B.4.1  Standard AS Interface Descriptor */
static struct usb_interface_descriptor as_interface_alt_0_desc = {
	.bLength =		USB_DT_INTERFACE_SIZE,
	.bDescriptorType =	USB_DT_INTERFACE,
	.bAlternateSetting =	0,
	.bNumEndpoints =	0,
	.bInterfaceClass =	USB_CLASS_AUDIO,
	.bInterfaceSubClass =	USB_SUBCLASS_AUDIOSTREAMING,
};

static struct usb_interface_descriptor as_interface_alt_1_desc = {
	.bLength =		USB_DT_INTERFACE_SIZE,
	.bDescriptorType =	USB_DT_INTERFACE,
	.bAlternateSetting =	1,
	.bNumEndpoints =	1,
	.bInterfaceClass =	USB_CLASS_AUDIO,
	.bInterfaceSubClass =	USB_SUBCLASS_AUDIOSTREAMING,
};

/* B.4.2  Class-Specific AS Interface Descriptor */
static struct uac_as_header_descriptor_v1 as_header_desc = {
	.bLength =		UAC_DT_AS_HEADER_SIZE,
	.bDescriptorType =	USB_DT_CS_INTERFACE,
	.bDescriptorSubtype =	UAC_AS_GENERAL,
	.bTerminalLink =	INPUT_TERMINAL_ID,
	.bDelay =		1,
	.wFormatTag =		UAC_FORMAT_TYPE_I_PCM,
};

DECLARE_UAC_FORMAT_TYPE_I_DISCRETE_DESC(1);

static struct uac_format_type_i_discrete_descriptor_1 as_type_i_desc = {
	.bLength =		UAC_FORMAT_TYPE_I_DISCRETE_DESC_SIZE(1),
	.bDescriptorType =	USB_DT_CS_INTERFACE,
	.bDescriptorSubtype =	UAC_FORMAT_TYPE,
	.bFormatType =		UAC_FORMAT_TYPE_I,
	.bSubframeSize =	2,
	.bBitResolution =	16,
	.bSamFreqType =		1,
};

/* Standard ISO OUT Endpoint Descriptor */
static struct usb_endpoint_descriptor as_out_ep_desc __initdata = {
	.bLength =		USB_DT_ENDPOINT_AUDIO_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,
	.bEndpointAddress =	USB_DIR_OUT,
	.bmAttributes =		USB_ENDPOINT_SYNC_ADAPTIVE
				| USB_ENDPOINT_XFER_ISOC,
	.wMaxPacketSize =	__constant_cpu_to_le16(OUT_EP_MAX_PACKET_SIZE),
	.bInterval =		4,
};

/* Class-specific AS ISO OUT Endpoint Descriptor */
static struct uac_iso_endpoint_descriptor as_iso_out_desc __initdata = {
	.bLength =		UAC_ISO_ENDPOINT_DESC_SIZE,
	.bDescriptorType =	USB_DT_CS_ENDPOINT,
	.bDescriptorSubtype =	UAC_EP_GENERAL,
	.bmAttributes = 	1,
	.bLockDelayUnits =	1,
	.wLockDelay =		__constant_cpu_to_le16(1),
};

static struct usb_descriptor_header *f_audio_desc[] __initdata = {
	(struct usb_descriptor_header *)&ac_interface_desc,
	(struct usb_descriptor_header *)&ac_header_desc,

	(struct usb_descriptor_header *)&input_terminal_desc,
	(struct usb_descriptor_header *)&output_terminal_desc,
	(struct usb_descriptor_header *)&feature_unit_desc,

	(struct usb_descriptor_header *)&as_interface_alt_0_desc,
	(struct usb_descriptor_header *)&as_interface_alt_1_desc,
	(struct usb_descriptor_header *)&as_header_desc,

	(struct usb_descriptor_header *)&as_type_i_desc,

	(struct usb_descriptor_header *)&as_out_ep_desc,
	(struct usb_descriptor_header *)&as_iso_out_desc,
	NULL,
};

