• 導(dǎo)語(yǔ)
  該篇文章奖地，主要介紹createBond操作在Android的調(diào)用流程橄唬，Android7.0為例。

1. 調(diào)用流程圖

framework->HAL

bluedroid stack內(nèi)部

2. 調(diào)用詳解

• 具體的藍(lán)牙應(yīng)用APP下發(fā)createBond操作参歹；
• 調(diào)用到framework層的createBond（）方法仰楚，該方法通過(guò)AIDL進(jìn)行進(jìn)程間通信，繼續(xù)調(diào)用；

@RequiresPermission(Manifest.permission.BLUETOOTH_ADMIN)
    public boolean createBond() {
        if (sService == null) {
            Log.e(TAG, "BT not enabled. Cannot create bond to Remote Device");
            return false;
        }
        try {
            Log.i(TAG, "createBond() for device " + getAddress() +
                    " called by pid: " + Process.myPid() +
                    " tid: " + Process.myTid());
            return sService.createBond(this, TRANSPORT_AUTO);   //此處為跳轉(zhuǎn)代碼
        } catch (RemoteException e) {Log.e(TAG, "", e);}
        return false;
    }

private static IBluetooth sService;    //IBluetooth AIDL定義

• BluetoothDevice.java中還有一個(gè)createBondOutOfBand（）方法僧界，該方法用于帶外傳輸（非2.4GHz）侨嘀。如通過(guò)NFC來(lái)實(shí)現(xiàn)藍(lán)牙MAC和link key的交換，以達(dá)到“不用配對(duì)”的用戶體驗(yàn)捂襟；

    public boolean createBondOutOfBand(int transport, OobData oobData) {
        try {
            return sService.createBondOutOfBand(this, transport, oobData);
        } catch (RemoteException e) {Log.e(TAG, "", e);}
        return false;
    }

• createBond（）方法中的transport參數(shù)咬腕，0代表未知設(shè)備類型，1代表BR/EDR葬荷，2代表LE涨共；
• createBond（）會(huì)進(jìn)入到AdapterService中的createBond()方法；

private static class AdapterServiceBinder extends IBluetooth.Stub {

     boolean createBond(BluetoothDevice device, int transport, OobData oobData) {
        enforceCallingOrSelfPermission(BLUETOOTH_ADMIN_PERM,
            "Need BLUETOOTH ADMIN permission");
        DeviceProperties deviceProp = mRemoteDevices.getDeviceProperties(device);
        if (deviceProp != null && deviceProp.getBondState() != BluetoothDevice.BOND_NONE) {
            return false;
        }

        // Pairing is unreliable while scanning, so cancel discovery
        // Note, remove this when native stack improves
        cancelDiscoveryNative();     //取消掃描操作

        Message msg = mBondStateMachine.obtainMessage(BondStateMachine.CREATE_BOND);
        msg.obj = device;
        msg.arg1 = transport;

        if (oobData != null) {   //使用帶外傳輸宠漩，完成綁定過(guò)程
            Bundle oobDataBundle = new Bundle();
            oobDataBundle.putParcelable(BondStateMachine.OOBDATA, oobData);
            msg.setData(oobDataBundle);
        }
        mBondStateMachine.sendMessage(msg);   //發(fā)送信息給狀態(tài)機(jī)
        return true;
    }

• BondStateMachine接收到CREATE_BOND消息會(huì)會(huì)調(diào)用其內(nèi)部的createBond方法举反；

    private boolean createBond(BluetoothDevice dev, int transport, OobData oobData,
                               boolean transition) {
        if (dev.getBondState() == BluetoothDevice.BOND_NONE) {
            infoLog("Bond address is:" + dev);
            byte[] addr = Utils.getBytesFromAddress(dev.getAddress());
            boolean result;
            if (oobData != null) {
                result = mAdapterService.createBondOutOfBandNative(addr, transport, oobData);
            } else {
                result = mAdapterService.createBondNative(addr, transport);  //JNI
            }

            if (!result) {
                sendIntent(dev, BluetoothDevice.BOND_NONE,
                           BluetoothDevice.UNBOND_REASON_REMOVED);
                return false;
            } else if (transition) {
                transitionTo(mPendingCommandState);
            }
            return true;
        }
        return false;
    }

