android学习笔记 按电源键屏幕唤醒和屏幕睡眠流程（从上层到kernel）

一. 屏幕的唤醒

      首先inputread在读取到有keyboard事件上报后，会调用到keydispatch的notifykey，去询问wm是否会对这次按键特殊处理,如果WM不处理，则此处会点亮或者熄灭屏幕。

     inputReader.cpp                                 KeyboardInputMapper::processKey

                                                                       getDispatcher()->notifyKey

     inputDispacher.cpp                            InputDispatcher::notifyKey

                                                                      mPolicy->interceptKeyBeforeQueueing

    com_android_server_inputManager.cpp                NativeInputManager::interceptKeyBeforeQueueing

                                                                                             env->CallIntMethod(mCallbacksObj,
                                                                                            gCallbacksClassInfo.interceptKeyBeforeQueueing,
                                                                                             when, action, flags, keyCode, scanCode, policyFlags, isScreenOn);             //此处gCallbacksClassInfo中的各种方法就是InputManager的对应的方法，在JNI初始化的时候就注册了，详情请参看 register_android_server_InputManager函数，通过jniRegisterNativeMethods将 inputmanager的各种callback注册到gCallbacksClassInfo中。

 返回的wmaction就是后面WM对此次按键事件的policy，通过此返回值，此处会决定下一步的动作。

  InputManager.java                                               interceptKeyBeforeQueueing

                                                                                  mWindowManagerService.mInputMonitor.interceptKeyBeforeQueueing

WindowmanagerService.java                             InputMonitor::interceptKeyBeforeQueueing

                                                                                  mPolicy.interceptKeyBeforeQueueing

PhonewindowManager.java                                interceptKeyBeforeQueueing   

                                                                                  //摘录部分代码：

"font-weight: bold; ">    public int interceptKeyBeforeQueueing(long whenNanos, int action, int flags,
            int keyCode, int scanCode, int policyFlags, boolean isScreenOn) {
        final boolean down = action == KeyEvent.ACTION_DOWN;
        final boolean canceled = (flags & KeyEvent.FLAG_CANCELED) != 0;

        final boolean isInjected = (policyFlags & WindowManagerPolicy.FLAG_INJECTED) != 0;

        // If screen is off then we treat the case where the keyguard is open but hidden
        // the same as if it were open and in front.
        // This will prevent any keys other than the power button from waking the screen
        // when the keyguard is hidden by another activity.

        final boolean keyguardActive = (isScreenOn ?
                                        mKeyguardMediator.isShowingAndNotHidden() :
                                        mKeyguardMediator.isShowing());

        int result; //result即为返回到wmaction
        if (isScreenOn || isInjected) {
            // When the screen is on or if the key is injected pass the key to the application.
            result = ACTION_PASS_TO_USER;
        } else {//我们现在走的应该是这个
            // When the screen is off and the key is not injected, determine whether
            // to wake the device but don't pass the key to the application.
            result = 0;

            final boolean isWakeKey = (policyFlags
                    & (WindowManagerPolicy.FLAG_WAKE | WindowManagerPolicy.FLAG_WAKE_DROPPED)) != 0;
            if (down && isWakeKey) {
                if (keyguardActive) {

                       //也就是说，如果当前屏幕是灭的，且按的键是可以唤醒屏幕的，那么WM会首先将此次按键传递给keyguard，由keyguard来唤醒屏幕，并作出相应的动作，否则就自己点亮屏幕，通过返回的policy来通知下层。

                    // If the keyguard is showing, let it decide what to do with the wake key.
                  "color:#ff0000;">  mKeyguardMediator.onWakeKeyWhenKeyguardShowingTq(keyCode);
                } else {
                    // Otherwise, wake the device ourselves.

                    result |= ACTION_POKE_USER_ACTIVITY;
                }
            }
        }"font-weight: bold; ">
....................
}

       keyguarViewMediator.java                    onWakeKeyWhenKeyguardShowingTq

                                                                              wakeWhenReadyLocked

                                                                                           mHandler.obtainMessage(WAKE_WHEN_READY, keyCode, 0);

