Android RIL源码研究笔记 の ril_event

    Android源码目录hardware/ril/libril目录中总共包含5个C/CPP文件，它们分别是ril_commands.h、ril_unsol_commands.h、ril_event.h、ril_event.cpp和ril.cpp。这篇文章主要分析ril_event的相关代码。

   ril_event主要处理电话模块涉及的端口、modem等产生的事件，并将多个事件按时间顺序进行组织，并保存在事件队别中，主要使用了三个队列，分别是：watch_table[]，timer_list和pending_list。代码是以C语言方式实现的，先来看头文件ril_event.h：

 

// 每次监视的最大的文件描述符句柄数，可以根据需要自行修改 #define MAX_FD_EVENTS 8 // ril_event的回调函数 typedef void (*ril_event_cb)(int fd, short events, void *userdata); struct ril_event { // 用于将ril_event串成双向链表的前向指针和后向指针 struct ril_event *next; struct ril_event *prev; //ril事件相关的文件描述符句柄（可以是文件、管道、Socket等） int fd; //这个事件在监控列表中的索引 int index; //当一个事件处理完后（即从watch_table移到pending_list中等待处理）， //persist参数决定这个事件是否一直存在于监控列表watch_table[]中 bool persist; //事件的超时时间 struct timeval timeout; //回调函数及其传入的参数 ril_event_cb func; void *param; }; //以下是ril事件相关的一些操作函数 // 初始化内部数据结构 void ril_event_init(); // 初始化一个ril事件 void ril_event_set(struct ril_event * ev, int fd, bool persist, ril_event_cb func, void * param); // 将事件添加到监控列表watch_table[]中 void ril_event_add(struct ril_event * ev); // 增加一个timer事件到timer_list链表中 void ril_timer_add(struct ril_event * ev, struct timeval * tv); // 将指定的事件从监控列表watch_table[]中移除 void ril_event_del(struct ril_event * ev); // 事件循环 void ril_event_loop();

接着分析ril_event .cpp文件：

 

