summaryrefslogtreecommitdiff
path: root/drivers/bluetooth/hci_h5.c
blob: f6f4974505600a2884f56c01be22bd6a79492f04 (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
/*
 *
 *  Bluetooth HCI Three-wire UART driver
 *
 *  Copyright (C) 2012  Intel Corporation
 *
 *
 *  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/kernel.h>
#include <linux/errno.h>
#include <linux/skbuff.h>

#include <net/bluetooth/bluetooth.h>
#include <net/bluetooth/hci_core.h>

#include "hci_uart.h"

#define HCI_3WIRE_ACK_PKT	0
#define HCI_3WIRE_LINK_PKT	15

/* Sliding window size */
#define H5_TX_WIN_MAX		4

#define H5_ACK_TIMEOUT	msecs_to_jiffies(250)
#define H5_SYNC_TIMEOUT	msecs_to_jiffies(100)

/*
 * Maximum Three-wire packet:
 *     4 byte header + max value for 12-bit length + 2 bytes for CRC
 */
#define H5_MAX_LEN (4 + 0xfff + 2)

/* Convenience macros for reading Three-wire header values */
#define H5_HDR_SEQ(hdr)		((hdr)[0] & 0x07)
#define H5_HDR_ACK(hdr)		(((hdr)[0] >> 3) & 0x07)
#define H5_HDR_CRC(hdr)		(((hdr)[0] >> 6) & 0x01)
#define H5_HDR_RELIABLE(hdr)	(((hdr)[0] >> 7) & 0x01)
#define H5_HDR_PKT_TYPE(hdr)	((hdr)[1] & 0x0f)
#define H5_HDR_LEN(hdr)		((((hdr)[1] >> 4) & 0xff) + ((hdr)[2] << 4))

#define SLIP_DELIMITER	0xc0
#define SLIP_ESC	0xdb
#define SLIP_ESC_DELIM	0xdc
#define SLIP_ESC_ESC	0xdd

/* H5 state flags */
enum {
	H5_RX_ESC,	/* SLIP escape mode */
	H5_TX_ACK_REQ,	/* Pending ack to send */
};

struct h5 {
	struct sk_buff_head	unack;		/* Unack'ed packets queue */
	struct sk_buff_head	rel;		/* Reliable packets queue */
	struct sk_buff_head	unrel;		/* Unreliable packets queue */

	unsigned long		flags;

	struct sk_buff		*rx_skb;	/* Receive buffer */
	size_t			rx_pending;	/* Expecting more bytes */
	u8			rx_ack;		/* Last ack number received */

	int			(*rx_func) (struct hci_uart *hu, u8 c);

	struct timer_list	timer;		/* Retransmission timer */

	u8			tx_seq;		/* Next seq number to send */
	u8			tx_ack;		/* Next ack number to send */
	u8			tx_win;		/* Sliding window size */

	enum {
		H5_UNINITIALIZED,
		H5_INITIALIZED,
		H5_ACTIVE,
	} state;

	enum {
		H5_AWAKE,
		H5_SLEEPING,
		H5_WAKING_UP,
	} sleep;
};

static void h5_reset_rx(struct h5 *h5);

static void h5_link_control(struct hci_uart *hu, const void *data, size_t len)
{
	struct h5 *h5 = hu->priv;
	struct sk_buff *nskb;

	nskb = alloc_skb(3, GFP_ATOMIC);
	if (!nskb)
		return;

	bt_cb(nskb)->pkt_type = HCI_3WIRE_LINK_PKT;

	memcpy(skb_put(nskb, len), data, len);

	skb_queue_tail(&h5->unrel, nskb);
}

static u8 h5_cfg_field(struct h5 *h5)
{
	u8 field = 0;

	/* Sliding window size (first 3 bits) */
	field |= (h5->tx_win & 7);

	return field;
}

static void h5_timed_event(unsigned long arg)
{
	const unsigned char sync_req[] = { 0x01, 0x7e };
	unsigned char conf_req[] = { 0x03, 0xfc, 0x01 };
	struct hci_uart *hu = (struct hci_uart *) arg;
	struct h5 *h5 = hu->priv;
	struct sk_buff *skb;
	unsigned long flags;

