// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 *  Bluetooth HCI UART driver
 *
 *  Copyright (C) 2002-2003  Fabrizio Gennari <fabrizio.gennari@philips.com>
 *  Copyright (C) 2004-2005  Marcel Holtmann <marcel@holtmann.org>
 */

#include <linux/module.h>

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/interrupt.h>
#include <linux/ptrace.h>
#include <linux/poll.h>

#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/signal.h>
#include <linux/ioctl.h>
#include <linux/skbuff.h>
#include <linux/bitrev.h>
#include <linux/unaligned.h>

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

#include "hci_uart.h"

static bool txcrc = true;
static bool hciextn = true;

#define BCSP_TXWINSIZE  4

#define BCSP_ACK_PKT    0x05
#define BCSP_LE_PKT     0x06

struct bcsp_struct {
        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 rx_count;
        struct  sk_buff *rx_skb;
        u8      rxseq_txack;            /* rxseq == txack. */
        u8      rxack;                  /* Last packet sent by us that the peer ack'ed */
        struct  timer_list tbcsp;
        struct  hci_uart *hu;

        enum {
                BCSP_W4_PKT_DELIMITER,
                BCSP_W4_PKT_START,
                BCSP_W4_BCSP_HDR,
                BCSP_W4_DATA,
                BCSP_W4_CRC
        } rx_state;

        enum {
                BCSP_ESCSTATE_NOESC,
                BCSP_ESCSTATE_ESC
        } rx_esc_state;

        u8      use_crc;
        u16     message_crc;
        u8      txack_req;              /* Do we need to send ack's to the peer? */

        /* Reliable packet sequence number - used to assign seq to each rel pkt. */
        u8      msgq_txseq;
};

/* ---- BCSP CRC calculation ---- */

/* Table for calculating CRC for polynomial 0x1021, LSB processed first,
 * initial value 0xffff, bits shifted in reverse order.
 */

static const u16 crc_table[] = {
        0x0000, 0x1081, 0x2102, 0x3183,
        0x4204, 0x5285, 0x6306, 0x7387,
        0x8408, 0x9489, 0xa50a, 0xb58b,
        0xc60c, 0xd68d, 0xe70e, 0xf78f
};

/* Initialise the crc calculator */
#define BCSP_CRC_INIT(x) x = 0xffff

/* Update crc with next data byte
 *
 * Implementation note
 *     The data byte is treated as two nibbles.  The crc is generated
 *     in reverse, i.e., bits are fed into the register from the top.
 */
static void bcsp_crc_update(u16 *crc, u8 d)
{
        u16 reg = *crc;

        reg = (reg >> 4) ^ crc_table[(reg ^ d) & 0x000f];
        reg = (reg >> 4) ^ crc_table[(reg ^ (d >> 4)) & 0x000f];

        *crc = reg;
}

/* ---- BCSP core ---- */

static void bcsp_slip_msgdelim(struct sk_buff *skb)
{
        const char pkt_delim = 0xc0;

        skb_put_data(skb, &pkt_delim, 1);
}

static void bcsp_slip_one_byte(struct sk_buff *skb, u8 c)
{
        const char esc_c0[2] = { 0xdb, 0xdc };
        const char esc_db[2] = { 0xdb, 0xdd };

        switch (c) {
        case 0xc0:
                skb_put_data(skb, &esc_c0, 2);
                break;
        case 0xdb:
                skb_put_data(skb, &esc_db, 2);
                break;
        default:
                skb_put_data(skb, &c, 1);
        }
}

static int bcsp_enqueue(struct hci_uart *hu, struct sk_buff *skb)
{
        struct bcsp_struct *bcsp = hu->priv;

        if (skb->len > 0xFFF) {
                BT_ERR("Packet too long");
                kfree_skb(skb);
                return 0;
        }

        switch (hci_skb_pkt_type(skb)) {
        case HCI_ACLDATA_PKT:
        case HCI_COMMAND_PKT:
                skb_queue_tail(&bcsp->rel, skb);
                break;

