Android 上面的蓝牙inquiry 是在设置界面，打开蓝牙就会自动搜索周边的蓝牙设备，其最终调用到协议栈的start_discovery接口，此篇文章分析该接口的调用流程以及与controller交互过程。

static int start_discovery(void)

{

    /* sanity check */

    if (interface_ready() == FALSE)

        return BT_STATUS_NOT_READY;

    return btif_dm_start_discovery();

}
bt_status_t btif_dm_start_discovery(void)

{

    tBTA_DM_INQ inq_params;

    tBTA_SERVICE_MASK services = ;

    tBTA_DM_BLE_PF_FILT_PARAMS adv_filt_param;

#if (defined(BLE_INCLUDED) && (BLE_INCLUDED == TRUE))

    memset(&adv_filt_param, , sizeof(tBTA_DM_BLE_PF_FILT_PARAMS));

    /* Cleanup anything remaining on index 0 */

    BTA_DmBleScanFilterSetup(BTA_DM_BLE_SCAN_COND_DELETE, , &adv_filt_param, NULL,

                             bte_scan_filt_param_cfg_evt, );

    /* Add an allow-all filter on index 0*/

    adv_filt_param.dely_mode = IMMEDIATE_DELY_MODE;

    adv_filt_param.feat_seln = ALLOW_ALL_FILTER;

    adv_filt_param.filt_logic_type = BTA_DM_BLE_PF_FILT_LOGIC_OR;

    adv_filt_param.list_logic_type = BTA_DM_BLE_PF_LIST_LOGIC_OR;

    adv_filt_param.rssi_low_thres = LOWEST_RSSI_VALUE;

    adv_filt_param.rssi_high_thres = LOWEST_RSSI_VALUE;

    BTA_DmBleScanFilterSetup(BTA_DM_BLE_SCAN_COND_ADD, , &adv_filt_param, NULL,

                             bte_scan_filt_param_cfg_evt, );

    /* TODO: Do we need to handle multiple inquiries at the same time? */

    /* Set inquiry params and call API */

    inq_params.mode = BTA_DM_GENERAL_INQUIRY|BTA_BLE_GENERAL_INQUIRY;//设置inquiry模式，ble和bredr

#else

    inq_params.mode = BTA_DM_GENERAL_INQUIRY;

#endif

    inq_params.duration = BTIF_DM_DEFAULT_INQ_MAX_DURATION;//设置超时时间

    inq_params.max_resps = BTIF_DM_DEFAULT_INQ_MAX_RESULTS;//设置接收的最大的response数量

    inq_params.report_dup = TRUE;

    inq_params.filter_type = BTA_DM_INQ_CLR;//

    /* TODO: Filter device by BDA needs to be implemented here */

    /* Will be enabled to TRUE once inquiry busy level has been received */

    btif_dm_inquiry_in_progress = FALSE;

    /* find nearby devices */

    BTA_DmSearch(&inq_params, services, bte_search_devices_evt);//执行搜索

    return BT_STATUS_SUCCESS;

}

上面代码的主要做的事情是，设置相关的搜索的参数，然后调用BTA_DmSearch(&inq_params, services, bte_search_devices_evt); 进行搜索。

我们这里再次整理一下 传入BTA_DmSearch的参数：

    inq_params.mode = BTA_DM_GENERAL_INQUIRY|BTA_BLE_GENERAL_INQUIRY;

    inq_params.duration = BTIF_DM_DEFAULT_INQ_MAX_DURATION;

    inq_params.max_resps = BTIF_DM_DEFAULT_INQ_MAX_RESULTS;

    inq_params.report_dup = TRUE;

    inq_params.filter_type = BTA_DM_INQ_CLR;//

    tBTA_SERVICE_MASK services = ;

    bte_search_devices_evt 是一个回调函数，实现也是在btif_dm.c，最终会被赋值给

    bta_dm_search_cb.p_search_cback = bte_search_devices_evt

我们看看BTA_DmSearch具体的实现，

/*******************************************************************************

**

** Function         BTA_DmSearch

**

** Description      This function searches for peer Bluetooth devices. It performs

**                  an inquiry and gets the remote name for devices. Service

**                  discovery is done if services is non zero

**

**

** Returns          void

**

*******************************************************************************/

void BTA_DmSearch(tBTA_DM_INQ *p_dm_inq, tBTA_SERVICE_MASK services, tBTA_DM_SEARCH_CBACK *p_cback)

