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本文主要讲解Android端Bluetooth Stack(Fluoride),接收到蓝牙Controller上报的ACL链路数据后在蓝牙协议栈的处理流程,如下图。
ACL: 异步无连接(Asynchronous Connection-oriented Link[logical transport]),主要用于分组数据传送,比如车载场景连接手机蓝牙时。
L2CAP: 逻辑链路控制和适配协议(Logical Link Control and Adaptation Protocol),负责管理逻辑层提供的逻辑链路。基于该协议不同应用可共享同一个逻辑链路。
BTU : Bluetooth Upper Layer,This is the main task of the Bluetooth Upper Layers unit. It sits in aloop waiting for messages, and dispatches them to the appropiate handlers.
BTA : Bluetooth application layer
Phy: 蓝牙物理层
代码流程分析:
对接蓝牙驱动接收数据,接收从controller传来的ACL Data
hci_layer_android.cc
- class BluetoothHciCallbacks : public IBluetoothHciCallbacks {
- ......
- Return<void> initializationComplete(Status status) {
- CHECK(status == Status::SUCCESS);
- initialization_complete();
- return Void();
- }
-
- Return<void> hciEventReceived(const hidl_vec<uint8_t>& event) {
- BT_HDR* packet = WrapPacketAndCopy(MSG_HC_TO_STACK_HCI_EVT, event);
- hci_event_received(FROM_HERE, packet);
- return Void();
- }
-
- // 接收到controller传来的ACL Data
- Return<void> aclDataReceived(const hidl_vec<uint8_t>& data) {
- BT_HDR* packet = WrapPacketAndCopy(MSG_HC_TO_STACK_HCI_ACL, data);
- acl_event_received(packet);
- return Void();
- }
-
- Return<void> scoDataReceived(const hidl_vec<uint8_t>& data) {
- BT_HDR* packet = WrapPacketAndCopy(MSG_HC_TO_STACK_HCI_SCO, data);
- sco_data_received(packet);
- return Void();
- }
- ......
- };
将数据进行重组、分发
通过注册的callback分发至上层模块
hci_layer.cc
- void acl_event_received(BT_HDR* packet) {
- btsnoop->capture(packet, true);
- packet_fragmenter->reassemble_and_dispatch(packet);
- }
-
- // Callback for the fragmenter to dispatch up a completely reassembled packet
- static void dispatch_reassembled(BT_HDR* packet) {
- // Events should already have been dispatched before this point
- CHECK((packet->event & MSG_EVT_MASK) != MSG_HC_TO_STACK_HCI_EVT);
- CHECK(!send_data_upwards.is_null());
-
- send_data_upwards.Run(FROM_HERE, packet);
- }
该回调的注册地方是在bte初始化启动的时候,通过 hci->set_data_cb注册数据接收callback。
bte_main.cc
- void bte_main_boot_entry(void) {
- module_init(get_module(INTEROP_MODULE));
- module_init(get_module(PROFILE_CONFIG_MODULE));
-
- hci = hci_layer_get_interface();
- if (!hci) {
- LOG_ERROR(LOG_TAG, "%s could not get hci layer interface.", __func__);
- return;
- }
-
- hci->set_data_cb(base::Bind(&post_to_hci_message_loop));
-
- module_init(get_module(STACK_CONFIG_MODULE));
- }
对应的callback回调处理函数
- void post_to_hci_message_loop(const tracked_objects::Location& from_here,
- BT_HDR* p_msg) {
- ......
- hci_message_loop->task_runner()->PostTask(
- from_here, base::Bind(&btu_hci_msg_process, p_msg));
- ......
- }
将Acl数据传递至L2CAP层处理
btu_task.cc
- void btu_hci_msg_process(BT_HDR* p_msg) {
- /* Determine the input message type. */
- switch (p_msg->event & BT_EVT_MASK) {
- case BT_EVT_TO_BTU_HCI_ACL:
- /* All Acl Data goes to L2CAP */
- l2c_rcv_acl_data(p_msg);
- break;
- ......
