Bluedroid code analysis-gki

1. Overview

Gki to library libbt-brcm_gki.so (static Lib ?) To bluedroid.

This layer is an adaptation layer that adapts to OS-related processes and memory-related management and can be used to transmit messages between threads.
The gki_cb variable is used to centrally manage processes.

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. Main Functions of thread 2.1

-Gki_init () initialization variable gki_cb
-Gki_create_task () Creation thread
-Gki_destroy_task () destroy thread
-The gki_run () time-related execution function is unknown.

2.2 features

Use the pthread library to implement thread-related functions

Gki manages three threads

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

3. Main Functions of event 3.1

-Gki_wait (): Wait for the event to occur.
-Gki_send_event () sends an event to the specified process
-Gki_send_msg () sends the buffer to the specified process
-Gki_read_mbox () reads the buffer from mailbox

3.2 features

Tgki_cb. OS .thread_evt_mutex [] the event mutex tgki_cb. OS .thread_evt_cond [] the event's condition variable token [] indicates the event token of the current process [] [] pointing to the first event token in the mailbox of the Process [] point to the last event in the mailbox of the process

First, we need to understand the use of POSIX mutex lock and conditional variables.
Tip: It is worth mentioning that the pthread_cond_wait () function is called to unlock the mutex lock in the parameter until it is awakened and then re-locks the mutex lock.

How gki events work
Use gki_send_event ()/gki_send_msg () to send events/mbox events. The receiving thread can detect events through gki_wait () and process different events differently.
For mbox events, gki_read_mbox () needs to be recycled to obtain the mbox buffer.
Tip: events can be sent to other threads or to the local thread.

Each thread has four mailboxes.

There are 16 events (EVT: 0 ~ 15)
-Four reserved events are used to receive the mailbox message EVT: 0 ~ 3
-Four retention events are used to time out EVT: 4 ~ 7
-A total of 8 General events are used by the app EVT: 8 ~ 15

It can be obtained by event_mask (EVT) in sequence.