hci_h5.c

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/*
 *
 *  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 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;

    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 };
    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) {
        h5_link_control(hu, sync_rsp, 2);
    } else if (memcmp(data, sync_rsp, 2) == 0) {
        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(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;
    }

    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);
    }

    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, 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;
    }

    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);
    }

    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->tx_win)
        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 (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 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);
}