#define LOG_TAG "RILC" #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <fcntl.h> #include <utils/Log.h> #include <ril_event.h> #include <string.h> #include <sys/time.h> #include <time.h> #include <pthread.h> // 使用互斥量mutex进行线程同步，可参见《Linux程序设计》相关章节 static pthread_mutex_t listMutex; #define MUTEX_ACQUIRE() pthread_mutex_lock(&listMutex) #define MUTEX_RELEASE() pthread_mutex_unlock(&listMutex) #define MUTEX_INIT() pthread_mutex_init(&listMutex, NULL) #define MUTEX_DESTROY() pthread_mutex_destroy(&listMutex) // 两个timeval类型的值相加 #ifndef timeradd #define timeradd(tvp, uvp, vvp) \ do { \ (vvp)->tv_sec = (tvp)->tv_sec + (uvp)->tv_sec; \ (vvp)->tv_usec = (tvp)->tv_usec + (uvp)->tv_usec; \ if ((vvp)->tv_usec >= 1000000) { \ (vvp)->tv_sec++; \ (vvp)->tv_usec -= 1000000; \ } \ } while (0) #endif // 两个timeval类型的值进行比较 #ifndef timercmp #define timercmp(a, b, op) \ ((a)->tv_sec == (b)->tv_sec \ ? (a)->tv_usec op (b)->tv_usec \ : (a)->tv_sec op (b)->tv_sec) #endif // 两个timeval类型的值相减 #ifndef timersub #define timersub(a, b, res) \ do { \ (res)->tv_sec = (a)->tv_sec - (b)->tv_sec; \ (res)->tv_usec = (a)->tv_usec - (b)->tv_usec; \ if ((res)->tv_usec < 0) { \ (res)->tv_usec += 1000000; \ (res)->tv_sec -= 1; \ } \ } while(0); #endi // 保存Rild中所有设备文件句柄，便于使用select函数完成事件的监听 static fd_set readFds; // 记录readFds中最大fd值+1 static int nfds = 0; // 为了统一管理ril事件，Android提供如下三个队列： // 监控事件列表，需要检测的事件都需要先存入该列表中 static struct ril_event * watch_table[MAX_FD_EVENTS]; // timer事件队列，事件超时后即移入pending_list队列中 static struct ril_event timer_list; // 待处理的事件队列，即事件已经触发，后续需要调用事件的回调函数 static struct ril_event pending_list; #define DEBUG 0 #if DEBUG #define dlog(x...) LOGD( x ) static void dump_event(struct ril_event * ev) { dlog("~~~~ Event %x ~~~~", (unsigned int)ev); dlog(" next = %x", (unsigned int)ev->next); dlog(" prev = %x", (unsigned int)ev->prev); dlog(" fd = %d", ev->fd); dlog(" pers = %d", ev->persist); dlog(" timeout = %ds + %dus", (int)ev->timeout.tv_sec, (int)ev->timeout.tv_usec); dlog(" func = %x", (unsigned int)ev->func); dlog(" param = %x", (unsigned int)ev->param); dlog("~~~~~~~~~~~~~~~~~~"); } #else #define dlog(x...) do {} while(0) #define dump_event(x) do {} while(0) #endif // 获取此刻timeval值 static void getNow(struct timeval * tv) { #ifdef HAVE_POSIX_CLOCKS struct timespec ts; clock_gettime(CLOCK_MONOTONIC, &ts); tv->tv_sec = ts.tv_sec; tv->tv_usec = ts.tv_nsec/1000; #else gettimeofday(tv, NULL); #endif } // 初始化指定的ril_event链表 static void init_list(struct ril_event * list) { memset(list, 0, sizeof(struct ril_event)); list->next = list; list->prev = list; list->fd = -1; } // 增加一个ril_event事件到ril_event队列头 static void addToList(struct ril_event * ev, struct ril_event * list) { ev->next = list; ev->prev = list->prev; ev->prev->next = ev; list->prev = ev; dump_event(ev); } // 从ril_event队列中移除指定的ril_event static void removeFromList(struct ril_event * ev) { dlog("~~~~ Removing event ~~~~"); dump_event(ev); ev->next->prev = ev->prev; ev->prev->next = ev->next; ev->next = NULL; ev->prev = NULL; } // 从watch_table[]中移除指定索引的事件 static void removeWatch(struct ril_event * ev, int index) { // 索引index对应的事件置为空，同时事件ev的索引设为无效值-1 watch_table[index] = NULL; ev->index = -1; // 将该事件对应的文件描述符句柄从readFds中清除 FD_CLR(ev->fd, &readFds); if (ev->fd+1 == nfds) { int n = 0; for (int i = 0; i < MAX_FD_EVENTS; i++) { struct ril_event * rev = watch_table[i]; if ((rev != NULL) && (rev->fd > n)) { n = rev->fd; } } nfds = n + 1; dlog("~~~~ nfds = %d ~~~~", nfds); } } // 遍历timer_list队列中的事件，当事件超时时间到时 // 将事件移除，并添加到pending_list队列中 static void processTimeouts() { dlog("~~~~ +processTimeouts ~~~~"); MUTEX_ACQUIRE(); struct timeval now; struct ril_event * tev = timer_list.next; struct ril_event * next; getNow(&now); // walk list, see if now >= ev->timeout for any events dlog("~~~~ Looking for timers <= %ds + %dus ~~~~", (int)now.tv_sec, (int)now.tv_usec); while ((tev != &timer_list) && (timercmp(&now, &tev->timeout, >))) { // Timer expired dlog("~~~~ firing timer ~~~~"); next = tev->next; removeFromList(tev); addToList(tev, &pending_list); tev = next; } MUTEX_RELEASE(); dlog("~~~~ -processTimeouts ~~~~"); } // 遍历监控列表watch_table[]中的事件，并将有数据可读的事件 // 添加到pending_list链表中，同时如果事件的persist不为true // 则将该事件从watch_table[]中移除 static void processReadReadies(fd_set * rfds, int