• 進(jìn)行JNI調(diào)用，接著到createBondNative方法扒吁；

static jboolean createBondNative(JNIEnv* env, jobject obj, jbyteArray address, jint transport) {
    ALOGV("%s:",__FUNCTION__);

    jbyte *addr;
    jboolean result = JNI_FALSE;

    if (!sBluetoothInterface) return result;

    addr = env->GetByteArrayElements(address, NULL);
    if (addr == NULL) {
        jniThrowIOException(env, EINVAL);
        return result;
    }

    int ret = sBluetoothInterface->create_bond((bt_bdaddr_t *)addr, transport);      //調(diào)用HAL層接口
    env->ReleaseByteArrayElements(address, addr, 0);   
    result = (ret == BT_STATUS_SUCCESS) ? JNI_TRUE : JNI_FALSE;

    return result;
}

• createBondNative方法調(diào)用到HAL層的接口火鼻；

    /** Create Bluetooth Bonding */
    int (*create_bond)(const bt_bdaddr_t *bd_addr, int transport);

• 至此會(huì)進(jìn)入BlueDroid，繼續(xù)進(jìn)行調(diào)用雕崩；

static int create_bond(const bt_bdaddr_t *bd_addr, int transport)
{
    /* sanity check */
    if (interface_ready() == FALSE)
        return BT_STATUS_NOT_READY;

    return btif_dm_create_bond(bd_addr, transport);   //next
}

• 此處的btif_dm_create_bond函數(shù)不會(huì)進(jìn)行實(shí)際bond操作魁索，只是將事件拋出去，由其他的線程進(jìn)行處理盼铁；

此處的設(shè)計(jì)很巧妙蛾默，因?yàn)槿绻蠈铀械乃{(lán)牙相關(guān)操作事件下發(fā)下來(lái)，在此就進(jìn)行處理捉貌，在實(shí)際編碼中必然要加上很多的互斥操作，這就增加了設(shè)計(jì)的復(fù)雜性冬念。

bt_status_t btif_dm_create_bond(const bt_bdaddr_t *bd_addr, int transport)
{
    btif_dm_create_bond_cb_t create_bond_cb;
    create_bond_cb.transport = transport;
    bdcpy(create_bond_cb.bdaddr.address, bd_addr->address);

    bdstr_t bdstr;
    BTIF_TRACE_EVENT("%s: bd_addr=%s, transport=%d", __FUNCTION__, bdaddr_to_string(bd_addr, bdstr, sizeof(bdstr)), transport);
    if (pairing_cb.state != BT_BOND_STATE_NONE)
        return BT_STATUS_BUSY;

    btif_stats_add_bond_event(bd_addr, BTIF_DM_FUNC_CREATE_BOND, pairing_cb.state);

    btif_transfer_context(btif_dm_generic_evt, BTIF_DM_CB_CREATE_BOND,
                          (char *)&create_bond_cb, sizeof(btif_dm_create_bond_cb_t), NULL);

    return BT_STATUS_SUCCESS;
}

• btif_dm_generic_evt函數(shù)會(huì)接收這個(gè)事件并進(jìn)行后續(xù)處理趁窃；

        case BTIF_DM_CB_CREATE_BOND:
        {
            pairing_cb.timeout_retries = NUM_TIMEOUT_RETRIES;
            btif_dm_create_bond_cb_t *create_bond_cb = (btif_dm_create_bond_cb_t*)p_param;
            btif_dm_cb_create_bond(&create_bond_cb->bdaddr, create_bond_cb->transport);
        }
        break;

• btif_dm_cb_create_bond函數(shù)會(huì)對(duì)綁定事件進(jìn)行處理，此處對(duì)HID設(shè)備進(jìn)行了特別的處理急前；

static void btif_dm_cb_create_bond(bt_bdaddr_t *bd_addr, tBTA_TRANSPORT transport)
{
    BOOLEAN is_hid = check_cod(bd_addr, COD_HID_POINTING);
    bond_state_changed(BT_STATUS_SUCCESS, bd_addr, BT_BOND_STATE_BONDING);