	BT_DBG("%s", hu->hdev->name);

	if (h5->state == H5_UNINITIALIZED)
		h5_link_control(hu, sync_req, sizeof(sync_req));

	if (h5->state == H5_INITIALIZED) {
		conf_req[2] = h5_cfg_field(h5);
		h5_link_control(hu, conf_req, sizeof(conf_req));
	}

	if (h5->state != H5_ACTIVE) {
		mod_timer(&h5->timer, jiffies + H5_SYNC_TIMEOUT);
		goto wakeup;
	}

	if (h5->sleep != H5_AWAKE) {
		h5->sleep = H5_SLEEPING;
		goto wakeup;
	}

	BT_DBG("hu %p retransmitting %u pkts", hu, h5->unack.qlen);

	spin_lock_irqsave_nested(&h5->unack.lock, flags, SINGLE_DEPTH_NESTING);

	while ((skb = __skb_dequeue_tail(&h5->unack)) != NULL) {
		h5->tx_seq = (h5->tx_seq - 1) & 0x07;
		skb_queue_head(&h5->rel, skb);
	}

	spin_unlock_irqrestore(&h5->unack.lock, flags);

wakeup:
	hci_uart_tx_wakeup(hu);
}

static int h5_open(struct hci_uart *hu)
{
	struct h5 *h5;
	const unsigned char sync[] = { 0x01, 0x7e };

	BT_DBG("hu %p", hu);

	h5 = kzalloc(sizeof(*h5), GFP_KERNEL);
	if (!h5)
		return -ENOMEM;

	hu->priv = h5;

	skb_queue_head_init(&h5->unack);
	skb_queue_head_init(&h5->rel);
	skb_queue_head_init(&h5->unrel);

	h5_reset_rx(h5);

	init_timer(&h5->timer);
	h5->timer.function = h5_timed_event;
	h5->timer.data = (unsigned long) hu;

	h5->tx_win = H5_TX_WIN_MAX;

	set_bit(HCI_UART_INIT_PENDING, &hu->hdev_flags);

	/* Send initial sync request */
	h5_link_control(hu, sync, sizeof(sync));
	mod_timer(&h5->timer, jiffies + H5_SYNC_TIMEOUT);

	return 0;
}

static int h5_close(struct hci_uart *hu)
{
	struct h5 *h5 = hu->priv;

	skb_queue_purge(&h5->unack);
	skb_queue_purge(&h5->rel);
	skb_queue_purge(&h5->unrel);

	del_timer(&h5->timer);

	kfree(h5);

	return 0;
}

static void h5_pkt_cull(struct h5 *h5)
{
	struct sk_buff *skb, *tmp;
	unsigned long flags;
	int i, to_remove;
	u8 seq;

	spin_lock_irqsave(&h5->unack.lock, flags);

	to_remove = skb_queue_len(&h5->unack);
	if (to_remove == 0)
		goto unlock;

	seq = h5->tx_seq;

	while (to_remove > 0) {
		if (h5->rx_ack == seq)
			break;

		to_remove--;
		seq = (seq - 1) % 8;
	}

	if (seq != h5->rx_ack)
		BT_ERR("Controller acked invalid packet");

	i = 0;
	skb_queue_walk_safe(&h5->unack, skb, tmp) {
		if (i++ >= to_remove)
			break;