                                                                             mHandler.handleMessage

                                                                           handleWakeWhenReady

                                                                           mKeyguardViewManager.wakeWhenReadyTq

        KeyguardViewManager.java                mKeyguardView.wakeWhenReadyTq

        LockpatternKeyguardView.java            wakeWhenReadyTq

                                                                             getCallback().pokeWakelock();

        KeyguardViewMediator.java                  pokeWakelock

                                                                            mWakeLock.acquire();        // mWakeLock即为：mWakeLock = mPM.newWakeLock(
                PowerManager.FULL_WAKE_LOCK | PowerManager.ACQUIRE_CAUSES_WAKEUP,
                "keyguard");      具有ACQUIRE_CAUSE_WAKUPQ权限的唤醒锁，上层就是通过此锁来唤醒屏幕，接下来就是powermanager的流程了。

        PowerManager.java                              acquire

                                                                           mService.acquireWakeLock

         PowermanagerService.java                acquireWakeLock

                                                                            acquireWakeLockLocked//此处会检查唤醒锁的标志位，作出对应的处理。

                                                                             setPowerState       //此函数为powermanager的核心函数之一，会对屏幕背光/唤醒，睡眠等作出相应的处理

                                                                           setScreenStateLocked //此函数很关键

                                                                           Power.setScreenState

        power.java                                                setScreenState

       android_os_Power.cpp                          setScreenState

        power.c                                                      set_screen_state//此函数作为上层的最后一个函数，会打印出标志性的log，*** set_screen_state %d，如果打出这个log，至少证明从APP-HAL都是在正常干活的，那么问题只能是kernel的了，贴出代码看看：

int
set_screen_state(int on)
{
    //QEMU_FALLBACK(set_screen_state(on));

    LOGI("*** set_screen_state %d", on); //神奇的log标志

    initialize_fds();

    //LOGI("go_to_sleep eventTime=%lld now=%lld g_error=%s\n", eventTime,
      //      systemTime(), strerror(g_error));

    if (g_error) return g_error;

    char buf[32];
    int len;

    if(on)
        len = sprintf(buf, "%s", on_state);
    else
        len = sprintf(buf, "%s", off_state);
   "color:#cc0000;"> len = write(g_fds[REQUEST_STATE], buf, len);//此处就是写了kernel的设备文件接口。
    if(len < 0) {
        LOGE("Failed setting last user activity: g_error=%d\n", g_error);
    }
    return 0;
}

在此函数中写了底层的power控制的设备文件接口，对应的设备文件为：/sys/power/state

接下来的流程就是到了内核空间。

kernel/kernel/power/main.c                                    state_store        

  //此函数被宏power_attr(state)声明为设备文件接口 sys/power/state，宏power_attr的定义为（power.h）：

                                                                                                                       #define power_attr(_name) \
static struct kobj_attribute _name##_attr = {\
.attr = {\
.name = __stringify(_name),\
.mode = 0644, \
}, \
.show = _name##_show,\
.store = _name##_store, \
}

        

                                                                                          

static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
               const char *buf, size_t n)
{
#ifdef CONFIG_SUSPEND
#ifdef CONFIG_EARLYSUSPEND
    suspend_state_t state = PM_SUSPEND_ON;
#else
    suspend_state_t state = PM_SUSPEND_STANDBY;
#endif
    const char * const *s;
#endif
    char *p;
    int len;
    int error = -EINVAL;

    p = memchr(buf, '\n', n);
    len = p ? p - buf : n;

    /* First, check if we are requested to hibernate */
    if (len == 4 && !strncmp(buf, "disk", len)) {
        error = hibernate();
  goto Exit;
    }

#ifdef CONFIG_SUSPEND
    for (s = &pm_states[state]; state < PM_SUSPEND_MAX; s++, state++) {
        if (*s && len == strlen(*s) && !strncmp(buf, *s, len))
            break;