/* string IDs are assigned dynamically */

#define STRING_MANUFACTURER_IDX		0
#define STRING_PRODUCT_IDX		1

static char manufacturer[50];

static struct usb_string strings_dev[] = {
	[STRING_MANUFACTURER_IDX].s = manufacturer,
	[STRING_PRODUCT_IDX].s = DRIVER_DESC,
	{  } /* end of list */
};

static struct usb_gadget_strings stringtab_dev = {
	.language	= 0x0409,	/* en-us */
	.strings	= strings_dev,
};

static struct usb_gadget_strings *audio_strings[] = {
	&stringtab_dev,
	NULL,
};

/*
 * This function is an ALSA sound card following USB Audio Class Spec 1.0.
 */

/*-------------------------------------------------------------------------*/
struct f_audio_buf {
	u8 *buf;
	int actual;
	struct list_head list;
};

static struct f_audio_buf *f_audio_buffer_alloc(int buf_size)
{
	struct f_audio_buf *copy_buf;

	copy_buf = kzalloc(sizeof *copy_buf, GFP_ATOMIC);
	if (!copy_buf)
		return ERR_PTR(-ENOMEM);

	copy_buf->buf = kzalloc(buf_size, GFP_ATOMIC);
	if (!copy_buf->buf) {
		kfree(copy_buf);
		return ERR_PTR(-ENOMEM);
	}

	return copy_buf;
}

static void f_audio_buffer_free(struct f_audio_buf *audio_buf)
{
	kfree(audio_buf->buf);
	kfree(audio_buf);
}
/*-------------------------------------------------------------------------*/

struct f_audio {
	struct gaudio			card;

	/* endpoints handle full and/or high speeds */
	struct usb_ep			*out_ep;
	struct usb_endpoint_descriptor	*out_desc;

	spinlock_t			lock;
	struct f_audio_buf *copy_buf;
	struct work_struct playback_work;
	struct list_head play_queue;

	/* Control Set command */
	struct list_head cs;
	u8 set_cmd;
	struct usb_audio_control *set_con;
};

static inline struct f_audio *func_to_audio(struct usb_function *f)
{
	return container_of(f, struct f_audio, card.func);
}

/*-------------------------------------------------------------------------*/

static void f_audio_playback_work(struct work_struct *data)
{
	struct f_audio *audio = container_of(data, struct f_audio,
					playback_work);
	struct f_audio_buf *play_buf;

	spin_lock_irq(&audio->lock);
	if (list_empty(&audio->play_queue)) {
		spin_unlock_irq(&audio->lock);
		return;
	}
	play_buf = list_first_entry(&audio->play_queue,
			struct f_audio_buf, list);
	list_del(&play_buf->list);
	spin_unlock_irq(&audio->lock);

	u_audio_playback(&audio->card, play_buf->buf, play_buf->actual);
	f_audio_buffer_free(play_buf);

	return;
}

static int f_audio_out_ep_complete(struct usb_ep *ep, struct usb_request *req)
{
	struct f_audio *audio = req->context;
	struct usb_composite_dev *cdev = audio->card.func.config->cdev;
	struct f_audio_buf *copy_buf = audio->copy_buf;
	int err;

	if (!copy_buf)
		return -EINVAL;

	/* Copy buffer is full, add it to the play_queue */
	if (audio_buf_size - copy_buf->actual < req->actual) {
		list_add_tail(&copy_buf->list, &audio->play_queue);
		schedule_work(&audio->playback_work);
		copy_buf = f_audio_buffer_alloc(audio_buf_size);
		if (IS_ERR(copy_buf))
			return -ENOMEM;
	}

	memcpy(copy_buf->buf + copy_buf->actual, req->buf, req->actual);
	copy_buf->actual += req->actual;
	audio->copy_buf = copy_buf;

	err = usb_ep_queue(ep, req, GFP_ATOMIC);
	if (err)
		ERROR(cdev, "%s queue req: %d\n", ep->name, err);

	return 0;

