Implementing Health 2.1 HAL

  1. Install common binderized service. The binderized service dlopen()s passthrough implementations on the device, so there is no need to write your own.

    # Install default binderized implementation to vendor.
PRODUCT_PACKAGES += android.hardware.health@2.1-service

  2. Delete existing VINTF manifest entry. Search for android.hardware.health in your device manifest, and delete the whole <hal> entry for older versions of the HAL. Instead, when android.hardware.health@2.1-service is installed, a VINTF manifest fragment is installed to /vendor/etc/vintf, so there is no need to manually specify it in your device manifest. See Manifest fragments for details.

  3. Install the proper passthrough implemetation.

    1. If you want to use default implementation:

      # Install default passthrough implementation to vendor.
PRODUCT_PACKAGES += android.hardware.health@2.1-impl

# For non-A/B devices, install default passthrough implementation to recovery.
PRODUCT_PACKAGES += android.hardware.health@2.1-impl.recovery

      You are done. Otherwise, go to the next step.

    2. If you want to write your own implementation,

      1. Copy skeleton implementation from the appendix.

      2. Modify the implementation to suit your needs.

      3. Install the implementation.

      4. Update necessary SELinux permissions.

      5. Fix /charger symlink.

Upgrading with a customized libhealthd or from Health HAL 1.0 {#update-from-1-0}

libhealthd contains two functions: healthd_board_init() and healthd_board_battery_update(). Similarly, Health HAL 1.0 contains init() and update(), with an additional energyCounter() function.

  • healthd_board_init() / @1.0::IHealth.init() should be called before passing the healthd_config struct to your HealthImpl class. See HIDL_FETCH_IHealth in HealthImpl.cpp.

  • healthd_board_battery_update() / @1.0::IHealth.update() should be called in HealthImpl::UpdateHealthInfo(). Example:

    void HealthImpl::UpdateHealthInfo(HealthInfo* health_info) {
    struct BatteryProperties props;
    convertFromHealthInfo(health_info->legacy.legacy, &props);
    healthd_board_battery_update(&props);
    convertToHealthInfo(&props, health_info->legacy.legacy);
}

    For efficiency, you should move code in healthd_board_battery_update to HealthImpl::UpdateHealthInfo and modify health_info directly to avoid conversion to BatteryProperties.

  • Code for @1.0::IHealth.energyCounter() should be moved to HealthImpl::getEnergyCounter(). Example:

    Return<void> Health::getEnergyCounter(getEnergyCounter_cb _hidl_cb) {
    int64_t energy = /* ... */;
    _hidl_cb(Result::SUCCESS, energy);
    return Void();
}

Upgrading from Health HAL 2.0 {#update-from-2-0}

  • If you have implemented healthd_board_init() and/or healthd_board_battery_update() (instead of using libhealthd.default), see the section above for instructions to convert them.

  • If you have implemented get_storage_info() and/or get_disk_stats() (instead of using libhealthstoragedefault), implement HealthImpl::getDiskStats and/or HealthImpl::getStorageInfo directly. There is no need to override HealthImpl::getHealthInfo or HealthImpl::getHealthInfo_2_1 because they call getDiskStats and getStorageInfo to retrieve storage information.

Install the implementation {#install}

In device.mk:

# Install the passthrough implementation to vendor.
PRODUCT_PACKAGES += android.hardware.health@2.1-impl-<device>

# For non-A/B devices, also install the passthrough implementation to recovery.
PRODUCT_PACKAGES += android.hardware.health@2.1-impl-<device>.recovery

Update necessary SELinux permissions {#selinux}

For example (replace <device> with the device name):

# device/<manufacturer>/<device>/sepolicy/vendor/hal_health_default.te
# Add device specific permissions to hal_health_default domain, especially
# if a device-specific libhealthd is used and/or device-specific storage related
# APIs are implemented.

Fix /charger symlink {#charger-symlink}

If you are using /charger in your init.rc scripts, it is recommended (required for devices running in Android R) that the path is changed to /system/bin/charger instead.

