xref: /openbmc/linux/drivers/bluetooth/hci_h5.c (revision 6774def6)
1 /*
2  *
3  *  Bluetooth HCI Three-wire UART driver
4  *
5  *  Copyright (C) 2012  Intel Corporation
6  *
7  *
8  *  This program is free software; you can redistribute it and/or modify
9  *  it under the terms of the GNU General Public License as published by
10  *  the Free Software Foundation; either version 2 of the License, or
11  *  (at your option) any later version.
12  *
13  *  This program is distributed in the hope that it will be useful,
14  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
15  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16  *  GNU General Public License for more details.
17  *
18  *  You should have received a copy of the GNU General Public License
19  *  along with this program; if not, write to the Free Software
20  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
21  *
22  */
23 
24 #include <linux/kernel.h>
25 #include <linux/errno.h>
26 #include <linux/skbuff.h>
27 
28 #include <net/bluetooth/bluetooth.h>
29 #include <net/bluetooth/hci_core.h>
30 
31 #include "hci_uart.h"
32 
33 #define HCI_3WIRE_ACK_PKT	0
34 #define HCI_3WIRE_LINK_PKT	15
35 
36 /* Sliding window size */
37 #define H5_TX_WIN_MAX		4
38 
39 #define H5_ACK_TIMEOUT	msecs_to_jiffies(250)
40 #define H5_SYNC_TIMEOUT	msecs_to_jiffies(100)
41 
42 /*
43  * Maximum Three-wire packet:
44  *     4 byte header + max value for 12-bit length + 2 bytes for CRC
45  */
46 #define H5_MAX_LEN (4 + 0xfff + 2)
47 
48 /* Convenience macros for reading Three-wire header values */
49 #define H5_HDR_SEQ(hdr)		((hdr)[0] & 0x07)
50 #define H5_HDR_ACK(hdr)		(((hdr)[0] >> 3) & 0x07)
51 #define H5_HDR_CRC(hdr)		(((hdr)[0] >> 6) & 0x01)
52 #define H5_HDR_RELIABLE(hdr)	(((hdr)[0] >> 7) & 0x01)
53 #define H5_HDR_PKT_TYPE(hdr)	((hdr)[1] & 0x0f)
54 #define H5_HDR_LEN(hdr)		((((hdr)[1] >> 4) & 0xff) + ((hdr)[2] << 4))
55 
56 #define SLIP_DELIMITER	0xc0
57 #define SLIP_ESC	0xdb
58 #define SLIP_ESC_DELIM	0xdc
59 #define SLIP_ESC_ESC	0xdd
60 
61 /* H5 state flags */
62 enum {
63 	H5_RX_ESC,	/* SLIP escape mode */
64 	H5_TX_ACK_REQ,	/* Pending ack to send */
65 };
66 
67 struct h5 {
68 	struct sk_buff_head	unack;		/* Unack'ed packets queue */
69 	struct sk_buff_head	rel;		/* Reliable packets queue */
70 	struct sk_buff_head	unrel;		/* Unreliable packets queue */
71 
72 	unsigned long		flags;
73 
74 	struct sk_buff		*rx_skb;	/* Receive buffer */
75 	size_t			rx_pending;	/* Expecting more bytes */
76 	u8			rx_ack;		/* Last ack number received */
77 
78 	int			(*rx_func) (struct hci_uart *hu, u8 c);
79 