#if BLE_INCLUDED == TRUE
    int device_type;
    int addr_type;
    bdstr_t bdstr;
    bdaddr_to_string(bd_addr, bdstr, sizeof(bdstr));
    if (transport == BT_TRANSPORT_LE)
    {
        if (!btif_config_get_int((char const *)&bdstr,"DevType", &device_type))
        {
            btif_config_set_int(bdstr, "DevType", BT_DEVICE_TYPE_BLE);
        }
        if (btif_storage_get_remote_addr_type(bd_addr, &addr_type) != BT_STATUS_SUCCESS)
        {
            btif_storage_set_remote_addr_type(bd_addr, BLE_ADDR_PUBLIC);
        }
    }
    if((btif_config_get_int((char const *)&bdstr,"DevType", &device_type) &&
       (btif_storage_get_remote_addr_type(bd_addr, &addr_type) == BT_STATUS_SUCCESS) &&
       (device_type & BT_DEVICE_TYPE_BLE) == BT_DEVICE_TYPE_BLE) || (transport == BT_TRANSPORT_LE))
    {
        BTA_DmAddBleDevice(bd_addr->address, addr_type, device_type);
    }
#endif
// --ZafirTab-- 對(duì)HID設(shè)備的特殊處理
#if BLE_INCLUDED == TRUE
    if(is_hid && (device_type & BT_DEVICE_TYPE_BLE) == 0)
#else
    if(is_hid)
#endif
    {
        int status;
        status = btif_hh_connect(bd_addr);
        if(status != BT_STATUS_SUCCESS)
            bond_state_changed(status, bd_addr, BT_BOND_STATE_NONE);
    }
    else
    {
        BTA_DmBondByTransport((UINT8 *)bd_addr->address, transport);    // --ZafirTab--  next
    }
    /*  Track  originator of bond creation  */
    pairing_cb.is_local_initiated = TRUE;

}

• 此處我們直接看HID設(shè)備的bond醒陆；

void BTA_DmBondByTransport(BD_ADDR bd_addr, tBTA_TRANSPORT transport)
{
    tBTA_DM_API_BOND *p_msg =
        (tBTA_DM_API_BOND *)osi_malloc(sizeof(tBTA_DM_API_BOND));

    p_msg->hdr.event = BTA_DM_API_BOND_EVT;    //拋出的事件
    bdcpy(p_msg->bd_addr, bd_addr);
    p_msg->transport = transport;

    bta_sys_sendmsg(p_msg);
}

• BTA_DmBondByTransport函數(shù)也沒有對(duì)事件進(jìn)行直接處理，又將事件拋出去了裆针；
  BTA_DM_API_BOND_EVT事件對(duì)應(yīng)的是bta_dm_bond操作刨摩；

/* action function list */
const tBTA_DM_ACTION bta_dm_action[] =
{

    /* device manager local device API events */
    bta_dm_enable,            /* 0  BTA_DM_API_ENABLE_EVT */
    bta_dm_disable,           /* 1  BTA_DM_API_DISABLE_EVT */
    bta_dm_set_dev_name,      /* 2  BTA_DM_API_SET_NAME_EVT */
    bta_dm_set_visibility,    /* 3  BTA_DM_API_SET_VISIBILITY_EVT */
    bta_dm_acl_change,        /* 8  BTA_DM_ACL_CHANGE_EVT */
    bta_dm_add_device,        /* 9  BTA_DM_API_ADD_DEVICE_EVT */
    bta_dm_close_acl,        /* 10  BTA_DM_API_ADD_DEVICE_EVT */

    /* security API events */
    bta_dm_bond,              /* 11  BTA_DM_API_BOND_EVT */
    bta_dm_bond_cancel,       /* 12  BTA_DM_API_BOND_CANCEL_EVT */

