BlueDroid代码分析之GKI

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

typedef struct
{
    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];
    int                 no_timer_suspend;   /* 1: no suspend, 0 stop calling GKI_timer_update() */
    pthread_mutex_t     gki_timer_mutex;
    pthread_cond_t      gki_timer_cond;
#if (GKI_DEBUG == TRUE)
    pthread_mutex_t     GKI_trace_mutex;
#endif
} tGKI_OS;

typedef struct
{
    ...

    UINT8  *OSStack[GKI_MAX_TASKS];         /* pointer to beginning of stack */
    UINT16  OSStackSize[GKI_MAX_TASKS];     /* stack size available to each task */

    INT8   *OSTName[GKI_MAX_TASKS];         /* name of the task */

    UINT8   OSRdyTbl[GKI_MAX_TASKS];        /* current state of the task */
    UINT16  OSWaitEvt[GKI_MAX_TASKS];       /* events that have to be processed by the task */
    UINT16  OSWaitForEvt[GKI_MAX_TASKS];    /* events the task is waiting for*/

    UINT32  OSTicks;                        /* system ticks from start */
    UINT32  OSIdleCnt;                      /* idle counter */
    INT16   OSDisableNesting;               /* counter to keep track of interrupt disable nesting */
    INT16   OSLockNesting;                  /* counter to keep track of sched lock nesting */
    INT16   OSIntNesting;                   /* counter to keep track of interrupt nesting */

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

    INT32   OSWaitTmr   [GKI_MAX_TASKS];  /* ticks the task has to wait, for specific events */

    ...

    /* Buffer related variables
    */
    BUFFER_HDR_T    *OSTaskQFirst[GKI_MAX_TASKS][NUM_TASK_MBOX]; /* array of pointers to the first event in the task mailbox */
    BUFFER_HDR_T    *OSTaskQLast [GKI_MAX_TASKS][NUM_TASK_MBOX]; /* array of pointers to the last event in the task mailbox */

    /* Define the buffer pool management variables
    */
    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];

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

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

    BOOLEAN     timer_nesting;                      /* flag to prevent timer interrupt nesting */

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

#if (GKI_DEBUG == TRUE)
    UINT16      ExceptionCnt;                       /* number of GKI exceptions that have happened */
    EXCEPTION_T Exception[GKI_MAX_EXCEPTION];
#endif

} tGKI_COM_CB;

typedef struct
{
    tGKI_OS os;
    tGKI_COM_CB com;
} tGKI_CB;

tGKI_CB gki_cb

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

#define BTU_TASK        0
#define BTIF_TASK       1
#define 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

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

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