    }
    printk("##: enter %s\n", pm_states[state]);
    if (state < PM_SUSPEND_MAX && *s)
#ifdef CONFIG_EARLYSUSPEND  // android对linux的睡眠唤醒机制做了一些优化，也就是earlysuspen,laterresume机制,此处宏是有定义的，所以会先走android的那一套
        if (state == PM_SUSPEND_ON || valid_state(state)) {
            error = 0;
            printk("##: entering request_suspend_state()...\n");
            request_suspend_state(state);
        }
#else

        error = enter_state(state);
#endif
#endif

 Exit:
    printk("##: state_store() returns back.\n");
    return error ? error : n;
}

kernel/kernel/power/erlysuspend.c                                                              request_suspend_state

void request_suspend_state(suspend_state_t new_state)
{
    unsigned long irqflags;
    int old_sleep;

    /* when we get here, means userspace service work well, stop reboot watchdog */
    powerkey_wdt_stop();

    spin_lock_irqsave(&state_lock, irqflags);
    old_sleep = state & SUSPEND_REQUESTED;
    if (debug_mask & DEBUG_USER_STATE) {
        struct timespec ts;
        struct rtc_time tm;
        getnstimeofday(&ts);
        rtc_time_to_tm(ts.tv_sec, &tm);
        pr_info("request_suspend_state: %s (%d->%d) at %lld "
            "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n",
            new_state != PM_SUSPEND_ON ? "sleep" : "wakeup",
            requested_suspend_state, new_state,
            ktime_to_ns(ktime_get()),
            tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
            tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);

    }
    if (!old_sleep && new_state != PM_SUSPEND_ON) {
        state |= SUSPEND_REQUESTED;
        queue_work(suspend_work_queue, &early_suspend_work);
    }"color: rgb(255, 0, 0); background-color: rgb(255, 255, 255);"> "background-color: rgb(255, 255, 255); ">else if (old_sleep && new_state == PM_SUSPEND_ON) {
        state &= ~SUSPEND_REQUESTED;
        wake_lock(&main_wake_lock); //acquire    main ——wakelock
        queue_work(suspend_work_queue, &late_resume_work); //将唤醒的work起来，开始执行之前声明的late_resume_work

    }
    requested_suspend_state = new_state;
    spin_unlock_irqrestore(&state_lock, irqflags);
}

而 之前有声明static DECLARE_WORK(late_resume_work, late_resume); 故实际执行的函数是：late_resume。

kernel/kernel/power/erlysuspend.c                                         late_resume

static void late_resume(struct work_struct *work)
{
    struct early_suspend *pos;
    unsigned long irqflags;
    int abort = 0;

    mutex_lock(&early_suspend_lock);
    spin_lock_irqsave(&state_lock, irqflags);
    if (state == SUSPENDED)
        state &= ~SUSPENDED;
    else
        abort = 1;
    spin_unlock_irqrestore(&state_lock, irqflags);

    if (abort) {
        if (debug_mask & DEBUG_SUSPEND)
            pr_info("late_resume: abort, state %d\n", state);
        goto abort;
    }

    if (debug_mask & DEBUG_SUSPEND)
        pr_info("late_resume: call handlers\n");
    list_for_each_entry_reverse(pos, &early_suspend_handlers, link)
        if (pos->resume != NULL) {
            print_name_offset(NULL, pos->resume);
            pos->resume(pos);       //此处会调用到之前注册了laterresume的drv的对应的函数，调用到fb_resume之后，屏幕就唤醒刷屏，屏幕上夜就有了数据，屏幕唤醒的流程就结束了。
        }
    if (debug_mask & DEBUG_SUSPEND)
        pr_info("late_resume: done\n");
abort:
    mutex_unlock(&early_suspend_lock);
}

总结：  屏幕点亮过程是由inputread捕获后交由WM处理，由keyguard去申请唤醒锁，powermanagerservice去调用kernel的唤醒的过程，其中弯弯绕还是比较多的，涉及的东西也很多，wakelock机制我还没有搞的很清楚。

