在Android 8.0之后版本上添加Hidl Service

1. 编写hal文件并编译

2. 实现Hidl Interface

3. 编写hdil service

4. 配置manifest.xml

5. hidl client端调用

5.1 实现java调用hidl service的例子

5.2 实现C++ 调用hidl service的例子

6. github地址

本文以LED为例在aosp上添加HIDL，以熟悉整个过程。

1. 编写hal文件并编译

在hardware/interfaces/目录下创建led文件夹和基版本1.0，这个版本号分为两部分，major.minor。major版本不变得话，只能添加api，不能修改。

创建ILed.hal和types.hal

hardware/interfaces/led/1.0/ILed.hal

package android.hardware.led@1.0;interface ILed
{//get led status get() generates (LedStatus result);//set led status set(LedStatus  val) generates(int32_t  ret);getBrightnessRange() generates(bool ret,BrightnessRange range);setBrightnessValue(vec<int32_t> range) generates(bool ret);on() ;off() ;};

hardware/interfaces/led/1.0/types.hal

package android.hardware.led@1.0;enum LedStatus : uint32_t {LED_ON,LED_OFF,LED_BAD_VALUE,
};struct BrightnessRange {uint32_t min;uint32_t max;
};

添加完后，执行hardware/interfaces/update-makefiles.sh 会自动生成编译编译脚本，然后在

hardware/interfaces/led/1.0/ 路径下执行mm，会生成所需要得hidl库，接下来我们需要实现hidl interface，供client调用。

2. 实现Hidl Interface

首先实现ILed interface的子类ledImpl 得头文件和对应得cpp。

hardware/interfaces/led/1.0/default/ledImpl.h

#ifndef ANDROID_HARDWARE_LED_V1_0_LED_H
#define ANDROID_HARDWARE_LED_V1_0_LED_H
#include <android/hardware/led/1.0/ILed.h>#include <hidl/Status.h>#include <hidl/MQDescriptor.h>namespace android {
namespace hardware {
namespace led {
namespace V1_0 {
namespace implementation {using ::android::hardware::led::V1_0::LedStatus;
using ::android::hardware::led::V1_0::BrightnessRange;
using ::android::hardware::led::V1_0::ILed;
using ::android::hardware::hidl_array;
using ::android::hardware::hidl_string;
using ::android::hardware::hidl_vec;
using ::android::hardware::Return;
using ::android::hardware::Void;
using ::android::sp;struct ledImpl : public ILed {public:ledImpl();Return<LedStatus>  get() override ;Return<int32_t> set(LedStatus val) override;Return<void> on() override;Return<void> off() override;Return<void> getBrightnessRange(getBrightnessRange_cb _hidl_cb) override;Return<bool> setBrightnessValue(const hidl_vec<int32_t>& range) override;private:LedStatus state;
};extern "C" ILed* HIDL_FETCH_ILed(const char* name);
}  // namespace implementation
}  // namespace V1_0
}  // namespace led
}  // namespace hardware
}  // namespace android#endif //ANDROID_HARDWARE_LED_V1_0_LED_H

hardware/interfaces/led/1.0/default/ledImpl.cpp

#define LOG_TAG "LedService"#include <log/log.h>
#include "ledImpl.h"namespace android {
namespace hardware {
namespace led {
namespace V1_0 {
namespace implementation {ledImpl::ledImpl() {state = LedStatus::LED_BAD_VALUE;ALOGE("ledImpl Init status:%d", state);
}Return<void> ledImpl::on() {state = LedStatus::LED_ON;ALOGE("ledImpl on status:%d", state);return Void();
}Return<void> ledImpl::off() {state = LedStatus::LED_OFF;ALOGE("ledImpl off status:%d", state);    return Void();
}Return<LedStatus>  ledImpl::get() {return state;
}
Return<int32_t> ledImpl::set(LedStatus val) {if(val == LedStatus::LED_OFF || val == LedStatus::LED_ON)state = val;elsereturn -1;return 0;
}Return<void> ledImpl::getBrightnessRange(getBrightnessRange_cb _hidl_cb)
{ALOGE("ledImpl getBrightnessRange ");BrightnessRange range;range.max = 100;range.min = 1;_hidl_cb(true,range);return Void();}Return<bool> ledImpl::setBrightnessValue(const hidl_vec<int32_t>& range)
{ALOGE("ledImpl getBrightnessValue ");auto iter = range.begin();ALOGE("ledImpl getBrightnessValue range.begin: %d",*iter);iter = range.end();ALOGE("ledImpl getBrightnessValue range.end: %d",*iter);ALOGE("ledImpl getBrightnessValue range.size: %zu",range.size());return true;
}ILed* HIDL_FETCH_ILed(const char * /*name*/) {ALOGE("ledImpl HIDL_FETCH_ILed "); return new ledImpl();
}}  // namespace implementation
}  // namespace V1_0
}  // namespace led
}  // namespace hardware
}  // namespace android

hardware/interfaces/led/1.0/default/Android.bp

cc_library_shared {name: "android.hardware.led@1.0-impl",defaults: ["hidl_defaults"],srcs: ["ledImpl.cpp"],shared_libs: ["libhidlbase","libhidltransport","libhardware","liblog","libutils","android.hardware.led@1.0",],
}cc_binary {name: "android.hardware.led@1.0-service",init_rc: ["android.hardware.led@1.0-service.rc"],srcs: ["service.cpp","ledImpl.cpp"],shared_libs: ["liblog","libhardware","libhidlbase","libhidltransport","libutils","android.hardware.led@1.0",], }

