深入分析android5.1 healthd

转自:http://blog.csdn.net/kc58236582/article/details/47300413

healthd主要是读取电池节点的信息，传给BatteryService。或者在关机充电等使用。注意healthd中使用的是kernel的log。

下面先从main函数分析

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1. int main(int argc, char **argv) {  
2.     int ch;  
3.     int ret;  
4.   
5.     klog_set_level(KLOG_LEVEL);  
6.     healthd_mode_ops = &android_ops;  
7.   
8.     if (!strcmp(basename(argv[0]), "charger")) {//解析输入参数如果是charger的使用charger_ops，这里就不做介绍  
9.         healthd_mode_ops = &charger_ops;  
10.     } else {  
11.         while ((ch = getopt(argc, argv, "cr")) != -1) {//分析输入命令,各个命令对应不同的charger_ops  
12.             switch (ch) {  
13.             case 'c':  
14.                 healthd_mode_ops = &charger_ops;  
15.                 break;  
16.             case 'r':  
17.                 healthd_mode_ops = &recovery_ops;  
18.                 break;  
19.             case '?':  
20.             default:  
21.                 KLOG_ERROR(LOG_TAG, "Unrecognized healthd option: %c\n",  
22.                            optopt);  
23.                 exit(1);  
24.             }  
25.         }  
26.     }  
27.   
28.     ret = healthd_init();//healthd做初始化  
29.     if (ret) {  
30.         KLOG_ERROR("Initialization failed, exiting\n");  
31.         exit(2);  
32.     }  
33.   
34.     healthd_mainloop();//主函数  
35.     KLOG_ERROR("Main loop terminated, exiting\n");  
36.     return 3;  
37. }  

如果是正常开机，不走关机充电等，healthd_mode_ops = &android_ops;而这里面具体的函数在后面进行详细的介绍。

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1. static struct healthd_mode_ops android_ops = {  
2.     .init = healthd_mode_android_init,  
3.     .preparetowait = healthd_mode_android_preparetowait,  
4.     .heartbeat = healthd_mode_nop_heartbeat,  
5.     .battery_update = healthd_mode_android_battery_update,  
6. };  

下面分析下healthd_init函数，heathd使用了epoll进行IO复用。

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1. static int healthd_init() {  
2.     epollfd = epoll_create(MAX_EPOLL_EVENTS);  
3.     if (epollfd == -1) {  
4.         KLOG_ERROR(LOG_TAG,  
5.                    "epoll_create failed; errno=%d\n",  
6.                    errno);  
7.         return -1;  
8.     }  
9.   
10.     healthd_board_init(&healthd_config);  
11.     healthd_mode_ops->init(&healthd_config);  
12.     wakealarm_init();  
13.     uevent_init();  
14.     gBatteryMonitor = new BatteryMonitor();  
15.     gBatteryMonitor->init(&healthd_config);  
16.     return 0;  
17. }  

这里的healthd_mode_ops->init的函数是android_ops 的healthd_mode_android_init函数，这里主要是将binder通信的fd也加入epoll，而不像普通binder进程最后使用IPCThreadState::self()->joinThreadPool。这样所有的fd全在epoll管理，只用了一个线程

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1. int healthd_mode_android_preparetowait(void) {  
2.     IPCThreadState::self()->flushCommands();  
3.     return -1;  
4. }  
5.   
6. static void binder_event(uint32_t /*epevents*/) {  
7.     IPCThreadState::self()->handlePolledCommands();  
8. }  
9.   
10. void healthd_mode_android_init(struct healthd_config* /*config*/) {  
11.     ProcessState::self()->setThreadPoolMaxThreadCount(0);  
12.     IPCThreadState::self()->disableBackgroundScheduling(true);  
13.     IPCThreadState::self()->setupPolling(&gBinderFd);  
14.   
15.     if (gBinderFd >= 0) {  
16.         if (healthd_register_event(gBinderFd, binder_event))  
17.             KLOG_ERROR(LOG_TAG,  
18.                        "Register for binder events failed\n");  
19.     }  
20.   
21.     gBatteryPropertiesRegistrar = new BatteryPropertiesRegistrar();  
22.     gBatteryPropertiesRegistrar->publish();  
23. }  

gBatteryPropertiesRegistrar->publish将"batteryproperties"这个Service加入到ServiceManager中