n) { dlog("~~~~ +processReadReadies (%d) ~~~~", n); MUTEX_ACQUIRE(); for (int i = 0; (i < MAX_FD_EVENTS) && (n > 0); i++) { struct ril_event * rev = watch_table[i]; if (rev != NULL && FD_ISSET(rev->fd, rfds)) { addToList(rev, &pending_list); if (rev->persist == false) { removeWatch(rev, i); } n--; } } MUTEX_RELEASE(); dlog("~~~~ -processReadReadies (%d) ~~~~", n); } // 依次调用待处理队列pending_list中的事件的回调函数 static void firePending() { dlog("~~~~ +firePending ~~~~"); struct ril_event * ev = pending_list.next; while (ev != &pending_list) { struct ril_event * next = ev->next; removeFromList(ev); ev->func(ev->fd, 0, ev->param); ev = next; } dlog("~~~~ -firePending ~~~~"); } // 计算timer_list链表中下一个事件的新的超时时间 static int calcNextTimeout(struct timeval * tv) { struct ril_event * tev = timer_list.next; struct timeval now; getNow(&now); // Sorted list, so calc based on first node if (tev == &timer_list) { // no pending timers return -1; } dlog("~~~~ now = %ds + %dus ~~~~", (int)now.tv_sec, (int)now.tv_usec); dlog("~~~~ next = %ds + %dus ~~~~", (int)tev->timeout.tv_sec, (int)tev->timeout.tv_usec); if (timercmp(&tev->timeout, &now, >)) { timersub(&tev->timeout, &now, tv); } else { // timer already expired. tv->tv_sec = tv->tv_usec = 0; } return 0; } // 初始化内部数据结构（互斥量、FD集合、三个事件队列） void ril_event_init() { MUTEX_INIT(); FD_ZERO(&readFds); init_list(&timer_list); init_list(&pending_list); memset(watch_table, 0, sizeof(watch_table)); } // 初始化一个ril事件 void ril_event_set(struct ril_event * ev, int fd, bool persist, ril_event_cb func, void * param) { dlog("~~~~ ril_event_set %x ~~~~", (unsigned int)ev); memset(ev, 0, sizeof(struct ril_event)); ev->fd = fd; ev->index = -1; ev->persist = persist; ev->func = func; ev->param = param; //linux的文件上锁函数，给文件描述符fd上非阻塞的文件锁 fcntl(fd, F_SETFL, O_NONBLOCK); } // 将事件添加到监控列表watch_table[]中 void ril_event_add(struct ril_event * ev) { dlog("~~~~ +ril_event_add ~~~~"); MUTEX_ACQUIRE(); for (int i = 0; i < MAX_FD_EVENTS; i++) { if (watch_table[i] == NULL) { watch_table[i] = ev; ev->index = i; dlog("~~~~ added at %d ~~~~", i); dump_event(ev); FD_SET(ev->fd, &readFds); if (ev->fd >= nfds) nfds = ev->fd+1; dlog("~~~~ nfds = %d ~~~~", nfds); break; } } MUTEX_RELEASE(); dlog("~~~~ -ril_event_add ~~~~"); } // 增加一个timer事件到timer_list链表中 void ril_timer_add(struct ril_event * ev, struct timeval * tv) { dlog("~~~~ +ril_timer_add ~~~~"); MUTEX_ACQUIRE(); struct ril_event * list; if (tv != NULL) { // add to timer list list = timer_list.next; ev->fd = -1; // make sure fd is invalid struct timeval now; getNow(&now); timeradd(&now, tv, &ev->timeout); // 根据timeout值从小到大在链表中排序 while (timercmp(&list->timeout, &ev->timeout, < ) && (list != &timer_list)) { list = list->next; } // 循环结束后，list指向链表中第一个timeout值大于ev的事件 // 将新加入的事件ev加到list此刻指向的事件前面 addToList(ev, list); } MUTEX_RELEASE(); dlog("~~~~ -ril_timer_add ~~~~"); } // 将事件从watch_table[]中移除 void ril_event_del(struct ril_event * ev) { dlog("~~~~ +ril_event_del ~~~~"); MUTEX_ACQUIRE(); if (ev->index < 0 || ev->index >= MAX_FD_EVENTS) { MUTEX_RELEASE(); return; } removeWatch(ev, ev->index); MUTEX_RELEASE(); dlog("~~~~ -ril_event_del ~~~~"); } #if DEBUG // 打印监控列表中可用的事件 static void printReadies(fd_set * rfds) { for (int i = 0; (i < MAX_FD_EVENTS); i++) { struct ril_event * rev = watch_table[i]; if (rev != NULL && FD_ISSET(rev->fd, rfds)) { dlog("DON: fd=%d is ready", rev->fd); } } } #else #define printReadies(rfds) do {} while(0) #endif void ril_event_loop() { int n; fd_set rfds; struct timeval tv; struct timeval * ptv; for (;;) { // make local copy of read fd_set memcpy(&rfds, &readFds, sizeof(fd_set)); // 根据timer_list来计算select函数的等待时间 // timer_list之前已按事件的超时时间排好序了 if (-1 == calcNextTimeout(&tv)) { // no pending timers; block indefinitely dlog("~~~~ no timers; blocking indefinitely ~~~~"); ptv = NULL; } else { dlog("~~~~ blocking for %ds + %dus ~~~~", (int)tv.tv_sec, (int)tv.tv_usec); ptv = &tv; } printReadies(&rfds); // 使用select函数实现多路IO复用 n = select(nfds, &rfds, NULL, NULL, ptv); printReadies(&rfds); dlog("~~~~ %d events fired ~~~~", n); if (n < 0) { if (errno == EINTR) continue; LOGE("ril_event: select error (%d)", errno); // bail? return; } // Check for timeouts processTimeouts(); // Check for read-ready processReadReadies(&rfds, n); // Fire away firePending(); } }