android 4.4 电池电量管理底层分析(C\C++层)

参考文献:http://blog.csdn.net/wlwl0071986/article/details/38778897

简介:

Linux电池驱动用于和PMIC交互、负责监听电池产生的相关事件,例如低电报警、电量发生变化、高温报警、USB插拔等等。

Android电池服务,用来监听内核上报的电池事件,并将最新的电池数据上报给系统,系统收到新数据后会去更新电池显示状态、剩余电量等信息。如果收到过温报警和低电报警,系统会自动触发关机流程,保护电池和机器不受到危害。

Android电池服务的启动和运行流程:

android 4.4 电池电量管理底层分析(C\C++层)_第1张图片

Android电源管理底层用的是Linux powersupply框架,从Android 4.4开始,Google专门提供了一个healthd来监控电源状态。它的路径在:system/core/healthd文件夹下,编译出来的文件为/sbin/healthd。

android 4.4 电池电量管理底层分析(C\C++层)_第2张图片

电池系统从底层向Framework层上报数据的流程:

android 4.4 电池电量管理底层分析(C\C++层)_第3张图片


这里我把文章框架按语言分成 C/C++ 层与Java层。(这篇介绍C/C++ 层, Java 层请看另外一篇博客http://blog.csdn.net/daweibalang717/article/details/40615453),

关于C/C++ 层与驱动交互的代码我不全部贴出,只给出路径,大家可以自己查找阅读,这里值讲述关键函数。


一、关系图:

android 4.4 电池电量管理底层分析(C\C++层)_第4张图片

二、Healthd

  包含两个文件:\system\core\healthd\healthd.h ,\system\core\healthd\healthd.cpp 

   简要说明:

    health.h 是个头文件,只要声明函数与变量,不做过多介绍。我们说下healthd.cpp ,

int main(int argc, char **argv) {
    int ch;

    klog_set_level(KLOG_LEVEL);

    while ((ch = getopt(argc, argv, "n")) != -1) {
        switch (ch) {
        case 'n':
            nosvcmgr = true;
            break;
        case '?':
        default:
            KLOG_WARNING(LOG_TAG, "Unrecognized healthd option: %c\n", ch);
        }
    }

    healthd_board_init(&healthd_config);
    wakealarm_init();
    uevent_init();
    binder_init();
    gBatteryMonitor = new BatteryMonitor();
    gBatteryMonitor->init(&healthd_config, nosvcmgr);

    healthd_mainloop();
    return 0;
}

这是main函数,跟Java中的main是一样的,作为程序的入口。这里做一些初始化工作,获得BatteryMonitor的指针对象。我们索要关注的是healthd_mainloop()的调用,仅凭函数名就能知道会进入一个无限循环,这样也就能达到监控电源状态的目的了。下面我们看一下这个函数:

static void healthd_mainloop(void) {
    struct epoll_event ev;
    int epollfd;
    int maxevents = 0;

    epollfd = epoll_create(MAX_EPOLL_EVENTS);
    if (epollfd == -1) {
        KLOG_ERROR(LOG_TAG,
                   "healthd_mainloop: epoll_create failed; errno=%d\n",
                   errno);
        return;
    }

    if (uevent_fd >= 0) {
        ev.events = EPOLLIN;
        ev.data.ptr = (void *)uevent_event;
        if (epoll_ctl(epollfd, EPOLL_CTL_ADD, uevent_fd, &ev) == -1)
            KLOG_ERROR(LOG_TAG,
                       "healthd_mainloop: epoll_ctl for uevent_fd failed; errno=%d\n",
                       errno);
        else
            maxevents++;
    }

    if (wakealarm_fd >= 0) {
        ev.events = EPOLLIN | EPOLLWAKEUP;
        ev.data.ptr = (void *)wakealarm_event;
        if (epoll_ctl(epollfd, EPOLL_CTL_ADD, wakealarm_fd, &ev) == -1)
            KLOG_ERROR(LOG_TAG,
                       "healthd_mainloop: epoll_ctl for wakealarm_fd failed; errno=%d\n",
                       errno);
        else
            maxevents++;
   }

    if (binder_fd >= 0) {
        ev.events = EPOLLIN | EPOLLWAKEUP;
        ev.data.ptr= (void *)binder_event;
        if (epoll_ctl(epollfd, EPOLL_CTL_ADD, binder_fd, &ev) == -1)
            KLOG_ERROR(LOG_TAG,
                       "healthd_mainloop: epoll_ctl for binder_fd failed; errno=%d\n",
                       errno);
        else
            maxevents++;
   }

    while (1) {
        struct epoll_event events[maxevents];
        int nevents;