- }
- }
先根据handle查找到对应的LCB(link control block,定义参考下面代码),之后再根据CID取出对应CCB(channel control block,定义参考下面代码),最后通过来L2CAP状态机处理数据。
l2c_main.cc
- void l2c_rcv_acl_data(BT_HDR* p_msg) {
- tL2C_LCB* p_lcb;
- tL2C_CCB* p_ccb = NULL;
- ......
- /* Find the LCB based on the handle */
- p_lcb = l2cu_find_lcb_by_handle(handle);
-
- /* Look through all active CCBs on a link for a match based
- * on the local CID. If passed the link pointer is NULL, all
- * active links are searched. the CCB for this CID */
- p_ccb = l2cu_find_ccb_by_cid(p_lcb, rcv_cid);
- ......
-
- /* Basic mode packets go straight to the state machine */
- if (p_ccb->peer_cfg.fcr.mode == L2CAP_FCR_BASIC_MODE)
- l2c_csm_execute(p_ccb, L2CEVT_L2CAP_DATA, p_msg);
- else {
- /* eRTM or streaming mode, so we need to validate states first */
- if ((p_ccb->chnl_state == CST_OPEN) ||
- (p_ccb->chnl_state == CST_CONFIG))
- l2c_fcr_proc_pdu(p_ccb, p_msg);
- else
- osi_free(p_msg);
- }
- ......
- }
tL2C_LCB及tL2C_CCB的定义如下,两者的关系是一个LCB中可以有多个CCB通过不同的CID区分。
- /* Define a link control block. There is one link control block between
- * this device and any other device (i.e. BD ADDR).
- */
- typedef struct t_l2c_linkcb {
- bool in_use; /* true when in use, false when not */
- tL2C_LINK_STATE link_state;
-
- uint16_t handle; /* The handle used with LM */
-
- tL2C_CCB_Q ccb_queue; /* Queue of CCBs on this LCB */
-
- tL2C_CCB* p_pending_ccb; /* ccb of waiting channel during link disconnect */
- alarm_t* info_resp_timer; /* Timer entry for info resp timeout evt */
- RawAddress remote_bd_addr; /* The BD address of the remote */
-
- uint8_t link_role; /* Master or slave */
- ......
- } tL2C_LCB;
-
- /* Define a channel control block (CCB). There may be many channel control
- * blocks between the same two Bluetooth devices (i.e. on the same link).
- * Each CCB has unique local and remote CIDs. All channel control blocks on
- * the same physical link and are chained together.
- */
- typedef struct t_l2c_ccb {
- ......
- tL2C_CHNL_STATE chnl_state; /* Channel state */
- uint16_t local_cid; /* Local CID */
- uint16_t remote_cid; /* Remote CID */
- tL2C_RCB* p_rcb; /* Registration CB for this Channel */
- ......
- } tL2C_CCB;
-
- typedef struct {
- bool in_use;
- uint16_t psm;
- uint16_t real_psm; /* This may be a dummy RCB for an o/b connection but */
- /* this is the real PSM that we need to connect to */
- #if (L2CAP_UCD_INCLUDED == TRUE)
- tL2C_UCD_REG ucd;
- #endif
-
- tL2CAP_APPL_INFO api;
- } tL2C_RCB;
-
- typedef struct {
- tL2CA_CONNECT_IND_CB* pL2CA_ConnectInd_Cb;
- tL2CA_CONNECT_CFM_CB* pL2CA_ConnectCfm_Cb;
- tL2CA_CONNECT_PND_CB* pL2CA_ConnectPnd_Cb;
- tL2CA_CONFIG_IND_CB* pL2CA_ConfigInd_Cb;
- tL2CA_CONFIG_CFM_CB* pL2CA_ConfigCfm_Cb;
- tL2CA_DISCONNECT_IND_CB* pL2CA_DisconnectInd_Cb;
- tL2CA_DISCONNECT_CFM_CB* pL2CA_DisconnectCfm_Cb;
- tL2CA_QOS_VIOLATION_IND_CB* pL2CA_QoSViolationInd_Cb;
- tL2CA_DATA_IND_CB* pL2CA_DataInd_Cb;
- tL2CA_CONGESTION_STATUS_CB* pL2CA_CongestionStatus_Cb;
- tL2CA_TX_COMPLETE_CB* pL2CA_TxComplete_Cb;
- } tL2CAP_APPL_INFO;
L2CAP状态机处理函数
l2c_csm.cc
- // This function executes the state machine.