80 	struct timer_list	timer;		/* Retransmission timer */
81 
82 	u8			tx_seq;		/* Next seq number to send */
83 	u8			tx_ack;		/* Next ack number to send */
84 	u8			tx_win;		/* Sliding window size */
85 
86 	enum {
87 		H5_UNINITIALIZED,
88 		H5_INITIALIZED,
89 		H5_ACTIVE,
90 	} state;
91 
92 	enum {
93 		H5_AWAKE,
94 		H5_SLEEPING,
95 		H5_WAKING_UP,
96 	} sleep;
97 };
98 
99 static void h5_reset_rx(struct h5 *h5);
100 
101 static void h5_link_control(struct hci_uart *hu, const void *data, size_t len)
102 {
103 	struct h5 *h5 = hu->priv;
104 	struct sk_buff *nskb;
105 
106 	nskb = alloc_skb(3, GFP_ATOMIC);
107 	if (!nskb)
108 		return;
109 
110 	bt_cb(nskb)->pkt_type = HCI_3WIRE_LINK_PKT;
111 
112 	memcpy(skb_put(nskb, len), data, len);
113 
114 	skb_queue_tail(&h5->unrel, nskb);
115 }
116 
117 static u8 h5_cfg_field(struct h5 *h5)
118 {
119 	u8 field = 0;
120 
121 	/* Sliding window size (first 3 bits) */
122 	field |= (h5->tx_win & 7);
123 
124 	return field;
125 }
126 
127 static void h5_timed_event(unsigned long arg)
128 {
129 	const unsigned char sync_req[] = { 0x01, 0x7e };
130 	unsigned char conf_req[] = { 0x03, 0xfc, 0x01 };
131 	struct hci_uart *hu = (struct hci_uart *) arg;
132 	struct h5 *h5 = hu->priv;
133 	struct sk_buff *skb;
134 	unsigned long flags;
135 
136 	BT_DBG("%s", hu->hdev->name);
137 
138 	if (h5->state == H5_UNINITIALIZED)
139 		h5_link_control(hu, sync_req, sizeof(sync_req));
140 
141 	if (h5->state == H5_INITIALIZED) {
142 		conf_req[2] = h5_cfg_field(h5);
143 		h5_link_control(hu, conf_req, sizeof(conf_req));
144 	}
145 
146 	if (h5->state != H5_ACTIVE) {
147 		mod_timer(&h5->timer, jiffies + H5_SYNC_TIMEOUT);
148 		goto wakeup;
149 	}
150 
151 	if (h5->sleep != H5_AWAKE) {
152 		h5->sleep = H5_SLEEPING;
153 		goto wakeup;
154 	}
155 
156 	BT_DBG("hu %p retransmitting %u pkts", hu, h5->unack.qlen);
157 
158 	spin_lock_irqsave_nested(&h5->unack.lock, flags, SINGLE_DEPTH_NESTING);
159 
160 	while ((skb = __skb_dequeue_tail(&h5->unack)) != NULL) {
161 		h5->tx_seq = (h5->tx_seq - 1) & 0x07;
162 		skb_queue_head(&h5->rel, skb);
163 	}
164 
165 	spin_unlock_irqrestore(&h5->unack.lock, flags);
166 
167 wakeup:
168 	hci_uart_tx_wakeup(hu);
169 }
170 
171 static int h5_open(struct hci_uart *hu)
172 {
173 	struct h5 *h5;
174 	const unsigned char sync[] = { 0x01, 0x7e };
175 
176 	BT_DBG("hu %p", hu);
177 
178 	h5 = kzalloc(sizeof(*h5), GFP_KERNEL);
179 	if (!h5)
180 		return -ENOMEM;
181 
182 	hu->priv = h5;
183 
184 	skb_queue_head_init(&h5->unack);
185 	skb_queue_head_init(&h5->rel);
186 	skb_queue_head_init(&h5->unrel);
187 
188 	h5_reset_rx(h5);
189 