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1. void BatteryPropertiesRegistrar::publish() {  
2.     defaultServiceManager()->addService(String16("batteryproperties"), this);  
3. }  

接下来再来看下wakealarm_init

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1. static void wakealarm_init(void) {  
2.     wakealarm_fd = timerfd_create(CLOCK_BOOTTIME_ALARM, TFD_NONBLOCK);  
3.     if (wakealarm_fd == -1) {  
4.         KLOG_ERROR(LOG_TAG, "wakealarm_init: timerfd_create failed\n");  
5.         return;  
6.     }  
7.   
8.     if (healthd_register_event(wakealarm_fd, wakealarm_event))  
9.         KLOG_ERROR(LOG_TAG,  
10.                    "Registration of wakealarm event failed\n");  
11.   
12.     wakealarm_set_interval(healthd_config.periodic_chores_interval_fast);  
13. }  

wakealarm_init设置alarm唤醒的interval，再来看下时间处理函数

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1. static void wakealarm_event(uint32_t /*epevents*/) {  
2.     unsigned long long wakeups;  
3.   
4.     if (read(wakealarm_fd, &wakeups, sizeof(wakeups)) == -1) {//出错结束  
5.         KLOG_ERROR(LOG_TAG, "wakealarm_event: read wakealarm fd failed\n");  
6.         return;  
7.     }  
8.     KLOG_ERROR(LOG_TAG, "wakealarm_event\n");  
9.     periodic_chores();  
10. }  

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1. static void periodic_chores() {  
2.     healthd_battery_update();  
3. }  

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1. void healthd_battery_update(void) {  
2.     // Fast wake interval when on charger (watch for overheat);  
3.     // slow wake interval when on battery (watch for drained battery).  
4.     KLOG_ERROR(LOG_TAG, "healthd_battery_update enter\n");  
5.    int new_wake_interval = gBatteryMonitor->update() ?//调用主要的update函数，根据返回值，如果当前在充电返回true  
6.        healthd_config.periodic_chores_interval_fast ://时间设置1分钟  
7.            healthd_config.periodic_chores_interval_slow;  
8.     KLOG_ERROR(LOG_TAG, "kangchen healthd_battery_update after\n");  
9.     if (new_wake_interval != wakealarm_wake_interval)  
10.             wakealarm_set_interval(new_wake_interval);  
11.   
12.     // During awake periods poll at fast rate.  If wake alarm is set at fast  
13.     // rate then just use the alarm; if wake alarm is set at slow rate then  
14.     // poll at fast rate while awake and let alarm wake up at slow rate when  
15.     // asleep.  
16.   
17.     if (healthd_config.periodic_chores_interval_fast == -1)  
18.         awake_poll_interval = -1;  
19.     else  
20.         awake_poll_interval =  
21.             new_wake_interval == healthd_config.periodic_chores_interval_fast ?//当前时间是一分钟，epoll为永远阻塞，否则为1分钟  
22.                 -1 : healthd_config.periodic_chores_interval_fast * 1000;  
23. }  

接下来再来看看uEvent的，

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1. static void uevent_init(void) {  
2.     uevent_fd = uevent_open_socket(64*1024, true);  
3.   
4.     if (uevent_fd < 0) {  
5.         KLOG_ERROR(LOG_TAG, "uevent_init: uevent_open_socket failed\n");  
6.         return;  
7.     }  
8.       
9.     fcntl(uevent_fd, F_SETFL, O_NONBLOCK);  
10.     if (healthd_register_event(uevent_fd, uevent_event))  
11.         KLOG_ERROR(LOG_TAG,  
12.                    "register for uevent events failed\n");  
13. }  