二、 屏幕睡眠

和屏幕唤醒的过程很类似，如下：

 inputReader.cpp                                 KeyboardInputMapper::processKey

                                                                       getDispatcher()->notifyKey

     inputDispacher.cpp                            InputDispatcher::notifyKey

                                                                   mPolicy->interceptKeyBeforeQueueing

    com_android_server_inputManager.cpp                NativeInputManager::interceptKeyBeforeQueueing

  InputManager.java                                               interceptKeyBeforeQueueing

                                                                                  mWindowManagerService.mInputMonitor.interceptKeyBeforeQueueing

WindowmanagerService.java                             InputMonitor::interceptKeyBeforeQueueing

                                                                                  mPolicy.interceptKeyBeforeQueueing

PhonewindowManager.java                                interceptKeyBeforeQueueing   

                                                                                     //同上面的分析，此处返回的action是被或上了ACTION_GO_TO_SLEEP的（见1975行对 KeyEvent.KEYCODE_POWER的处理）.......一级一级的返回后.....

 com_android_server_inputManager.cpp                               NativeInputManager::interceptKeyBeforeQueueing      //返回值中含有gotosleep的flag，故走到gotosleep分支

                                                                                                          android_server_PowerManagerService_goToSleep

com_android_server_PowerManagerService.cpp                android_server_PowerManagerService_goToSleep          //同上面的inputmanager，此处也会调用到PowerManagerService的gotosleep,也是用 register_android_server_PowerManagerService方法来对应起来。

                                                                                                          env->CallVoidMethod(gPowerManagerServiceObj, gPowerManagerServiceClassInfo.goToSleep,
                nanoseconds_to_milliseconds(eventTime));

PowermanagerService.java                                                     goToSleep

                                                                                                        goToSleepWithReason

goToSleepLocked

                                             setPowerState(SCREEN_OFF, false, reason);

                                                                                                        setPowerState

                                                                                                        setScreenStateLocked

                                                                                                          Power.setScreenState(false)

power.java                                                                                      setScreenState

android_os_power.java                                                               setScreenState

power.c                                                                                           set_screen_state 

kernel/kernel/power/main.c                                                          state_store 

kernel/kernel/power/earlysuspend.c                                           request_suspend_state             //此处流程和唤醒大同小异，不在赘述

                                                                                                              early_suspend

static void early_suspend(struct work_struct *work)
{
    struct early_suspend *pos;
    unsigned long irqflags;
    int abort = 0;

    mutex_lock(&early_suspend_lock);
    spin_lock_irqsave(&state_lock, irqflags);
    if (state == SUSPEND_REQUESTED)
        state |= SUSPENDED;
    else
        abort = 1;
    spin_unlock_irqrestore(&state_lock, irqflags);

    if (abort) {
        if (debug_mask & DEBUG_SUSPEND)
            pr_info("early_suspend: abort, state %d\n", state);
        mutex_unlock(&early_suspend_lock);
        goto abort;
    }

    if (debug_mask & DEBUG_SUSPEND)
        pr_info("early_suspend: call handlers\n");
    list_for_each_entry(pos, &early_suspend_handlers, link) {
        if (pos->suspend != NULL) {
            print_name_offset(NULL, pos->suspend);
            "background-color: rgb(204, 204, 204);">pos->suspend(pos); //调用注册了earlysuspend的drv的suspend函数，调用到了fb_suspend，屏幕就会进入睡眠，睡眠的过程就结束了
        }

    }
    mutex_unlock(&early_suspend_lock);

    if (debug_mask & DEBUG_SUSPEND)
        pr_info("early_suspend: sync\n");

    //sys_sync();//let screen up faster
abort:
    spin_lock_irqsave(&state_lock, irqflags);
    if (state == SUSPEND_REQUESTED_AND_SUSPENDED)
        wake_unlock(&main_wake_lock);          //earlysuspend完毕后，检查当前是否还有wakelock是active状态，如果没有，则会进入深睡眠（linux的suspend）
    spin_unlock_irqrestore(&state_lock, irqflags);
}