- void l2c_csm_execute(tL2C_CCB* p_ccb, uint16_t event, void* p_data) {
- ......
- switch (p_ccb->chnl_state) {
- case CST_OPEN:
- l2c_csm_open(p_ccb, event, p_data);
- break;
- ......
- }
Android L2CAP 定义的state及event如下:(图源网络,侵权可联系作者删除)
通过pL2CA_DataInd_Cb将数据回调到RFCOMM
- // This function handles events when the channel is in OPEN state.
- static void l2c_csm_open(tL2C_CCB* p_ccb, uint16_t event, void* p_data) {
- ......
- case L2CEVT_L2CAP_DATA: /* Peer data packet rcvd */
- if ((p_ccb->p_rcb) && (p_ccb->p_rcb->api.pL2CA_DataInd_Cb))
- (*p_ccb->p_rcb->api.pL2CA_DataInd_Cb)(p_ccb->local_cid,
- (BT_HDR*)p_data);
- break;
- ......
- }
在RFCOMM task开启时会向L2CAP注册该pL2CA_DataInd_Cb回调接口
rfc_l2cap_if.cc
- void rfcomm_l2cap_if_init(void) {
- tL2CAP_APPL_INFO* p_l2c = &rfc_cb.rfc.reg_info;
- p_l2c->pL2CA_ConnectInd_Cb = RFCOMM_ConnectInd;
- p_l2c->pL2CA_ConnectCfm_Cb = RFCOMM_ConnectCnf;
- p_l2c->pL2CA_ConnectPnd_Cb = NULL;
- p_l2c->pL2CA_ConfigInd_Cb = RFCOMM_ConfigInd;
- p_l2c->pL2CA_ConfigCfm_Cb = RFCOMM_ConfigCnf;
- p_l2c->pL2CA_DisconnectInd_Cb = RFCOMM_DisconnectInd;
- p_l2c->pL2CA_DisconnectCfm_Cb = NULL;
- p_l2c->pL2CA_QoSViolationInd_Cb = RFCOMM_QoSViolationInd;
- p_l2c->pL2CA_DataInd_Cb = RFCOMM_BufDataInd;
- p_l2c->pL2CA_CongestionStatus_Cb = RFCOMM_CongestionStatusInd;
- p_l2c->pL2CA_TxComplete_Cb = NULL;
-
- L2CA_Register(BT_PSM_RFCOMM, p_l2c);
- }
通过RFCOMM 状态机处理数据
- void RFCOMM_BufDataInd(uint16_t lcid, BT_HDR* p_buf) {
- ......
- event = rfc_parse_data(p_mcb, &rfc_cb.rfc.rx_frame, p_buf);
- p_port = port_find_dlci_port(rfc_cb.rfc.rx_frame.dlci);
- rfc_port_sm_execute(p_port, event, p_buf);
- ......
- }
RFCOMM 状态机处理函数
rfc_port_fsm.cc
- void rfc_port_sm_execute(tPORT* p_port, uint16_t event, void* p_data) {
- ......
- case RFC_STATE_OPENED:
- rfc_port_sm_opened(p_port, event, p_data);
- break;
- ......
- }
Android定义的RFCOMM Port State如下:
RFCOMM Port State | 描述 |
---|---|
RFC_STATE_CLOSED | |
RFC_STATE_SABME_WAIT_UA | |
RFC_STATE_ORIG_WAIT_SEC_CHECK | |
RFC_STATE_TERM_WAIT_SEC_CHECK | |
RFC_STATE_OPENED | |
RFC_STATE_DISC_WAIT_UA |
跟据不同的event类型执行逻辑
- void rfc_port_sm_opened(tPORT* p_port, uint16_t event, void* p_data) {
- switch (event) {
- ......
- case RFC_EVENT_UIH:
- rfc_port_uplink_data(p_port, (BT_HDR*)p_data);
- return;
- ......
