Merge "health AIDL: Add readme" am: 9af94c627c am: fe5ba8ae61 am: 1c4e695225 am: 60ff9fd511
Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/1875620 Change-Id: Ifb7a1b6b43a6575aa7f9626f8a2f4dad608972ec
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health/aidl/README.md
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health/aidl/README.md
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# Health AIDL HAL
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## Determine whether the example service implementation is sufficient {#determine}
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You need a custom implementation if any of the following is true:
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* You are migrating from a custom
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[health 2.1 HIDL HAL implementation](../2.1/README.md).
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* System properties `ro.charger.enable_suspend` and/or `ro.charger.no_ui`
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are set to a `true` value. See [below](#charger-sysprops).
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* The device supports offline charging mode, and the `service`
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declaration with `class charger` in `init.rc` is different from the one
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provided by the example implementation. See [below](#charger-init-rc).
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If the example HAL service is sufficient, [install it](#use-example). Otherwise,
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[implement a custom HAL service](#use-custom).
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### System properties for charger {#charger-sysprops}
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The health AIDL HAL service also provides functionalities of `charger`. As a
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result, the system charger at `/system/bin/charger` is deprecated.
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However, the health AIDL HAL service is not allowed to read `ro.charger.*`
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system properties. These properties include:
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* `ro.charger.enable_suspend`. If set, you need a custom health AIDL HAL
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service. See [below](#charger-enable-suspend).
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* `ro.charger.no_ui`. If set, you need a custom health AIDL HAL service.
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See [below](#charger-no-ui).
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* `ro.charger.draw_split_screen`. The system property is deprecated.
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* `ro.charger.draw_split_offset`. The system property is deprecated.
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* `ro.charger.disable_init_blank`. The system property is deprecated.
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If you need to set any of the deprecated system properties, contact
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[OWNERS](OWNERS).
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### Default `service` declaration for charger in `init.rc` {#charger-init-rc}
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See
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[android.hardware.health-service.example.rc](default/android.hardware.health-service.example.rc).
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Check the `service` declaration in your device-specific `init.rc` file that
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has `class charger`. Most likely, the declaration looks something like this
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(Below is an excerpt from Pixel 3):
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```text
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service vendor.charger /system/bin/charger
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class charger
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seclabel u:r:charger:s0
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user system
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group system wakelock input
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capabilities SYS_BOOT
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file /dev/kmsg w
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file /sys/fs/pstore/console-ramoops-0 r
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file /sys/fs/pstore/console-ramoops r
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file /proc/last_kmsg r
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```
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Compare each line against the one provided by the example health AIDL HAL
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service in
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[android.hardware.health-service.example.rc](default/android.hardware.health-service.example.rc).
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Specifically:
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* You may ignore the `service` line. The name of the service does not matter.
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* If your service belongs to additional classes beside `charger`, you need a
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custom health AIDL service.
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* You may ignore the `seclabel` line. When the health AIDL service runs in
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charger mode, its original SELinux domain is kept.
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* If your service has a different `user` (not `system`), you need a custom
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health AIDL service.
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* If your service belongs to additional `group`s beside
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`system wakelock input`, you need a custom health AIDL service.
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* If your service requires additional capabilities beside `SYS_BOOT`,
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you need a custom health AIDL service.
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* If your service requires additional `file`s to be opened prior to execution,
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you need a custom health AIDL service.
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## Using the example health AIDL HAL service {#use-example}
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If you [determined](#determine) that the example health AIDL HAL service works
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for your device, install it with
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```mk
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PRODUCT_PACKAGES += android.hardware.health-service.example
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```
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Then, delete any existing `service` with `class charger` in your device-specific
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`init.rc` files, because
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[android.hardware.health-service.example.rc](default/android.hardware.health-service.example.rc)
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already contains an entry for charger.
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If your device supports charger mode and it has custom charger resources,
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[move charger resources to `/vendor`](#charger-res)
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## Implementing a custom health AIDL HAL service {#use-custom}
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### Override the `Health` class {#health-impl}
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See [`Health.h`](default/include/health-impl/Health.h) for its class
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declaration. Inherit the class to customize for your device.
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```c++
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namespace aidl::android::hardware::health {
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class HealthImpl : public Health {
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// ...
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};
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} // namespace aidl::android::hardware::health
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int main(int, char**) {
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// ...
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auto binder = ndk::SharedRefBase::make<aidl::android::hardware::health::HealthImpl>(
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"default", std::move(config));
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// ...
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}
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```
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* The logic to modify `healthd_config`, traditionally in `healthd_board_init()`
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should be called before passing the `healthd_config` struct to your
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`HealthImpl` class in [`main()`](#main).
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* The following functions are similar to the ones in the health 2.1 HIDL HAL:
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| AIDL implementation | HIDL implementation |
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|-------------------------------------|-----------------------------|
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| `Health::getChargeCounterUah` | `Health::getChargeCounter` |
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| `Health::getCurrentNowMicroamps` | `Health::getCurrentNow` |
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| `Health::getCurrentAverageMicroamps`| `Health::getCurrentAverage` |
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| `Health::getCapacity` | `Health::getCapacity` |
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| `Health::getChargeStatus` | `Health::getChargeStatus` |
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| `Health::getEnergyCounterNwh` | `Health::getEnergyCounter` |
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| `Health::getDiskStats` | `Health::getDiskStats` |
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| `Health::getStorageInfo` | `Health::getStorageInfo` |
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| `Health::BinderEvent` | `BinderHealth::BinderEvent` |
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| `Health::dump` | `Health::debug` |
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| `Health::ShouldKeepScreenOn` | `Health::shouldKeepScreenOn`|
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| `Health::UpdateHealthInfo` | `Health::UpdateHealthInfo` |
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### Implement `main()` {#main}
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See the [`main.cpp`](default/main.cpp) for the example health AIDL service for
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an example.