看看uevent_event的处理函数,获取uevent后主要判断是否是电源系统的，如果是调用healthd_battery_update函数

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1. static void uevent_event(uint32_t /*epevents*/) {  
2.     char msg[UEVENT_MSG_LEN+2];  
3.     char *cp;  
4.     int n;  
5.   
6.     n = uevent_kernel_multicast_recv(uevent_fd, msg, UEVENT_MSG_LEN);  
7.     if (n <= 0)  
8.         return;  
9.     if (n >= UEVENT_MSG_LEN)   /* overflow -- discard */  
10.         return;  
11.   
12.     msg[n] = '\0';  
13.     msg[n+1] = '\0';  
14.     cp = msg;  
15.     KLOG_ERROR(LOG_TAG, "uevent_event\n");  
16.     while (*cp) {  
17.         if (!strcmp(cp, "SUBSYSTEM=" POWER_SUPPLY_SUBSYSTEM)) {//是这个子系统的调用healthd_battery_update函数  
18.             healthd_battery_update();  
19.             break;  
20.         }  
21.   
22.         /* advance to after the next \0 */  
23.         while (*cp++)  
24.             ;  
25.     }  
26. }  

下面分析下healthd_mainloop这个主函数，主函数主要是epoll函数监听3个fd，有事件就处理。

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1. static void healthd_mainloop(void) {  
2.     while (1) {  
3.         struct epoll_event events[eventct];  
4.         int nevents;  
5.         int timeout = awake_poll_interval;  
6.         int mode_timeout;  
7.   
8.         mode_timeout = healthd_mode_ops->preparetowait();  
9.         if (timeout < 0 || (mode_timeout > 0 && mode_timeout < timeout))  
10.             timeout = mode_timeout;  
11.         nevents = epoll_wait(epollfd, events, eventct, timeout);//epoll_wait等待各个fd的事件，timeout为超时时间  
12.         KLOG_ERROR(LOG_TAG, "kangchen healthd_mainloop epoll_wait\n");  
13.         if (nevents == -1) {  
14.             if (errno == EINTR)  
15.                 continue;  
16.             KLOG_ERROR(LOG_TAG, "healthd_mainloop: epoll_wait failed\n");  
17.             break;  
18.         }  
19.   
20.         for (int n = 0; n < nevents; ++n) {  
21.             if (events[n].data.ptr)//遍历各个fd的事件上来，每个处理函数处理  
22.                 (*(void (*)(int))events[n].data.ptr)(events[n].events);  
23.         }  
24.   
25.         if (!nevents)//当什么事件没有的时候，是因为epoll超时设置走下来的，这时候也要update下  
26.             periodic_chores();  
27.   
28.         healthd_mode_ops->heartbeat();  
29.     }  
30.   
31.     return;  
32. }  