- }
- }
Android定义的RFCOMM支持的帧(Frame)类型如下
类型 | 描述 |
---|---|
RFC_EVENT_OPEN | |
RFC_EVENT_CLOSE | |
RFC_EVENT_CLEAR | |
RFC_EVENT_DATA | |
RFC_EVENT_TIMEOUT | |
RFC_EVENT_SABM | Set Asynchronous Balanced Mode (startup command) |
RFC_EVENT_UA | Unnumbered Acknowledgement (response when connected) |
RFC_EVENT_DISC | Disconnect (disconect command) |
RFC_EVENT_DM | Disconnected Mode (response to a command when disconected) |
RFC_EVENT_UIH | Unnumbered Information with Header check |
- void rfc_port_uplink_data(tPORT* p_port, BT_HDR* p_buf) {
- PORT_DataInd(p_port->rfc.p_mcb, p_port->dlci, p_buf);
- }
当从对等方接收到数据缓冲区时,从RFCOMM层调用此函数。
通过数据链路连接标识符(DLCI,Data Link Connection Identifier)找到对应的port,安卓支持最多30个port。
然后通过callback回调给上层应用。
port_rfc.cc
- void PORT_DataInd(tRFC_MCB* p_mcb, uint8_t dlci, BT_HDR* p_buf) {
- tPORT* p_port = port_find_mcb_dlci_port(p_mcb, dlci);
-
- /* If client registered callout callback with flow control we can just deliver
- * receive data */
- if (p_port->p_data_co_callback) {
- /* Another packet is delivered to user. Send credits to peer if required */
- if (p_port->p_data_co_callback(p_port->inx, (uint8_t*)p_buf, -1,
- DATA_CO_CALLBACK_TYPE_INCOMING)) {
- port_flow_control_peer(p_port, true, 1);
- } else {
- port_flow_control_peer(p_port, false, 0);
- }
- // osi_free(p_buf);
- return;
- }
-
- /* If client registered callback we can just deliver receive data */
- if (p_port->p_data_callback) {
- /* Another packet is delivered to user. Send credits to peer if required */
- port_flow_control_peer(p_port, true, 1);
- p_port->p_data_callback(p_port->inx, (uint8_t*)(p_buf + 1) + p_buf->offset,
- p_buf->len);
- osi_free(p_buf);
- return;
- }
-
- if (p_port->p_callback && events) p_port->p_callback(events, p_port->inx);
- }
以AG为例子上层应用注册PORT Callback的地方是在AG服务初始时。
bta_ag_rfc.cc
- // Setup RFCOMM port for use by AG.
- void bta_ag_setup_port(tBTA_AG_SCB* p_scb, uint16_t handle) {
- uint16_t i = bta_ag_scb_to_idx(p_scb) - 1;
-
- /* set up data callback if using pass through mode */
- if (bta_ag_cb.parse_mode == BTA_AG_PASS_THROUGH) {
- PORT_SetDataCallback(handle, bta_ag_data_cback_tbl[i]);
- }
-
- PORT_SetEventMask(handle, BTA_AG_PORT_EV_MASK);
- PORT_SetEventCallback(handle, bta_ag_port_cback_tbl[i]);
- }
- int PORT_SetEventCallback(uint16_t port_handle, tPORT_CALLBACK* p_port_cb) {
- .....
- p_port = &rfc_cb.port.port[port_handle - 1];
- p_port->p_callback = p_port_cb;
- .....
- }
bta_ag_port_cback_tbl定义如下
- const tBTA_AG_PORT_CBACK bta_ag_port_cback_tbl[] = {
- bta_ag_port_cback_1, bta_ag_port_cback_2, bta_ag_port_cback_3};
实现为如下函数:
该函数用来处理RFCOMM Port callback,会发送一个BTA_AG_RFC_DATA_EVT消息,参考bta_sys_sendmsg的传输流程请看《BTA消息分发流程》,最终会调用到bta_ag_sm_execute函数
bta_ag_rfc.cc
- static void bta_ag_port_cback(UNUSED_ATTR uint32_t code, uint16_t port_handle,
- uint16_t handle) {
- .......
