Power Supply 文件節點和電池服務屬性對照

背景

Android 電池服務是基於Android Linux的Power Supply驅動實現的，Power Supply驅動將電池各種狀態屬性值在發生改變時寫入到sysfs文件系統下目錄節點上，提供給用戶空間程序訪問，並上報uevent事件，通知用戶空間程序讀取電池狀態變化結果。寫本文檔的目的主要是理清Android電池服務關心的重要屬性在sysfs文件系統中的對應關係，方便測試和程序設計。

對照關係

要理清Android系統中power supply文件節點和電池服務屬性的對照關係，首先從Android Q源碼中摘出Android關心的電池相關屬性結構：

struct BatteryProperties {
    bool chargerAcOnline;
    bool chargerUsbOnline;
    bool chargerWirelessOnline;
    int maxChargingCurrent;
    int maxChargingVoltage;
    int batteryStatus;
    int batteryHealth;
    bool batteryPresent;
    int batteryLevel;
    int batteryVoltage;
    int batteryTemperature;
    int batteryCurrent;
    int batteryCycleCount;
    int batteryFullCharge;
    int batteryChargeCounter;
    String8 batteryTechnology;
};

對照關係：

chargerAcOnline "/sys/class/power_supply/ac/online"

chargerUsbOnline "/sys/class/power_supply/usb/online"

chargerWirelessOnline "/sys/class/power_supply/Wireless/online"

maxChargingCurrent "/sys/class/power_supply/ac(usb, Wireless)/online"

maxChargingVoltage "/sys/class/power_supply/ac(usb, Wireless)/online"

batteryStatus "/sys/class/power_supply/battery/status"

batteryHealth "/sys/class/power_supply/battery/health"

batteryPresent 有"/sys/class/power_supply/battery"目錄時，batteryPresent值爲true，否則爲false

batteryLevel "/sys/class/power_supply/battery/capacity"

batteryVoltage "/sys/class/power_supply/battery/voltage_now"

batteryTemperature "/sys/class/power_supply/battery/temp"

batteryCurrent "/sys/class/power_supply/battery/current_now"

batteryCycleCount "/sys/class/power_supply/battery/cycle_count"

batteryFullCharge "/sys/class/power_supply/battery/charge_full"

batteryChargeCounter "/sys/class/power_supply/battery/charge_counter"

batteryTechnology "/sys/class/power_supply/battery/technology"

Android 處理Power Supply關鍵代碼

Android電池服務處理Power Supply的代碼在Healthd中，在Android Q中是[email protected],作爲一個Hal層服務。處理Power Supply的核心代碼在"android/system/core/healthd/BatteryMonitor.cpp"文件中：

//init 初始化power supply文件節點路徑
void BatteryMonitor::init(struct healthd_config *hc) {
    String8 path;
    char pval[PROPERTY_VALUE_MAX];

    mHealthdConfig = hc;
    std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(POWER_SUPPLY_SYSFS_PATH), closedir);
    if (dir == NULL) {
        KLOG_ERROR(LOG_TAG, "Could not open %s\n", POWER_SUPPLY_SYSFS_PATH);
    } else {
        struct dirent* entry;

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

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

            // 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:
                mBatteryDevicePresent = true;

                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;
                    }
                }

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

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

                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;
            }
        }
    }

    // Typically the case for devices which do not have a battery and
    // and are always plugged into AC mains.
    if (!mBatteryDevicePresent) {
        KLOG_WARNING(LOG_TAG, "No battery devices found\n");
        hc->periodic_chores_interval_fast = -1;
        hc->periodic_chores_interval_slow = -1;
    } else {
        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 (mHealthdConfig->batteryCurrentNowPath.isEmpty())
            KLOG_WARNING(LOG_TAG, "BatteryCurrentNowPath not found\n");
        if (mHealthdConfig->batteryFullChargePath.isEmpty())
            KLOG_WARNING(LOG_TAG, "BatteryFullChargePath not found\n");
        if (mHealthdConfig->batteryCycleCountPath.isEmpty())
            KLOG_WARNING(LOG_TAG, "BatteryCycleCountPath not found\n");
    }

    if (property_get("ro.boot.fake_battery", pval, NULL) > 0
                                               && strtol(pval, NULL, 10) != 0) {
        mBatteryFixedCapacity = FAKE_BATTERY_CAPACITY;
        mBatteryFixedTemperature = FAKE_BATTERY_TEMPERATURE;
    }
}