        IPCThreadState::self()->flushCommands();
        nevents = epoll_wait(epollfd, events, maxevents, awake_poll_interval);

        if (nevents == -1) {
            if (errno == EINTR)
                continue;
            KLOG_ERROR(LOG_TAG, "healthd_mainloop: epoll_wait failed\n");
            break;
        }

        for (int n = 0; n < nevents; ++n) {
            if (events[n].data.ptr)
                (*(void (*)())events[n].data.ptr)();
        }

        if (!nevents)
            periodic_chores();
    }

    return;
}

我们来看一下这个函数都干了哪些事情呢?首先,代码:epollfd = epoll_create(MAX_EPOLL_EVENTS);创建一个 epoll 实例,并要求内核分配一个可以保存 size 个描述符的空间( 关于epoll,Linux中的字符 设备驱动中有一个函数是poll,Linux 2.5.44版本后被epoll取代,请参考:http://baike.baidu.com/view/1385104.htm?fr=aladdin ), 然后把函数赋值 ev.data.ptr = (void *)uevent_event; 在while(1) 的 调用  nevents = epoll_wait(epollfd, events, maxevents, awake_poll_interval); 等待EPOLL事件的发生,相当于监听。当收到监听后,就是在
        for (int n = 0; n < nevents; ++n) {
            if (events[n].data.ptr)
                (*(void (*)())events[n].data.ptr)();
        }

for循环中调用 事件赋值 ev.data.ptr = (void *)uevent_event; 所赋值的函数, 其实相当于Java中的回调接口。我们这里值关注 uevent_event 函数。因为这个是跟电池属性相关的。 uevent_event 函数如下:

static void uevent_event(void) {
    char msg[UEVENT_MSG_LEN+2];
    char *cp;
    int n;

    n = uevent_kernel_multicast_recv(uevent_fd, msg, UEVENT_MSG_LEN);
    if (n <= 0)
        return;
    if (n >= UEVENT_MSG_LEN)   /* overflow -- discard */
        return;

    msg[n] = '\0';
    msg[n+1] = '\0';
    cp = msg;

    while (*cp) {
        if (!strcmp(cp, "SUBSYSTEM=" POWER_SUPPLY_SUBSYSTEM)) {
            battery_update();
            break;
        }

        /* advance to after the next \0 */
        while (*cp++)
            ;
    }
}

它会读取socket中的字符串,然后判断事件来源是否是由kernel的power_supply发出的,代码if (!strcmp(cp, "SUBSYSTEM=" POWER_SUPPLY_SUBSYSTEM)) ,如果是,那就调用battery_update()更新电源状态。下面来看看battery_update()是如何更新电源状态的:

static void battery_update(void) {
    // Fast wake interval when on charger (watch for overheat);
    // slow wake interval when on battery (watch for drained battery).

   int new_wake_interval = gBatteryMonitor->update() ?
       healthd_config.periodic_chores_interval_fast :
           healthd_config.periodic_chores_interval_slow;

    if (new_wake_interval != wakealarm_wake_interval)
            wakealarm_set_interval(new_wake_interval);

    // During awake periods poll at fast rate.  If wake alarm is set at fast
    // rate then just use the alarm; if wake alarm is set at slow rate then
    // poll at fast rate while awake and let alarm wake up at slow rate when
    // asleep.

    if (healthd_config.periodic_chores_interval_fast == -1)
        awake_poll_interval = -1;
    else
        awake_poll_interval =
            new_wake_interval == healthd_config.periodic_chores_interval_fast ?
                -1 : healthd_config.periodic_chores_interval_fast * 1000;
}
主要就是这一句:gBatteryMonitor->update() , gBatteryMonitor 是在mian 函数中初始化的BatteryMonitor的指针对象。 看关系图,这里就由Healthd 跳到 BatteryMonitor了。

下面,我们看一下BatteryMonitor


三、BatteryMonitor

  包含两个文件:\system\core\healthd\BatteryMonitor.h ,\system\core\healthd\BatteryMonitor.cpp

   简要说明:

    BatteryMonitor.h 是个头文件,只要声明函数与变量,不做过多介绍。我们说下BatteryMonitor.cpp

    上面说到,battery_update() 中会调用gBatteryMonitor->update() ,那BatteryMonitor.cpp 中的 update()都做了什么了?代码如下:

bool BatteryMonitor::update(void) {
    struct BatteryProperties props;
    bool logthis;

    props.chargerAcOnline = false;
    props.chargerUsbOnline = false;
    props.chargerWirelessOnline = false;
    props.batteryStatus = BATTERY_STATUS_UNKNOWN;
    props.batteryHealth = BATTERY_HEALTH_UNKNOWN;
    props.batteryCurrentNow = INT_MIN;
    props.batteryChargeCounter = INT_MIN;

