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  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 */
 62enum {
 63	H5_RX_ESC,	/* SLIP escape mode */
 64	H5_TX_ACK_REQ,	/* Pending ack to send */
 65};
 66
 67struct 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
 99static void h5_reset_rx(struct h5 *h5);
100
101static 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
117static 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
127static 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
167wakeup:
168	hci_uart_tx_wakeup(hu);
169}
170
171static 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
205static 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
220static 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) % 8;
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
258unlock:
259	spin_unlock_irqrestore(&h5->unack.lock, flags);
260}
261
262static 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
319static 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
356static int h5_rx_crc(struct hci_uart *hu, unsigned char c)
357{
358	struct h5 *h5 = hu->priv;
359
360	h5_complete_rx_pkt(hu);
361	h5_reset_rx(h5);
362
363	return 0;
364}
365
366static int h5_rx_payload(struct hci_uart *hu, unsigned char c)
367{
368	struct h5 *h5 = hu->priv;
369	const unsigned char *hdr = h5->rx_skb->data;
370
371	if (H5_HDR_CRC(hdr)) {
372		h5->rx_func = h5_rx_crc;
373		h5->rx_pending = 2;
374	} else {
375		h5_complete_rx_pkt(hu);
376		h5_reset_rx(h5);
377	}
378
379	return 0;
380}
381
382static int h5_rx_3wire_hdr(struct hci_uart *hu, unsigned char c)
383{
384	struct h5 *h5 = hu->priv;
385	const unsigned char *hdr = h5->rx_skb->data;
386
387	BT_DBG("%s rx: seq %u ack %u crc %u rel %u type %u len %u",
388	       hu->hdev->name, H5_HDR_SEQ(hdr), H5_HDR_ACK(hdr),
389	       H5_HDR_CRC(hdr), H5_HDR_RELIABLE(hdr), H5_HDR_PKT_TYPE(hdr),
390	       H5_HDR_LEN(hdr));
391
392	if (((hdr[0] + hdr[1] + hdr[2] + hdr[3]) & 0xff) != 0xff) {
393		BT_ERR("Invalid header checksum");
394		h5_reset_rx(h5);
395		return 0;
396	}
397
398	if (H5_HDR_RELIABLE(hdr) && H5_HDR_SEQ(hdr) != h5->tx_ack) {
399		BT_ERR("Out-of-order packet arrived (%u != %u)",
400		       H5_HDR_SEQ(hdr), h5->tx_ack);
401		h5_reset_rx(h5);
402		return 0;
403	}
404
405	if (h5->state != H5_ACTIVE &&
406	    H5_HDR_PKT_TYPE(hdr) != HCI_3WIRE_LINK_PKT) {
407		BT_ERR("Non-link packet received in non-active state");
408		h5_reset_rx(h5);
409	}
410
411	h5->rx_func = h5_rx_payload;
412	h5->rx_pending = H5_HDR_LEN(hdr);
413
414	return 0;
415}
416
417static int h5_rx_pkt_start(struct hci_uart *hu, unsigned char c)
418{
419	struct h5 *h5 = hu->priv;
420
421	if (c == SLIP_DELIMITER)
422		return 1;
423
424	h5->rx_func = h5_rx_3wire_hdr;
425	h5->rx_pending = 4;
426
427	h5->rx_skb = bt_skb_alloc(H5_MAX_LEN, GFP_ATOMIC);
428	if (!h5->rx_skb) {
429		BT_ERR("Can't allocate mem for new packet");
430		h5_reset_rx(h5);
431		return -ENOMEM;
432	}
433
434	h5->rx_skb->dev = (void *) hu->hdev;
435
436	return 0;
437}
438
439static int h5_rx_delimiter(struct hci_uart *hu, unsigned char c)
440{
441	struct h5 *h5 = hu->priv;
442
443	if (c == SLIP_DELIMITER)
444		h5->rx_func = h5_rx_pkt_start;
445
446	return 1;
447}
448
449static void h5_unslip_one_byte(struct h5 *h5, unsigned char c)
450{
451	const u8 delim = SLIP_DELIMITER, esc = SLIP_ESC;
452	const u8 *byte = &c;
453
454	if (!test_bit(H5_RX_ESC, &h5->flags) && c == SLIP_ESC) {
455		set_bit(H5_RX_ESC, &h5->flags);
456		return;
457	}
458
