1 files changed, 765 insertions, 0 deletions

diff --git a/drivers/bluetooth/hci_h5.c b/drivers/bluetooth/hci_h5.c
new file mode 100644
index 000000000..3455cecc9
--- /dev/null
+++ b/drivers/bluetooth/hci_h5.c
@@ -0,0 +1,765 @@
+/*
+ *
+ *  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 void h5_peer_reset(struct hci_uart *hu)
+{
+	struct h5 *h5 = hu->priv;
+
+	BT_ERR("Peer device has reset");
+
+	h5->state = H5_UNINITIALIZED;
+
+	del_timer(&h5->timer);
+
+	skb_queue_purge(&h5->rel);
+	skb_queue_purge(&h5->unrel);
+	skb_queue_purge(&h5->unack);
+
+	h5->tx_seq = 0;
+	h5->tx_ack = 0;
+
+	/* Send reset request to upper stack */
+	hci_reset_dev(hu->hdev);
+}
+
+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;
+
+	del_timer_sync(&h5->timer);
+
+	skb_queue_purge(&h5->unack);
+	skb_queue_purge(&h5->rel);
+	skb_queue_purge(&h5->unrel);
+
+	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) & 0x07;
+	}
+
+	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) {
+		if (h5->state == H5_ACTIVE)
+			h5_peer_reset(hu);
+		h5_link_control(hu, sync_rsp, 2);
+	} else if (memcmp(data, sync_rsp, 2) == 0) {
+		if (h5->state == H5_ACTIVE)
+			h5_peer_reset(hu);
+		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)
+{
+	h5_complete_rx_pkt(hu);
+
+	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);
+	}
+
+	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);
+		return 0;
+	}
+
+	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, const void *data, int count)
+{
+	struct h5 *h5 = hu->priv;
+	const 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);
+	}
+
+	skb = skb_dequeue(&h5->unrel);
+	if (skb != 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;
+
+	skb = skb_dequeue(&h5->rel);
+	if (skb != 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 const struct hci_uart_proto h5p = {
+	.id		= HCI_UART_3WIRE,
+	.name		= "Three-wire (H5)",
+	.open		= h5_open,
+	.close		= h5_close,
+	.recv		= h5_recv,
+	.enqueue	= h5_enqueue,
+	.dequeue	= h5_dequeue,
+	.flush		= h5_flush,
+};
+
+int __init h5_init(void)
+{
+	return hci_uart_register_proto(&h5p);
+}
+
+int __exit h5_deinit(void)
+{
+	return hci_uart_unregister_proto(&h5p);
+}