Power Supply 文件节点和电池服务属性对照
背景
Android 电池服务是基于Android Linux的Power Supply驱动实现的，Power Supply驱动将电池各种状态属性值在发生改变时写入到sysfs文件系统下目录节点上，提供给用户空间程序访问，并上报uevent事件，通知用户空间程序读取电池状态变化结果。写本文档的目的主要是理清Android电池服务关心的重要属性在sysfs文件系统中的对应关系，方便测试和程序设计。
对照关系
要理清Android系统中power supply文件节点和电池服务属性的对照关系，首先从Android Q源码中摘出Android关心的电池相关属性结构：
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;
};对照关系：
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"目录时，batteryPresent值为true，否则为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 处理Power Supply关键代码
Android电池服务处理Power Supply的代码在Healthd中，在Android Q中是[email protected],作为一个Hal层服务。处理Power Supply的核心代码在"android/system/core/healthd/BatteryMonitor.cpp"文件中：
//init 初始化power supply文件节点路径
void BatteryMonitor::init(struct healthd_config *hc) {
String8 path;
char pval[PROPERTY_VALUE_MAX];
mHealthdConfig = hc;
std::unique_ptr 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 从power supply文件节点更新电池属性
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;
}