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

        default:
                BT_ERR("Unknown packet type");
                kfree_skb(skb);
                break;
        }

        return 0;
}

static struct sk_buff *bcsp_prepare_pkt(struct bcsp_struct *bcsp, u8 *data,
                                        int len, int pkt_type)
{
        struct sk_buff *nskb;
        u8 hdr[4], chan;
        u16 BCSP_CRC_INIT(bcsp_txmsg_crc);
        int rel, i;

        switch (pkt_type) {
        case HCI_ACLDATA_PKT:
                chan = 6;       /* BCSP ACL channel */
                rel = 1;        /* reliable channel */
                break;
        case HCI_COMMAND_PKT:
                chan = 5;       /* BCSP cmd/evt channel */
                rel = 1;        /* reliable channel */
                break;
        case HCI_SCODATA_PKT:
                chan = 7;       /* BCSP SCO channel */
                rel = 0;        /* unreliable channel */
                break;
        case BCSP_LE_PKT:
                chan = 1;       /* BCSP LE channel */
                rel = 0;        /* unreliable channel */
                break;
        case BCSP_ACK_PKT:
                chan = 0;       /* BCSP internal channel */
                rel = 0;        /* unreliable channel */
                break;
        default:
                BT_ERR("Unknown packet type");
                return NULL;
        }

        if (hciextn && chan == 5) {
                __le16 opcode = ((struct hci_command_hdr *)data)->opcode;

                /* Vendor specific commands */
                if (hci_opcode_ogf(__le16_to_cpu(opcode)) == 0x3f) {
                        u8 desc = *(data + HCI_COMMAND_HDR_SIZE);

                        if ((desc & 0xf0) == 0xc0) {
                                data += HCI_COMMAND_HDR_SIZE + 1;
                                len  -= HCI_COMMAND_HDR_SIZE + 1;
                                chan = desc & 0x0f;
                        }
                }
        }

        /* Max len of packet: (original len +4(bcsp 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;

        hci_skb_pkt_type(nskb) = pkt_type;

        bcsp_slip_msgdelim(nskb);

        hdr[0] = bcsp->rxseq_txack << 3;
        bcsp->txack_req = 0;
        BT_DBG("We request packet no %u to card", bcsp->rxseq_txack);

        if (rel) {
                hdr[0] |= 0x80 + bcsp->msgq_txseq;
                BT_DBG("Sending packet with seqno %u", bcsp->msgq_txseq);
                bcsp->msgq_txseq = (bcsp->msgq_txseq + 1) & 0x07;
        }

        if (bcsp->use_crc)
                hdr[0] |= 0x40;

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

        /* Put BCSP header */
        for (i = 0; i < 4; i++) {
                bcsp_slip_one_byte(nskb, hdr[i]);

                if (bcsp->use_crc)
                        bcsp_crc_update(&bcsp_txmsg_crc, hdr[i]);
        }

        /* Put payload */
        for (i = 0; i < len; i++) {
                bcsp_slip_one_byte(nskb, data[i]);

                if (bcsp->use_crc)
                        bcsp_crc_update(&bcsp_txmsg_crc, data[i]);
        }

        /* Put CRC */
        if (bcsp->use_crc) {
                bcsp_txmsg_crc = bitrev16(bcsp_txmsg_crc);
                bcsp_slip_one_byte(nskb, (u8)((bcsp_txmsg_crc >> 8) & 0x00ff));
                bcsp_slip_one_byte(nskb, (u8)(bcsp_txmsg_crc & 0x00ff));
        }

        bcsp_slip_msgdelim(nskb);
        return nskb;
}

/* This is a rewrite of pkt_avail in ABCSP */
static struct sk_buff *bcsp_dequeue(struct hci_uart *hu)
{
        struct bcsp_struct *bcsp = hu->priv;
        unsigned long flags;
        struct sk_buff *skb;

        /* First of all, check for unreliable messages in the queue,
         * since they have priority
         */

        skb = skb_dequeue(&bcsp->unrel);
        if (skb != NULL) {
                struct sk_buff *nskb;

                nskb = bcsp_prepare_pkt(bcsp, skb->data, skb->len,
                                        hci_skb_pkt_type(skb));
                if (nskb) {
                        kfree_skb(skb);
                        return nskb;
                } else {
                        skb_queue_head(&bcsp->unrel, skb);
                        BT_ERR("Could not dequeue pkt because alloc_skb failed");
                }
        }

        /* Now, try to send a reliable pkt. We can only send a
         * reliable packet if the number of packets sent but not yet ack'ed
         * is < than the winsize
         */