3. 编写hdil service

接下来，使用相应功能填写存根并设置守护进程。可以使用passthrough方式和binder方式，示例：

hardware/interfaces/led/1.0/default/service.cpp

#define LOG_TAG "android.hardware.led@1.0-service"#include <android/hardware/led/1.0/ILed.h>
#include <hidl/LegacySupport.h>
#include "ledImpl.h"
using android::hardware::led::V1_0::ILed;
using android::hardware::led::V1_0::implementation::ledImpl;
using android::hardware::defaultPassthroughServiceImplementation;
using android::hardware::configureRpcThreadpool;
using android::hardware::joinRpcThreadpool;
using android::sp;int main() {
#if 0
// Passthrough   dlopen so方式return defaultPassthroughServiceImplementation<Iled>();
#else
// Binder 方式sp<ILed> service = new ledImpl();configureRpcThreadpool(1, true /*callerWillJoin*/);if(android::OK !=  service->registerAsService())return 1; joinRpcThreadpool();
#endif
}

4. 配置manifest.xml

add the code to the manifest.xm 以至于hwservicemanager 查找到指定的hidl service

About HIDL configures

device/<vendorxxx>/<devicexxx>/manifest.xml

 <hal format="hidl"><name>android.hardware.led</name><transport>hwbinder</transport>  //hwbinder 或者passthrough （直通模式）  <version>1.0</version><interface><name>ILed</name><instance>default</instance></interface></hal>

5. hidl client端调用

hidl service运行后，可以通过C++和Java两种方式调用，非常方便，通过java直接访问，就省去了jni。

5.1 实现java调用hidl service的例子

将以下内容添加到 Android.mk 中：

 LOCAL_JAVA_LIBRARIES += android.hardware.led-V1.0-java/*LOCAL_STATIC_JAVA_LIBRARIES += android.hardware.led-V1.0-java-static
*/

或将以下内容添加到 Android.bp 中：

  shared_libs: [/* … */"android.hardware.led-V1.0-java",],

该库还存在静态版：android.hardware.led-V1.0-java-static。

将以下内容添加到您的 Java 文件中：

  import android.hardware.led.V1_0.ILed;...// retry to wait until the service starts up if it is in the manifestILed server = ILed.getService(/* retry */); // throws NoSuchElementException if not availableserver.on();

5.2 实现C++ 调用hidl service的例子

首先将 HAL 库添加到 makefile 中：

  Make：LOCAL_SHARED_LIBRARIES += android.hardware.led@1.0Soong：shared_libs: [ …, android.hardware.led@1.0 ]

接下来，添加 HAL 头文件：

  #include <android/hardware/led/1.0/ILed.h>…// in code:sp<ILed> client = ILed::getService();client->on();

下面是我的Demo clinet

 #define LOG_TAG "LED_CLINET"
#include <android/hardware/led/1.0/ILed.h>
#include <log/log.h>using android::hardware::led::V1_0::ILed;
using android::hardware::led::V1_0::LedStatus;
using android::hardware::led::V1_0::BrightnessRange;
using android::hardware::hidl_vec;
using android::sp;int main(){// BrightnessRange range;sp<ILed> service = ILed::getService();if( service == nullptr ){ALOGE("Can't find ILed service...");return -1;}ALOGE("ILed ON");service->on();ALOGE("ILed OFF");service->off();ALOGE("ILed set");service->set(LedStatus::LED_ON);ALOGE("ILed get");LedStatus ret = service->get();ALOGE("ILed get: %d",ret);service->getBrightnessRange([](bool ret1,BrightnessRange range){ALOGE("ILed getBrightnessRange ret: %d",ret1);ALOGE("ILed getBrightnessRange Max: %d",range.max);ALOGE("ILed getBrightnessRange Min: %d",range.min);});int32_t array[] = {5, 6, 7};hidl_vec<int32_t> hv1 = std::vector<int32_t>(array, array + 3);bool ret2 = service->setBrightnessValue(hv1);ALOGE("ILed getBrightnessValue bool: %d",ret2);return 0;
}

6. github地址

需要看代码的可以去我的github，里面有相关的hidl代码，和C++调用示例

gitHub地址链接