init函数主要将healthd_config 对象传入，并且将里面的成员的一些地址信息去初始化保存起来。主要是保存一些地址信息，以及充电方式。

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1. void BatteryMonitor::init(struct healthd_config *hc) {  
2.     String8 path;  
3.     char pval[PROPERTY_VALUE_MAX];  
4.   
5.     mHealthdConfig = hc;//将外面传进来的heathdconfig的指针赋给成员变量  
6.     DIR* dir = opendir(POWER_SUPPLY_SYSFS_PATH);//打开地址 /sys/class/power_supply  
7.     if (dir == NULL) {  
8.         KLOG_ERROR(LOG_TAG, "Could not open %s\n", POWER_SUPPLY_SYSFS_PATH);  
9.     } else {  
10.         struct dirent* entry;  
11.   
12.         while ((entry = readdir(dir))) {  
13.             const char* name = entry->d_name;  
14.   
15.             if (!strcmp(name, ".") || !strcmp(name, ".."))  
16.                 continue;  
17.   
18.             char buf[20];  
19.             // Look for "type" file in each subdirectory  
20.             path.clear();  
21.             path.appendFormat("%s/%s/type", POWER_SUPPLY_SYSFS_PATH, name);  
22.             switch(readPowerSupplyType(path)) {//读取各个目录下type的值，比如/sys/class/power_supply/battery 下type的值为Battery，在readPowerSupplyType读取并且转化为ANDROID_POWER_SUPPLY_TYPE_BATTERY  
23.             case ANDROID_POWER_SUPPLY_TYPE_AC:  
24.                 if (mHealthdConfig->acChargeHeathPath.isEmpty()) {  
25.                     path.clear();  
26.                     path.appendFormat("%s/%s/health", POWER_SUPPLY_SYSFS_PATH,  
27.                                       name);  
28.                     if (access(path, R_OK) == 0)  
29.                         mHealthdConfig->acChargeHeathPath = path;//配置路径  
30.                 }  
31.                 path.clear();  
32.                 path.appendFormat("%s/%s/online", POWER_SUPPLY_SYSFS_PATH, name);  
33.                 if (access(path.string(), R_OK) == 0)  
34.                     mChargerNames.add(String8(name));//chargername 就是当前目录名字：ac  
35.                 break;  
36.   
37.             case ANDROID_POWER_SUPPLY_TYPE_USB://usb 类似ac  
38.                 if (mHealthdConfig->usbChargeHeathPath.isEmpty()) {  
39.                     path.clear();  
40.                     path.appendFormat("%s/%s/health", POWER_SUPPLY_SYSFS_PATH,  
41.                                       name);  
42.                     if (access(path, R_OK) == 0)  
43.                         mHealthdConfig->usbChargeHeathPath = path;  
44.                 }  
45.                 path.clear();  
46.                 path.appendFormat("%s/%s/online", POWER_SUPPLY_SYSFS_PATH, name);  
47.                 if (access(path.string(), R_OK) == 0)  
48.                     mChargerNames.add(String8(name));  
49.                 break;  
50.   
51.             case ANDROID_POWER_SUPPLY_TYPE_WIRELESS://类似  
52.                 path.clear();  
53.                 path.appendFormat("%s/%s/online", POWER_SUPPLY_SYSFS_PATH, name);  
54.                 if (access(path.string(), R_OK) == 0)  
55.                     mChargerNames.add(String8(name));  
56.                 break;  
57.   
58.             case ANDROID_POWER_SUPPLY_TYPE_BATTERY://battery  
59.                 mBatteryDevicePresent = true;  
60.   
61.                 if (mHealthdConfig->batteryStatusPath.isEmpty()) {  
62.                     path.clear();  
63.                     path.appendFormat("%s/%s/status", POWER_SUPPLY_SYSFS_PATH,  
64.                                       name);  
65.                     if (access(path, R_OK) == 0)  
66.                         mHealthdConfig->batteryStatusPath = path;  
67.                 }  
68.   
69.                 if (mHealthdConfig->batteryHealthPath.isEmpty()) {  
70.                     path.clear();  
71.                     path.appendFormat("%s/%s/health", POWER_SUPPLY_SYSFS_PATH,  
72.                                       name);  
73.                     if (access(path, R_OK) == 0)  
74.                         mHealthdConfig->batteryHealthPath = path;  
75.                 }  
76.   
77.                 if (mHealthdConfig->batteryPresentPath.isEmpty()) {  
78.                     path.clear();  
79.                     path.appendFormat("%s/%s/present", POWER_SUPPLY_SYSFS_PATH,  
80.                                       name);  
81.                     if (access(path, R_OK) == 0)  
82.                         mHealthdConfig->batteryPresentPath = path;  
83.                 }  
84.   
85.                 if (mHealthdConfig->batteryCapacityPath.isEmpty()) {  
86.                     path.clear();  
87.                     path.appendFormat("%s/%s/capacity", POWER_SUPPLY_SYSFS_PATH,  
88.                                       name);  
