Bluedroid协议栈HCI线程分析

蓝牙进程中有多个线程,其中HCI 线程是负责处理蓝牙主机端和控制器的数据处理和收发的工作。

本篇文章就是分析一下该线程的数据处理流程。

1.跟HCI相关的接口

首先看看hci的相关的接口:在hci_layer.c中:

const hci_t *hci_layer_get_interface() {
  buffer_allocator = buffer_allocator_get_interface();
  hal = hci_hal_get_interface();//hal模块
  btsnoop = btsnoop_get_interface();
  hci_inject = hci_inject_get_interface();
  packet_fragmenter = packet_fragmenter_get_interface();//组装分块
  vendor = vendor_get_interface();//vendor模块
  low_power_manager = low_power_manager_get_interface();
  init_layer_interface();
  return &interface;
}

主要是结构是:hal,packet_fragmenter以及vendor,下面看看这个接口的结构:

hal模块接口

static const hci_hal_t interface = {
  hal_init,
  hal_open,//通过vendor模块发送指令VENDOR_OPEN_USERIAL,打开host与controller的通信节点,并且在hci线程中一直poll该节点,有数据就传上层协议栈
  hal_close,
  read_data,
  packet_finished,
  transmit_data,
};

const hci_hal_t *hci_hal_h4_get_interface() {
  vendor = vendor_get_interface();//获取了vendor接口
  return &interface;
}

分析代码发现hal_open主要是通过vendor来和底层的模块通信的。可见hal层在vendor的上面。

packet_fragmenter模块接口

static const packet_fragmenter_t interface = {
  init,
  cleanup,
  fragment_and_dispatch,//分片,然后回调到hci_layer,通过hal层发送
  reassemble_and_dispatch//重装,然后回调到hci_layer,塞到btu_hci_queue队列里面
};

const packet_fragmenter_t *packet_fragmenter_get_interface() {
  controller = controller_get_interface();//获取控制器的接口
  buffer_allocator = buffer_allocator_get_interface();
  return &interface;
}

该模块主要负责数据的分片和重组,当hci向下发送数据的时候,会将数据放置到packet_queue,然后调用到该模块的fragment_and_dispatch,然后经过HAL模块发送到vendor,最后抵达controller

当controller有数据上传的时候,底层的bt driver会将数据发送到host与controller的通信节点。hci_thread会一直poll这个节点,然后读出数据,经过hal以及fragment_and_dispatch,最后送到btu线程。

vendor模块接口

static const vendor_t interface = {
  vendor_open,//加载libbt-vendor模块并对模块初始化
  vendor_close,
  send_command,//通过libbt-vendor进行发送op命令,非hci opcode
  send_async_command,
  set_callback,
};

const vendor_t *vendor_get_interface() {
  buffer_allocator = buffer_allocator_get_interface();
  return &interface;
}

vendor模块主要是初始化libbt-vendor模块,一些与厂商相关的接口定义。具体的实现是厂商自己的实现,比如打开底层的通信节点,downloaf 卡片的patch等等。

 

2.线程的创建

线程的创建在hci_layer.c里面,在hci 模块的start_up函数里面:

static future_t *start_up(void) {
  LOG_INFO("%s", __func__);
...  
command_queue = fixed_queue_new(SIZE_MAX);//创建命令队列,用于发送命令
packet_queue = fixed_queue_new(SIZE_MAX);//创建数据队列,用于发送数据
  thread = thread_new("hci_thread");//创建hci线程
...
  packet_fragmenter->init(&packet_fragmenter_callbacks);//初始化“组装分块”模块

  fixed_queue_register_dequeue(command_queue, thread_get_reactor(thread), event_command_ready, NULL);//hci_thread绑定命令队列
  fixed_queue_register_dequeue(packet_queue, thread_get_reactor(thread), event_packet_ready, NULL);//hci_thread 绑定数据队列
...
  vendor->open(btif_local_bd_addr.address, &interface);//调用vendor模块的open
  hal->init(&hal_callbacks, thread);//初始化hal模块
...
 thread_post(thread, event_finish_startup, NULL);//继续完成hci模块的启动工作,这里主要做的是继续初始化vendor模块
...