}

static void f_audio_complete(struct usb_ep *ep, struct usb_request *req)
{
	struct f_audio *audio = req->context;
	int status = req->status;
	u32 data = 0;
	struct usb_ep *out_ep = audio->out_ep;

	switch (status) {

	case 0:				/* normal completion? */
		if (ep == out_ep)
			f_audio_out_ep_complete(ep, req);
		else if (audio->set_con) {
			memcpy(&data, req->buf, req->length);
			audio->set_con->set(audio->set_con, audio->set_cmd,
					le16_to_cpu(data));
			audio->set_con = NULL;
		}
		break;
	default:
		break;
	}
}

static int audio_set_intf_req(struct usb_function *f,
		const struct usb_ctrlrequest *ctrl)
{
	struct f_audio		*audio = func_to_audio(f);
	struct usb_composite_dev *cdev = f->config->cdev;
	struct usb_request	*req = cdev->req;
	u8			id = ((le16_to_cpu(ctrl->wIndex) >> 8) & 0xFF);
	u16			len = le16_to_cpu(ctrl->wLength);
	u16			w_value = le16_to_cpu(ctrl->wValue);
	u8			con_sel = (w_value >> 8) & 0xFF;
	u8			cmd = (ctrl->bRequest & 0x0F);
	struct usb_audio_control_selector *cs;
	struct usb_audio_control *con;

	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, entity %d\n",
			ctrl->bRequest, w_value, len, id);

	list_for_each_entry(cs, &audio->cs, list) {
		if (cs->id == id) {
			list_for_each_entry(con, &cs->control, list) {
				if (con->type == con_sel) {
					audio->set_con = con;
					break;
				}
			}
			break;
		}
	}

	audio->set_cmd = cmd;
	req->context = audio;
	req->complete = f_audio_complete;

	return len;
}

static int audio_get_intf_req(struct usb_function *f,
		const struct usb_ctrlrequest *ctrl)
{
	struct f_audio		*audio = func_to_audio(f);
	struct usb_composite_dev *cdev = f->config->cdev;
	struct usb_request	*req = cdev->req;
	int			value = -EOPNOTSUPP;
	u8			id = ((le16_to_cpu(ctrl->wIndex) >> 8) & 0xFF);
	u16			len = le16_to_cpu(ctrl->wLength);
	u16			w_value = le16_to_cpu(ctrl->wValue);
	u8			con_sel = (w_value >> 8) & 0xFF;
	u8			cmd = (ctrl->bRequest & 0x0F);
	struct usb_audio_control_selector *cs;
	struct usb_audio_control *con;

	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, entity %d\n",
			ctrl->bRequest, w_value, len, id);

	list_for_each_entry(cs, &audio->cs, list) {
		if (cs->id == id) {
			list_for_each_entry(con, &cs->control, list) {
				if (con->type == con_sel && con->get) {
					value = con->get(con, cmd);
					break;
				}
			}
			break;
		}
	}

	req->context = audio;
	req->complete = f_audio_complete;
	memcpy(req->buf, &value, len);

	return len;
}

static int audio_set_endpoint_req(struct usb_function *f,
		const struct usb_ctrlrequest *ctrl)
{
	struct usb_composite_dev *cdev = f->config->cdev;
	int			value = -EOPNOTSUPP;
	u16			ep = le16_to_cpu(ctrl->wIndex);
	u16			len = le16_to_cpu(ctrl->wLength);
	u16			w_value = le16_to_cpu(ctrl->wValue);

	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, endpoint %d\n",
			ctrl->bRequest, w_value, len, ep);

	switch (ctrl->bRequest) {
	case UAC_SET_CUR:
		value = 0;
		break;

	case UAC_SET_MIN:
		break;

	case UAC_SET_MAX:
		break;

	case UAC_SET_RES:
		break;

	case UAC_SET_MEM:
		break;

	default:
		break;
	}

	return value;
}

static int audio_get_endpoint_req(struct usb_function *f,
		const struct usb_ctrlrequest *ctrl)
{
	struct usb_composite_dev *cdev = f->config->cdev;
	int value = -EOPNOTSUPP;
	u8 ep = ((le16_to_cpu(ctrl->wIndex) >> 8) & 0xFF);
	u16 len = le16_to_cpu(ctrl->wLength);
	u16 w_value = le16_to_cpu(ctrl->wValue);