		__skb_unlink(skb, &h5->unack);
		kfree_skb(skb);
	}

	if (skb_queue_empty(&h5->unack))
		del_timer(&h5->timer);

unlock:
	spin_unlock_irqrestore(&h5->unack.lock, flags);
}

static void h5_handle_internal_rx(struct hci_uart *hu)
{
	struct h5 *h5 = hu->priv;
	const unsigned char sync_req[] = { 0x01, 0x7e };
	const unsigned char sync_rsp[] = { 0x02, 0x7d };
	unsigned char conf_req[] = { 0x03, 0xfc, 0x01 };
	const unsigned char conf_rsp[] = { 0x04, 0x7b };
	const unsigned char wakeup_req[] = { 0x05, 0xfa };
	const unsigned char woken_req[] = { 0x06, 0xf9 };
	const unsigned char sleep_req[] = { 0x07, 0x78 };
	const unsigned char *hdr = h5->rx_skb->data;
	const unsigned char *data = &h5->rx_skb->data[4];

	BT_DBG("%s", hu->hdev->name);

	if (H5_HDR_PKT_TYPE(hdr) != HCI_3WIRE_LINK_PKT)
		return;

	if (H5_HDR_LEN(hdr) < 2)
		return;

	conf_req[2] = h5_cfg_field(h5);

	if (memcmp(data, sync_req, 2) == 0) {
		h5_link_control(hu, sync_rsp, 2);
	} else if (memcmp(data, sync_rsp, 2) == 0) {
		h5->state = H5_INITIALIZED;
		h5_link_control(hu, conf_req, 3);
	} else if (memcmp(data, conf_req, 2) == 0) {
		h5_link_control(hu, conf_rsp, 2);
		h5_link_control(hu, conf_req, 3);
	} else if (memcmp(data, conf_rsp, 2) == 0) {
		if (H5_HDR_LEN(hdr) > 2)
			h5->tx_win = (data[2] & 7);
		BT_DBG("Three-wire init complete. tx_win %u", h5->tx_win);
		h5->state = H5_ACTIVE;
		hci_uart_init_ready(hu);
		return;
	} else if (memcmp(data, sleep_req, 2) == 0) {
		BT_DBG("Peer went to sleep");
		h5->sleep = H5_SLEEPING;
		return;
	} else if (memcmp(data, woken_req, 2) == 0) {
		BT_DBG("Peer woke up");
		h5->sleep = H5_AWAKE;
	} else if (memcmp(data, wakeup_req, 2) == 0) {
		BT_DBG("Peer requested wakeup");
		h5_link_control(hu, woken_req, 2);
		h5->sleep = H5_AWAKE;
	} else {
		BT_DBG("Link Control: 0x%02hhx 0x%02hhx", data[0], data[1]);
		return;
	}

	hci_uart_tx_wakeup(hu);
}

static void h5_complete_rx_pkt(struct hci_uart *hu)
{
	struct h5 *h5 = hu->priv;
	const unsigned char *hdr = h5->rx_skb->data;

	if (H5_HDR_RELIABLE(hdr)) {
		h5->tx_ack = (h5->tx_ack + 1) % 8;
		set_bit(H5_TX_ACK_REQ, &h5->flags);
		hci_uart_tx_wakeup(hu);
	}

	h5->rx_ack = H5_HDR_ACK(hdr);

	h5_pkt_cull(h5);

	switch (H5_HDR_PKT_TYPE(hdr)) {
	case HCI_EVENT_PKT:
	case HCI_ACLDATA_PKT:
	case HCI_SCODATA_PKT:
		bt_cb(h5->rx_skb)->pkt_type = H5_HDR_PKT_TYPE(hdr);

		/* Remove Three-wire header */
		skb_pull(h5->rx_skb, 4);

		hci_recv_frame(hu->hdev, h5->rx_skb);
		h5->rx_skb = NULL;

		break;

	default:
		h5_handle_internal_rx(hu);
		break;
	}

	h5_reset_rx(h5);
}

static int h5_rx_crc(struct hci_uart *hu, unsigned char c)
{
	struct h5 *h5 = hu->priv;

	h5_complete_rx_pkt(hu);
	h5_reset_rx(h5);

	return 0;
}

static int h5_rx_payload(struct hci_uart *hu, unsigned char c)
{
	struct h5 *h5 = hu->priv;
	const unsigned char *hdr = h5->rx_skb->data;

	if (H5_HDR_CRC(hdr)) {
		h5->rx_func = h5_rx_crc;
		h5->rx_pending = 2;
	} else {
		h5_complete_rx_pkt(hu);
		h5_reset_rx(h5);
	}

	return 0;
}

static int h5_rx_3wire_hdr(struct hci_uart *hu, unsigned char c)
{
	struct h5 *h5 = hu->priv;
	const unsigned char *hdr = h5->rx_skb->data;