{

    tBTA_DM_API_SEARCH    *p_msg;

    if ((p_msg = (tBTA_DM_API_SEARCH *) GKI_getbuf(sizeof(tBTA_DM_API_SEARCH))) != NULL)

    {

        memset(p_msg, , sizeof(tBTA_DM_API_SEARCH));

        p_msg->hdr.event = BTA_DM_API_SEARCH_EVT;

        memcpy(&p_msg->inq_params, p_dm_inq, sizeof(tBTA_DM_INQ));

        p_msg->services = services;

        p_msg->p_cback = p_cback;

        p_msg->rs_res  = BTA_DM_RS_NONE;

        bta_sys_sendmsg(p_msg);

    }

}

这里发现就是组装了一个msg，然后发送给btu 线程处理，这里整理一下发送给btu 线程的参数：

p_msg->hdr.event = BTA_DM_API_SEARCH_EVT;
memcpy(&p_msg->inq_params, p_dm_inq, sizeof(tBTA_DM_INQ)); 上面赋值的参数
p_msg->services = services;//service = 0
p_msg->p_cback = p_cback;//bte_search_devices_evt

p_msg->rs_res = BTA_DM_RS_NONE;

我们查找一下， BTA_DM_API_SEARCH_EVT 执行的函数：bta_dm_search_start

/*******************************************************************************

**

** Function         bta_dm_search_start

**

** Description      Starts an inquiry

**

**

** Returns          void

**

*******************************************************************************/

void bta_dm_search_start (tBTA_DM_MSG *p_data)

{

    tBTM_INQUIRY_CMPL result;

#if (BLE_INCLUDED == TRUE && BTA_GATT_INCLUDED == TRUE)

    UINT16 len = (UINT16)(sizeof(tBT_UUID) * p_data->search.num_uuid);

    bta_dm_gattc_register();

#endif

    if (p_bta_dm_cfg->avoid_scatter &&

        (p_data->search.rs_res == BTA_DM_RS_NONE) && bta_dm_check_av(BTA_DM_API_SEARCH_EVT))

    {

        memcpy(&bta_dm_cb.search_msg, &p_data->search, sizeof(tBTA_DM_API_SEARCH));

        return;

    }

    BTM_ClearInqDb(NULL);

    /* save search params */

    bta_dm_search_cb.p_search_cback = p_data->search.p_cback;

    bta_dm_search_cb.services = p_data->search.services;

#if (BLE_INCLUDED == TRUE && BTA_GATT_INCLUDED == TRUE)

    utl_freebuf((void **)&bta_dm_search_cb.p_srvc_uuid);

    if ((bta_dm_search_cb.num_uuid = p_data->search.num_uuid) !=  &&

         p_data->search.p_uuid != NULL)//如果在搜索的时候设置了uuid，那么也会将这个值copy给bta_dm_search_cb.p_srvc_uuid

    {

        bta_dm_search_cb.p_srvc_uuid = (tBT_UUID *)GKI_getbuf(len)

        memcpy(bta_dm_search_cb.p_srvc_uuid, p_data->search.p_uuid, len);

    }

#endif

    result.status = BTM_StartInquiry(   (tBTM_INQ_PARMS*)&p_data->search.inq_params,

                        bta_dm_inq_results_cb,//扫描到设备调用此函数

                        (tBTM_CMPL_CB*) bta_dm_inq_cmpl_cb);//扫描完成会调用到此函数

    if (result.status != BTM_CMD_STARTED)