	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, endpoint %d\n",
			ctrl->bRequest, w_value, len, ep);

	switch (ctrl->bRequest) {
	case UAC_GET_CUR:
	case UAC_GET_MIN:
	case UAC_GET_MAX:
	case UAC_GET_RES:
		value = 3;
		break;
	case UAC_GET_MEM:
		break;
	default:
		break;
	}

	return value;
}

static int
f_audio_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
	struct usb_composite_dev *cdev = f->config->cdev;
	struct usb_request	*req = cdev->req;
	int			value = -EOPNOTSUPP;
	u16			w_index = le16_to_cpu(ctrl->wIndex);
	u16			w_value = le16_to_cpu(ctrl->wValue);
	u16			w_length = le16_to_cpu(ctrl->wLength);

	/* composite driver infrastructure handles everything; interface
	 * activation uses set_alt().
	 */
	switch (ctrl->bRequestType) {
	case USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE:
		value = audio_set_intf_req(f, ctrl);
		break;

	case USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE:
		value = audio_get_intf_req(f, ctrl);
		break;

	case USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_ENDPOINT:
		value = audio_set_endpoint_req(f, ctrl);
		break;

	case USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_ENDPOINT:
		value = audio_get_endpoint_req(f, ctrl);
		break;

	default:
		ERROR(cdev, "invalid control req%02x.%02x v%04x i%04x l%d\n",
			ctrl->bRequestType, ctrl->bRequest,
			w_value, w_index, w_length);
	}

	/* respond with data transfer or status phase? */
	if (value >= 0) {
		DBG(cdev, "audio req%02x.%02x v%04x i%04x l%d\n",
			ctrl->bRequestType, ctrl->bRequest,
			w_value, w_index, w_length);
		req->zero = 0;
		req->length = value;
		value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
		if (value < 0)
			ERROR(cdev, "audio response on err %d\n", value);
	}

	/* device either stalls (value < 0) or reports success */
	return value;
}

static int f_audio_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
	struct f_audio		*audio = func_to_audio(f);
	struct usb_composite_dev *cdev = f->config->cdev;
	struct usb_ep *out_ep = audio->out_ep;
	struct usb_request *req;
	int i = 0, err = 0;

	DBG(cdev, "intf %d, alt %d\n", intf, alt);

	if (intf == 1) {
		if (alt == 1) {
			usb_ep_enable(out_ep, audio->out_desc);
			out_ep->driver_data = audio;
			audio->copy_buf = f_audio_buffer_alloc(audio_buf_size);
			if (IS_ERR(audio->copy_buf))
				return -ENOMEM;

			/*
			 * allocate a bunch of read buffers
			 * and queue them all at once.
			 */
			for (i = 0; i < req_count && err == 0; i++) {
				req = usb_ep_alloc_request(out_ep, GFP_ATOMIC);
				if (req) {
					req->buf = kzalloc(req_buf_size,
							GFP_ATOMIC);
					if (req->buf) {
						req->length = req_buf_size;
						req->context = audio;
						req->complete =
							f_audio_complete;
						err = usb_ep_queue(out_ep,
							req, GFP_ATOMIC);
						if (err)
							ERROR(cdev,
							"%s queue req: %d\n",
							out_ep->name, err);
					} else
						err = -ENOMEM;
				} else
					err = -ENOMEM;
			}

		} else {
			struct f_audio_buf *copy_buf = audio->copy_buf;
			if (copy_buf) {
				list_add_tail(&copy_buf->list,
						&audio->play_queue);
				schedule_work(&audio->playback_work);
			}
		}
	}

	return err;
}

static void f_audio_disable(struct usb_function *f)
{
	return;
}

/*-------------------------------------------------------------------------*/

static void f_audio_build_desc(struct f_audio *audio)
{
	struct gaudio *card = &audio->card;
	u8 *sam_freq;
	int rate;

	/* Set channel numbers */
	input_terminal_desc.bNrChannels = u_audio_get_playback_channels(card);
	as_type_i_desc.bNrChannels = u_audio_get_playback_channels(card);

	/* Set sample rates */
	rate = u_audio_get_playback_rate(card);
	sam_freq = as_type_i_desc.tSamFreq[0];
	memcpy(sam_freq, &rate, 3);

	/* Todo: Set Sample bits and other parameters */

	return;
}

/* audio function driver setup/binding */
static int __init
f_audio_bind(struct usb_configuration *c, struct usb_function *f)
{
	struct usb_composite_dev *cdev = c->cdev;
	struct f_audio		*audio = func_to_audio(f);
	int			status;
	struct usb_ep		*ep;

	f_audio_build_desc(audio);

