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 = 0; tBTA_DM_BLE_PF_FILT_PARAMS adv_filt_param; #if (defined(BLE_INCLUDED) && (BLE_INCLUDED == TRUE)) memset(&adv_filt_param, 0, sizeof(tBTA_DM_BLE_PF_FILT_PARAMS)); /* Cleanup anything remaining on index 0 */ BTA_DmBleScanFilterSetup(BTA_DM_BLE_SCAN_COND_DELETE, 0, &adv_filt_param, NULL, bte_scan_filt_param_cfg_evt, 0); /* 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, 0, &adv_filt_param, NULL, bte_scan_filt_param_cfg_evt, 0); /* 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;//0 /* 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;//0 tBTA_SERVICE_MASK services = 0; 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, 0, 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) != 0 && 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 = 0; 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 = 0; /* 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：
- 将一些参数保存在tBTM_INQUIRY_VAR_ST *p_inq = &btm_cb.btm_inq_vars 这个结构。
- p_inq->scan_type = INQ_GENERAL;
- p_inq->inqparms = *p_inqparms;
- p_inq->state = BTM_INQ_ACTIVE_STATE;
- 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 = 0; /* Clear the results counter */
- p_inq->inq_active = p_inqparms->mode = 0x11（BLE|BREDR）
- 做BLE 的inquiry ：btm_ble_start_inquiry((UINT8)(p_inqparms->mode & BTM_BLE_INQUIRY_MASK),p_inqparms->duration)
- 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 != 0) { /* 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, 0, 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, 0))//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。