    {

        result.num_resp = ;

        bta_dm_inq_cmpl_cb ((void *)&result);//如果开始失败，直接调用回调函数汇报

    }

}

上面的代码执行完，我们看看bta_dm_search_cb的各个结构的值：

bta_dm_search_cb.p_search_cback = bte_search_devices_evt

bta_dm_search_cb.services = 0；

bta_dm_search_cb.num_uuid  =0；

bta_dm_search_cb.p_srvc_uuid = NULL;

下面继续看看BTM_StartInquiry 的实现，这里可以简单分析一下，传入的三个参数：

第一个参数是，上面组装的inquiry相关的设置。

第二个参数是 扫描到设备调用

第三个参数是 扫描完成 （inquiry complete）的时候调用

/*******************************************************************************

**

** Function         BTM_StartInquiry

**

** Description      This function is called to start an inquiry.

**

** Parameters:      p_inqparms - pointer to the inquiry information

**                      mode - GENERAL or LIMITED inquiry, BR/LE bit mask seperately

**                      duration - length in 1.28 sec intervals (If '0', the inquiry is CANCELLED)

**                      max_resps - maximum amount of devices to search for before ending the inquiry

**                      filter_cond_type - BTM_CLR_INQUIRY_FILTER, BTM_FILTER_COND_DEVICE_CLASS, or

**                                         BTM_FILTER_COND_BD_ADDR

**                      filter_cond - value for the filter (based on filter_cond_type)

**

**                  p_results_cb   - Pointer to the callback routine which gets called

**                                upon receipt of an inquiry result. If this field is

**                                NULL, the application is not notified.

**

**                  p_cmpl_cb   - Pointer to the callback routine which gets called

**                                upon completion.  If this field is NULL, the

**                                application is not notified when completed.

** Returns          tBTM_STATUS

**                  BTM_CMD_STARTED if successfully initiated

**                  BTM_BUSY if already in progress

**                  BTM_ILLEGAL_VALUE if parameter(s) are out of range

**                  BTM_NO_RESOURCES if could not allocate resources to start the command

**                  BTM_WRONG_MODE if the device is not up.

**

*******************************************************************************/

tBTM_STATUS BTM_StartInquiry (tBTM_INQ_PARMS *p_inqparms, tBTM_INQ_RESULTS_CB *p_results_cb,

                              tBTM_CMPL_CB *p_cmpl_cb)

{

    tBTM_STATUS  status = BTM_CMD_STARTED;

    tBTM_INQUIRY_VAR_ST *p_inq = &btm_cb.btm_inq_vars;

        p_inq->scan_type = INQ_GENERAL;

...

    /* Save the inquiry parameters to be used upon the completion of setting/clearing the inquiry filter */

    p_inq->inqparms = *p_inqparms;//保存inquiry的参数

    /* Initialize the inquiry variables */

    p_inq->state = BTM_INQ_ACTIVE_STATE;//active

    p_inq->p_inq_cmpl_cb = p_cmpl_cb;

    p_inq->p_inq_results_cb = p_results_cb;

    p_inq->inq_cmpl_info.num_resp = ;         /* Clear the results counter */

    p_inq->inq_active = p_inqparms->mode;//0x11

/* start LE inquiry here if requested */

    if ((p_inqparms->mode & BTM_BLE_INQUIRY_MASK))

    {

         if ((status = btm_ble_start_inquiry((UINT8)(p_inqparms->mode & BTM_BLE_INQUIRY_MASK),

                                            p_inqparms->duration)) != BTM_CMD_STARTED)

        {

            BTM_TRACE_ERROR("Err Starting LE Inquiry.");

            p_inq->inqparms.mode &= ~ BTM_BLE_INQUIRY_MASK;

        }

#if (!defined(BTA_HOST_INTERLEAVE_SEARCH) || BTA_HOST_INTERLEAVE_SEARCH == FALSE)

        p_inqparms->mode &= ~BTM_BLE_INQUIRY_MASK;//开始inquiry之后，mode参数置0

#endif

    }

    /* BR/EDR inquiry portion */

...