	/* allocate instance-specific interface IDs, and patch descriptors */
	status = usb_interface_id(c, f);
	if (status < 0)
		goto fail;
	ac_interface_desc.bInterfaceNumber = status;

	status = usb_interface_id(c, f);
	if (status < 0)
		goto fail;
	as_interface_alt_0_desc.bInterfaceNumber = status;
	as_interface_alt_1_desc.bInterfaceNumber = status;

	status = -ENODEV;

	/* allocate instance-specific endpoints */
	ep = usb_ep_autoconfig(cdev->gadget, &as_out_ep_desc);
	if (!ep)
		goto fail;
	audio->out_ep = ep;
	ep->driver_data = cdev;	/* claim */

	status = -ENOMEM;

	/* supcard all relevant hardware speeds... we expect that when
	 * hardware is dual speed, all bulk-capable endpoints work at
	 * both speeds
	 */

	/* copy descriptors, and track endpoint copies */
	if (gadget_is_dualspeed(c->cdev->gadget)) {
		c->highspeed = true;
		f->hs_descriptors = usb_copy_descriptors(f_audio_desc);
	} else
		f->descriptors = usb_copy_descriptors(f_audio_desc);

	return 0;

fail:

	return status;
}

static void
f_audio_unbind(struct usb_configuration *c, struct usb_function *f)
{
	struct f_audio		*audio = func_to_audio(f);

	usb_free_descriptors(f->descriptors);
	kfree(audio);
}

/*-------------------------------------------------------------------------*/

static int generic_set_cmd(struct usb_audio_control *con, u8 cmd, int value)
{
	con->data[cmd] = value;

	return 0;
}

static int generic_get_cmd(struct usb_audio_control *con, u8 cmd)
{
	return con->data[cmd];
}

/* Todo: add more control selecotor dynamically */
int __init control_selector_init(struct f_audio *audio)
{
	INIT_LIST_HEAD(&audio->cs);
	list_add(&feature_unit.list, &audio->cs);

	INIT_LIST_HEAD(&feature_unit.control);
	list_add(&mute_control.list, &feature_unit.control);
	list_add(&volume_control.list, &feature_unit.control);

	volume_control.data[UAC__CUR] = 0xffc0;
	volume_control.data[UAC__MIN] = 0xe3a0;
	volume_control.data[UAC__MAX] = 0xfff0;
	volume_control.data[UAC__RES] = 0x0030;

	return 0;
}

/**
 * audio_bind_config - add USB audio fucntion to a configuration
 * @c: the configuration to supcard the USB audio function
 * Context: single threaded during gadget setup
 *
 * Returns zero on success, else negative errno.
 */
int __init audio_bind_config(struct usb_configuration *c)
{
	struct f_audio *audio;
	int status;

	/* allocate and initialize one new instance */
	audio = kzalloc(sizeof *audio, GFP_KERNEL);
	if (!audio)
		return -ENOMEM;

	audio->card.func.name = "g_audio";
	audio->card.gadget = c->cdev->gadget;

	INIT_LIST_HEAD(&audio->play_queue);
	spin_lock_init(&audio->lock);

	/* set up ASLA audio devices */
	status = gaudio_setup(&audio->card);
	if (status < 0)
		goto setup_fail;

	audio->card.func.strings = audio_strings;
	audio->card.func.bind = f_audio_bind;
	audio->card.func.unbind = f_audio_unbind;
	audio->card.func.set_alt = f_audio_set_alt;
	audio->card.func.setup = f_audio_setup;
	audio->card.func.disable = f_audio_disable;
	audio->out_desc = &as_out_ep_desc;

	control_selector_init(audio);

	INIT_WORK(&audio->playback_work, f_audio_playback_work);

	status = usb_add_function(c, &audio->card.func);
	if (status)
		goto add_fail;

	INFO(c->cdev, "audio_buf_size %d, req_buf_size %d, req_count %d\n",
		audio_buf_size, req_buf_size, req_count);

	return status;

add_fail:
	gaudio_cleanup();
setup_fail:
	kfree(audio);
	return status;
}