- BT_HDR* p_buf = (BT_HDR*)osi_malloc(sizeof(BT_HDR));
- p_buf->event = BTA_AG_RFC_DATA_EVT;
- p_buf->layer_specific = handle;
- bta_sys_sendmsg(p_buf);
- .......
- }
bta ag 状态机执行函数,这一步的操作是:
1、取出当前状态的event-action关联表,
2、获取当前event对应的state,设置为下一个state;
3、执行当前event对应的action;
bta_ag_main.cc
- void bta_ag_sm_execute(tBTA_AG_SCB* p_scb, uint16_t event,
- tBTA_AG_DATA* p_data) {
-
- /* look up the state table for the current state */
- state_table = bta_ag_st_tbl[p_scb->state];
-
- /* set next state */
- p_scb->state = state_table[event][BTA_AG_NEXT_STATE];
-
- /* execute action functions */
- for (i = 0; i < BTA_AG_ACTIONS; i++) {
- action = state_table[event][i];
- if (action != BTA_AG_IGNORE) {
- (*bta_ag_action[action])(p_scb, p_data);
- } else {
- break;
- }
- }
- ......
- }
BTA_AG中定义了4个状态,其中每个状态还定义了每个Event对应的Action1、Action 2及Next State
- /* state table */
- const tBTA_AG_ST_TBL bta_ag_st_tbl[] = {bta_ag_st_init, bta_ag_st_opening,
- bta_ag_st_open, bta_ag_st_closing};
读取并处理来自RFCOMM的数据
bta_ag_act.cc
- void bta_ag_rfc_data(tBTA_AG_SCB* p_scb, UNUSED_ATTR tBTA_AG_DATA* p_data) {
- ...
- /* do the following */
- for (;;) {
- /* read data from rfcomm; if bad status, we're done */
- if (PORT_ReadData(p_scb->conn_handle, buf, BTA_AG_RFC_READ_MAX, &len) !=
- PORT_SUCCESS) {
- break;
- }
- ...
- /* run AT command interpreter on data */
- bta_ag_at_parse(&p_scb->at_cb, buf, len);
- if ((p_scb->sco_idx != BTM_INVALID_SCO_INDEX) &&
- bta_ag_sco_is_open(p_scb)) {
- APPL_TRACE_IMP("%s change link policy for SCO", __func__);
- bta_sys_sco_open(BTA_ID_AG, p_scb->app_id, p_scb->peer_addr);
- } else {
- if (strstr(buf, "AT+IPHONEACCEV") != NULL) {
- APPL_TRACE_IMP("%s: AT+IPHONEACCEV received, not setting idle", __func__);
- } else {
- APPL_TRACE_IMP("%s: resetting idle timer", __func__);
- bta_sys_idle(BTA_ID_AG, p_scb->app_id, p_scb->peer_addr);
- }
- }
-
- /* no more data to read, we're done */
- if (len < BTA_AG_RFC_READ_MAX) {
- break;
- }
- }
- }
解析RFCOMM上报的AT指令,未完待续。
- /**
- * Parse AT commands. This function will take the input character string and parse it * * for AT commands according to the AT command table passed in the control block.
- **/
- void bta_ag_process_at(tBTA_AG_AT_CB* p_cb) {
- ......
- /* if arguments match command capabilities */
- if ((arg_type & p_cb->p_at_tbl[idx].arg_type) != 0) {
- /* if it's a set integer check max, min range */
- if (arg_type == BTA_AG_AT_SET &&
- p_cb->p_at_tbl[idx].fmt == BTA_AG_AT_INT) {
- int_arg = utl_str2int(p_arg);
- if (int_arg < (int16_t)p_cb->p_at_tbl[idx].min ||
- int_arg > (int16_t)p_cb->p_at_tbl[idx].max) {
- /* arg out of range; error */
- (*p_cb->p_err_cback)(p_cb->p_user, false, NULL);
- } else {
- (*p_cb->p_cmd_cback)(p_cb->p_user, p_cb->p_at_tbl[idx].command_id,
- arg_type, p_arg, int_arg);
- }
- } else {
- (*p_cb->p_cmd_cback)(p_cb->p_user, p_cb->p_at_tbl[idx].command_id,
- arg_type, p_arg, int_arg);
- }
- }
- ......
- }
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