Search for service charger in your device configuration directory to see if this change applies to your device. Below is an example of how the script should look like:

service charger /system/bin/charger
    class charger
    user system
    group system wakelock input
    capabilities SYS_BOOT
    file /dev/kmsg w
    file /sys/fs/pstore/console-ramoops-0 r
    file /sys/fs/pstore/console-ramoops r
    file /proc/last_kmsg r

Appendix: sample code for the implementation {#impl}

device/<manufacturer>/<device>/health/Android.bp {#android_bp}

cc_library_shared {
    name: "android.hardware.health@2.1-impl-<device>",
    stem: "android.hardware.health@2.0-impl-2.1-<device>",

    // Install to vendor and recovery.
    proprietary: true,
    recovery_available: true,

    relative_install_path: "hw",

    shared_libs: [
        "libbase",
        "libcutils",
        "libhidlbase",
        "liblog",
        "libutils",
        "android.hardware.health@2.1",
        "android.hardware.health@2.0",
    ],

    static_libs: [
        "android.hardware.health@1.0-convert",
        "libbatterymonitor",
        "libhealthloop",
        "libhealth2impl",
        // "libhealthd.<device>"
    ],

    srcs: [
        "HealthImpl.cpp",
    ],

    // No vintf_fragments because both -impl and -service should have been
    // installed.
}

device/<manufacturer>/<device>/health/HealthImpl.cpp {#health_impl_cpp}

#include <memory>
#include <string_view>

#include <health/utils.h>
#include <health2impl/Health.h>
#include <hidl/Status.h>

using ::android::sp;
using ::android::hardware::Return;
using ::android::hardware::Void;
using ::android::hardware::health::InitHealthdConfig;
using ::android::hardware::health::V2_1::IHealth;
using ::android::hidl::base::V1_0::IBase;

using namespace std::literals;

namespace android {
namespace hardware {
namespace health {
namespace V2_1 {
namespace implementation {

// android::hardware::health::V2_1::implementation::Health implements most
// defaults. Uncomment functions that you need to override.
class HealthImpl : public Health {
  public:
    HealthImpl(std::unique_ptr<healthd_config>&& config)
        : Health(std::move(config)) {}

    // A subclass can override this if these information should be retrieved
    // differently.
    // Return<void> getChargeCounter(getChargeCounter_cb _hidl_cb) override;
    // Return<void> getCurrentNow(getCurrentNow_cb _hidl_cb) override;
    // Return<void> getCurrentAverage(getCurrentAverage_cb _hidl_cb) override;
    // Return<void> getCapacity(getCapacity_cb _hidl_cb) override;
    // Return<void> getEnergyCounter(getEnergyCounter_cb _hidl_cb) override;
    // Return<void> getChargeStatus(getChargeStatus_cb _hidl_cb) override;
    // Return<void> getStorageInfo(getStorageInfo_cb _hidl_cb) override;
    // Return<void> getDiskStats(getDiskStats_cb _hidl_cb) override;
    // Return<void> getHealthInfo(getHealthInfo_cb _hidl_cb) override;

    // Functions introduced in Health HAL 2.1.
    // Return<void> getHealthConfig(getHealthConfig_cb _hidl_cb) override;
    // Return<void> getHealthInfo_2_1(getHealthInfo_2_1_cb _hidl_cb) override;
    // Return<void> shouldKeepScreenOn(shouldKeepScreenOn_cb _hidl_cb) override;

  protected:
    // A subclass can override this to modify any health info object before
    // returning to clients. This is similar to healthd_board_battery_update().
    // By default, it does nothing.
    // void UpdateHealthInfo(HealthInfo* health_info) override;
};

}  // namespace implementation
}  // namespace V2_1
}  // namespace health
}  // namespace hardware
}  // namespace android

extern "C" IHealth* HIDL_FETCH_IHealth(const char* instance) {
    using ::android::hardware::health::V2_1::implementation::HealthImpl;
    if (instance != "default"sv) {
        return nullptr;
    }
    auto config = std::make_unique<healthd_config>();
    InitHealthdConfig(config.get());

    // healthd_board_init(config.get());

    return new HealthImpl(std::move(config));
}