190 	init_timer(&h5->timer);
191 	h5->timer.function = h5_timed_event;
192 	h5->timer.data = (unsigned long) hu;
193 
194 	h5->tx_win = H5_TX_WIN_MAX;
195 
196 	set_bit(HCI_UART_INIT_PENDING, &hu->hdev_flags);
197 
198 	/* Send initial sync request */
199 	h5_link_control(hu, sync, sizeof(sync));
200 	mod_timer(&h5->timer, jiffies + H5_SYNC_TIMEOUT);
201 
202 	return 0;
203 }
204 
205 static int h5_close(struct hci_uart *hu)
206 {
207 	struct h5 *h5 = hu->priv;
208 
209 	del_timer_sync(&h5->timer);
210 
211 	skb_queue_purge(&h5->unack);
212 	skb_queue_purge(&h5->rel);
213 	skb_queue_purge(&h5->unrel);
214 
215 	kfree(h5);
216 
217 	return 0;
218 }
219 
220 static void h5_pkt_cull(struct h5 *h5)
221 {
222 	struct sk_buff *skb, *tmp;
223 	unsigned long flags;
224 	int i, to_remove;
225 	u8 seq;
226 
227 	spin_lock_irqsave(&h5->unack.lock, flags);
228 
229 	to_remove = skb_queue_len(&h5->unack);
230 	if (to_remove == 0)
231 		goto unlock;
232 
233 	seq = h5->tx_seq;
234 
235 	while (to_remove > 0) {
236 		if (h5->rx_ack == seq)
237 			break;
238 
239 		to_remove--;
240 		seq = (seq - 1) & 0x07;
241 	}
242 
243 	if (seq != h5->rx_ack)
244 		BT_ERR("Controller acked invalid packet");
245 
246 	i = 0;
247 	skb_queue_walk_safe(&h5->unack, skb, tmp) {
248 		if (i++ >= to_remove)
249 			break;
250 
251 		__skb_unlink(skb, &h5->unack);
252 		kfree_skb(skb);
253 	}
254 
255 	if (skb_queue_empty(&h5->unack))
256 		del_timer(&h5->timer);
257 
258 unlock:
259 	spin_unlock_irqrestore(&h5->unack.lock, flags);
260 }
261 
262 static void h5_handle_internal_rx(struct hci_uart *hu)
263 {
264 	struct h5 *h5 = hu->priv;
265 	const unsigned char sync_req[] = { 0x01, 0x7e };
266 	const unsigned char sync_rsp[] = { 0x02, 0x7d };
267 	unsigned char conf_req[] = { 0x03, 0xfc, 0x01 };
268 	const unsigned char conf_rsp[] = { 0x04, 0x7b };
269 	const unsigned char wakeup_req[] = { 0x05, 0xfa };
270 	const unsigned char woken_req[] = { 0x06, 0xf9 };
271 	const unsigned char sleep_req[] = { 0x07, 0x78 };
272 	const unsigned char *hdr = h5->rx_skb->data;
273 	const unsigned char *data = &h5->rx_skb->data[4];
274 
275 	BT_DBG("%s", hu->hdev->name);
276 
277 	if (H5_HDR_PKT_TYPE(hdr) != HCI_3WIRE_LINK_PKT)
278 		return;
279 
280 	if (H5_HDR_LEN(hdr) < 2)
281 		return;
282 
283 	conf_req[2] = h5_cfg_field(h5);
284 
285 	if (memcmp(data, sync_req, 2) == 0) {
286 		h5_link_control(hu, sync_rsp, 2);
287 	} else if (memcmp(data, sync_rsp, 2) == 0) {
288 		h5->state = H5_INITIALIZED;
289 		h5_link_control(hu, conf_req, 3);
290 	} else if (memcmp(data, conf_req, 2) == 0) {
291 		h5_link_control(hu, conf_rsp, 2);
