Android中RIL层详细分析与总结

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用read()得方法去唤醒fd，把可执行得弹出来，ril_event 去复位定时器，把缓冲区清空

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* A write on the wakeup fd is done just to pop us out of select()

* We empty the buffer here and then ril_event will reset the timers on the * way back down */

static void processWakeupCallback(int fd, short flags, void *param) {

char buff[16]; int ret;

LOGD(\ LOGV(\ /* empty our wakeup socket out */ do {

ret = read(s_fdWakeupRead, &buff, sizeof(buff)); } while (ret > 0 || (ret < 0 && errno == EINTR)); }

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rilEventAddWakeup的作用是：作为ril_event_add(ev);和triggerEvLoop();入口函数，真正的把数据数组 watch_table[i] = ev上去，等待selcet轮询，最后写入

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static void rilEventAddWakeup(struct ril_event *ev) {

ril_event_add(ev); triggerEvLoop(); }

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- // Add event to watch list

void ril_event_add(struct ril_event * ev)

{

LOGD(\ dlog(\ MUTEX_ACQUIRE();

for (int i = 0; i < MAX_FD_EVLL) { //1:

watch_table[i] = ev;//把上面ril_event_add函数添加的事件_wakeupfd_event结构体添加到这个数组来 ev->index = i;

dlog(\ dump_event(ev);

//2:

FD_SET(ev->fd, &readFds);//把上面数组，放到readFds来 if (ev->fd >= nfds) nfds = ev->fd+1; dlog(\ break;ENTS; i++) { if (watch_table[i] == NU } }

MUTEX_RELEASE();

dlog(\}

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就是上面管道读完，收到数据后，再通过写端，写到对应的数组去(readFs)

static void triggerEvLoop() {

int ret;

LOGD(\ if (!pthread_equal(pthread_self(), s_tid_dispatch)) { /* trigger event loop to wakeup. No reason to do this, * if we're in the event loop thread */ do {

ret = write (s_fdWakeupWrite, \ } while (ret < 0 && errno == EINTR); } }

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上面工作一做完，说明通过pipe机制已经把数据读到，并放入数组，而数组且放在readFs队列中，等待ril_event_loop()函数t轮询

下面为ril_event_loop()开始轮询的整个过程：

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void ril_event_loop()

{ int n; fd_set rfds; struct timeval tv; struct timeval * ptv;

LOGD(\ for (;;) {//死循环的轮询

// make local copy of read fd_set

LOGD(\

memcpy(&rfds, &readFds, sizeof(fd_set));把上面通过管道机制读到得数据，换个名字，放到rfds

去

if (-1 == calcNextTimeout(&tv)) {// 获取超时参数，若失败则返回-1。 // no pending timers; block indefinitely

dlog(\ ptv = NULL;

} else {// 获取成功，则使用该值。

dlog(\ ptv = &tv; }

printReadies(&rfds);

LOGD(\ LOGI(\ //初始化到这里结束。

n = select(nfds, &rfds, NULL, NULL, ptv);//等待

fd唤醒，通过selcet多路I/o复用

机制去唤醒管道来的数据

LOGD(\ LOGI(\ printReadies(&rfds);

dlog(\ if (n < 0) {

if (errno == EINTR) continue;

LOGE(\ // bail? return; }

LOGD(\processTimeouts();--\ // Check for timeouts

processTimeouts();// 处理定时消息 ,处理ril_event_init ->pending_list // Check for read-ready

LOGD(\

processReadReadies(&rfds, n); // 处理侦听消息 ,处理ril_event_init ->watch_list // Fire away

LOGD(\ firePending(); // 处理挂起消息

LOGD(\ } }

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static void processTimeouts()

{

LOGD(\LOGI(\

dlog(\ MUTEX_ACQUIRE();

struct timeval now;

struct ril_event * tev = timer_list.next; struct ril_event * next; getNow(&now);//获取当前时间

// walk list, see if now >= ev->timeout for any events

dlog(\

while ((tev != &timer_list) && (timercmp(&now, &tev->timeout, >))) {// 查找所有当前时间点以前的消息 // Timer expired

dlog(\ next = tev->next;

removeFromList(tev);//从定时消息队列中移除,就是已经做完的内容 addToList(tev, &pending_list); // 添加至挂起列表（pending_list）中 tev = next; }

MUTEX_RELEASE();

dlog(\}

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static void addToList(struct ril_event * ev, struct ril_event * list) {

LOGD(\ ev->next = list; ev->prev = list->prev; ev->prev->next = ev; list->prev = ev; dump_event(ev); }

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static void processReadReadies(fd_set * rfds, int n) {

LOGD(\LOGI(\

dlog(\ MUTEX_ACQUIRE();

for (int i = 0; (i < MAX_FD_EVENTS) && (n > 0); i++) { // 此处判断描述符是否在当前循环的等待列表中。 struct ril_event * rev = watch_table[i]; if (rev != NULL && FD_ISSET(rev->fd, rfds)) {

addToList(rev, &pending_list);// 添加至挂起列表（pending_list）中

if (rev->persist == false) { // 会判断ril_event的persist参数，以决定是否从watch_list移除该消息。 removeWatch(rev, i); } n--;