//update 從power supply文件節點更新電池屬性
bool BatteryMonitor::update(void) {
    bool logthis;

    initBatteryProperties(&props);

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

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

    if (!mHealthdConfig->batteryCurrentNowPath.isEmpty())
        props.batteryCurrent = getIntField(mHealthdConfig->batteryCurrentNowPath) / 1000;

    if (!mHealthdConfig->batteryFullChargePath.isEmpty())
        props.batteryFullCharge = getIntField(mHealthdConfig->batteryFullChargePath);

    if (!mHealthdConfig->batteryCycleCountPath.isEmpty())
        props.batteryCycleCount = getIntField(mHealthdConfig->batteryCycleCountPath);

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

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

    std::string buf;

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

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

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

    unsigned int i;
    double MaxPower = 0;

    for (i = 0; i < mChargerNames.size(); i++) {
        String8 path;
        path.appendFormat("%s/%s/online", POWER_SUPPLY_SYSFS_PATH,
                          mChargerNames[i].string());
        if (getIntField(path)) {
            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());
            }
            path.clear();
            path.appendFormat("%s/%s/current_max", POWER_SUPPLY_SYSFS_PATH,
                              mChargerNames[i].string());
            int ChargingCurrent =
                    (access(path.string(), R_OK) == 0) ? getIntField(path) : 0;

            path.clear();
            path.appendFormat("%s/%s/voltage_max", POWER_SUPPLY_SYSFS_PATH,
                              mChargerNames[i].string());

            int ChargingVoltage =
                (access(path.string(), R_OK) == 0) ? getIntField(path) :
                DEFAULT_VBUS_VOLTAGE;

            double power = ((double)ChargingCurrent / MILLION) *
                           ((double)ChargingVoltage / MILLION);
            if (MaxPower < power) {
                props.maxChargingCurrent = ChargingCurrent;
                props.maxChargingVoltage = ChargingVoltage;
                MaxPower = power;
            }
        }
    }

    logthis = !healthd_board_battery_update(&props);

    if (logthis) {
        char dmesgline[256];
        size_t len;
        if (props.batteryPresent) {
            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);

            len = strlen(dmesgline);
            if (!mHealthdConfig->batteryCurrentNowPath.isEmpty()) {
                len += snprintf(dmesgline + len, sizeof(dmesgline) - len,
                                " c=%d", props.batteryCurrent);
            }

            if (!mHealthdConfig->batteryFullChargePath.isEmpty()) {
                len += snprintf(dmesgline + len, sizeof(dmesgline) - len,
                                " fc=%d", props.batteryFullCharge);
            }

            if (!mHealthdConfig->batteryCycleCountPath.isEmpty()) {
                len += snprintf(dmesgline + len, sizeof(dmesgline) - len,
                                " cc=%d", props.batteryCycleCount);
            }
        } else {
            len = snprintf(dmesgline, sizeof(dmesgline),
                 "battery none");
        }

        snprintf(dmesgline + len, sizeof(dmesgline) - len, " chg=%s%s%s",
                 props.chargerAcOnline ? "a" : "",
                 props.chargerUsbOnline ? "u" : "",
                 props.chargerWirelessOnline ? "w" : "");

        KLOG_WARNING(LOG_TAG, "%s\n", dmesgline);
    }

    healthd_mode_ops->battery_update(&props);
    return props.chargerAcOnline | props.chargerUsbOnline |
            props.chargerWirelessOnline;
}

Power Supply 文件節點和電池服務屬性對照

背景

對照關係

Android 處理Power Supply關鍵代碼

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Power Supply 文件節點和電池服務屬性對照

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