292 		h5_link_control(hu, conf_req, 3);
293 	} else if (memcmp(data, conf_rsp, 2) == 0) {
294 		if (H5_HDR_LEN(hdr) > 2)
295 			h5->tx_win = (data[2] & 7);
296 		BT_DBG("Three-wire init complete. tx_win %u", h5->tx_win);
297 		h5->state = H5_ACTIVE;
298 		hci_uart_init_ready(hu);
299 		return;
300 	} else if (memcmp(data, sleep_req, 2) == 0) {
301 		BT_DBG("Peer went to sleep");
302 		h5->sleep = H5_SLEEPING;
303 		return;
304 	} else if (memcmp(data, woken_req, 2) == 0) {
305 		BT_DBG("Peer woke up");
306 		h5->sleep = H5_AWAKE;
307 	} else if (memcmp(data, wakeup_req, 2) == 0) {
308 		BT_DBG("Peer requested wakeup");
309 		h5_link_control(hu, woken_req, 2);
310 		h5->sleep = H5_AWAKE;
311 	} else {
312 		BT_DBG("Link Control: 0x%02hhx 0x%02hhx", data[0], data[1]);
313 		return;
314 	}
315 
316 	hci_uart_tx_wakeup(hu);
317 }
318 
319 static void h5_complete_rx_pkt(struct hci_uart *hu)
320 {
321 	struct h5 *h5 = hu->priv;
322 	const unsigned char *hdr = h5->rx_skb->data;
323 
324 	if (H5_HDR_RELIABLE(hdr)) {
325 		h5->tx_ack = (h5->tx_ack + 1) % 8;
326 		set_bit(H5_TX_ACK_REQ, &h5->flags);
327 		hci_uart_tx_wakeup(hu);
328 	}
329 
330 	h5->rx_ack = H5_HDR_ACK(hdr);
331 
332 	h5_pkt_cull(h5);
333 
334 	switch (H5_HDR_PKT_TYPE(hdr)) {
335 	case HCI_EVENT_PKT:
336 	case HCI_ACLDATA_PKT:
337 	case HCI_SCODATA_PKT:
338 		bt_cb(h5->rx_skb)->pkt_type = H5_HDR_PKT_TYPE(hdr);
339 
340 		/* Remove Three-wire header */
341 		skb_pull(h5->rx_skb, 4);
342 
343 		hci_recv_frame(hu->hdev, h5->rx_skb);
344 		h5->rx_skb = NULL;
345 
346 		break;
347 
348 	default:
349 		h5_handle_internal_rx(hu);
350 		break;
351 	}
352 
353 	h5_reset_rx(h5);
354 }
355 
356 static int h5_rx_crc(struct hci_uart *hu, unsigned char c)
357 {
358 	h5_complete_rx_pkt(hu);
359 
360 	return 0;
361 }
362 
363 static int h5_rx_payload(struct hci_uart *hu, unsigned char c)
364 {
365 	struct h5 *h5 = hu->priv;
366 	const unsigned char *hdr = h5->rx_skb->data;
367 
368 	if (H5_HDR_CRC(hdr)) {
369 		h5->rx_func = h5_rx_crc;
370 		h5->rx_pending = 2;
371 	} else {
372 		h5_complete_rx_pkt(hu);
373 	}
374 
375 	return 0;
376 }
377 
378 static int h5_rx_3wire_hdr(struct hci_uart *hu, unsigned char c)
379 {
380 	struct h5 *h5 = hu->priv;
381 	const unsigned char *hdr = h5->rx_skb->data;
382 
383 	BT_DBG("%s rx: seq %u ack %u crc %u rel %u type %u len %u",
384 	       hu->hdev->name, H5_HDR_SEQ(hdr), H5_HDR_ACK(hdr),
385 	       H5_HDR_CRC(hdr), H5_HDR_RELIABLE(hdr), H5_HDR_PKT_TYPE(hdr),
386 	       H5_HDR_LEN(hdr));
387 
388 	if (((hdr[0] + hdr[1] + hdr[2] + hdr[3]) & 0xff) != 0xff) {
389 		BT_ERR("Invalid header checksum");