89.                     if (access(path, R_OK) == 0)  
90.                         mHealthdConfig->batteryCapacityPath = path;  
91.                 }  
92.   
93.                 if (mHealthdConfig->batteryVoltagePath.isEmpty()) {  
94.                     path.clear();  
95.                     path.appendFormat("%s/%s/voltage_now",  
96.                                       POWER_SUPPLY_SYSFS_PATH, name);  
97.                     if (access(path, R_OK) == 0) {  
98.                         mHealthdConfig->batteryVoltagePath = path;  
99.                     } else {  
100.                         path.clear();  
101.                         path.appendFormat("%s/%s/batt_vol",  
102.                                           POWER_SUPPLY_SYSFS_PATH, name);  
103.                         if (access(path, R_OK) == 0)  
104.                             mHealthdConfig->batteryVoltagePath = path;  
105.                     }  
106.                 }  
107.   
108.                 if (mHealthdConfig->batteryCurrentNowPath.isEmpty()) {  
109.                     path.clear();  
110.                     path.appendFormat("%s/%s/current_now",  
111.                                       POWER_SUPPLY_SYSFS_PATH, name);  
112.                     if (access(path, R_OK) == 0)  
113.                         mHealthdConfig->batteryCurrentNowPath = path;  
114.                 }  
115.   
116.                 if (mHealthdConfig->batteryCurrentAvgPath.isEmpty()) {  
117.                     path.clear();  
118.                     path.appendFormat("%s/%s/current_avg",  
119.                                       POWER_SUPPLY_SYSFS_PATH, name);  
120.                     if (access(path, R_OK) == 0)  
121.                         mHealthdConfig->batteryCurrentAvgPath = path;  
122.                 }  
123.   
124.                 if (mHealthdConfig->batteryChargeCounterPath.isEmpty()) {  
125.                     path.clear();  
126.                     path.appendFormat("%s/%s/charge_counter",  
127.                                       POWER_SUPPLY_SYSFS_PATH, name);  
128.                     if (access(path, R_OK) == 0)  
129.                         mHealthdConfig->batteryChargeCounterPath = path;  
130.                 }  
131.   
132.                 if (mHealthdConfig->batteryTemperaturePath.isEmpty()) {  
133.                     path.clear();  
134.                     path.appendFormat("%s/%s/temp", POWER_SUPPLY_SYSFS_PATH,  
135.                                       name);  
136.                     if (access(path, R_OK) == 0) {  
137.                         mHealthdConfig->batteryTemperaturePath = path;  
138.                     } else {  
139.                         path.clear();  
140.                         path.appendFormat("%s/%s/batt_temp",  
141.                                           POWER_SUPPLY_SYSFS_PATH, name);  
142.                         if (access(path, R_OK) == 0)  
143.                             mHealthdConfig->batteryTemperaturePath = path;  
144.                     }  
145.                 }  
146.   
147.                 if (mHealthdConfig->batteryTechnologyPath.isEmpty()) {  
148.                     path.clear();  
149.                     path.appendFormat("%s/%s/technology",  
150.                                       POWER_SUPPLY_SYSFS_PATH, name);  
151.                     if (access(path, R_OK) == 0)  
152.                         mHealthdConfig->batteryTechnologyPath = path;  
153.                 }  
154.   
155.                 break;  
156.   
157.             case ANDROID_POWER_SUPPLY_TYPE_UNKNOWN:  
158.                 break;  
159.             }  
160.         }  
161.         closedir(dir);  
162.     }  
163.   
164.     if (!mChargerNames.size())  
165.         KLOG_ERROR(LOG_TAG, "No charger supplies found\n");  
166.     if (!mBatteryDevicePresent) {//主要由battery该成员变量就为true  
167.         KLOG_WARNING(LOG_TAG, "No battery devices found\n");  
168.         hc->periodic_chores_interval_fast = -1;  
169.         hc->periodic_chores_interval_slow = -1;  
170.     } else {  
171.         if (mHealthdConfig->batteryStatusPath.isEmpty())  
172.             KLOG_WARNING(LOG_TAG, "BatteryStatusPath not found\n");  
173. 。。。。。。。。。。。。。//这里都是一些警告  
174.     }  
175.   
176.     if (property_get("ro.boot.fake_battery", pval, NULL) > 0  
177.                                                && strtol(pval, NULL, 10) != 0) {  
178.         mBatteryFixedCapacity = FAKE_BATTERY_CAPACITY;  
179.         mBatteryFixedTemperature = FAKE_BATTERY_TEMPERATURE;  
180.     }  
181. }  