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If you need to modify `healthd_config`, do it before passing it to the
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constructor of `HealthImpl` (or `Health` if you did not implement a subclass
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of it).
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```c++
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int main(int argc, char** argv) {
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auto config = std::make_unique<healthd_config>();
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::android::hardware::health::InitHealthdConfig(config.get());
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healthd_board_init(config.get());
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auto binder = ndk::SharedRefBase::make<Health>("default", std::move(config));
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// ...
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}
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```
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If your device does not support off-line charging mode, or does not have a UI
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for charger (`ro.charger.no_ui=true`), skip the invocation of
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`ChargerModeMain()` in `main()`.
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### SELinux rules
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Add device specific permissions to the domain where the health HAL
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process is executed, especially if a device-specific `libhealthd` is used
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and/or device-specific storage related APIs are implemented.
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If you did not define a separate domain, the domain is likely
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`hal_health_default`. The device-specific rules for it is likely at
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`device/<manufacturer>/<device>/sepolicy/vendor/hal_health_default.te`.
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### Implementing charger {#charger}
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#### Move charger resources to `/vendor`
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Ensure that charger resources are installed to `/vendor`, not `/product`.
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`animation.txt` must be moved to the following location:
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```text
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/vendor/etc/res/values/charger/animation.txt
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```
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Charger resources in `/system` is not read by the health HAL service in
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`/vendor`. Specifically, resources should be installed to the following
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location:
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```
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/vendor/etc/res/images/charger/*.png
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```
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If resources are not found in these locations, the health HAL service falls
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back to the following locations:
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```
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/vendor/etc/res/images/charger/default/*.png
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```
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You can use the default resources by installing the default module:
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```makefile
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PRODUCT_PACKAGES += charger_res_images_vendor
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```
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#### Modify `init.rc` for charger
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It is recommended that you move the existing `service` entry with
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`class charger` to the `init.rc` file in your custom health service.
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Modify the entry to invoke the health service binary with `--charger` argument.
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See
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[android.hardware.health-service.example.rc](default/android.hardware.health-service.example.rc)
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for an example:
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```text
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service vendor.charger-tuna /vendor/bin/hw/android.hardware.health-service-tuna --charger
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# ...
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```
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#### No charger mode {#no-charger}
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If your device does not support off-line charging mode, skip the invocation of
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`ChargerModeMain()` in `main()`.
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```c++
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int main(int, char**) {
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// ...
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// Skip checking if arguments contain "--charger"
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auto hal_health_loop = std::make_shared<HalHealthLoop>(binder, binder);
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return hal_health_loop->StartLoop();
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}
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```
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You may optionally delete the `service` entry with `class charger` in the
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`init.rc` file.
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#### No charger UI {#charger-no-ui}
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If your device does not have a UI for charger (`ro.charger.no_ui=true`), skip
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the invocation of `ChargerModeMain()` in `main()`.
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You may want to keep the `KernelLogger` so that charger still logs battery
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information to the kernel logs.
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```c++
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int main(int argc, char** argv) {
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// ...
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if (argc >= 2 && argv[1] == "--charger"sv) {
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android::base::InitLogging(argv, &android::base::KernelLogger);
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// fallthrough to HalHealthLoop::StartLoop()
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}
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auto hal_health_loop = std::make_shared<HalHealthLoop>(binder, binder);
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return hal_health_loop->StartLoop();
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}
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```
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#### Enable suspend {#charger-enable-suspend}
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If your device has `ro.charger.enable_suspend=true`, implement a new class,
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`ChargerCallbackImpl`, that inherits from
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[`ChargerCallback`](default/include/health-impl/ChargerUtils.h). Then
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override the `ChargerEnableSuspend` function to return `true`. Then pass an
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instance of `ChargerCallbackImpl` to `ChargerModeMain()` instead.
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```c++
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namespace aidl::android::hardware::health {
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class ChargerCallbackImpl : public ChargerCallback {
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bool ChargerEnableSuspend() override { return true; }
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};
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} // namespace aidl::android::hardware::health
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int main(int argc, char** argv) {
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// ...
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if (argc >= 2 && argv[1] == "--charger"sv) {
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android::base::InitLogging(argv, &android::base::KernelLogger);
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#if !CHARGER_FORCE_NO_UI
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return ChargerModeMain(binder,
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std::make_shared<aidl::android::hardware::health::ChargerCallbackImpl>(binder));
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#endif
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}
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// ...
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}
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```
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#### SELinux rules for charger
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If your health AIDL service runs in a domain other than `hal_health_default`,
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add `charger_type` to it so the health HAL service can have charger-specific
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permissions. Example (assuming that your health AIDL service runs in domain
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`hal_health_tuna`:
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```text
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type hal_health_tuna, charger_type, domain;
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hal_server_domain(hal_health_default, hal_health)
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```
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[comment: TODO(b/170338625): explain recovery]: #
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