Bluedroid 之GKI框架

1. 概述

GKI以库libbt-brcm_gki.so(Static Lib?)的形式提供给BlueDroid使用

该层是一个适配层，适配了OS相关的进程、内存相关的管理，还可以用于线程间传递消息 
主要通过变量gki_cb实现对进程的统一管理

<span style="font-family: 'Courier New';">typedef <span class="kwrd">struct</span>
{
    pthread_mutex_t     GKI_mutex;
    pthread_t           thread_id[GKI_MAX_TASKS];
    pthread_mutex_t     thread_evt_mutex[GKI_MAX_TASKS];
    pthread_cond_t      thread_evt_cond[GKI_MAX_TASKS];
    pthread_mutex_t     thread_timeout_mutex[GKI_MAX_TASKS];
    pthread_cond_t      thread_timeout_cond[GKI_MAX_TASKS];
    <span class="kwrd">int</span>                 no_timer_suspend;   <span class="rem">/* 1: no suspend, 0 stop calling GKI_timer_update() */</span>
    pthread_mutex_t     gki_timer_mutex;
    pthread_cond_t      gki_timer_cond;
<span class="preproc">#if</span> (GKI_DEBUG == TRUE)
    pthread_mutex_t     GKI_trace_mutex;
<span class="preproc">#endif</span>
} tGKI_OS;

typedef <span class="kwrd">struct</span>
{
    ...

    UINT8  *OSStack[GKI_MAX_TASKS];         <span class="rem">/* pointer to beginning of stack */</span>
    UINT16  OSStackSize[GKI_MAX_TASKS];     <span class="rem">/* stack size available to each task */</span>


    INT8   *OSTName[GKI_MAX_TASKS];         <span class="rem">/* name of the task */</span>

    UINT8   OSRdyTbl[GKI_MAX_TASKS];        <span class="rem">/* current state of the task */</span>
    UINT16  OSWaitEvt[GKI_MAX_TASKS];       <span class="rem">/* events that have to be processed by the task */</span>
    UINT16  OSWaitForEvt[GKI_MAX_TASKS];    <span class="rem">/* events the task is waiting for*/</span>

    UINT32  OSTicks;                        <span class="rem">/* system ticks from start */</span>
    UINT32  OSIdleCnt;                      <span class="rem">/* idle counter */</span>
    INT16   OSDisableNesting;               <span class="rem">/* counter to keep track of interrupt disable nesting */</span>
    INT16   OSLockNesting;                  <span class="rem">/* counter to keep track of sched lock nesting */</span>
    INT16   OSIntNesting;                   <span class="rem">/* counter to keep track of interrupt nesting */</span>

    <span class="rem">/* Timer related variables</span>
<span class="rem">    */</span>
    INT32   OSTicksTilExp;      <span class="rem">/* Number of ticks till next timer expires */</span>
<span class="preproc">#if</span> (defined(GKI_DELAY_STOP_SYS_TICK) && (GKI_DELAY_STOP_SYS_TICK > 0))
    UINT32  OSTicksTilStop;     <span class="rem">/* inactivity delay timer; OS Ticks till stopping system tick */</span>
<span class="preproc">#endif</span>
    INT32   OSNumOrigTicks;     <span class="rem">/* Number of ticks between last timer expiration to the next one */</span>

    INT32   OSWaitTmr   [GKI_MAX_TASKS];  <span class="rem">/* ticks the task has to wait, for specific events */</span>

    ...

    <span class="rem">/* Buffer related variables</span>
<span class="rem">    */</span>
    BUFFER_HDR_T    *OSTaskQFirst[GKI_MAX_TASKS][NUM_TASK_MBOX]; <span class="rem">/* array of pointers to the first event in the task mailbox */</span>
    BUFFER_HDR_T    *OSTaskQLast [GKI_MAX_TASKS][NUM_TASK_MBOX]; <span class="rem">/* array of pointers to the last event in the task mailbox */</span>

    <span class="rem">/* Define the buffer pool management variables</span>
<span class="rem">    */</span>
    FREE_QUEUE_T    freeq[GKI_NUM_TOTAL_BUF_POOLS];

    UINT16   pool_buf_size[GKI_NUM_TOTAL_BUF_POOLS];
    UINT16   pool_max_count[GKI_NUM_TOTAL_BUF_POOLS];
    UINT16   pool_additions[GKI_NUM_TOTAL_BUF_POOLS];