    if (!mHealthdConfig->batteryPresentPath.isEmpty())
        props.batteryPresent = getBooleanField(mHealthdConfig->batteryPresentPath);
    else
        props.batteryPresent = true;

    props.batteryLevel = getIntField(mHealthdConfig->batteryCapacityPath);
    props.batteryVoltage = getIntField(mHealthdConfig->batteryVoltagePath) / 1000;

    if (!mHealthdConfig->batteryCurrentNowPath.isEmpty())
        props.batteryCurrentNow = getIntField(mHealthdConfig->batteryCurrentNowPath);

    if (!mHealthdConfig->batteryChargeCounterPath.isEmpty())
        props.batteryChargeCounter = getIntField(mHealthdConfig->batteryChargeCounterPath);

    props.batteryTemperature = getIntField(mHealthdConfig->batteryTemperaturePath);

    const int SIZE = 128;
    char buf[SIZE];
    String8 btech;

    if (readFromFile(mHealthdConfig->batteryStatusPath, buf, SIZE) > 0)
        props.batteryStatus = getBatteryStatus(buf);

    if (readFromFile(mHealthdConfig->batteryHealthPath, buf, SIZE) > 0)
        props.batteryHealth = getBatteryHealth(buf);

    if (readFromFile(mHealthdConfig->batteryTechnologyPath, buf, SIZE) > 0)
        props.batteryTechnology = String8(buf);

    unsigned int i;

    for (i = 0; i < mChargerNames.size(); i++) {
        String8 path;
        path.appendFormat("%s/%s/online", POWER_SUPPLY_SYSFS_PATH,
                          mChargerNames[i].string());

        if (readFromFile(path, buf, SIZE) > 0) {
            if (buf[0] != '0') {
                path.clear();
                path.appendFormat("%s/%s/type", POWER_SUPPLY_SYSFS_PATH,
                                  mChargerNames[i].string());
                switch(readPowerSupplyType(path)) {
                case ANDROID_POWER_SUPPLY_TYPE_AC:
                    props.chargerAcOnline = true;
                    break;
                case ANDROID_POWER_SUPPLY_TYPE_USB:
                    props.chargerUsbOnline = true;
                    break;
                case ANDROID_POWER_SUPPLY_TYPE_WIRELESS:
                    props.chargerWirelessOnline = true;
                    break;
                default:
                    KLOG_WARNING(LOG_TAG, "%s: Unknown power supply type\n",
                                 mChargerNames[i].string());
                }
            }
        }
    }

    logthis = !healthd_board_battery_update(&props);

    if (logthis) {
        char dmesgline[256];
        snprintf(dmesgline, sizeof(dmesgline),
                 "battery l=%d v=%d t=%s%d.%d h=%d st=%d",
                 props.batteryLevel, props.batteryVoltage,
                 props.batteryTemperature < 0 ? "-" : "",
                 abs(props.batteryTemperature / 10),
                 abs(props.batteryTemperature % 10), props.batteryHealth,
                 props.batteryStatus);

        if (!mHealthdConfig->batteryCurrentNowPath.isEmpty()) {
            char b[20];

            snprintf(b, sizeof(b), " c=%d", props.batteryCurrentNow / 1000);
            strlcat(dmesgline, b, sizeof(dmesgline));
        }

        KLOG_INFO(LOG_TAG, "%s chg=%s%s%s\n", dmesgline,
                  props.chargerAcOnline ? "a" : "",
                  props.chargerUsbOnline ? "u" : "",
                  props.chargerWirelessOnline ? "w" : "");
    }

    if (mBatteryPropertiesRegistrar != NULL)
        mBatteryPropertiesRegistrar->notifyListeners(props);

    return props.chargerAcOnline | props.chargerUsbOnline |
            props.chargerWirelessOnline;
}
这个函数首先定义了BatteryProperties props; 这个属性集(为了减少介绍的复杂度,大家可以简单的认为只是一个包含各种属性的类),然后给这个属性集 props 里面的属性赋值。然后在最后会在最后判断有无注册监听 ,如果有的话,调用注册的监听,把属性传入监听:

   if (mBatteryPropertiesRegistrar != NULL)
        mBatteryPropertiesRegistrar->notifyListeners(props);
调用的就是上面的东西。 到目前为止,我们知道了health 里面有个无线循环,监控驱动事件,然后调用BatteryProperties中的update方法。 然后update会读取各种属性值,然后调用注册的监听。如下图

android 4.4 电池电量管理底层分析(C\C++层)_第5张图片

  那么问题来了------->挖掘机技术哪家强?哈哈,开个玩笑。下面我们就要分两个分支来讲述:

(1)这些属性是从哪里来的。

(2)属性变化后调用的监听是谁注册的。




首先,(1)这些属性是从哪里来的。

     我们先看一下 上面的 healthd.cpp 的main 函数初始化 BatteryMonitor 时,调用了

   gBatteryMonitor = new BatteryMonitor();
    gBatteryMonitor->init(&healthd_config, nosvcmgr);
  这个init 初始化的时候都干了些什么呢

void BatteryMonitor::init(struct healthd_config *hc, bool nosvcmgr) {
    String8 path;

    mHealthdConfig = hc;
    DIR* dir = opendir(POWER_SUPPLY_SYSFS_PATH);
    if (dir == NULL) {
        KLOG_ERROR(LOG_TAG, "Could not open %s\n", POWER_SUPPLY_SYSFS_PATH);
    } else {
        struct dirent* entry;

        while ((entry = readdir(dir))) {
            const char* name = entry->d_name;

            if (!strcmp(name, ".") || !strcmp(name, ".."))
                continue;

            char buf[20];
            // Look for "type" file in each subdirectory
            path.clear();
            path.appendFormat("%s/%s/type", POWER_SUPPLY_SYSFS_PATH, name);
            switch(readPowerSupplyType(path)) {
            case ANDROID_POWER_SUPPLY_TYPE_AC:
            case ANDROID_POWER_SUPPLY_TYPE_USB:
            case ANDROID_POWER_SUPPLY_TYPE_WIRELESS:
                path.clear();
                path.appendFormat("%s/%s/online", POWER_SUPPLY_SYSFS_PATH, name);
                if (access(path.string(), R_OK) == 0)
                    mChargerNames.add(String8(name));
                break;

            case ANDROID_POWER_SUPPLY_TYPE_BATTERY:
                if (mHealthdConfig->batteryStatusPath.isEmpty()) {
                    path.clear();
                    path.appendFormat("%s/%s/status", POWER_SUPPLY_SYSFS_PATH,
                                      name);
                    if (access(path, R_OK) == 0)
                        mHealthdConfig->batteryStatusPath = path;
                }

                if (mHealthdConfig->batteryHealthPath.isEmpty()) {
                    path.clear();
                    path.appendFormat("%s/%s/health", POWER_SUPPLY_SYSFS_PATH,
                                      name);
                    if (access(path, R_OK) == 0)
                        mHealthdConfig->batteryHealthPath = path;
                }

                if (mHealthdConfig->batteryPresentPath.isEmpty()) {
                    path.clear();
                    path.appendFormat("%s/%s/present", POWER_SUPPLY_SYSFS_PATH,
                                      name);
                    if (access(path, R_OK) == 0)
                        mHealthdConfig->batteryPresentPath = path;
                }

                if (mHealthdConfig->batteryCapacityPath.isEmpty()) {
                    path.clear();
                    path.appendFormat("%s/%s/capacity", POWER_SUPPLY_SYSFS_PATH,
                                      name);
                    if (access(path, R_OK) == 0)
                        mHealthdConfig->batteryCapacityPath = path;
                }

                if (mHealthdConfig->batteryVoltagePath.isEmpty()) {
                    path.clear();
                    path.appendFormat("%s/%s/voltage_now",
                                      POWER_SUPPLY_SYSFS_PATH, name);
                    if (access(path, R_OK) == 0) {
                        mHealthdConfig->batteryVoltagePath = path;
                    } else {
                        path.clear();
                        path.appendFormat("%s/%s/batt_vol",
                                          POWER_SUPPLY_SYSFS_PATH, name);
                        if (access(path, R_OK) == 0)
                            mHealthdConfig->batteryVoltagePath = path;
                    }
                }

                if (mHealthdConfig->batteryCurrentNowPath.isEmpty()) {
                    path.clear();
                    path.appendFormat("%s/%s/current_now",
                                      POWER_SUPPLY_SYSFS_PATH, name);
                    if (access(path, R_OK) == 0)
                        mHealthdConfig->batteryCurrentNowPath = path;
                }

                if (mHealthdConfig->batteryChargeCounterPath.isEmpty()) {
                    path.clear();
                    path.appendFormat("%s/%s/charge_counter",
                                      POWER_SUPPLY_SYSFS_PATH, name);
                    if (access(path, R_OK) == 0)
                        mHealthdConfig->batteryChargeCounterPath = path;
                }

                if (mHealthdConfig->batteryTemperaturePath.isEmpty()) {
                    path.clear();
                    path.appendFormat("%s/%s/temp", POWER_SUPPLY_SYSFS_PATH,
                                      name);
                    if (access(path, R_OK) == 0) {
                        mHealthdConfig->batteryTemperaturePath = path;
                    } else {
                        path.clear();
                        path.appendFormat("%s/%s/batt_temp",
                                          POWER_SUPPLY_SYSFS_PATH, name);
                        if (access(path, R_OK) == 0)
                            mHealthdConfig->batteryTemperaturePath = path;
                    }
                }