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

        if (bcsp->unack.qlen < BCSP_TXWINSIZE) {
                skb = skb_dequeue(&bcsp->rel);
                if (skb != NULL) {
                        struct sk_buff *nskb;

                        nskb = bcsp_prepare_pkt(bcsp, skb->data, skb->len,
                                                hci_skb_pkt_type(skb));
                        if (nskb) {
                                __skb_queue_tail(&bcsp->unack, skb);
                                mod_timer(&bcsp->tbcsp, jiffies + HZ / 4);
                                spin_unlock_irqrestore(&bcsp->unack.lock, flags);
                                return nskb;
                        } else {
                                skb_queue_head(&bcsp->rel, skb);
                                BT_ERR("Could not dequeue pkt because alloc_skb failed");
                        }
                }
        }

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

        /* We could not send a reliable packet, either because there are
         * none or because there are too many unack'ed pkts. Did we receive
         * any packets we have not acknowledged yet ?
         */

        if (bcsp->txack_req) {
                /* if so, craft an empty ACK pkt and send it on BCSP unreliable
                 * channel 0
                 */
                struct sk_buff *nskb = bcsp_prepare_pkt(bcsp, NULL, 0, BCSP_ACK_PKT);
                return nskb;
        }

        /* We have nothing to send */
        return NULL;
}

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

/* Remove ack'ed packets */
static void bcsp_pkt_cull(struct bcsp_struct *bcsp)
{
        struct sk_buff *skb, *tmp;
        unsigned long flags;
        int i, pkts_to_be_removed;
        u8 seqno;

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

        pkts_to_be_removed = skb_queue_len(&bcsp->unack);
        seqno = bcsp->msgq_txseq;

        while (pkts_to_be_removed) {
                if (bcsp->rxack == seqno)
                        break;
                pkts_to_be_removed--;
                seqno = (seqno - 1) & 0x07;
        }

        if (bcsp->rxack != seqno)
                BT_ERR("Peer acked invalid packet");

        BT_DBG("Removing %u pkts out of %u, up to seqno %u",
               pkts_to_be_removed, skb_queue_len(&bcsp->unack),
               (seqno - 1) & 0x07);

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

                __skb_unlink(skb, &bcsp->unack);
                dev_kfree_skb_irq(skb);
        }

        if (skb_queue_empty(&bcsp->unack))
                timer_delete(&bcsp->tbcsp);

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

        if (i != pkts_to_be_removed)
                BT_ERR("Removed only %u out of %u pkts", i, pkts_to_be_removed);
}

/* Handle BCSP link-establishment packets. When we
 * detect a "sync" packet, symptom that the BT module has reset,
 * we do nothing :) (yet)
 */
static void bcsp_handle_le_pkt(struct hci_uart *hu)
{
        struct bcsp_struct *bcsp = hu->priv;
        u8 conf_pkt[4]     = { 0xad, 0xef, 0xac, 0xed };
        u8 conf_rsp_pkt[4] = { 0xde, 0xad, 0xd0, 0xd0 };
        u8 sync_pkt[4]     = { 0xda, 0xdc, 0xed, 0xed };

        /* spot "conf" pkts and reply with a "conf rsp" pkt */
        if (bcsp->rx_skb->data[1] >> 4 == 4 && bcsp->rx_skb->data[2] == 0 &&
            !memcmp(&bcsp->rx_skb->data[4], conf_pkt, 4)) {
                struct sk_buff *nskb = alloc_skb(4, GFP_ATOMIC);

                BT_DBG("Found a LE conf pkt");
                if (!nskb)
                        return;
                skb_put_data(nskb, conf_rsp_pkt, 4);
                hci_skb_pkt_type(nskb) = BCSP_LE_PKT;

                skb_queue_head(&bcsp->unrel, nskb);
                hci_uart_tx_wakeup(hu);
        }
        /* Spot "sync" pkts. If we find one...disaster! */
        else if (bcsp->rx_skb->data[1] >> 4 == 4 && bcsp->rx_skb->data[2] == 0 &&
                 !memcmp(&bcsp->rx_skb->data[4], sync_pkt, 4)) {
                BT_ERR("Found a LE sync pkt, card has reset");
        }
}

static inline void bcsp_unslip_one_byte(struct bcsp_struct *bcsp, unsigned char byte)
{
        const u8 c0 = 0xc0, db = 0xdb;