• bta_dm_bond函數(shù)會(huì)調(diào)用btm_sec_bond_by_transport函數(shù)來(lái)啟動(dòng)SSP或者SMP；此處分支較多世吨，我們后續(xù)以2.1 即BR/EDR繼續(xù)分析澡刹；

tBTM_STATUS btm_sec_bond_by_transport (BD_ADDR bd_addr, tBT_TRANSPORT transport,
                                       UINT8 pin_len, UINT8 *p_pin, UINT32 trusted_mask[])
{
    tBTM_SEC_DEV_REC *p_dev_rec;
    tBTM_STATUS      status;
    UINT8            *p_features;
    UINT8            ii;
    tACL_CONN        *p= btm_bda_to_acl(bd_addr, transport);
    BTM_TRACE_API ("btm_sec_bond_by_transport BDA: %02x:%02x:%02x:%02x:%02x:%02x",
                    bd_addr[0], bd_addr[1], bd_addr[2], bd_addr[3], bd_addr[4], bd_addr[5]);

    BTM_TRACE_DEBUG("btm_sec_bond_by_transport: Transport used %d" , transport);

    /* Other security process is in progress */
    if (btm_cb.pairing_state != BTM_PAIR_STATE_IDLE)
    {
        BTM_TRACE_ERROR ("BTM_SecBond: already busy in state: %s", btm_pair_state_descr(btm_cb.pairing_state));
        return(BTM_WRONG_MODE);
    }

    if ((p_dev_rec = btm_find_or_alloc_dev (bd_addr)) == NULL)
    {
        return(BTM_NO_RESOURCES);
    }

    BTM_TRACE_DEBUG ("before update sec_flags=0x%x", p_dev_rec->sec_flags);

    /* Finished if connection is active and already paired */
    if ( ((p_dev_rec->hci_handle != BTM_SEC_INVALID_HANDLE) && transport == BT_TRANSPORT_BR_EDR
         &&  (p_dev_rec->sec_flags & BTM_SEC_AUTHENTICATED))
#if (BLE_INCLUDED == TRUE)
        ||((p_dev_rec->ble_hci_handle != BTM_SEC_INVALID_HANDLE) && transport == BT_TRANSPORT_LE
         &&  (p_dev_rec->sec_flags & BTM_SEC_LE_AUTHENTICATED))
#endif

         )
    {
        BTM_TRACE_WARNING("BTM_SecBond -> Already Paired");
        return(BTM_SUCCESS);
    }

    /* Tell controller to get rid of the link key if it has one stored */
    if ((BTM_DeleteStoredLinkKey (bd_addr, NULL)) != BTM_SUCCESS)
        return(BTM_NO_RESOURCES);

    /* Save the PIN code if we got a valid one */
    if (p_pin && (pin_len <= PIN_CODE_LEN) && (pin_len != 0))
    {
        btm_cb.pin_code_len = pin_len;
        p_dev_rec->pin_code_length = pin_len;
        memcpy (btm_cb.pin_code, p_pin, PIN_CODE_LEN);
    }

    memcpy (btm_cb.pairing_bda, bd_addr, BD_ADDR_LEN);

    btm_cb.pairing_flags = BTM_PAIR_FLAGS_WE_STARTED_DD;

    p_dev_rec->security_required = BTM_SEC_OUT_AUTHENTICATE;
    p_dev_rec->is_originator     = TRUE;
    if (trusted_mask)
        BTM_SEC_COPY_TRUSTED_DEVICE(trusted_mask, p_dev_rec->trusted_mask);

