Implement the 2.1 HAL instead!

It is strongly recommended that you implement the 2.1 HAL directly. See hardware/interfaces/health/2.1/README.md for more details.

Upgrading from Health 1.0 HAL

Remove android.hardware.health@1.0* from PRODUCT_PACKAGES in device/<manufacturer>/<device>/device.mk
If the device does not have a vendor-specific libhealthd AND does not implement storage-related APIs, just do the following:
```
PRODUCT_PACKAGES += android.hardware.health@2.0-service
```
Otherwise, continue to the next step.
Create directory device/<manufacturer>/<device>/health

Create device/<manufacturer>/<device>/health/Android.bp (or equivalent device/<manufacturer>/<device>/health/Android.mk)

cc_binary {
    name: "android.hardware.health@2.0-service.<device>",
    init_rc: ["android.hardware.health@2.0-service.<device>.rc"],
    proprietary: true,
    relative_install_path: "hw",
    srcs: [
        "HealthService.cpp",
    ],

    cflags: [
        "-Wall",
        "-Werror",
    ],

    static_libs: [
        "android.hardware.health@2.0-impl",
        "android.hardware.health@1.0-convert",
        "libhealthservice",
        "libbatterymonitor",
    ],

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

    header_libs: ["libhealthd_headers"],

    overrides: [
        "healthd",
    ],
}

(recommended) To remove healthd from the build, keep "overrides" section.
To keep healthd in the build, remove "overrides" section.

Create device/<manufacturer>/<device>/health/android.hardware.health@2.0-service.<device>.rc

service vendor.health-hal-2-0 /vendor/bin/hw/android.hardware.health@2.0-service.<device>
    class hal
    user system
    group system
    capabilities WAKE_ALARM
    file /dev/kmsg w

Create device/<manufacturer>/<device>/health/HealthService.cpp:

#include <health2/service.h>
int main() { return health_service_main(); }

libhealthd dependency:

If the device has a vendor-specific libhealthd.<soc>, add it to static_libs.

If the device does not have a vendor-specific libhealthd, add the following lines to HealthService.cpp:

#include <healthd/healthd.h>
void healthd_board_init(struct healthd_config*) {}

int healthd_board_battery_update(struct android::BatteryProperties*) {
    // return 0 to log periodic polled battery status to kernel log
    return 0;
}

Storage related APIs:
1. If the device does not implement IHealth.getDiskStats and IHealth.getStorageInfo, add libhealthstoragedefault to static_libs.
2. If the device implements one of these two APIs, add and implement the following functions in HealthService.cpp:
```
void get_storage_info(std::vector<struct StorageInfo>& info) {
    // ...
}
void get_disk_stats(std::vector<struct DiskStats>& stats) {
    // ...
}
```

Update necessary SELinux permissions. For example,

# device/<manufacturer>/<device>/sepolicy/vendor/file_contexts
/vendor/bin/hw/android\.hardware\.health@2\.0-service\.<device> u:object_r:hal_health_default_exec:s0

# 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.

Implementing health HAL in recovery. The health HAL is used for battery status checks during OTA for non-A/B devices. If the health HAL is not implemented in recovery, is_battery_ok() will always return true.

If the device does not have a vendor-specific libhealthd, nothing needs to be done. A "backup" implementation is provided in android.hardware.health@2.0-impl-default, which is always installed to recovery image by default.
If the device does have a vendor-specific libhealthd, implement the following module and include it in PRODUCT_PACKAGES (replace <device> with appropriate strings):

// Android.bp
cc_library_shared {
    name: "android.hardware.health@2.0-impl-<device>",
    recovery_available: true,
    relative_install_path: "hw",
    static_libs: [
        "android.hardware.health@2.0-impl",
        "libhealthd.<device>"
        // Include the following or implement device-specific storage APIs
        "libhealthstoragedefault",
    ],
    srcs: [
        "HealthImpl.cpp",
    ],
    overrides: [
        "android.hardware.health@2.0-impl-default",
    ],
}

// HealthImpl.cpp
#include <health2/Health.h>
#include <healthd/healthd.h>
using android::hardware::health::V2_0::IHealth;
using android::hardware::health::V2_0::implementation::Health;
extern "C" IHealth* HIDL_FETCH_IHealth(const char* name) {
    const static std::string providedInstance{"default"};
    if (providedInstance != name) return nullptr;
    return Health::initInstance(&gHealthdConfig).get();
}

# device.mk
PRODUCT_PACKAGES += android.hardware.health@2.0-impl-<device>