 这里主要关注一下队列的绑定,当往command_queue里面塞数据的时候,event_command_ready就会被调用来处理这个数据,注意这里都是在hci_thread 里面执行的。同理往数据队列里面塞数据,event_packet_ready就会被执行。

3.数据的发送和接收

  3.1数据的发送

看代码可以发现,event_command_ready和event_packet_ready 他们都会调用同一个接口来发送数据,packet_fragmenter模块里面的:

packet_fragmenter->fragment_and_dispatch(wait_entry->command);

 

也就是说,所有的数据都会先进行fragment以及dispatch的过程,我们这里主要关注数据的流向,那么也就是dispatch的流程:

static void fragment_and_dispatch(BT_HDR *packet) {
...
  callbacks->fragmented(packet, true);
}

 

发现最后是通过回调函数来发送,packet_fragmenter_callbacks_t:,看看其结构:

typedef struct {
  packet_fragmented_cb fragmented;
 packet_reassembled_cb reassembled;
  transmit_finished_cb transmit_finished;
} packet_fragmenter_callbacks_t;
static void transmit_fragment(BT_HDR *packet, bool send_transmit_finished) {
  uint16_t event = packet->event & MSG_EVT_MASK;
  serial_data_type_t type = event_to_data_type(event);
  btsnoop->capture(packet, false);//记录btsnoop数据
  hal->transmit_data(type, packet->data + packet->offset, packet->len);//调用hal接口发送数据
}

 

我们继续看hal的相关的接口:

static uint16_t transmit_data(serial_data_type_t type, uint8_t *data, uint16_t length) {
...
  while (length > 0) {
    ssize_t ret = write(uart_fd, data + transmitted_length, length);
...
  return transmitted_length;
}

 

hal层调用的接口很简单,主要就是往hal_open返回的节点描述符写数据,这个数据最终会经过内核抵达硬件设备端。

发送数据的流程就结束了。

3.2数据的接收

这里应该首先分析一下hal_open的流程:该流程是在event_finish_startup函数里执行,是hci_thread线程一开始就执行的函数:

static void event_finish_startup(UNUSED_ATTR void *context) {
  LOG_INFO("%s", __func__);
  if(!hal->open())
      return;
  vendor->send_async_command(VENDOR_CONFIGURE_FIRMWARE, NULL);
}
static bool hal_open() {
  int fd_array[CH_MAX];
  int number_of_ports = vendor->send_command(VENDOR_OPEN_USERIAL, &fd_array);//通过vendor接口去打开底层的设备节点,存储在fd_array中

  uart_fd = fd_array[0];
  uart_stream = eager_reader_new(uart_fd, &allocator_malloc, HCI_HAL_SERIAL_BUFFER_SIZE, SIZE_MAX, "hci_single_channel");
  eager_reader_register(uart_stream, thread_get_reactor(thread), event_uart_has_bytes, NULL);//hci_thread线程一直poll设备节点,有数据就会调用event_uart_has_bytes来处理
  return true;
}

 

现在我们知道,只要底层有数据传上来,那么hal层的函数event_uart_has_bytes就会去处理这些数据,那么看看event_uart_has_bytes的实现:

static void event_uart_has_bytes(eager_reader_t *reader, UNUSED_ATTR void *context) {
  if (stream_has_interpretation) {
    callbacks->data_ready(current_data_type);//最终调用该函数
  } else {
    uint8_t type_byte;
    if (eager_reader_read(reader, &type_byte, 1, true) == 0) {
      LOG_ERROR("%s could not read HCI message type", __func__);
      return;
    }
...
    stream_has_interpretation = true;
    current_data_type = type_byte;
  }
}

 

最终调用:

static const hci_hal_callbacks_t hal_callbacks = {
hal_says_data_ready
};

 