    /* Before beginning the inquiry the current filter must be cleared, so initiate the command */

    if ((status = btm_set_inq_event_filter (p_inqparms->filter_cond_type,

                                            &p_inqparms->filter_cond)) != BTM_CMD_STARTED)//这里没有看到BRRDR的扫描，而只有这个清楚过滤的函数，那我可以想象，肯定是这个函数做完之后会自动开始bredr设备的inquiry

        p_inq->state = BTM_INQ_INACTIVE_STATE;

    return (status);

}

上面的代码主要做了三件事：

  1. 将一些参数保存在tBTM_INQUIRY_VAR_ST *p_inq = &btm_cb.btm_inq_vars  这个结构。
    1. p_inq->scan_type = INQ_GENERAL;
    2. p_inq->inqparms = *p_inqparms;
    3. p_inq->state = BTM_INQ_ACTIVE_STATE;
    4. p_inq->p_inq_cmpl_cb = p_cmpl_cb;
    5. p_inq->p_inq_results_cb = p_results_cb;

    6. p_inq->inq_cmpl_info.num_resp = 0; /* Clear the results counter */

    7. p_inq->inq_active = p_inqparms->mode = 0x11（BLE|BREDR）
  2. 做BLE 的inquiry ：btm_ble_start_inquiry((UINT8)(p_inqparms->mode & BTM_BLE_INQUIRY_MASK),p_inqparms->duration)
  3. 做BREDR的inquiry：btm_set_inq_event_filter (p_inqparms->filter_cond_type,&p_inqparms->filter_cond)

btm_ble_start_inquiry

tBTM_STATUS btm_ble_start_inquiry (UINT8 mode, UINT8   duration)

{

    tBTM_STATUS status = BTM_CMD_STARTED;

    tBTM_BLE_CB *p_ble_cb = &btm_cb.ble_ctr_cb;

    tBTM_INQUIRY_VAR_ST      *p_inq = &btm_cb.btm_inq_vars;

...

    if (!BTM_BLE_IS_SCAN_ACTIVE(p_ble_cb->scan_activity))//如果没有scan 正在进行，开始scan

    {

        btsnd_hcic_ble_set_scan_params(BTM_BLE_SCAN_MODE_ACTI,//active scan

                                        BTM_BLE_LOW_LATENCY_SCAN_INT,

                                        BTM_BLE_LOW_LATENCY_SCAN_WIN,

                                        btm_cb.ble_ctr_cb.addr_mgnt_cb.own_addr_type,

                                        SP_ADV_ALL);

#if (defined BLE_PRIVACY_SPT && BLE_PRIVACY_SPT == TRUE)

        /* enable IRK list */

        btm_ble_enable_resolving_list_for_platform(BTM_BLE_RL_SCAN);

#endif

        p_ble_cb->inq_var.scan_duplicate_filter  = BTM_BLE_DUPLICATE_DISABLE;

        status = btm_ble_start_scan();//开始scan

    }

    else if ((p_ble_cb->inq_var.scan_interval != BTM_BLE_LOW_LATENCY_SCAN_INT) ||

            (p_ble_cb->inq_var.scan_window != BTM_BLE_LOW_LATENCY_SCAN_WIN)) {//如果已经有正在scan的行为，先停掉当前的scan，启动新的scan

        btsnd_hcic_ble_set_scan_enable(BTM_BLE_SCAN_DISABLE, BTM_BLE_DUPLICATE_ENABLE);

        btsnd_hcic_ble_set_scan_params(BTM_BLE_SCAN_MODE_ACTI,

                                        BTM_BLE_LOW_LATENCY_SCAN_INT,

                                        BTM_BLE_LOW_LATENCY_SCAN_WIN,

                                        btm_cb.ble_ctr_cb.addr_mgnt_cb.own_addr_type,

                                        SP_ADV_ALL);

        btsnd_hcic_ble_set_scan_enable(BTM_BLE_SCAN_ENABLE, BTM_BLE_DUPLICATE_DISABLE);

