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BlueDroid代码分析之GKI

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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



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