下面我们继续跟下代码，简单看看earlysuspend到deepsleep的过程，从wake_unlock开始

kernel/kernel/power/wakelock.c                                      wake_unlock

void wake_unlock(struct wake_lock *lock)
{
    int type;
    unsigned long irqflags;
    spin_lock_irqsave(&list_lock, irqflags);
    type = lock->flags & WAKE_LOCK_TYPE_MASK;
#ifdef CONFIG_WAKELOCK_STAT
    wake_unlock_stat_locked(lock, 0);
#endif
    if (debug_mask & DEBUG_WAKE_LOCK)
        pr_info("wake_unlock: %s\n", lock->name);
    lock->flags &= ~(WAKE_LOCK_ACTIVE | WAKE_LOCK_AUTO_EXPIRE);
    list_del(&lock->link);
    list_add(&lock->link, &inactive_locks);
    if (type == WAKE_LOCK_SUSPEND) {
        long has_lock = has_wake_lock_locked(type); //判断当前是否还有wake_lock是active的
        if (has_lock > 0) {
            if (debug_mask & DEBUG_EXPIRE)

                pr_info("wake_unlock: %s, start expire timer, "
                    "%ld\n", lock->name, has_lock);
            mod_timer(&expire_timer, jiffies + has_lock);
        } else {
            if (del_timer(&expire_timer))
                if (debug_mask & DEBUG_EXPIRE)
                    pr_info("wake_unlock: %s, stop expire "
                        "timer\n", lock->name);
            if (has_lock == 0) {
                if (sprd_suspend_enable) {
                    queue_work(suspend_work_queue, &suspend_work); //起suspend_work，根据声明，此处的work对应的函数即是suspend
                }

            }
        }
        if (lock == &main_wake_lock) {
            if (debug_mask & DEBUG_SUSPEND)
                print_active_locks(WAKE_LOCK_SUSPEND);
#ifdef CONFIG_WAKELOCK_STAT
            update_sleep_wait_stats_locked(0);
#endif
        }
    }
    spin_unlock_irqrestore(&list_lock, irqflags);
}

kernel/kernel/power/wakelock.c                                        suspend

static void suspend(struct work_struct *work)
{
    int ret;
    int entry_event_num;

    add_pm_message(get_sys_cnt(), "suspend--enter: ", 0, 0, 0);

    if (has_wake_lock(WAKE_LOCK_SUSPEND)) {
        if (debug_mask & DEBUG_SUSPEND)
            pr_info("suspend: abort suspend\n");
        return;
    }

    entry_event_num = current_event_num;
    sys_sync();
    if (debug_mask & DEBUG_SUSPEND)
        pr_info("suspend: enter suspend\n");
    ret = pm_suspend(requested_suspend_state);
    if (debug_mask & DEBUG_EXIT_SUSPEND) {

        struct timespec ts;
        struct rtc_time tm;
        getnstimeofday(&ts);
        rtc_time_to_tm(ts.tv_sec, &tm);
        pr_info("suspend: exit suspend, ret = %d "
            "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n", ret,
            tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
            tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
    }

    if (current_event_num == entry_event_num) {
        if (debug_mask & DEBUG_SUSPEND)
            pr_info("suspend: pm_suspend returned with no event\n");
        wake_lock_timeout(&unknown_wakeup, HZ / 2);
    }
    add_pm_message(get_sys_cnt(), "suspend--leave: ", 0, 0, 0);
}

kernel/kernel/power/suspend.c                                   pm_suspend

int pm_suspend(suspend_state_t state)
{
    if (state > PM_SUSPEND_ON && state <= PM_SUSPEND_MAX)
        return enter_state(state); //是不是和main.c里的state_store函数中liunx的suspend一样？豁然开朗。
    return -EINVAL;
}

接下来就是linux的suspend了，没有再仔细看过，惭愧惭愧。

总的来说，屏幕的睡眠是和上层的keyguard没有关系，是在WM和PMS以及相关的JNI的配合下对kernel的操作完成的。

屏幕唤醒和睡眠就写到这里，而背光的点亮过程，大部分处理是在PMS中，是在HAL层操作了lights的设备文件并不涉及到唤醒和睡眠，显得比较简单，有时间也写出来分享。