#if BLE_INCLUDED == TRUE && SMP_INCLUDED == TRUE
    if (transport == BT_TRANSPORT_LE)
    {
        btm_ble_init_pseudo_addr (p_dev_rec, bd_addr);
        p_dev_rec->sec_flags &= ~ BTM_SEC_LE_MASK;

        if (SMP_Pair(bd_addr) == SMP_STARTED)
        {
            btm_cb.pairing_flags |= BTM_PAIR_FLAGS_LE_ACTIVE;
            p_dev_rec->sec_state = BTM_SEC_STATE_AUTHENTICATING;
            btm_sec_change_pairing_state (BTM_PAIR_STATE_WAIT_AUTH_COMPLETE);
            return BTM_CMD_STARTED;
        }

        btm_cb.pairing_flags = 0;
        return(BTM_NO_RESOURCES);
    }
#endif

    p_dev_rec->sec_flags &= ~(BTM_SEC_LINK_KEY_KNOWN | BTM_SEC_AUTHENTICATED | BTM_SEC_ENCRYPTED
                                  | BTM_SEC_ROLE_SWITCHED  | BTM_SEC_LINK_KEY_AUTHED);

    BTM_TRACE_DEBUG ("after update sec_flags=0x%x", p_dev_rec->sec_flags);
    if (!controller_get_interface()->supports_simple_pairing())
    {
        /* The special case when we authenticate keyboard.  Set pin type to fixed */
        /* It would be probably better to do it from the application, but it is */
        /* complicated */
        if (((p_dev_rec->dev_class[1] & BTM_COD_MAJOR_CLASS_MASK) == BTM_COD_MAJOR_PERIPHERAL)
            && (p_dev_rec->dev_class[2] & BTM_COD_MINOR_KEYBOARD)
            && (btm_cb.cfg.pin_type != HCI_PIN_TYPE_FIXED))
        {
            btm_cb.pin_type_changed = TRUE;
            btsnd_hcic_write_pin_type (HCI_PIN_TYPE_FIXED);
        }
    }

    for (ii = 0; ii <= HCI_EXT_FEATURES_PAGE_MAX; ii++)
    {
        p_features = p_dev_rec->features[ii];
        BTM_TRACE_EVENT("  remote_features page[%1d] = %02x-%02x-%02x-%02x",
                         ii, p_features[0], p_features[1], p_features[2], p_features[3]);
        BTM_TRACE_EVENT("                              %02x-%02x-%02x-%02x",
                             p_features[4], p_features[5], p_features[6], p_features[7]);
    }

    BTM_TRACE_EVENT ("BTM_SecBond: Remote sm4: 0x%x  HCI Handle: 0x%04x", p_dev_rec->sm4, p_dev_rec->hci_handle);

#if BTM_SEC_FORCE_RNR_FOR_DBOND == TRUE
    p_dev_rec->sec_flags &= ~BTM_SEC_NAME_KNOWN;
#endif

    /* If connection already exists... */
    if (p && p->hci_handle != BTM_SEC_INVALID_HANDLE)
    {
        if (!btm_sec_start_authentication (p_dev_rec))
            return(BTM_NO_RESOURCES);

        btm_sec_change_pairing_state (BTM_PAIR_STATE_WAIT_PIN_REQ);

        /* Mark lcb as bonding */
        l2cu_update_lcb_4_bonding (bd_addr, TRUE);
        return(BTM_CMD_STARTED);
    }

    BTM_TRACE_DEBUG ("sec mode: %d sm4:x%x", btm_cb.security_mode, p_dev_rec->sm4);
    if (!controller_get_interface()->supports_simple_pairing()
        || (p_dev_rec->sm4 == BTM_SM4_KNOWN))
    {
        if ( btm_sec_check_prefetch_pin (p_dev_rec) )
            return (BTM_CMD_STARTED);
    }
    if ((btm_cb.security_mode == BTM_SEC_MODE_SP ||
         btm_cb.security_mode == BTM_SEC_MODE_SP_DEBUG ||
         btm_cb.security_mode == BTM_SEC_MODE_SC) &&
         BTM_SEC_IS_SM4_UNKNOWN(p_dev_rec->sm4))
    {
        /* local is 2.1 and peer is unknown */
        if ((p_dev_rec->sm4 & BTM_SM4_CONN_PEND) == 0)
        {
            /* we are not accepting connection request from peer
             * -> RNR (to learn if peer is 2.1)
             * RNR when no ACL causes HCI_RMT_HOST_SUP_FEAT_NOTIFY_EVT */
            btm_sec_change_pairing_state (BTM_PAIR_STATE_GET_REM_NAME);
            BTM_ReadRemoteDeviceName(bd_addr, NULL, BT_TRANSPORT_BR_EDR);
        }
        else
        {
            /* We are accepting connection request from peer */
            btm_sec_change_pairing_state (BTM_PAIR_STATE_WAIT_PIN_REQ);
        }
        BTM_TRACE_DEBUG ("State:%s sm4: 0x%x sec_state:%d",
            btm_pair_state_descr (btm_cb.pairing_state), p_dev_rec->sm4, p_dev_rec->sec_state);
        return BTM_CMD_STARTED;
    }