	BT_DBG("%s rx: seq %u ack %u crc %u rel %u type %u len %u",
	       hu->hdev->name, H5_HDR_SEQ(hdr), H5_HDR_ACK(hdr),
	       H5_HDR_CRC(hdr), H5_HDR_RELIABLE(hdr), H5_HDR_PKT_TYPE(hdr),
	       H5_HDR_LEN(hdr));

	if (((hdr[0] + hdr[1] + hdr[2] + hdr[3]) & 0xff) != 0xff) {
		BT_ERR("Invalid header checksum");
		h5_reset_rx(h5);
		return 0;
	}

	if (H5_HDR_RELIABLE(hdr) && H5_HDR_SEQ(hdr) != h5->tx_ack) {
		BT_ERR("Out-of-order packet arrived (%u != %u)",
		       H5_HDR_SEQ(hdr), h5->tx_ack);
		h5_reset_rx(h5);
		return 0;
	}

	if (h5->state != H5_ACTIVE &&
	    H5_HDR_PKT_TYPE(hdr) != HCI_3WIRE_LINK_PKT) {
		BT_ERR("Non-link packet received in non-active state");
		h5_reset_rx(h5);
	}

	h5->rx_func = h5_rx_payload;
	h5->rx_pending = H5_HDR_LEN(hdr);

	return 0;
}

static int h5_rx_pkt_start(struct hci_uart *hu, unsigned char c)
{
	struct h5 *h5 = hu->priv;

	if (c == SLIP_DELIMITER)
		return 1;

	h5->rx_func = h5_rx_3wire_hdr;
	h5->rx_pending = 4;

	h5->rx_skb = bt_skb_alloc(H5_MAX_LEN, GFP_ATOMIC);
	if (!h5->rx_skb) {
		BT_ERR("Can't allocate mem for new packet");
		h5_reset_rx(h5);
		return -ENOMEM;
	}

	h5->rx_skb->dev = (void *) hu->hdev;

	return 0;
}

static int h5_rx_delimiter(struct hci_uart *hu, unsigned char c)
{
	struct h5 *h5 = hu->priv;

	if (c == SLIP_DELIMITER)
		h5->rx_func = h5_rx_pkt_start;

	return 1;
}

static void h5_unslip_one_byte(struct h5 *h5, unsigned char c)
{
	const u8 delim = SLIP_DELIMITER, esc = SLIP_ESC;
	const u8 *byte = &c;

	if (!test_bit(H5_RX_ESC, &h5->flags) && c == SLIP_ESC) {
		set_bit(H5_RX_ESC, &h5->flags);
		return;
	}

	if (test_and_clear_bit(H5_RX_ESC, &h5->flags)) {
		switch (c) {
		case SLIP_ESC_DELIM:
			byte = &delim;
			break;
		case SLIP_ESC_ESC:
			byte = &esc;
			break;
		default:
			BT_ERR("Invalid esc byte 0x%02hhx", c);
			h5_reset_rx(h5);
			return;
		}
	}

	memcpy(skb_put(h5->rx_skb, 1), byte, 1);
	h5->rx_pending--;

	BT_DBG("unsliped 0x%02hhx, rx_pending %zu", *byte, h5->rx_pending);
}

static void h5_reset_rx(struct h5 *h5)
{
	if (h5->rx_skb) {
		kfree_skb(h5->rx_skb);
		h5->rx_skb = NULL;
	}

	h5->rx_func = h5_rx_delimiter;
	h5->rx_pending = 0;
	clear_bit(H5_RX_ESC, &h5->flags);
}

static int h5_recv(struct hci_uart *hu, void *data, int count)
{
	struct h5 *h5 = hu->priv;
	unsigned char *ptr = data;