    }

    if (status == BTM_CMD_STARTED)

    {

        p_inq->inq_active |= mode;//置位

        p_ble_cb->scan_activity |= mode;

        if (duration != )

        {

            /* start inquiry timer */

            btu_start_timer (&p_inq->inq_timer_ent, BTU_TTYPE_BLE_INQUIRY, duration);//开始定时器，当定时器时间到的时候会 disable scan

        }

    }

    return status;

}

上面的代码的逻辑非常的简单，需要留意一下就是 p_inq->inq_active |= mode 和 p_ble_cb->scan_activity |= mode;

现在Ble 的扫描就开始了，持续时间10s = 10*1000ms，定时器超时时间到了之后会取消scan。

从上面我们还可以看出从inquiry 下发的ble scan的优先级还是很高，它会停掉当前的scan的行为。如果此时后台有observe 行为，也会被停掉。

btm_set_inq_event_filter

static tBTM_STATUS btm_set_inq_event_filter (UINT8 filter_cond_type,

                                             tBTM_INQ_FILT_COND *p_filt_cond)

{

...

    btm_cb.btm_inq_vars.inqfilt_active = TRUE;设置了标志位

    /* Filter the inquiry results for the specified condition type and value */

    if (btsnd_hcic_set_event_filter(HCI_FILTER_INQUIRY_RESULT, filter_cond_type,

                                    p_cond, condition_length))

        return (BTM_CMD_STARTED);

    else

        return (BTM_NO_RESOURCES);

}

上面主要是发送了HCI_FILTER_INQUIRY_RESULT ，以及设置了状态位：btm_cb.btm_inq_vars.inqfilt_active = TRUE

搜索的行为肯定是在这个函数的完成事件中进行的。

static void btu_hcif_hdl_command_complete (UINT16 opcode, UINT8 *p, UINT16 evt_len,

                                           void *p_cplt_cback)

{

    switch (opcode)

    {

        case HCI_INQUIRY_CANCEL:

            /* Tell inquiry processing that we are done */

            btm_process_cancel_complete(HCI_SUCCESS, BTM_BR_INQUIRY_MASK);

            break;

        case HCI_SET_EVENT_FILTER:

            btm_event_filter_complete (p);//执行此函数

            break;
void btm_event_filter_complete (UINT8 *p)

{

    UINT8            hci_status;

    tBTM_STATUS      status;

    tBTM_INQUIRY_VAR_ST *p_inq = &btm_cb.btm_inq_vars;

    tBTM_CMPL_CB   *p_cb = p_inq->p_inqfilter_cmpl_cb;

...

    /* Only process the inquiry filter; Ignore the connection filter until it

       is used by the upper layers */

    if (p_inq->inqfilt_active == TRUE ) //在命令下发的时候已经设置

    {

        /* Extract the returned status from the buffer */

        STREAM_TO_UINT8 (hci_status, p);

        if (hci_status != HCI_SUCCESS)

        {

            /* If standalone operation, return the error status; if embedded in the inquiry, continue the inquiry */

            BTM_TRACE_WARNING ("BTM Warning: Set Event Filter Failed (HCI returned 0x%x)", hci_status);

            status = BTM_ERR_PROCESSING;

        }

        else

            status = BTM_SUCCESS;

        /* If the set filter was initiated externally (via BTM_SetInqEventFilter), call the

           callback function to notify the initiator that it has completed */

        if (p_inq->state == BTM_INQ_INACTIVE_STATE)//此时是active状态

        {

            p_inq->inqfilt_active = FALSE;

            if (p_cb)