459	if (test_and_clear_bit(H5_RX_ESC, &h5->flags)) {
460		switch (c) {
461		case SLIP_ESC_DELIM:
462			byte = &delim;
463			break;
464		case SLIP_ESC_ESC:
465			byte = &esc;
466			break;
467		default:
468			BT_ERR("Invalid esc byte 0x%02hhx", c);
469			h5_reset_rx(h5);
470			return;
471		}
472	}
473
474	memcpy(skb_put(h5->rx_skb, 1), byte, 1);
475	h5->rx_pending--;
476
477	BT_DBG("unsliped 0x%02hhx, rx_pending %zu", *byte, h5->rx_pending);
478}
479
480static void h5_reset_rx(struct h5 *h5)
481{
482	if (h5->rx_skb) {
483		kfree_skb(h5->rx_skb);
484		h5->rx_skb = NULL;
485	}
486
487	h5->rx_func = h5_rx_delimiter;
488	h5->rx_pending = 0;
489	clear_bit(H5_RX_ESC, &h5->flags);
490}
491
492static int h5_recv(struct hci_uart *hu, void *data, int count)
493{
494	struct h5 *h5 = hu->priv;
495	unsigned char *ptr = data;
496
497	BT_DBG("%s pending %zu count %d", hu->hdev->name, h5->rx_pending,
498	       count);
499
500	while (count > 0) {
501		int processed;
502
503		if (h5->rx_pending > 0) {
504			if (*ptr == SLIP_DELIMITER) {
505				BT_ERR("Too short H5 packet");
506				h5_reset_rx(h5);
507				continue;
508			}
509
510			h5_unslip_one_byte(h5, *ptr);
511
512			ptr++; count--;
513			continue;
514		}
515
516		processed = h5->rx_func(hu, *ptr);
517		if (processed < 0)
518			return processed;
519
520		ptr += processed;
521		count -= processed;
522	}
523
524	return 0;
525}
526
527static int h5_enqueue(struct hci_uart *hu, struct sk_buff *skb)
528{
529	struct h5 *h5 = hu->priv;
530
531	if (skb->len > 0xfff) {
532		BT_ERR("Packet too long (%u bytes)", skb->len);
533		kfree_skb(skb);
534		return 0;
535	}
536
537	if (h5->state != H5_ACTIVE) {
538		BT_ERR("Ignoring HCI data in non-active state");
539		kfree_skb(skb);
540		return 0;
541	}
542
543	switch (bt_cb(skb)->pkt_type) {
544	case HCI_ACLDATA_PKT:
545	case HCI_COMMAND_PKT:
546		skb_queue_tail(&h5->rel, skb);
547		break;
548
549	case HCI_SCODATA_PKT:
550		skb_queue_tail(&h5->unrel, skb);
551		break;
552
553	default:
554		BT_ERR("Unknown packet type %u", bt_cb(skb)->pkt_type);
555		kfree_skb(skb);
556		break;
557	}
558
559	return 0;
560}
561
562static void h5_slip_delim(struct sk_buff *skb)
563{
564	const char delim = SLIP_DELIMITER;
565
566	memcpy(skb_put(skb, 1), &delim, 1);
567}
568
569static void h5_slip_one_byte(struct sk_buff *skb, u8 c)
570{
571	const char esc_delim[2] = { SLIP_ESC, SLIP_ESC_DELIM };
572	const char esc_esc[2] = { SLIP_ESC, SLIP_ESC_ESC };
573
574	switch (c) {
575	case SLIP_DELIMITER:
576		memcpy(skb_put(skb, 2), &esc_delim, 2);
577		break;
578	case SLIP_ESC:
579		memcpy(skb_put(skb, 2), &esc_esc, 2);
580		break;
581	default:
582		memcpy(skb_put(skb, 1), &c, 1);
583	}
584}
585
586static bool valid_packet_type(u8 type)
587{
588	switch (type) {
589	case HCI_ACLDATA_PKT:
590	case HCI_COMMAND_PKT:
591	case HCI_SCODATA_PKT:
592	case HCI_3WIRE_LINK_PKT:
593	case HCI_3WIRE_ACK_PKT:
594		return true;
595	default:
596		return false;
597	}
598}
599
600static struct sk_buff *h5_prepare_pkt(struct hci_uart *hu, u8 pkt_type,
601				      const u8 *data, size_t len)
602{
603	struct h5 *h5 = hu->priv;
604	struct sk_buff *nskb;
605	u8 hdr[4];
606	int i;
607
608	if (!valid_packet_type(pkt_type)) {
609		BT_ERR("Unknown packet type %u", pkt_type);
610		return NULL;
611	}
612
613	/*
614	 * Max len of packet: (original len + 4 (H5 hdr) + 2 (crc)) * 2
615	 * (because bytes 0xc0 and 0xdb are escaped, worst case is when
616	 * the packet is all made of 0xc0 and 0xdb) + 2 (0xc0
617	 * delimiters at start and end).