下面就是update函数，将数据封装在BatteryProperties 中，并且通过healthd_mode_ops->battery_update把BatteryProperties 发给上层。

[java] view plaincopy

1. bool BatteryMonitor::update(void) {  
2.     bool logthis;  
3.   
4.     props.chargerAcOnline = false;  
5.     props.chargerUsbOnline = false;  
6.     props.chargerWirelessOnline = false;  
7.     props.batteryStatus = BATTERY_STATUS_UNKNOWN;  
8.     props.batteryHealth = BATTERY_HEALTH_UNKNOWN;  
9. //都是从之前配置的mHealthd中取地址，读取节点信息，保存到props成员变量中  
10.     if (!mHealthdConfig->batteryPresentPath.isEmpty())  
11.         props.batteryPresent = getBooleanField(mHealthdConfig->batteryPresentPath);  
12.     else  
13.         props.batteryPresent = mBatteryDevicePresent;  
14.   
15.     props.batteryLevel = mBatteryFixedCapacity ?  
16.         mBatteryFixedCapacity :  
17.         getIntField(mHealthdConfig->batteryCapacityPath);  
18.     props.batteryVoltage = getIntField(mHealthdConfig->batteryVoltagePath) / 1000;  
19.   
20.     props.batteryTemperature = mBatteryFixedTemperature ?  
21.         mBatteryFixedTemperature :  
22.         getIntField(mHealthdConfig->batteryTemperaturePath);  
23.   
24.     const int SIZE = 128;  
25.     char buf[SIZE];  
26.     String8 btech;  
27.   
28.     if (readFromFile(mHealthdConfig->batteryStatusPath, buf, SIZE) > 0)  
29.         props.batteryStatus = getBatteryStatus(buf);  
30.   
31.     if (readFromFile(mHealthdConfig->batteryHealthPath, buf, SIZE) > 0)  
32.         props.batteryHealth = getBatteryHealth(buf);  
33.   
34.     if (readFromFile(mHealthdConfig->batteryTechnologyPath, buf, SIZE) > 0)  
35.         props.batteryTechnology = String8(buf);  
36.   
37.     if (readFromFile(mHealthdConfig->acChargeHeathPath, buf, SIZE) > 0)  
38.         props.acChargeHeath= String8(buf);  
39.   
40.     if (readFromFile(mHealthdConfig->usbChargeHeathPath, buf, SIZE) > 0)  
41.         props.usbChargeHeath= String8(buf);  
42.   
43.     unsigned int i;  
44.   
45.     for (i = 0; i < mChargerNames.size(); i++) {//遍历之前保存的各个充电方式  
46.         String8 path;  
47.         path.appendFormat("%s/%s/online", POWER_SUPPLY_SYSFS_PATH,  
48.                           mChargerNames[i].string());//路径就是每个目录下的online字段，比如/sys/class/power_supply/usb 下的online  
49.   
50.         if (readFromFile(path, buf, SIZE) > 0) {  
51.             if (buf[0] != '0') {//读取online里面的内容，如果当前在usb线上充电，那么usb下online里面的内容为1  
52.                 path.clear();  
53.                 path.appendFormat("%s/%s/type", POWER_SUPPLY_SYSFS_PATH,  
54.                                   mChargerNames[i].string());//这里看看是哪个type的  
55.                 switch(readPowerSupplyType(path)) {  
56.                 case ANDROID_POWER_SUPPLY_TYPE_AC:  
57.                     props.chargerAcOnline = true;  
58.                     break;  
59.                 case ANDROID_POWER_SUPPLY_TYPE_USB://将其值赋成true  
60.                     props.chargerUsbOnline = true;  
61.                     break;  
62.                 case ANDROID_POWER_SUPPLY_TYPE_WIRELESS:  
63.                     props.chargerWirelessOnline = true;  
64.                     break;  
65.                 default:  
66.                     KLOG_WARNING(LOG_TAG, "%s: Unknown power supply type\n",  
67.                                  mChargerNames[i].string());  
68.                 }  
69.             }  
70.         }  
71.     }  
72.   
73.     logthis = !healthd_board_battery_update(&props);  
74.   
75.     if (logthis) {  
76.         char dmesgline[256];  
77.   
78.         if (props.batteryPresent) {  
79.             snprintf(dmesgline, sizeof(dmesgline),  
80.                  "battery l=%d v=%d t=%s%d.%d h=%d st=%d",  
81.                  props.batteryLevel, props.batteryVoltage,  
82.                  props.batteryTemperature < 0 ? "-" : "",  
83.                  abs(props.batteryTemperature / 10),  
84.                  abs(props.batteryTemperature % 10), props.batteryHealth,  
85.                  props.batteryStatus);  
86.   
87.             if (!mHealthdConfig->batteryCurrentNowPath.isEmpty()) {  
88.                 int c = getIntField(mHealthdConfig->batteryCurrentNowPath);  
89.                 char b[20];  
90.   
91.                 snprintf(b, sizeof(b), " c=%d", c / 1000);  
92.                 strlcat(dmesgline, b, sizeof(dmesgline));  
93.             }  
94.         } else {  
95.             snprintf(dmesgline, sizeof(dmesgline),  
96.                  "battery none");  
97.         }  
98.   
99.         KLOG_WARNING(LOG_TAG, "%s chg=%s%s%s\n", dmesgline,  
100.                      props.chargerAcOnline ? "a" : "",  
101.                      props.chargerUsbOnline ? "u" : "",  
102.                      props.chargerWirelessOnline ? "w" : "");  
103.     }  
104.   
105.     healthd_mode_ops->battery_update(&props);//将数据传到上层的BatteryService  
106.     return props.chargerAcOnline | props.chargerUsbOnline |//返回当前是否属于充电  
107.             props.chargerWirelessOnline;  
108. }  