390 		h5_reset_rx(h5);
391 		return 0;
392 	}
393 
394 	if (H5_HDR_RELIABLE(hdr) && H5_HDR_SEQ(hdr) != h5->tx_ack) {
395 		BT_ERR("Out-of-order packet arrived (%u != %u)",
396 		       H5_HDR_SEQ(hdr), h5->tx_ack);
397 		h5_reset_rx(h5);
398 		return 0;
399 	}
400 
401 	if (h5->state != H5_ACTIVE &&
402 	    H5_HDR_PKT_TYPE(hdr) != HCI_3WIRE_LINK_PKT) {
403 		BT_ERR("Non-link packet received in non-active state");
404 		h5_reset_rx(h5);
405 		return 0;
406 	}
407 
408 	h5->rx_func = h5_rx_payload;
409 	h5->rx_pending = H5_HDR_LEN(hdr);
410 
411 	return 0;
412 }
413 
414 static int h5_rx_pkt_start(struct hci_uart *hu, unsigned char c)
415 {
416 	struct h5 *h5 = hu->priv;
417 
418 	if (c == SLIP_DELIMITER)
419 		return 1;
420 
421 	h5->rx_func = h5_rx_3wire_hdr;
422 	h5->rx_pending = 4;
423 
424 	h5->rx_skb = bt_skb_alloc(H5_MAX_LEN, GFP_ATOMIC);
425 	if (!h5->rx_skb) {
426 		BT_ERR("Can't allocate mem for new packet");
427 		h5_reset_rx(h5);
428 		return -ENOMEM;
429 	}
430 
431 	h5->rx_skb->dev = (void *) hu->hdev;
432 
433 	return 0;
434 }
435 
436 static int h5_rx_delimiter(struct hci_uart *hu, unsigned char c)
437 {
438 	struct h5 *h5 = hu->priv;
439 
440 	if (c == SLIP_DELIMITER)
441 		h5->rx_func = h5_rx_pkt_start;
442 
443 	return 1;
444 }
445 
446 static void h5_unslip_one_byte(struct h5 *h5, unsigned char c)
447 {
448 	const u8 delim = SLIP_DELIMITER, esc = SLIP_ESC;
449 	const u8 *byte = &c;
450 
451 	if (!test_bit(H5_RX_ESC, &h5->flags) && c == SLIP_ESC) {
452 		set_bit(H5_RX_ESC, &h5->flags);
453 		return;
454 	}
455 
456 	if (test_and_clear_bit(H5_RX_ESC, &h5->flags)) {
457 		switch (c) {
458 		case SLIP_ESC_DELIM:
459 			byte = &delim;
460 			break;
461 		case SLIP_ESC_ESC:
462 			byte = &esc;
463 			break;
464 		default:
465 			BT_ERR("Invalid esc byte 0x%02hhx", c);
466 			h5_reset_rx(h5);
467 			return;
468 		}
469 	}
470 
471 	memcpy(skb_put(h5->rx_skb, 1), byte, 1);
472 	h5->rx_pending--;
473 
474 	BT_DBG("unsliped 0x%02hhx, rx_pending %zu", *byte, h5->rx_pending);
475 }
476 
477 static void h5_reset_rx(struct h5 *h5)
478 {
479 	if (h5->rx_skb) {
480 		kfree_skb(h5->rx_skb);
481 		h5->rx_skb = NULL;
482 	}
483 
484 	h5->rx_func = h5_rx_delimiter;
485 	h5->rx_pending = 0;
486 	clear_bit(H5_RX_ESC, &h5->flags);
487 }
488 
489 static int h5_recv(struct hci_uart *hu, void *data, int count)
490 {
491 	struct h5 *h5 = hu->priv;
492 	unsigned char *ptr = data;
493 
494 	BT_DBG("%s pending %zu count %d", hu->hdev->name, h5->rx_pending,
495 	       count);
496 
497 	while (count > 0) {
498 		int processed;
499 
500 		if (h5->rx_pending > 0) {