    /* both local and peer are 2.1  */
    status = btm_sec_dd_create_conn(p_dev_rec);

    if (status != BTM_CMD_STARTED)
    {
        btm_sec_change_pairing_state (BTM_PAIR_STATE_IDLE);
    }

    return status;
}

• 從btm_sec_dd_create_conn函數(shù)繼續(xù)后續(xù)分析；

static tBTM_STATUS btm_sec_dd_create_conn (tBTM_SEC_DEV_REC *p_dev_rec)
{
    tL2C_LCB *p_lcb = l2cu_find_lcb_by_bd_addr(p_dev_rec->bd_addr, BT_TRANSPORT_BR_EDR);
    if (p_lcb && (p_lcb->link_state == LST_CONNECTED || p_lcb->link_state == LST_CONNECTING))
    {
       BTM_TRACE_WARNING("%s Connection already exists", __func__);
       return BTM_CMD_STARTED;
    }

    /* Make sure an L2cap link control block is available */
    if (!p_lcb && (p_lcb = l2cu_allocate_lcb (p_dev_rec->bd_addr, TRUE, BT_TRANSPORT_BR_EDR)) == NULL)
    {
        BTM_TRACE_WARNING ("Security Manager: failed allocate LCB [%02x%02x%02x%02x%02x%02x]",
                            p_dev_rec->bd_addr[0], p_dev_rec->bd_addr[1], p_dev_rec->bd_addr[2],
                            p_dev_rec->bd_addr[3], p_dev_rec->bd_addr[4], p_dev_rec->bd_addr[5]);

        return(BTM_NO_RESOURCES);
    }

    /* set up the control block to indicated dedicated bonding */
    btm_cb.pairing_flags |= BTM_PAIR_FLAGS_DISC_WHEN_DONE;

    if (l2cu_create_conn(p_lcb, BT_TRANSPORT_BR_EDR) == FALSE)
    {
        BTM_TRACE_WARNING ("Security Manager: failed create  [%02x%02x%02x%02x%02x%02x]",
                            p_dev_rec->bd_addr[0], p_dev_rec->bd_addr[1], p_dev_rec->bd_addr[2],
                            p_dev_rec->bd_addr[3], p_dev_rec->bd_addr[4], p_dev_rec->bd_addr[5]);

        l2cu_release_lcb(p_lcb);
        return(BTM_NO_RESOURCES);
    }

    btm_acl_update_busy_level (BTM_BLI_PAGE_EVT);

    BTM_TRACE_DEBUG ("Security Manager: btm_sec_dd_create_conn [%02x%02x%02x%02x%02x%02x]",
                      p_dev_rec->bd_addr[0], p_dev_rec->bd_addr[1], p_dev_rec->bd_addr[2],
                      p_dev_rec->bd_addr[3], p_dev_rec->bd_addr[4], p_dev_rec->bd_addr[5]);

    btm_sec_change_pairing_state (BTM_PAIR_STATE_WAIT_PIN_REQ);

    return(BTM_CMD_STARTED);
}

• 調(diào)用l2cu_create_conn函數(shù)發(fā)送HCI指令給Controller耘婚；

BOOLEAN l2cu_create_conn (tL2C_LCB *p_lcb, tBT_TRANSPORT transport)
{
    int             xx;
    tL2C_LCB        *p_lcb_cur = &l2cb.lcb_pool[0];
#if BTM_SCO_INCLUDED == TRUE
    BOOLEAN         is_sco_active;
#endif