    <span class="rem">/* Define the buffer pool start addresses</span>
<span class="rem">    */</span>
    UINT8   *pool_start[GKI_NUM_TOTAL_BUF_POOLS];   <span class="rem">/* array of pointers to the start of each buffer pool */</span>
    UINT8   *pool_end[GKI_NUM_TOTAL_BUF_POOLS];     <span class="rem">/* array of pointers to the end of each buffer pool */</span>
    UINT16   pool_size[GKI_NUM_TOTAL_BUF_POOLS];    <span class="rem">/* actual size of the buffers in a pool */</span>

    <span class="rem">/* Define the buffer pool access control variables */</span>
    <span class="kwrd">void</span>        *p_user_mempool;                    <span class="rem">/* User O/S memory pool */</span>
    UINT16      pool_access_mask;                   <span class="rem">/* Bits are set if the corresponding buffer pool is a restricted pool */</span>
    UINT8       pool_list[GKI_NUM_TOTAL_BUF_POOLS]; <span class="rem">/* buffer pools arranged in the order of size */</span>
    UINT8       curr_total_no_of_pools;             <span class="rem">/* number of fixed buf pools + current number of dynamic pools */</span>

    BOOLEAN     timer_nesting;                      <span class="rem">/* flag to prevent timer interrupt nesting */</span>

    <span class="rem">/* Time queue arrays */</span>
    TIMER_LIST_Q *timer_queues[GKI_MAX_TIMER_QUEUES];
    <span class="rem">/* System tick callback */</span>
    SYSTEM_TICK_CBACK *p_tick_cb;
    BOOLEAN     system_tick_running;                <span class="rem">/* TRUE if system tick is running. Valid only if p_tick_cb is not NULL */</span>

<span class="preproc">#if</span> (GKI_DEBUG == TRUE)
    UINT16      ExceptionCnt;                       <span class="rem">/* number of GKI exceptions that have happened */</span>
    EXCEPTION_T Exception[GKI_MAX_EXCEPTION];
<span class="preproc">#endif</span>

} tGKI_COM_CB;

typedef <span class="kwrd">struct</span>
{
    tGKI_OS os;
    tGKI_COM_CB com;
} tGKI_CB;

tGKI_CB gki_cb</span>

2. 线程

2.1 主要函数

- GKI_init() 初始化变量gki_cb 
- GKI_create_task() 创建线程 
- GKI_destroy_task() 销毁线程 
- GKI_run() 时间相关执行函数，目前不知道有何效果

2.2 功能

使用pthread库实现线程相关功能

GKI管理三个线程

<span class="preproc">#define</span> BTU_TASK        0
<span class="preproc">#define</span> BTIF_TASK       1
<span class="preproc">#define</span> A2DP_MEDIA_TASK 2

3. 事件

3.1 主要函数

- GKI_wait() 等待事件的发生 
- GKI_send_event()向指定进程发送事件 
- GKI_send_msg() 向指定进程发送buffer 
- GKI_read_mbox() 从mailbox中读取buffer

3.2 功能

<span style="font-family: 'Courier New';">tGKI_CB.os.thread_evt_mutex[] 事件的互斥锁
tGKI_CB.os.thread_evt_cond[]  事件的条件变量
tGKI_CB.com.OSWaitEvt[]       表示当前进程的事件
tGKI_CB.com.OSTaskQFirst[][]  指向进程的mailbox中第一个事件
tGKI_CB.com.OSTaskQLast[][]   指向进程的mailbox中最后一个事件</span>

首先我们要了解Posix互斥锁和条件变量的使用
tip: 值得一提的是pthread_cond_wait()函数在调用后解锁参数中的互斥锁，直至被唤醒后重新对该互斥锁加锁

GKI事件的原理 
通过GKI_send_event()/GKI_send_msg()发送事件/MBox事件，接收线程通过GKI_wait()可检测事件的发生，并对不同的事件进行不同的处理
对于MBox事件，需要再循环调用GKI_read_mbox()来得到MBOX Buffer 
tip: 事件可以除了可以发往其他线程，也可以发往本线程

每个线程都有四个Mailbox

事件有16个(evt: 0~15)
- 4个保留事件用于Mailbox消息的接收 evt: 0~3 
- 4个保留事件用于超时 evt: 4~7 
- 8个通用事件共APP使用 evt: 8~15

可依次由EVENT_MASK(evt)得到