501 			if (*ptr == SLIP_DELIMITER) {
502 				BT_ERR("Too short H5 packet");
503 				h5_reset_rx(h5);
504 				continue;
505 			}
506 
507 			h5_unslip_one_byte(h5, *ptr);
508 
509 			ptr++; count--;
510 			continue;
511 		}
512 
513 		processed = h5->rx_func(hu, *ptr);
514 		if (processed < 0)
515 			return processed;
516 
517 		ptr += processed;
518 		count -= processed;
519 	}
520 
521 	return 0;
522 }
523 
524 static int h5_enqueue(struct hci_uart *hu, struct sk_buff *skb)
525 {
526 	struct h5 *h5 = hu->priv;
527 
528 	if (skb->len > 0xfff) {
529 		BT_ERR("Packet too long (%u bytes)", skb->len);
530 		kfree_skb(skb);
531 		return 0;
532 	}
533 
534 	if (h5->state != H5_ACTIVE) {
535 		BT_ERR("Ignoring HCI data in non-active state");
536 		kfree_skb(skb);
537 		return 0;
538 	}
539 
540 	switch (bt_cb(skb)->pkt_type) {
541 	case HCI_ACLDATA_PKT:
542 	case HCI_COMMAND_PKT:
543 		skb_queue_tail(&h5->rel, skb);
544 		break;
545 
546 	case HCI_SCODATA_PKT:
547 		skb_queue_tail(&h5->unrel, skb);
548 		break;
549 
550 	default:
551 		BT_ERR("Unknown packet type %u", bt_cb(skb)->pkt_type);
552 		kfree_skb(skb);
553 		break;
554 	}
555 
556 	return 0;
557 }
558 
559 static void h5_slip_delim(struct sk_buff *skb)
560 {
561 	const char delim = SLIP_DELIMITER;
562 
563 	memcpy(skb_put(skb, 1), &delim, 1);
564 }
565 
566 static void h5_slip_one_byte(struct sk_buff *skb, u8 c)
567 {
568 	const char esc_delim[2] = { SLIP_ESC, SLIP_ESC_DELIM };
569 	const char esc_esc[2] = { SLIP_ESC, SLIP_ESC_ESC };
570 
571 	switch (c) {
572 	case SLIP_DELIMITER:
573 		memcpy(skb_put(skb, 2), &esc_delim, 2);
574 		break;
575 	case SLIP_ESC:
576 		memcpy(skb_put(skb, 2), &esc_esc, 2);
577 		break;
578 	default:
579 		memcpy(skb_put(skb, 1), &c, 1);
580 	}
581 }
582 
583 static bool valid_packet_type(u8 type)
584 {
585 	switch (type) {
586 	case HCI_ACLDATA_PKT:
587 	case HCI_COMMAND_PKT:
588 	case HCI_SCODATA_PKT:
589 	case HCI_3WIRE_LINK_PKT:
590 	case HCI_3WIRE_ACK_PKT:
591 		return true;
592 	default:
593 		return false;
594 	}
595 }
596 
597 static struct sk_buff *h5_prepare_pkt(struct hci_uart *hu, u8 pkt_type,
598 				      const u8 *data, size_t len)
599 {
600 	struct h5 *h5 = hu->priv;
601 	struct sk_buff *nskb;
602 	u8 hdr[4];
603 	int i;
604 
605 	if (!valid_packet_type(pkt_type)) {
606 		BT_ERR("Unknown packet type %u", pkt_type);
607 		return NULL;
608 	}
609 
610 	/*
611 	 * Max len of packet: (original len + 4 (H5 hdr) + 2 (crc)) * 2
612 	 * (because bytes 0xc0 and 0xdb are escaped, worst case is when
613 	 * the packet is all made of 0xc0 and 0xdb) + 2 (0xc0
614 	 * delimiters at start and end).