接下来看看healthd_mode_ops->battery_update是怎么把数据传到上层的

[java] view plaincopy

1. void healthd_mode_android_battery_update(  
2.     struct android::BatteryProperties *props) {  
3.     if (gBatteryPropertiesRegistrar != NULL)  
4.         gBatteryPropertiesRegistrar->notifyListeners(*props);  
5.   
6.     return;  
7. }  

上层会通过binder通信，注册一个回调到BatteryPropertiesRegistrar

[java] view plaincopy

1. void BatteryPropertiesRegistrar::registerListener(const sp<IBatteryPropertiesListener>& listener) {  
2.     {  
3.         if (listener == NULL)  
4.             return;  
5.         Mutex::Autolock _l(mRegistrationLock);  
6.         // check whether this is a duplicate  
7.         for (size_t i = 0; i < mListeners.size(); i++) {  
8.             if (mListeners[i]->asBinder() == listener->asBinder()) {  
9.                 return;  
10.             }  
11.         }  
12.   
13.         mListeners.add(listener);  
14.         listener->asBinder()->linkToDeath(this);  
15.     }  
16.     healthd_battery_update();  
17. }  

而update函数就是调用了notifyListeners遍历各个listener传到上层BatteryService

[java] view plaincopy

1. void BatteryPropertiesRegistrar::notifyListeners(struct BatteryProperties props) {  
2.     Mutex::Autolock _l(mRegistrationLock);  
3.     for (size_t i = 0; i < mListeners.size(); i++) {  
4.         mListeners[i]->batteryPropertiesChanged(props);  
5.     }  
6. }  

再来看看BatteryService中，在onStart中通过ServiceManager，和batteryproperties这个Service通信，将BatteryListener这个listenter注册到batteryproperties中去

[java] view plaincopy

1. @Override  
2. public void onStart() {  
3.     IBinder b = ServiceManager.getService("batteryproperties");  
4.     final IBatteryPropertiesRegistrar batteryPropertiesRegistrar =  
5.             IBatteryPropertiesRegistrar.Stub.asInterface(b);  
6.     try {  
7.         batteryPropertiesRegistrar.registerListener(new BatteryListener());  
8.     } catch (RemoteException e) {  
9.         // Should never happen.  
10.     }  
11.   
12.     publishBinderService("battery", new BinderService());  
13.     publishLocalService(BatteryManagerInternal.class, new LocalService());  
14. }  

再来看看BatteryListener 的batteryPropertiesChanged接口，当下面调这个接口，就会调用BatteryService的update函数，然后就是BatteryService的一些主要流程就不分析了。

[java] view plaincopy

1. private final class BatteryListener extends IBatteryPropertiesListener.Stub {  
2.     @Override  
3.     public void batteryPropertiesChanged(BatteryProperties props) {  
4.         final long identity = Binder.clearCallingIdentity();  
5.         try {  
6.             BatteryService.this.update(props);  
7.         } finally {  
8.             Binder.restoreCallingIdentity(identity);  
9.         }  
10.    }  
11. }  