这个函数之前有分析过,这里简单介绍其流程:

static void hal_says_data_ready(serial_data_type_t type) {
  packet_receive_data_t *incoming = &incoming_packets[PACKET_TYPE_TO_INBOUND_INDEX(type)];
  uint8_t byte;
  while (hal->read_data(type, &byte, 1, false) != 0) {
    switch (incoming->state) {
      case BRAND_NEW:
...
      case BODY:
        incoming->buffer->data[incoming->index] = byte;
...
        break;
      case IGNORE:
        incoming->bytes_remaining--;
...
          hal->packet_finished(type);
          return;
        }
        break;
      case FINISHED:
        LOG_ERROR("%s the state machine should not have been left in the finished state.", __func__);
        break;
    }

    if (incoming->state == FINISHED) {
      incoming->buffer->len = incoming->index;
      btsnoop->capture(incoming->buffer, true);//保存btsnoop文件

      if (type != DATA_TYPE_EVENT) {
        packet_fragmenter->reassemble_and_dispatch(incoming->buffer);//acl data处理流程
      } else if (!filter_incoming_event(incoming->buffer)) {//event 处理流程
        // Dispatch the event by event code
        uint8_t *stream = incoming->buffer->data;
        uint8_t event_code;
        STREAM_TO_UINT8(event_code, stream);

        data_dispatcher_dispatch(
          interface.event_dispatcher,
          event_code,
          incoming->buffer
        );
      }

      // We don't control the buffer anymore
      incoming->buffer = NULL;
      incoming->state = BRAND_NEW;
      hal->packet_finished(type);

      // We return after a packet is finished for two reasons:
      // 1. The type of the next packet could be different.
      // 2. We don't want to hog cpu time.
      return;
    }
  }

}

 

从上面的代码我们发现,主要是经过两个路径来上报数据的:

  1. packet_fragmenter->reassemble_and_dispatch(incoming->buffer); 
  2. data_dispatcher_dispatch(interface.event_dispatcher,event_code,incoming->buffer);

首先看一下 第一个路径:

static void reassemble_and_dispatch(UNUSED_ATTR BT_HDR *packet) {
...
    callbacks->reassembled(packet);
}

 上面的callback 定义在hci_layer.c

static void dispatch_reassembled(BT_HDR *packet) {
...
  if (upwards_data_queue) {
    fixed_queue_enqueue(upwards_data_queue, packet);//把数据放到upwards_data_queue,这个队列其实就是btu_hci_msg_queue
  }
}

 这个队列是在bte_main_boot_entry 时候注册的:

hci = hci_layer_get_interface();
    btu_hci_msg_queue = fixed_queue_new(SIZE_MAX);
    data_dispatcher_register_default(hci->event_dispatcher, btu_hci_msg_queue);
    hci->set_data_queue(btu_hci_msg_queue);//设置upwards_data_queue

 

从这里我们知道,最终的数据送到了btu_hci_msg_queue,那么就由btu 线程继续处理了。 

下面继续看看data_dispatcher_dispatch(interface.event_dispatcher,event_code,incoming->buffer); 

bool data_dispatcher_dispatch(data_dispatcher_t *dispatcher, data_dispatcher_type_t type, void *data) {
  fixed_queue_t *queue = hash_map_get(dispatcher->dispatch_table, (void *)type);
  if (!queue)
    queue = dispatcher->default_queue;//这里的queue其实也是btu_hci_msg_queue

  if (queue)
    fixed_queue_enqueue(queue, data);

  return queue != NULL;
}

 

上面的queue也是在bte_main_boot_entry 里面注册的。

  data_dispatcher_register_default(hci->event_dispatcher, btu_hci_msg_queue);

 

void data_dispatcher_register_default(data_dispatcher_t *dispatcher, fixed_queue_t *queue) {
  assert(dispatcher != NULL);
  dispatcher->default_queue = queue;
}

 

我们知道hci->event_dispatcher->default_queue = btu_hci_msg_queue

那和上面的第一种case一样:最终的数据送到了btu_hci_msg_queue,那么就由btu 线程继续处理了。

总结

最后总结一下hci_thread处理的数据流程:

  1. 当hci向下发送数据的时候,会将数据放置到packet_queue,然后调用到fragment_and_dispatch,然后经过HAL模块发write到vendor,最后抵达controller

  2. 当controller有数据上传的时候,底层的bt driver会将数据发送到host与controller的通信节点。hci_thread会一直poll这个节点,调用 hal_says_data_ready读出数据,数据经过hal以及fragment_and_dispatch(或者data_dispatcher_dispatch),将数据送到btu_hci_msg_queue,然后由btu 线程继续处理。

posted @ 2018-06-23 19:27  雪山飞燕  阅读(2375)  评论(1编辑  收藏  举报