platform_hardware_interfaces/health/2.0/README.md

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

1. Remove android.hardware.health@1.0* from PRODUCT_PACKAGES in device/<manufacturer>/<device>/device.mk

2. 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.

3. Create directory device/<manufacturer>/<device>/health

4. 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",
       ],
   }
   

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

5. 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
   

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

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

7. libhealthd dependency:

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

   2. 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;
      }
      

8. 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) {
          // ...
      }
      

9. 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.
   

10. 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.

    1. 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.

    2. 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>