drivers/bluetooth/hci_h5.c - kernel/msm-4.19 - Gitiles

 /*
  *
  *  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

 #define H5_TXWINSIZE	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

 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 */

 	struct sk_buff		*rx_skb;	/* Receive buffer */
 	size_t			rx_pending;	/* Expecting more bytes */
 	bool			rx_esc;		/* SLIP escape mode */
 	u8			rx_ack;		/* Last ack number received */

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

 	struct timer_list	timer;		/* Retransmission timer */

 	bool			tx_ack_req;	/* Pending ack to send */
 	u8			tx_seq;		/* Next seq number to send */
 	u8			tx_ack;		/* Next ack number to send */
 };

 static void h5_reset_rx(struct h5 *h5);

 static void h5_timed_event(unsigned long arg)
 {
 	struct hci_uart *hu = (struct hci_uart *) arg;
 	struct h5 *h5 = hu->priv;
 	struct sk_buff *skb;
 	unsigned long flags;

 	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);

 	hci_uart_tx_wakeup(hu);
 }

 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 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;

 	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 };
 	const unsigned char conf_req[] = { 0x03, 0xfc, 0x01 };
 	const unsigned char conf_rsp[] = { 0x04, 0x7b, 0x01 };
 	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;

 	if (memcmp(data, sync_req, 2) == 0) {
 		h5_link_control(hu, sync_rsp, 2);
 	} else if (memcmp(data, sync_rsp, 2) == 0) {
 		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) {
 		BT_DBG("Three-wire init sequence complete");
 		hci_uart_init_ready(hu);
 		return;
 	} 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;
 		h5->tx_ack_req = true;
 		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(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;
 	}

 	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 (!h5->rx_esc && c == SLIP_ESC) {
 		h5->rx_esc = true;
 		return;
 	}

 	if (h5->rx_esc) {
 		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;
 		}

 		h5->rx_esc = false;
 	}

 	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;
 	h5->rx_esc = false;
 }

 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;
 	}

 	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 struct sk_buff *h5_build_pkt(struct hci_uart *hu, bool rel, u8 pkt_type,
 				    const u8 *data, size_t len)
 {
 	struct h5 *h5 = hu->priv;
 	struct sk_buff *nskb;
 	u8 hdr[4];
 	int i;

 	/*
 	 * 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;
 	h5->tx_ack_req = false;

 	if (rel) {
 		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_prepare_pkt(struct hci_uart *hu, u8 pkt_type,
 				      const u8 *data, size_t len)
 {
 	bool rel;

 	switch (pkt_type) {
 	case HCI_ACLDATA_PKT:
 	case HCI_COMMAND_PKT:
 		rel = true;
 		break;
 	case HCI_SCODATA_PKT:
 	case HCI_3WIRE_LINK_PKT:
 	case HCI_3WIRE_ACK_PKT:
 		rel = false;
 		break;
 	default:
 		BT_ERR("Unknown packet type %u", pkt_type);
 		return NULL;
 	}

 	return h5_build_pkt(hu, rel, pkt_type, data, len);
 }

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

 	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_TXWINSIZE)
 		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 (h5->tx_ack_req)
 		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);
 }
	/*
	*
	* 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

	#define H5_TXWINSIZE 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

	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 */

	struct sk_buff rx_skb; / Receive buffer */
	size_t rx_pending; /* Expecting more bytes */
	bool rx_esc; /* SLIP escape mode */
	u8 rx_ack; /* Last ack number received */

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

	struct timer_list timer; /* Retransmission timer */

	bool tx_ack_req; /* Pending ack to send */
	u8 tx_seq; /* Next seq number to send */
	u8 tx_ack; /* Next ack number to send */
	};

	static void h5_reset_rx(struct h5 *h5);

	static void h5_timed_event(unsigned long arg)
	{
	struct hci_uart hu = (struct hci_uart ) arg;
	struct h5 *h5 = hu->priv;
	struct sk_buff *skb;
	unsigned long flags;

	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);

	hci_uart_tx_wakeup(hu);
	}

	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 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;

	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 };
	const unsigned char conf_req[] = { 0x03, 0xfc, 0x01 };
	const unsigned char conf_rsp[] = { 0x04, 0x7b, 0x01 };
	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;

	if (memcmp(data, sync_req, 2) == 0) {
	h5_link_control(hu, sync_rsp, 2);
	} else if (memcmp(data, sync_rsp, 2) == 0) {
	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) {
	BT_DBG("Three-wire init sequence complete");
	hci_uart_init_ready(hu);
	return;
	} 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;
	h5->tx_ack_req = true;
	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(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;
	}

	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 (!h5->rx_esc && c == SLIP_ESC) {
	h5->rx_esc = true;
	return;
	}

	if (h5->rx_esc) {
	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;
	}

	h5->rx_esc = false;
	}

	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;
	h5->rx_esc = false;
	}

	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;
	}

	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 struct sk_buff h5_build_pkt(struct hci_uart hu, bool rel, u8 pkt_type,
	const u8 *data, size_t len)
	{
	struct h5 *h5 = hu->priv;
	struct sk_buff *nskb;
	u8 hdr[4];
	int i;

	/*
	* 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;
	h5->tx_ack_req = false;

	if (rel) {
	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_prepare_pkt(struct hci_uart hu, u8 pkt_type,
	const u8 *data, size_t len)
	{
	bool rel;

	switch (pkt_type) {
	case HCI_ACLDATA_PKT:
	case HCI_COMMAND_PKT:
	rel = true;
	break;
	case HCI_SCODATA_PKT:
	case HCI_3WIRE_LINK_PKT:
	case HCI_3WIRE_ACK_PKT:
	rel = false;
	break;
	default:
	BT_ERR("Unknown packet type %u", pkt_type);
	return NULL;
	}

	return h5_build_pkt(hu, rel, pkt_type, data, len);
	}

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

	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_TXWINSIZE)
	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 (h5->tx_ack_req)
	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);
	}