        switch (bcsp->rx_esc_state) {
        case BCSP_ESCSTATE_NOESC:
                switch (byte) {
                case 0xdb:
                        bcsp->rx_esc_state = BCSP_ESCSTATE_ESC;
                        break;
                default:
                        skb_put_data(bcsp->rx_skb, &byte, 1);
                        if ((bcsp->rx_skb->data[0] & 0x40) != 0 &&
                            bcsp->rx_state != BCSP_W4_CRC)
                                bcsp_crc_update(&bcsp->message_crc, byte);
                        bcsp->rx_count--;
                }
                break;

        case BCSP_ESCSTATE_ESC:
                switch (byte) {
                case 0xdc:
                        skb_put_data(bcsp->rx_skb, &c0, 1);
                        if ((bcsp->rx_skb->data[0] & 0x40) != 0 &&
                            bcsp->rx_state != BCSP_W4_CRC)
                                bcsp_crc_update(&bcsp->message_crc, 0xc0);
                        bcsp->rx_esc_state = BCSP_ESCSTATE_NOESC;
                        bcsp->rx_count--;
                        break;

                case 0xdd:
                        skb_put_data(bcsp->rx_skb, &db, 1);
                        if ((bcsp->rx_skb->data[0] & 0x40) != 0 &&
                            bcsp->rx_state != BCSP_W4_CRC)
                                bcsp_crc_update(&bcsp->message_crc, 0xdb);
                        bcsp->rx_esc_state = BCSP_ESCSTATE_NOESC;
                        bcsp->rx_count--;
                        break;

                default:
                        BT_ERR("Invalid byte %02x after esc byte", byte);
                        kfree_skb(bcsp->rx_skb);
                        bcsp->rx_skb = NULL;
                        bcsp->rx_state = BCSP_W4_PKT_DELIMITER;
                        bcsp->rx_count = 0;
                }
        }
}

static void bcsp_complete_rx_pkt(struct hci_uart *hu)
{
        struct bcsp_struct *bcsp = hu->priv;
        int pass_up = 0;

        if (bcsp->rx_skb->data[0] & 0x80) {     /* reliable pkt */
                BT_DBG("Received seqno %u from card", bcsp->rxseq_txack);

                /* check the rx sequence number is as expected */
                if ((bcsp->rx_skb->data[0] & 0x07) == bcsp->rxseq_txack) {
                        bcsp->rxseq_txack++;
                        bcsp->rxseq_txack %= 0x8;
                } else {
                        /* handle re-transmitted packet or
                         * when packet was missed
                         */
                        BT_ERR("Out-of-order packet arrived, got %u expected %u",
                               bcsp->rx_skb->data[0] & 0x07, bcsp->rxseq_txack);

                        /* do not process out-of-order packet payload */
                        pass_up = 2;
                }

                /* send current txack value to all received reliable packets */
                bcsp->txack_req = 1;

                /* If needed, transmit an ack pkt */
                hci_uart_tx_wakeup(hu);
        }

        bcsp->rxack = (bcsp->rx_skb->data[0] >> 3) & 0x07;
        BT_DBG("Request for pkt %u from card", bcsp->rxack);

        /* handle received ACK indications,
         * including those from out-of-order packets
         */
        bcsp_pkt_cull(bcsp);

        if (pass_up != 2) {
                if ((bcsp->rx_skb->data[1] & 0x0f) == 6 &&
                    (bcsp->rx_skb->data[0] & 0x80)) {
                        hci_skb_pkt_type(bcsp->rx_skb) = HCI_ACLDATA_PKT;
                        pass_up = 1;
                } else if ((bcsp->rx_skb->data[1] & 0x0f) == 5 &&
                           (bcsp->rx_skb->data[0] & 0x80)) {
                        hci_skb_pkt_type(bcsp->rx_skb) = HCI_EVENT_PKT;
                        pass_up = 1;
                } else if ((bcsp->rx_skb->data[1] & 0x0f) == 7) {
                        hci_skb_pkt_type(bcsp->rx_skb) = HCI_SCODATA_PKT;
                        pass_up = 1;
                } else if ((bcsp->rx_skb->data[1] & 0x0f) == 1 &&
                           !(bcsp->rx_skb->data[0] & 0x80)) {
                        bcsp_handle_le_pkt(hu);
                        pass_up = 0;
                } else {
                        pass_up = 0;
                }
        }

        if (pass_up == 0) {
                struct hci_event_hdr hdr;
                u8 desc = (bcsp->rx_skb->data[1] & 0x0f);

                if (desc != 0 && desc != 1) {
                        if (hciextn) {
                                desc |= 0xc0;
                                skb_pull(bcsp->rx_skb, 4);
                                memcpy(skb_push(bcsp->rx_skb, 1), &desc, 1);