615 	 */
616 	nskb = alloc_skb((len + 6) * 2 + 2, GFP_ATOMIC);
617 	if (!nskb)
618 		return NULL;
619 
620 	bt_cb(nskb)->pkt_type = pkt_type;
621 
622 	h5_slip_delim(nskb);
623 
624 	hdr[0] = h5->tx_ack << 3;
625 	clear_bit(H5_TX_ACK_REQ, &h5->flags);
626 
627 	/* Reliable packet? */
628 	if (pkt_type == HCI_ACLDATA_PKT || pkt_type == HCI_COMMAND_PKT) {
629 		hdr[0] |= 1 << 7;
630 		hdr[0] |= h5->tx_seq;
631 		h5->tx_seq = (h5->tx_seq + 1) % 8;
632 	}
633 
634 	hdr[1] = pkt_type | ((len & 0x0f) << 4);
635 	hdr[2] = len >> 4;
636 	hdr[3] = ~((hdr[0] + hdr[1] + hdr[2]) & 0xff);
637 
638 	BT_DBG("%s tx: seq %u ack %u crc %u rel %u type %u len %u",
639 	       hu->hdev->name, H5_HDR_SEQ(hdr), H5_HDR_ACK(hdr),
640 	       H5_HDR_CRC(hdr), H5_HDR_RELIABLE(hdr), H5_HDR_PKT_TYPE(hdr),
641 	       H5_HDR_LEN(hdr));
642 
643 	for (i = 0; i < 4; i++)
644 		h5_slip_one_byte(nskb, hdr[i]);
645 
646 	for (i = 0; i < len; i++)
647 		h5_slip_one_byte(nskb, data[i]);
648 
649 	h5_slip_delim(nskb);
650 
651 	return nskb;
652 }
653 
654 static struct sk_buff *h5_dequeue(struct hci_uart *hu)
655 {
656 	struct h5 *h5 = hu->priv;
657 	unsigned long flags;
658 	struct sk_buff *skb, *nskb;
659 
660 	if (h5->sleep != H5_AWAKE) {
661 		const unsigned char wakeup_req[] = { 0x05, 0xfa };
662 
663 		if (h5->sleep == H5_WAKING_UP)
664 			return NULL;
665 
666 		h5->sleep = H5_WAKING_UP;
667 		BT_DBG("Sending wakeup request");
668 
669 		mod_timer(&h5->timer, jiffies + HZ / 100);
670 		return h5_prepare_pkt(hu, HCI_3WIRE_LINK_PKT, wakeup_req, 2);
671 	}
672 
673 	skb = skb_dequeue(&h5->unrel);
674 	if (skb != NULL) {
675 		nskb = h5_prepare_pkt(hu, bt_cb(skb)->pkt_type,
676 				      skb->data, skb->len);
677 		if (nskb) {
678 			kfree_skb(skb);
679 			return nskb;
680 		}
681 
682 		skb_queue_head(&h5->unrel, skb);
683 		BT_ERR("Could not dequeue pkt because alloc_skb failed");
684 	}
685 
686 	spin_lock_irqsave_nested(&h5->unack.lock, flags, SINGLE_DEPTH_NESTING);
687 
688 	if (h5->unack.qlen >= h5->tx_win)
689 		goto unlock;
690 
691 	skb = skb_dequeue(&h5->rel);
692 	if (skb != NULL) {
693 		nskb = h5_prepare_pkt(hu, bt_cb(skb)->pkt_type,
694 				      skb->data, skb->len);
695 		if (nskb) {
696 			__skb_queue_tail(&h5->unack, skb);
697 			mod_timer(&h5->timer, jiffies + H5_ACK_TIMEOUT);
698 			spin_unlock_irqrestore(&h5->unack.lock, flags);
699 			return nskb;
700 		}
701 
702 		skb_queue_head(&h5->rel, skb);
703 		BT_ERR("Could not dequeue pkt because alloc_skb failed");
704 	}
705 
706 unlock:
707 	spin_unlock_irqrestore(&h5->unack.lock, flags);
708 
709 	if (test_bit(H5_TX_ACK_REQ, &h5->flags))
710 		return h5_prepare_pkt(hu, HCI_3WIRE_ACK_PKT, NULL, 0);
711 
712 	return NULL;
713 }
714 
715 static int h5_flush(struct hci_uart *hu)
716 {
717 	BT_DBG("hu %p", hu);
718 	return 0;
719 }
720 
721 static struct hci_uart_proto h5p = {
722 	.id		= HCI_UART_3WIRE,
723 	.open		= h5_open,
724 	.close		= h5_close,
725 	.recv		= h5_recv,
726 	.enqueue	= h5_enqueue,
727 	.dequeue	= h5_dequeue,
728 	.flush		= h5_flush,
729 };
730 
731 int __init h5_init(void)
732 {
733 	int err = hci_uart_register_proto(&h5p);
734 
735 	if (!err)
736 		BT_INFO("HCI Three-wire UART (H5) protocol initialized");
737 	else
738 		BT_ERR("HCI Three-wire UART (H5) protocol init failed");
739 
740 	return err;
741 }
742 
743 int __exit h5_deinit(void)
744 {
745 	return hci_uart_unregister_proto(&h5p);
746 }
747