                (*p_cb) (&status);

        }

        else    /* An inquiry is active (the set filter command was internally generated),

                   process the next state of the process (Set a new filter or start the inquiry). */

        {

            if(status != BTM_SUCCESS)

            {

                /* Process the inquiry complete (Error Status) */

                btm_process_inq_complete (BTM_ERR_PROCESSING, (UINT8)(p_inq->inqparms.mode & BTM_BR_INQUIRY_MASK));

                /* btm_process_inq_complete() does not restore the following settings on periodic inquiry */

                p_inq->inqfilt_active = FALSE;

                p_inq->inq_active = BTM_INQUIRY_INACTIVE;

                p_inq->state = BTM_INQ_INACTIVE_STATE;

                return;

            }

            /* Check to see if a new filter needs to be set up */

            if (p_inq->state == BTM_INQ_CLR_FILT_STATE)

            {

                if ((status = btm_set_inq_event_filter (p_inq->inqparms.filter_cond_type, &p_inq->inqparms.filter_cond)) == BTM_CMD_STARTED)

                {

                    p_inq->state = BTM_INQ_SET_FILT_STATE;

                }

                else    /* Error setting the filter: Call the initiator's callback function to indicate a failure */

                {

                    p_inq->inqfilt_active = FALSE;

                    /* Process the inquiry complete (Error Status) */

                    btm_process_inq_complete (BTM_ERR_PROCESSING, (UINT8)(p_inq->inqparms.mode & BTM_BR_INQUIRY_MASK));

                }

            }

            else    /* Initiate the Inquiry or Periodic Inquiry */

            {

                p_inq->state = BTM_INQ_ACTIVE_STATE;//处于该状态

                p_inq->inqfilt_active = FALSE;//设置false

                btm_initiate_inquiry (p_inq);//开始扫描

            }

        }

    }

}

上面代码的做的主要的事情:

p_inq->state = BTM_INQ_ACTIVE_STATE;
p_inq->inqfilt_active = FALSE;
btm_initiate_inquiry (p_inq);

继续看btm_initiate_inquiry的实现：

static void btm_initiate_inquiry (tBTM_INQUIRY_VAR_ST *p_inq)

{

    const LAP       *lap;

    tBTM_INQ_PARMS  *p_inqparms = &p_inq->inqparms;

    btm_acl_update_busy_level (BTM_BLI_INQ_EVT);

...

    lap = (p_inq->inq_active & BTM_LIMITED_INQUIRY_ACTIVE) ? &limited_inq_lap : &general_inq_lap;//设置LAP

    {

        btm_clr_inq_result_flt();//清数据库

        /* Allocate memory to hold bd_addrs responding */

        if ((p_inq->p_bd_db = (tINQ_BDADDR *)GKI_getbuf(GKI_MAX_BUF_SIZE)) != NULL)

        {

            p_inq->max_bd_entries = (UINT16)(GKI_MAX_BUF_SIZE / sizeof(tINQ_BDADDR));

            memset(p_inq->p_bd_db, , GKI_MAX_BUF_SIZE);

/*            BTM_TRACE_DEBUG("btm_initiate_inquiry: memory allocated for %d bdaddrs",

                              p_inq->max_bd_entries); */

        }

        if (!btsnd_hcic_inquiry(*lap, p_inqparms->duration, ))//发送inquiry 命令

            btm_process_inq_complete (BTM_NO_RESOURCES, (UINT8)(p_inqparms->mode & BTM_BR_INQUIRY_MASK));

    }

}

上面代码中，重点就是btsnd_hcic_inquiry(*lap, p_inqparms->duration, 0)

其实现就是向controller 发送inquiry 的命令。这里注意其duration参数是10，对应的实际的值是10*1.28s,在12.8秒之后会有inquiry complete 事件传上来。

对于inquiry 的命令发送流程就分析到这里。

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