                                hdr.evt = 0xff;
                                hdr.plen = bcsp->rx_skb->len;
                                memcpy(skb_push(bcsp->rx_skb, HCI_EVENT_HDR_SIZE), &hdr, HCI_EVENT_HDR_SIZE);
                                hci_skb_pkt_type(bcsp->rx_skb) = HCI_EVENT_PKT;

                                hci_recv_frame(hu->hdev, bcsp->rx_skb);
                        } else {
                                BT_ERR("Packet for unknown channel (%u %s)",
                                       bcsp->rx_skb->data[1] & 0x0f,
                                       bcsp->rx_skb->data[0] & 0x80 ?
                                       "reliable" : "unreliable");
                                kfree_skb(bcsp->rx_skb);
                        }
                } else
                        kfree_skb(bcsp->rx_skb);
        } else if (pass_up == 1) {
                /* Pull out BCSP hdr */
                skb_pull(bcsp->rx_skb, 4);

                hci_recv_frame(hu->hdev, bcsp->rx_skb);
        } else {
                /* ignore packet payload of already ACKed re-transmitted
                 * packets or when a packet was missed in the BCSP window
                 */
                kfree_skb(bcsp->rx_skb);
        }

        bcsp->rx_state = BCSP_W4_PKT_DELIMITER;
        bcsp->rx_skb = NULL;
}

static u16 bscp_get_crc(struct bcsp_struct *bcsp)
{
        return get_unaligned_be16(&bcsp->rx_skb->data[bcsp->rx_skb->len - 2]);
}

/* Recv data */
static int bcsp_recv(struct hci_uart *hu, const void *data, int count)
{
        struct bcsp_struct *bcsp = hu->priv;
        const unsigned char *ptr;

        if (!test_bit(HCI_UART_REGISTERED, &hu->flags))
                return -EUNATCH;

        BT_DBG("hu %p count %d rx_state %d rx_count %ld",
               hu, count, bcsp->rx_state, bcsp->rx_count);

        ptr = data;
        while (count) {
                if (bcsp->rx_count) {
                        if (*ptr == 0xc0) {
                                BT_ERR("Short BCSP packet");
                                kfree_skb(bcsp->rx_skb);
                                bcsp->rx_skb = NULL;
                                bcsp->rx_state = BCSP_W4_PKT_START;
                                bcsp->rx_count = 0;
                        } else
                                bcsp_unslip_one_byte(bcsp, *ptr);

                        ptr++; count--;
                        continue;
                }

                switch (bcsp->rx_state) {
                case BCSP_W4_BCSP_HDR:
                        if ((0xff & (u8)~(bcsp->rx_skb->data[0] + bcsp->rx_skb->data[1] +
                            bcsp->rx_skb->data[2])) != bcsp->rx_skb->data[3]) {
                                BT_ERR("Error in BCSP hdr checksum");
                                kfree_skb(bcsp->rx_skb);
                                bcsp->rx_skb = NULL;
                                bcsp->rx_state = BCSP_W4_PKT_DELIMITER;
                                bcsp->rx_count = 0;
                                continue;
                        }
                        bcsp->rx_state = BCSP_W4_DATA;
                        bcsp->rx_count = (bcsp->rx_skb->data[1] >> 4) +
                                        (bcsp->rx_skb->data[2] << 4);   /* May be 0 */
                        continue;

                case BCSP_W4_DATA:
                        if (bcsp->rx_skb->data[0] & 0x40) {     /* pkt with crc */
                                bcsp->rx_state = BCSP_W4_CRC;
                                bcsp->rx_count = 2;
                        } else
                                bcsp_complete_rx_pkt(hu);
                        continue;

                case BCSP_W4_CRC:
                        if (bitrev16(bcsp->message_crc) != bscp_get_crc(bcsp)) {
                                BT_ERR("Checksum failed: computed %04x received %04x",
                                       bitrev16(bcsp->message_crc),
                                       bscp_get_crc(bcsp));