                if (mHealthdConfig->batteryTechnologyPath.isEmpty()) {
                    path.clear();
                    path.appendFormat("%s/%s/technology",
                                      POWER_SUPPLY_SYSFS_PATH, name);
                    if (access(path, R_OK) == 0)
                        mHealthdConfig->batteryTechnologyPath = path;
                }

                break;

            case ANDROID_POWER_SUPPLY_TYPE_UNKNOWN:
                break;
            }
        }
        closedir(dir);
    }

    if (!mChargerNames.size())
        KLOG_ERROR(LOG_TAG, "No charger supplies found\n");
    if (mHealthdConfig->batteryStatusPath.isEmpty())
        KLOG_WARNING(LOG_TAG, "BatteryStatusPath not found\n");
    if (mHealthdConfig->batteryHealthPath.isEmpty())
        KLOG_WARNING(LOG_TAG, "BatteryHealthPath not found\n");
    if (mHealthdConfig->batteryPresentPath.isEmpty())
        KLOG_WARNING(LOG_TAG, "BatteryPresentPath not found\n");
    if (mHealthdConfig->batteryCapacityPath.isEmpty())
        KLOG_WARNING(LOG_TAG, "BatteryCapacityPath not found\n");
    if (mHealthdConfig->batteryVoltagePath.isEmpty())
        KLOG_WARNING(LOG_TAG, "BatteryVoltagePath not found\n");
    if (mHealthdConfig->batteryTemperaturePath.isEmpty())
        KLOG_WARNING(LOG_TAG, "BatteryTemperaturePath not found\n");
    if (mHealthdConfig->batteryTechnologyPath.isEmpty())
        KLOG_WARNING(LOG_TAG, "BatteryTechnologyPath not found\n");

    if (nosvcmgr == false) {
            mBatteryPropertiesRegistrar = new BatteryPropertiesRegistrar(this);
            mBatteryPropertiesRegistrar->publish();
    }
}


在init()里会调用opendir(POWER_SUPPLY_SYSFS_PATH); 

opendir()函数的作用是:打开目录句柄,将返回一组目录流(一组目录字符串),说白了就是目录下的文件名。 

#define POWER_SUPPLY_SUBSYSTEM "power_supply"
#define POWER_SUPPLY_SYSFS_PATH "/sys/class/" POWER_SUPPLY_SUBSYSTEM
其实 opendir 打开的就是 sys/class/power_supply ,并返回这个路径下的所有文件。文件如下:
android 4.4 电池电量管理底层分析(C\C++层)_第6张图片

比如ac (充电器就叫AC)目录下面都有什么呢:


然后我们看init()代码里面,其实就是把各种路径读取出来,然后把路径赋值。 我们知道了init()干了什么,然后回归到主题:update() 中的属性从哪里来的。

我们只举一个例子。在update()中如何读取的当前电量级别(其他属性获取都是类似的)。在 update()函数中,获取当前电量等级代码如下:

    if (!mHealthdConfig->batteryCurrentNowPath.isEmpty())
        props.batteryCurrentNow = getIntField(mHealthdConfig->batteryCurrentNowPath);
会用getIntField() 去读取当前电量值。而且传入的参数是我们init()时获取的文件路径。 从路径下读取的值是什么呢,大家看下截图就明白了。如下:


看到没,其实就是读取文件里面的值。 100 是我当前手机的电量,我的手机是满电状态。

到此,我们第一个问题:

BatteryMonitor 中 update 方面里面如何获取的属性已经解决。就是根据路径,读取文件获得的。



下面来看第二个问题:

(2)属性变化后调用谁注册的监听。

在BatteryMonitor.cpp中的init()函数末尾 有这么一句:

    if (nosvcmgr == false) {
            mBatteryPropertiesRegistrar = new BatteryPropertiesRegistrar(this);
            mBatteryPropertiesRegistrar->publish();
    }

而在在BatteryMonitor.cpp中的update()函数末尾 有这么一句:

    if (mBatteryPropertiesRegistrar != NULL)
        mBatteryPropertiesRegistrar->notifyListeners(props);

由上面两个函数中的调用,我们很容易推测出 注册监听跟 BatteryPropertiesRegistrar有关。


我们来分析下 BatteryPropertiesRegistrar 有什么。


BatteryPropertiesRegistrar:

此类的相关文件有4个,具体路径:

\frameworks\native\include\batteryservice\IBatteryPropertiesRegistrar.h

\frameworks\native\services\batteryservice\IBatteryPropertiesRegistrar.cpp

\system\core\healthd\BatteryPropertiesRegistrar.cpp 

\system\core\healthd\BatteryPropertiesRegistrar.h


android 4.4 电池电量管理底层分析(C\C++层)_第7张图片


\frameworks\native\include\batteryservice\IBatteryPropertiesRegistrar.h文件内容:

#ifndef ANDROID_IBATTERYPROPERTIESREGISTRAR_H
#define ANDROID_IBATTERYPROPERTIESREGISTRAR_H

#include <binder/IInterface.h>
#include <batteryservice/IBatteryPropertiesListener.h>

namespace android {

// must be kept in sync with interface defined in IBatteryPropertiesRegistrar.aidl
enum {
    REGISTER_LISTENER = IBinder::FIRST_CALL_TRANSACTION,
    UNREGISTER_LISTENER,
};

class IBatteryPropertiesRegistrar : public IInterface {
public:
    DECLARE_META_INTERFACE(BatteryPropertiesRegistrar);

    virtual void registerListener(const sp<IBatteryPropertiesListener>& listener) = 0;
    virtual void unregisterListener(const sp<IBatteryPropertiesListener>& listener) = 0;
};

class BnBatteryPropertiesRegistrar : public BnInterface<IBatteryPropertiesRegistrar> {
public:
    virtual status_t onTransact(uint32_t code, const Parcel& data,
                                Parcel* reply, uint32_t flags = 0);
};

}; // namespace android

#endif // ANDROID_IBATTERYPROPERTIESREGISTRAR_H

咦,我们可以看到IBatteryPropertiesRegistrar 继承于  IInterface  ,还有一个类BnBatteryPropertiesRegistrar 继承于BnInterface。 而且还调用了
 DECLARE_META_INTERFACE(BatteryPropertiesRegistrar);
这个宏定义接口。如果你有看过我上篇 Binder 初解( http://blog.csdn.net/daweibalang717/article/details/41382603 )的话,你可以很轻易的看出这里是Binder的写法。而且明显是个 native service。 对于这四个文件的关系。你读完 Binder 初解后,就一目了然了。


\frameworks\native\services\batteryservice\IBatteryPropertiesRegistrar.cpp的内容

#define LOG_TAG "IBatteryPropertiesRegistrar"
//#define LOG_NDEBUG 0
#include <utils/Log.h>

#include <batteryservice/IBatteryPropertiesListener.h>
#include <batteryservice/IBatteryPropertiesRegistrar.h>
#include <stdint.h>
#include <sys/types.h>
#include <binder/Parcel.h>

namespace android {

class BpBatteryPropertiesRegistrar : public BpInterface<IBatteryPropertiesRegistrar> {
public:
    BpBatteryPropertiesRegistrar(const sp<IBinder>& impl)
        : BpInterface<IBatteryPropertiesRegistrar>(impl) {}

        void registerListener(const sp<IBatteryPropertiesListener>& listener) {
            Parcel data;
            data.writeInterfaceToken(IBatteryPropertiesRegistrar::getInterfaceDescriptor());
            data.writeStrongBinder(listener->asBinder());
            remote()->transact(REGISTER_LISTENER, data, NULL);
        }

        void unregisterListener(const sp<IBatteryPropertiesListener>& listener) {
            Parcel data;
            data.writeInterfaceToken(IBatteryPropertiesRegistrar::getInterfaceDescriptor());
            data.writeStrongBinder(listener->asBinder());
            remote()->transact(UNREGISTER_LISTENER, data, NULL);
        }
};

IMPLEMENT_META_INTERFACE(BatteryPropertiesRegistrar, "android.os.IBatteryPropertiesRegistrar");

status_t BnBatteryPropertiesRegistrar::onTransact(uint32_t code,
                                                  const Parcel& data,
                                                  Parcel* reply,
                                                  uint32_t flags)
{
    switch(code) {
        case REGISTER_LISTENER: {
            CHECK_INTERFACE(IBatteryPropertiesRegistrar, data, reply);
            sp<IBatteryPropertiesListener> listener =
                interface_cast<IBatteryPropertiesListener>(data.readStrongBinder());
            //这个方法并不是上面 BpBatteryPropertiesRegistrar中的registerListener(),他们就不是一个类。这个方法还未实现      
            registerListener(listener);
            return OK;
        }

        case UNREGISTER_LISTENER: {
            CHECK_INTERFACE(IBatteryPropertiesRegistrar, data, reply);
            sp<IBatteryPropertiesListener> listener =
                interface_cast<IBatteryPropertiesListener>(data.readStrongBinder());
 //这个方法并不是上面 BpBatteryPropertiesRegistrar中的unregisterListener(),他们就不是一个类。这个方法还未实现 
            unregisterListener(listener);
            return OK;
        }
    }
    return BBinder::onTransact(code, data, reply, flags);
};

// ----------------------------------------------------------------------------

}; // namespace android


 我们看到 这里是服务端与代理端的实现。 但是服务端 onTransact( )中调用的 registerListener(listener); 与unregisterListener(listener); 是没有实现的。这两个方法是在 
 