BatteryService接受healthd的数据都是被动的，healthd穿过来的。有没有主动去healthd查询的。

在BatteryManager中就有主动去healthd查询的，代码如下

[java] view plaincopy

1. private long queryProperty(int id) {  
2.     long ret;  
3.   
4.     if (mBatteryPropertiesRegistrar == null) {  
5.         IBinder b = ServiceManager.getService("batteryproperties");//获取batteryproperties Service  
6.         mBatteryPropertiesRegistrar =  
7.             IBatteryPropertiesRegistrar.Stub.asInterface(b);//接口转化下  
8.   
9.         if (mBatteryPropertiesRegistrar == null)  
10.             return Long.MIN_VALUE;  
11.     }  
12.   
13.     try {  
14.         BatteryProperty prop = new BatteryProperty();  
15.   
16.         if (mBatteryPropertiesRegistrar.getProperty(id, prop) == 0)//prop是输出  
17.             ret = prop.getLong();  
18.         else  
19.             ret = Long.MIN_VALUE;  
20.     } catch (RemoteException e) {  
21.         ret = Long.MIN_VALUE;  
22.     }  
23.   
24.     return ret;  
25. }  

再到healthd看看对应的接口

[java] view plaincopy

1. status_t BatteryPropertiesRegistrar::getProperty(int id, struct BatteryProperty *val) {  
2.     return healthd_get_property(id, val);  
3. }  

[java] view plaincopy

1. status_t healthd_get_property(int id, struct BatteryProperty *val) {  
2.     return gBatteryMonitor->getProperty(id, val);  
3. }  

java的BatteryProperty对象对应到这边是指针

[java] view plaincopy

1. status_t BatteryMonitor::getProperty(int id, struct BatteryProperty *val) {  
2.     status_t ret = BAD_VALUE;  
3.   
4.     val->valueInt64 = LONG_MIN;  
5.   
6.     switch(id) {  
7.     case BATTERY_PROP_CHARGE_COUNTER://根据不同ID，返回不同值  
8.         if (!mHealthdConfig->batteryChargeCounterPath.isEmpty()) {  
9.             val->valueInt64 =  
10.                 getIntField(mHealthdConfig->batteryChargeCounterPath);  
11.             ret = NO_ERROR;  
12.         } else {  
13.             ret = NAME_NOT_FOUND;  
14.         }  
15.         break;  
16.   
17.     case BATTERY_PROP_CURRENT_NOW:  
18.         if (!mHealthdConfig->batteryCurrentNowPath.isEmpty()) {  
19.             val->valueInt64 =  
20.                 getIntField(mHealthdConfig->batteryCurrentNowPath);  
21.             ret = NO_ERROR;  
22.         } else {  
23.             ret = NAME_NOT_FOUND;  
24.         }  
25.         break;  
26.   
27.     case BATTERY_PROP_CURRENT_AVG:  
28.         if (!mHealthdConfig->batteryCurrentAvgPath.isEmpty()) {  
29.             val->valueInt64 =  
30.                 getIntField(mHealthdConfig->batteryCurrentAvgPath);  
31.             ret = NO_ERROR;  
32.         } else {  
33.             ret = NAME_NOT_FOUND;  
34.         }  
35.         break;  
36.   
37.     case BATTERY_PROP_CAPACITY:  
38.         if (!mHealthdConfig->batteryCapacityPath.isEmpty()) {  
39.             val->valueInt64 =  
40.                 getIntField(mHealthdConfig->batteryCapacityPath);  
41.             ret = NO_ERROR;  
42.         } else {  
43.             ret = NAME_NOT_FOUND;  
44.         }  
45.         break;  
46.   
47.     case BATTERY_PROP_ENERGY_COUNTER:  
48.         if (mHealthdConfig->energyCounter) {  
49.             ret = mHealthdConfig->energyCounter(&val->valueInt64);  
50.         } else {  
51.             ret = NAME_NOT_FOUND;  
52.         }  
53.         break;  
54.   
55.     default:  
56.         break;  
57.     }  
58.   
59.     return ret;  
60. }