                                kfree_skb(bcsp->rx_skb);
                                bcsp->rx_skb = NULL;
                                bcsp->rx_state = BCSP_W4_PKT_DELIMITER;
                                bcsp->rx_count = 0;
                                continue;
                        }
                        skb_trim(bcsp->rx_skb, bcsp->rx_skb->len - 2);
                        bcsp_complete_rx_pkt(hu);
                        continue;

                case BCSP_W4_PKT_DELIMITER:
                        switch (*ptr) {
                        case 0xc0:
                                bcsp->rx_state = BCSP_W4_PKT_START;
                                break;
                        default:
                                /*BT_ERR("Ignoring byte %02x", *ptr);*/
                                break;
                        }
                        ptr++; count--;
                        break;

                case BCSP_W4_PKT_START:
                        switch (*ptr) {
                        case 0xc0:
                                ptr++; count--;
                                break;

                        default:
                                bcsp->rx_state = BCSP_W4_BCSP_HDR;
                                bcsp->rx_count = 4;
                                bcsp->rx_esc_state = BCSP_ESCSTATE_NOESC;
                                BCSP_CRC_INIT(bcsp->message_crc);

                                /* Do not increment ptr or decrement count
                                 * Allocate packet. Max len of a BCSP pkt=
                                 * 0xFFF (payload) +4 (header) +2 (crc)
                                 */

                                bcsp->rx_skb = bt_skb_alloc(0x1005, GFP_ATOMIC);
                                if (!bcsp->rx_skb) {
                                        BT_ERR("Can't allocate mem for new packet");
                                        bcsp->rx_state = BCSP_W4_PKT_DELIMITER;
                                        bcsp->rx_count = 0;
                                        return 0;
                                }
                                break;
                        }
                        break;
                }
        }
        return count;
}

        /* Arrange to retransmit all messages in the relq. */
static void bcsp_timed_event(struct timer_list *t)
{
        struct bcsp_struct *bcsp = timer_container_of(bcsp, t, tbcsp);
        struct hci_uart *hu = bcsp->hu;
        struct sk_buff *skb;
        unsigned long flags;

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

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

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

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

        hci_uart_tx_wakeup(hu);
}

static int bcsp_open(struct hci_uart *hu)
{
        struct bcsp_struct *bcsp;

        BT_DBG("hu %p", hu);

        bcsp = kzalloc_obj(*bcsp);
        if (!bcsp)
                return -ENOMEM;

        hu->priv = bcsp;
        bcsp->hu = hu;
        skb_queue_head_init(&bcsp->unack);
        skb_queue_head_init(&bcsp->rel);
        skb_queue_head_init(&bcsp->unrel);

        timer_setup(&bcsp->tbcsp, bcsp_timed_event, 0);

        bcsp->rx_state = BCSP_W4_PKT_DELIMITER;

        if (txcrc)
                bcsp->use_crc = 1;

        return 0;
}

static int bcsp_close(struct hci_uart *hu)
{
        struct bcsp_struct *bcsp = hu->priv;

        timer_shutdown_sync(&bcsp->tbcsp);

        hu->priv = NULL;

        BT_DBG("hu %p", hu);

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

        if (bcsp->rx_skb) {
                kfree_skb(bcsp->rx_skb);
                bcsp->rx_skb = NULL;
        }

        kfree(bcsp);
        return 0;
}

static const struct hci_uart_proto bcsp = {
        .id             = HCI_UART_BCSP,
        .name           = "BCSP",
        .open           = bcsp_open,
        .close          = bcsp_close,
        .enqueue        = bcsp_enqueue,
        .dequeue        = bcsp_dequeue,
        .recv           = bcsp_recv,
        .flush          = bcsp_flush
};

int __init bcsp_init(void)
{
        return hci_uart_register_proto(&bcsp);
}

int __exit bcsp_deinit(void)
{
        return hci_uart_unregister_proto(&bcsp);
}

module_param(txcrc, bool, 0644);
MODULE_PARM_DESC(txcrc, "Transmit CRC with every BCSP packet");

module_param(hciextn, bool, 0644);
MODULE_PARM_DESC(hciextn, "Convert HCI Extensions into BCSP packets");