	BT_DBG("%s pending %zu count %d", hu->hdev->name, h5->rx_pending,
	       count);

	while (count > 0) {
		int processed;

		if (h5->rx_pending > 0) {
			if (*ptr == SLIP_DELIMITER) {
				BT_ERR("Too short H5 packet");
				h5_reset_rx(h5);
				continue;
			}

			h5_unslip_one_byte(h5, *ptr);

			ptr++; count--;
			continue;
		}

		processed = h5->rx_func(hu, *ptr);
		if (processed < 0)
			return processed;

		ptr += processed;
		count -= processed;
	}

	return 0;
}

static int h5_enqueue(struct hci_uart *hu, struct sk_buff *skb)
{
	struct h5 *h5 = hu->priv;

	if (skb->len > 0xfff) {
		BT_ERR("Packet too long (%u bytes)", skb->len);
		kfree_skb(skb);
		return 0;
	}

	if (h5->state != H5_ACTIVE) {
		BT_ERR("Ignoring HCI data in non-active state");
		kfree_skb(skb);
		return 0;
	}

	switch (bt_cb(skb)->pkt_type) {
	case HCI_ACLDATA_PKT:
	case HCI_COMMAND_PKT:
		skb_queue_tail(&h5->rel, skb);
		break;

	case HCI_SCODATA_PKT:
		skb_queue_tail(&h5->unrel, skb);
		break;

	default:
		BT_ERR("Unknown packet type %u", bt_cb(skb)->pkt_type);
		kfree_skb(skb);
		break;
	}

	return 0;
}

static void h5_slip_delim(struct sk_buff *skb)
{
	const char delim = SLIP_DELIMITER;

	memcpy(skb_put(skb, 1), &delim, 1);
}

static void h5_slip_one_byte(struct sk_buff *skb, u8 c)
{
	const char esc_delim[2] = { SLIP_ESC, SLIP_ESC_DELIM };
	const char esc_esc[2] = { SLIP_ESC, SLIP_ESC_ESC };

	switch (c) {
	case SLIP_DELIMITER:
		memcpy(skb_put(skb, 2), &esc_delim, 2);
		break;
	case SLIP_ESC:
		memcpy(skb_put(skb, 2), &esc_esc, 2);
		break;
	default:
		memcpy(skb_put(skb, 1), &c, 1);
	}
}

static bool valid_packet_type(u8 type)
{
	switch (type) {
	case HCI_ACLDATA_PKT:
	case HCI_COMMAND_PKT:
	case HCI_SCODATA_PKT:
	case HCI_3WIRE_LINK_PKT:
	case HCI_3WIRE_ACK_PKT:
		return true;
	default:
		return false;
	}
}

static struct sk_buff *h5_prepare_pkt(struct hci_uart *hu, u8 pkt_type,
				      const u8 *data, size_t len)
{
	struct h5 *h5 = hu->priv;
	struct sk_buff *nskb;
	u8 hdr[4];
	int i;

	if (!valid_packet_type(pkt_type)) {
		BT_ERR("Unknown packet type %u", pkt_type);
		return NULL;
	}

	/*
	 * Max len of packet: (original len + 4 (H5 hdr) + 2 (crc)) * 2
	 * (because bytes 0xc0 and 0xdb are escaped, worst case is when
	 * the packet is all made of 0xc0 and 0xdb) + 2 (0xc0
	 * delimiters at start and end).
	 */
	nskb = alloc_skb((len + 6) * 2 + 2, GFP_ATOMIC);
	if (!nskb)
		return NULL;

	bt_cb(nskb)->pkt_type = pkt_type;

	h5_slip_delim(nskb);

	hdr[0] = h5->tx_ack << 3;
	clear_bit(H5_TX_ACK_REQ, &h5->flags);