\system\core\healthd\BatteryPropertiesRegistrar.cpp  中实现的。

 \system\core\healthd\BatteryPropertiesRegistrar.h 中的内容:

#ifndef HEALTHD_BATTERYPROPERTIES_REGISTRAR_H
#define HEALTHD_BATTERYPROPERTIES_REGISTRAR_H

#include "BatteryMonitor.h"

#include <binder/IBinder.h>
#include <utils/Mutex.h>
#include <utils/Vector.h>
#include <batteryservice/BatteryService.h>
#include <batteryservice/IBatteryPropertiesListener.h>
#include <batteryservice/IBatteryPropertiesRegistrar.h>

namespace android {

class BatteryMonitor;

class BatteryPropertiesRegistrar : public BnBatteryPropertiesRegistrar,
                                   public IBinder::DeathRecipient {
public:
    BatteryPropertiesRegistrar(BatteryMonitor* monitor);
    void publish();
    void notifyListeners(struct BatteryProperties props);

private:
    BatteryMonitor* mBatteryMonitor;
    Mutex mRegistrationLock;
    Vector<sp<IBatteryPropertiesListener> > mListeners;

    void registerListener(const sp<IBatteryPropertiesListener>& listener);
    void unregisterListener(const sp<IBatteryPropertiesListener>& listener);
    void binderDied(const wp<IBinder>& who);
};

};  // namespace android

#endif // HEALTHD_BATTERYPROPERTIES_REGISTRAR_H
这个类是对\frameworks\native\include\batteryservice\IBatteryPropertiesRegistrar.h 中的  BnBatteryPropertiesRegistrar的扩展,并继承于public IBinder::DeathRecipient

然后是\system\core\healthd\BatteryPropertiesRegistrar.cpp  的内容:

#include "BatteryPropertiesRegistrar.h"
#include <batteryservice/BatteryService.h>
#include <batteryservice/IBatteryPropertiesListener.h>
#include <batteryservice/IBatteryPropertiesRegistrar.h>
#include <binder/IServiceManager.h>
#include <utils/Errors.h>
#include <utils/Mutex.h>
#include <utils/String16.h>

namespace android {

BatteryPropertiesRegistrar::BatteryPropertiesRegistrar(BatteryMonitor* monitor) {
    mBatteryMonitor = monitor;
}

void BatteryPropertiesRegistrar::publish() {
    defaultServiceManager()->addService(String16("batterypropreg"), this);
}

void BatteryPropertiesRegistrar::notifyListeners(struct BatteryProperties props) {
    Mutex::Autolock _l(mRegistrationLock);
    for (size_t i = 0; i < mListeners.size(); i++) {
        mListeners[i]->batteryPropertiesChanged(props);
    }
}

void BatteryPropertiesRegistrar::registerListener(const sp<IBatteryPropertiesListener>& listener) {
    {
        Mutex::Autolock _l(mRegistrationLock);
        // check whether this is a duplicate
        for (size_t i = 0; i < mListeners.size(); i++) {
            if (mListeners[i]->asBinder() == listener->asBinder()) {
                return;
            }
        }

        mListeners.add(listener);
        listener->asBinder()->linkToDeath(this);
    }
    mBatteryMonitor->update();
}

void BatteryPropertiesRegistrar::unregisterListener(const sp<IBatteryPropertiesListener>& listener) {
    Mutex::Autolock _l(mRegistrationLock);
    for (size_t i = 0; i < mListeners.size(); i++) {
        if (mListeners[i]->asBinder() == listener->asBinder()) {
            mListeners[i]->asBinder()->unlinkToDeath(this);
            mListeners.removeAt(i);
            break;
        }
    }
}

void BatteryPropertiesRegistrar::binderDied(const wp<IBinder>& who) {
    Mutex::Autolock _l(mRegistrationLock);

    for (size_t i = 0; i < mListeners.size(); i++) {
        if (mListeners[i]->asBinder() == who) {
            mListeners.removeAt(i);
            break;
        }
    }
}

}  // namespace android

这个类是对 \system\core\healthd\BatteryPropertiesRegistrar.h 的实现。  真正 调用registerListener(listener); 与unregisterListener(listener); 的地方。


这个BatteryPropertiesRegistrar:其实就是注册监听的类,而且监听的接口叫IBatteryPropertiesListener。


IBatteryPropertiesListener :

文件路径:

\frameworks\native\include\batteryservice\IBatteryPropertiesListener.h

\frameworks\native\services\batteryservice\IBatteryPropertiesListener.cpp

文件内容:

