BlueDroid程式碼分析之GKI

1. 概述

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

該層是一個適配層，適配了OS相關的進程、記憶體相關的管理，還可以用於線程間傳遞訊息
主要通過變數gki_cb實現對進程的統一管理

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. 線程 2.1 主要函數

- GKI_init() 初始設定變數gki_cb
- GKI_create_task() 建立線程
- GKI_destroy_task() 銷毀線程
- GKI_run() 時間相關執行函數，目前不知道有何效果 2.2 功能

使用pthread庫實現線程相關功能

GKI管理三個線程

#define BTU_TASK        0#define BTIF_TASK       1#define A2DP_MEDIA_TASK 2

3. 事件 3.1 主要函數

- GKI_wait() 等待事件的發生
- GKI_send_event()向指定進程發送事件
- GKI_send_msg() 向指定進程發送buffer
- GKI_read_mbox() 從mailbox中讀取buffer 3.2 功能

tGKI_CB.os.thread_evt_mutex[] 事件的互斥鎖tGKI_CB.os.thread_evt_cond[]  事件的條件變數tGKI_CB.com.OSWaitEvt[]       表示當前進程的事件tGKI_CB.com.OSTaskQFirst[][]  指向進程的mailbox中第一個事件tGKI_CB.com.OSTaskQLast[][]   指向進程的mailbox中最後一個事件

首先我們要瞭解Posix互斥鎖和條件變數的使用
tip: 值得一提的是pthread_cond_wait()函數在調用後解鎖參數中的互斥鎖，直至被喚醒後重新對該互斥鎖加鎖

GKI事件的原理
通過GKI_send_event()/GKI_send_msg()發送事件/MBox事件，接收線程通過GKI_wait()可檢測事件的發生，並對不同的事件進行不同的處理
對於MBox事件，需要再迴圈調用GKI_read_mbox()來得到MBOX Buffer
tip: 事件可以除了可以發往其他線程，也可以發往本線程

每個線程都有四個Mailbox

事件有16個(evt: 0~15)
- 4個保留事件用於Mailbox訊息的接收 evt: 0~3
- 4個保留事件用於逾時 evt: 4~7
- 8個通用事件共APP使用 evt: 8~15

可依次由EVENT_MASK(evt)得到