618	 */
619	nskb = alloc_skb((len + 6) * 2 + 2, GFP_ATOMIC);
620	if (!nskb)
621		return NULL;
622
623	bt_cb(nskb)->pkt_type = pkt_type;
624
625	h5_slip_delim(nskb);
626
627	hdr[0] = h5->tx_ack << 3;
628	clear_bit(H5_TX_ACK_REQ, &h5->flags);
629
630	/* Reliable packet? */
631	if (pkt_type == HCI_ACLDATA_PKT || pkt_type == HCI_COMMAND_PKT) {
632		hdr[0] |= 1 << 7;
633		hdr[0] |= h5->tx_seq;
634		h5->tx_seq = (h5->tx_seq + 1) % 8;
635	}
636
637	hdr[1] = pkt_type | ((len & 0x0f) << 4);
638	hdr[2] = len >> 4;
639	hdr[3] = ~((hdr[0] + hdr[1] + hdr[2]) & 0xff);
640
641	BT_DBG("%s tx: seq %u ack %u crc %u rel %u type %u len %u",
642	       hu->hdev->name, H5_HDR_SEQ(hdr), H5_HDR_ACK(hdr),
643	       H5_HDR_CRC(hdr), H5_HDR_RELIABLE(hdr), H5_HDR_PKT_TYPE(hdr),
644	       H5_HDR_LEN(hdr));
645
646	for (i = 0; i < 4; i++)
647		h5_slip_one_byte(nskb, hdr[i]);
648
649	for (i = 0; i < len; i++)
650		h5_slip_one_byte(nskb, data[i]);
651
652	h5_slip_delim(nskb);
653
654	return nskb;
655}
656
657static struct sk_buff *h5_dequeue(struct hci_uart *hu)
658{
659	struct h5 *h5 = hu->priv;
660	unsigned long flags;
661	struct sk_buff *skb, *nskb;
662
663	if (h5->sleep != H5_AWAKE) {
664		const unsigned char wakeup_req[] = { 0x05, 0xfa };
665
666		if (h5->sleep == H5_WAKING_UP)
667			return NULL;
668
669		h5->sleep = H5_WAKING_UP;
670		BT_DBG("Sending wakeup request");
671
672		mod_timer(&h5->timer, jiffies + HZ / 100);
673		return h5_prepare_pkt(hu, HCI_3WIRE_LINK_PKT, wakeup_req, 2);
674	}
675
676	skb = skb_dequeue(&h5->unrel);
677	if (skb != NULL) {
678		nskb = h5_prepare_pkt(hu, bt_cb(skb)->pkt_type,
679				      skb->data, skb->len);
680		if (nskb) {
681			kfree_skb(skb);
682			return nskb;
683		}
684
685		skb_queue_head(&h5->unrel, skb);
686		BT_ERR("Could not dequeue pkt because alloc_skb failed");
687	}
688
689	spin_lock_irqsave_nested(&h5->unack.lock, flags, SINGLE_DEPTH_NESTING);
690
691	if (h5->unack.qlen >= h5->tx_win)
692		goto unlock;
693
694	skb = skb_dequeue(&h5->rel);
695	if (skb != NULL) {
696		nskb = h5_prepare_pkt(hu, bt_cb(skb)->pkt_type,
697				      skb->data, skb->len);
698		if (nskb) {
699			__skb_queue_tail(&h5->unack, skb);
700			mod_timer(&h5->timer, jiffies + H5_ACK_TIMEOUT);
701			spin_unlock_irqrestore(&h5->unack.lock, flags);
702			return nskb;
703		}
704
705		skb_queue_head(&h5->rel, skb);
706		BT_ERR("Could not dequeue pkt because alloc_skb failed");
707	}
708
709unlock:
710	spin_unlock_irqrestore(&h5->unack.lock, flags);
711
712	if (test_bit(H5_TX_ACK_REQ, &h5->flags))
713		return h5_prepare_pkt(hu, HCI_3WIRE_ACK_PKT, NULL, 0);
714
715	return NULL;
716}
717
718static int h5_flush(struct hci_uart *hu)
719{
720	BT_DBG("hu %p", hu);
721	return 0;
722}
723
724static struct hci_uart_proto h5p = {
725	.id		= HCI_UART_3WIRE,
726	.open		= h5_open,
727	.close		= h5_close,
728	.recv		= h5_recv,
729	.enqueue	= h5_enqueue,
730	.dequeue	= h5_dequeue,
731	.flush		= h5_flush,
732};
733
734int __init h5_init(void)
735{
736	int err = hci_uart_register_proto(&h5p);
737
738	if (!err)
739		BT_INFO("HCI Three-wire UART (H5) protocol initialized");
740	else
741		BT_ERR("HCI Three-wire UART (H5) protocol init failed");
742
743	return err;
744}
745
746int __exit h5_deinit(void)
747{
748	return hci_uart_unregister_proto(&h5p);
749}