	/* Reliable packet? */
	if (pkt_type == HCI_ACLDATA_PKT || pkt_type == HCI_COMMAND_PKT) {
		hdr[0] |= 1 << 7;
		hdr[0] |= h5->tx_seq;
		h5->tx_seq = (h5->tx_seq + 1) % 8;
	}

	hdr[1] = pkt_type | ((len & 0x0f) << 4);
	hdr[2] = len >> 4;
	hdr[3] = ~((hdr[0] + hdr[1] + hdr[2]) & 0xff);

	BT_DBG("%s tx: seq %u ack %u crc %u rel %u type %u len %u",
	       hu->hdev->name, H5_HDR_SEQ(hdr), H5_HDR_ACK(hdr),
	       H5_HDR_CRC(hdr), H5_HDR_RELIABLE(hdr), H5_HDR_PKT_TYPE(hdr),
	       H5_HDR_LEN(hdr));

	for (i = 0; i < 4; i++)
		h5_slip_one_byte(nskb, hdr[i]);

	for (i = 0; i < len; i++)
		h5_slip_one_byte(nskb, data[i]);

	h5_slip_delim(nskb);

	return nskb;
}

static struct sk_buff *h5_dequeue(struct hci_uart *hu)
{
	struct h5 *h5 = hu->priv;
	unsigned long flags;
	struct sk_buff *skb, *nskb;

	if (h5->sleep != H5_AWAKE) {
		const unsigned char wakeup_req[] = { 0x05, 0xfa };

		if (h5->sleep == H5_WAKING_UP)
			return NULL;

		h5->sleep = H5_WAKING_UP;
		BT_DBG("Sending wakeup request");

		mod_timer(&h5->timer, jiffies + HZ / 100);
		return h5_prepare_pkt(hu, HCI_3WIRE_LINK_PKT, wakeup_req, 2);
	}

	if ((skb = skb_dequeue(&h5->unrel)) != NULL) {
		nskb = h5_prepare_pkt(hu, bt_cb(skb)->pkt_type,
				      skb->data, skb->len);
		if (nskb) {
			kfree_skb(skb);
			return nskb;
		}

		skb_queue_head(&h5->unrel, skb);
		BT_ERR("Could not dequeue pkt because alloc_skb failed");
	}

	spin_lock_irqsave_nested(&h5->unack.lock, flags, SINGLE_DEPTH_NESTING);

	if (h5->unack.qlen >= h5->tx_win)
		goto unlock;

	if ((skb = skb_dequeue(&h5->rel)) != NULL) {
		nskb = h5_prepare_pkt(hu, bt_cb(skb)->pkt_type,
				      skb->data, skb->len);
		if (nskb) {
			__skb_queue_tail(&h5->unack, skb);
			mod_timer(&h5->timer, jiffies + H5_ACK_TIMEOUT);
			spin_unlock_irqrestore(&h5->unack.lock, flags);
			return nskb;
		}

		skb_queue_head(&h5->rel, skb);
		BT_ERR("Could not dequeue pkt because alloc_skb failed");
	}

unlock:
	spin_unlock_irqrestore(&h5->unack.lock, flags);

	if (test_bit(H5_TX_ACK_REQ, &h5->flags))
		return h5_prepare_pkt(hu, HCI_3WIRE_ACK_PKT, NULL, 0);

	return NULL;
}

static int h5_flush(struct hci_uart *hu)
{
	BT_DBG("hu %p", hu);
	return 0;
}

static struct hci_uart_proto h5p = {
	.id		= HCI_UART_3WIRE,
	.open		= h5_open,
	.close		= h5_close,
	.recv		= h5_recv,
	.enqueue	= h5_enqueue,
	.dequeue	= h5_dequeue,
	.flush		= h5_flush,
};

int __init h5_init(void)
{
	int err = hci_uart_register_proto(&h5p);

	if (!err)
		BT_INFO("HCI Three-wire UART (H5) protocol initialized");
	else
		BT_ERR("HCI Three-wire UART (H5) protocol init failed");

	return err;
}

int __exit h5_deinit(void)
{
	return hci_uart_unregister_proto(&h5p);
}