IBatteryPropertiesListener.h

#ifndef ANDROID_IBATTERYPROPERTIESLISTENER_H
#define ANDROID_IBATTERYPROPERTIESLISTENER_H

#include <binder/IBinder.h>
#include <binder/IInterface.h>

#include <batteryservice/BatteryService.h>

namespace android {

// must be kept in sync with interface defined in IBatteryPropertiesListener.aidl
enum {
        TRANSACT_BATTERYPROPERTIESCHANGED = IBinder::FIRST_CALL_TRANSACTION,
};

// ----------------------------------------------------------------------------

class IBatteryPropertiesListener : public IInterface {
public:
    DECLARE_META_INTERFACE(BatteryPropertiesListener);

    virtual void batteryPropertiesChanged(struct BatteryProperties props) = 0;
};

// ----------------------------------------------------------------------------

}; // namespace android

#endif 

咦,这个依然用的是Binder 机制。这里进行代理与服务端的声明。


IBatteryPropertiesListener.cpp:

#include <stdint.h>
#include <sys/types.h>
#include <batteryservice/IBatteryPropertiesListener.h>
#include <binder/Parcel.h>

namespace android {

class BpBatteryPropertiesListener : public BpInterface<IBatteryPropertiesListener>
{
public:
    BpBatteryPropertiesListener(const sp<IBinder>& impl)
        : BpInterface<IBatteryPropertiesListener>(impl)
    {
    }

    void batteryPropertiesChanged(struct BatteryProperties props)
    {
        Parcel data, reply;
        data.writeInterfaceToken(IBatteryPropertiesListener::getInterfaceDescriptor());
        data.writeInt32(1);
        props.writeToParcel(&data);
        status_t err = remote()->transact(TRANSACT_BATTERYPROPERTIESCHANGED, data, &reply, IBinder::FLAG_ONEWAY);
    }
};

IMPLEMENT_META_INTERFACE(BatteryPropertiesListener, "android.os.IBatteryPropertiesListener");

// ----------------------------------------------------------------------------

}; // namespace android

这里进行代理的实现。 但是并没有对服务端进行实现。这个应该是在BatteryService.java 中的:

    private final class BatteryListener extends IBatteryPropertiesListener.Stub {
        public void batteryPropertiesChanged(BatteryProperties props) {
            BatteryService.this.update(props);
       }

中进行实现的。


到这里我们对于第二个问题:属性变化后调用谁注册的监听。 还没有解决, 只是了解下注册类与注册接口。那么真正注册在那呢? 是在\frameworks\base\services\java\com\android\server\BatteryService.java中:

这个BatteryService 继承于Binder 类,在他的构造函数中,是这么注册的:

        mBatteryPropertiesListener = new BatteryListener();

        IBinder b = ServiceManager.getService("batterypropreg");
        mBatteryPropertiesRegistrar = IBatteryPropertiesRegistrar.Stub.asInterface(b);

        try {
            mBatteryPropertiesRegistrar.registerListener(mBatteryPropertiesListener);
        } catch (RemoteException e) {
            // Should never happen.
        }

大家不禁要问了。这里是Java 代码呀,怎么掉的C++的呢,这就是Binder机制了。 而且上面所述的 IBatteryPropertiesListener  、IBatteryPropertiesRegistrar 在Java层都有对应的aidl 文件。目录:

\frameworks\base\core\java\android\os\IBatteryPropertiesListener.aidl  

package android.os;

import android.os.BatteryProperties;

/**
 * {@hide}
 */

oneway interface IBatteryPropertiesListener {
    void batteryPropertiesChanged(in BatteryProperties props);
}


\frameworks\base\core\java\android\os\IBatteryPropertiesRegistrar.aidl


package android.os;

import android.os.IBatteryPropertiesListener;

/**
 * {@hide}
 */

interface IBatteryPropertiesRegistrar {
    void registerListener(IBatteryPropertiesListener listener);
    void unregisterListener(IBatteryPropertiesListener listener);
}

当编译的时候会自动生成 IBatteryPropertiesListener.java  与 IBatteryPropertiesRegistrar.java 文件。这个我就不多赘述了。


好吧,我们总结下第二个问题:

android 4.4 电池电量管理底层分析(C\C++层)_第8张图片

1、在BatteryService.java 实现回调函数中的接口,并注册到BatteryPropertiesRegistrar 中。

2、Healthd 中监控PMU 驱动,事件变更,调用BatteryMonitor中的update()函数中回调BatteryPropertiesRegistrar注册的接口,调用的就是BatteryService.java 实现的接口


到此,我们电池电量管理底层分析(C\C++层) 的分析已经完成。  如果你要了解 BatteryService.java 中被回调后执行了哪些事情,请观看我的博客 :

android 4.4 电池电量显示分析(低电量提醒与电池图标)Java 层 (http://blog.csdn.net/daweibalang717/article/details/40615453)




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