#if (BLE_INCLUDED == TRUE)
    tBT_DEVICE_TYPE     dev_type;
    tBLE_ADDR_TYPE      addr_type;


    BTM_ReadDevInfo(p_lcb->remote_bd_addr, &dev_type, &addr_type);

    if (transport == BT_TRANSPORT_LE)
    {
        if (!controller_get_interface()->supports_ble())
            return FALSE;

        p_lcb->ble_addr_type = addr_type;
        p_lcb->transport = BT_TRANSPORT_LE;

        return (l2cble_create_conn(p_lcb));
    }
#endif

    /* If there is a connection where we perform as a slave, try to switch roles
       for this connection */
    for (xx = 0, p_lcb_cur = &l2cb.lcb_pool[0]; xx < MAX_L2CAP_LINKS; xx++, p_lcb_cur++)
    {
        if (p_lcb_cur == p_lcb)
            continue;

        if ((p_lcb_cur->in_use) && (p_lcb_cur->link_role == HCI_ROLE_SLAVE))
        {

#if BTM_SCO_INCLUDED == TRUE
            /* The LMP_switch_req shall be sent only if the ACL logical transport
            is in active mode, when encryption is disabled, and all synchronous
            logical transports on the same physical link are disabled." */

            /* Check if there is any SCO Active on this BD Address */
            is_sco_active = btm_is_sco_active_by_bdaddr(p_lcb_cur->remote_bd_addr);

            L2CAP_TRACE_API ("l2cu_create_conn - btm_is_sco_active_by_bdaddr() is_sco_active = %s", \
                (is_sco_active == TRUE) ? "TRUE":"FALSE");

            if (is_sco_active == TRUE)
                continue; /* No Master Slave switch not allowed when SCO Active */
#endif
            /*4_1_TODO check  if btm_cb.devcb.local_features to be used instead */
            if (HCI_SWITCH_SUPPORTED(BTM_ReadLocalFeatures()))
            {
                /* mark this lcb waiting for switch to be completed and
                   start switch on the other one */
                p_lcb->link_state = LST_CONNECTING_WAIT_SWITCH;
                p_lcb->link_role  = HCI_ROLE_MASTER;

                if (BTM_SwitchRole (p_lcb_cur->remote_bd_addr, HCI_ROLE_MASTER, NULL) == BTM_CMD_STARTED)
                {
                    alarm_set_on_queue(p_lcb->l2c_lcb_timer,
                                       L2CAP_LINK_ROLE_SWITCH_TIMEOUT_MS,
                                       l2c_lcb_timer_timeout, p_lcb,
                                       btu_general_alarm_queue);
                    return (TRUE);
                }
            }
        }
    }

    p_lcb->link_state = LST_CONNECTING;

    return (l2cu_create_conn_after_switch (p_lcb));
}

• 至此Host端的操作流程告一段落罢浇，Controller根據(jù)HCI指令進(jìn)行后續(xù)的操作，這部分是由藍(lán)牙芯片提供商來(lái)設(shè)計(jì)的，我們?cè)诖瞬蛔鼋榻B嚷闭。

• 總結(jié)
  該篇文章挑選了藍(lán)牙API操作中的createBond進(jìn)行了詳細(xì)分析攒岛，旨在給讀者提供一個(gè)分析Android Bluetooth 調(diào)用流程的一個(gè)思路，也算是拋磚引玉胞锰。
  其中涉及到AIDL灾锯、binder、JNI等相關(guān)知識(shí)嗅榕，讀者如果有欠缺顺饮，可自行學(xué)習(xí)。
  當(dāng)上層下發(fā)的操作被stack正常執(zhí)行后誊册，stack后返回一個(gè)相應(yīng)的回調(diào)給上層领突，至于這個(gè)callback，上層是如何正常接收到的案怯，讀者可以沿著上文提到的思路倒推回去君旦，也順便檢測(cè)一下自己的代碼分析能力。