一.HIDL介绍

HIDL的全称是HAL interface definition language（硬件抽象层接口定义语言），是Android
Framework 与Android HAL之间的接口。HIDL 旨在用于进程间通信 (IPC)，进程之间的通信
采用 Binder 机制。

二.HIDL 与AIDL 的对比

三.HIDL接口添加 

HIDL接口路径：

hardware\interfaces\imw\1.0\

路径下有两个文件：

Android.bpIImwManager.hal

Android.bp：

hidl_interface {name: "vendor.isolution.hardware.imw@1.0",  //FQName 的全名root: "vendor.isolution.hardware",  //定义好的 package root name//system_ext_specific: true,srcs: ["IImwManager.hal",],interfaces: ["android.hidl.base@1.0", //编译过程中依赖的接口名称],gen_java: true,  //是否编译为 Java 使用的接口
}

IImwManager.hal文件：

package vendor.isolution.hardware.imw@1.0; // 当前package包名import IImwManagerClientCallback;  // 导入其它package包
import IUpdateEngineClientCallback;interface IImwManager   // 定义一个interface
{onCreate();onInitStart();onInitCompleted();onStart();onSystemAppStart();onBootanimationExit();onBootCompleted();onReboot();onRecovery();onSleep();onShutdown();};

HIDL生成的文件路径：

/out/soong/.intermediates/vendor/isolution/hardware/interfaces/imw/1.0/vendor.isolution.hardware.imw@1.0

编译后模块对应的文件：

vendor.isolution.hardware.imw@1.0.so

当 IHelloworld.hal 创建完成就可以创建对应的 HIDL 实现代码（Hidl Interface 和 service）:

service.端java代码：

import vendor.isolution.hardware.imw.V1_0.IImwManager; // 导入package包private IImwManager halManager = null;halManager.onCreate();
halManager.onInitStart();
halManager.onInitCompleted();
halManager.onStart();
halManager.onSystemAppStart();
halManager.onBootanimationExit();
halManager.onBootCompleted();
halManager.onReboot();
halManager.onRecovery();
halManager.onSleep();
halManager.onShutdown();

实现Hidl Interface:

hardware\interfaces\imw\1.0\default\ImwManager.h

#ifndef VENDOR_ISOLUTION_HARDWARE_IMW_V1_0_IMWMANAGER_H_
#define VENDOR_ISOLUTION_HARDWARE_IMW_V1_0_IMWMANAGER_H_#include <log/log.h>
#include <android/log.h>
#include <hardware/hardware.h>
#include <hardware/fingerprint.h>
#include <hidl/MQDescriptor.h>
#include <hidl/Status.h>#include <vendor/isolution/hardware/imw/1.0/IImwManager.h>using ::vendor::isolution::hardware::imw::V1_0::IImwManager;
using ::android::hardware::Return;
using ::android::hardware::Void;
using ::android::hardware::hidl_vec;
using ::android::hardware::hidl_string;
using ::android::sp;namespace vendor {
namespace isolution {
namespace hardware {
namespace imw {
namespace V1_0 {
namespace implementation {struct ImwManager : public IImwManager {public:ImwManager();~ImwManager();static IImwManager* getInstance();Return<void> setNotify(const sp<IImwManagerClientCallback>& clientCallback) override;Return<void> setNotifyUpdateEngine(const sp<IUpdateEngineClientCallback>& clientCallback) override;Return<void> onCreate() override;Return<void> onInitStart() override;Return<void> onInitCompleted() override;Return<void> onStart() override;Return<void> onSystemAppStart() override;Return<void> onBootanimationExit() override;Return<void> onBootCompleted() override;Return<void> onReboot() override;Return<void> onRecovery() override;Return<void> onSleep() override;Return<void> onShutdown() override;
};}  // namespace implementation
}  // namespace V1_0
}  // namespace imw
}  // namespace hardware
}  // namespace isolution
}  // namespace vendor

hardware\interfaces\imw\1.0\default\ImwManager.cpp

#include <utils/Log.h>#include <log/log.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <dirent.h>
#include <unistd.h>
#include <string.h>
#include <cutils/atomic.h>
#include <cutils/properties.h> // for property_get
#include <utils/misc.h>
#include <stdio.h>
#include <utils/threads.h>#include <fcntl.h>
#include <dlfcn.h>
#include <sys/shm.h>
#include <signal.h>#include "ImwManager.h"namespace vendor {
namespace isolution {
namespace hardware {
namespace imw {
namespace V1_0 {
namespace implementation {ImwManager::ImwManager() : mClientCallback(nullptr) {sInstance = this; // keep track of the most recent instanceonCreate();
}ImwManager::~ImwManager()
{ALOGW("~ImwManager\n");
}IImwManager* ImwManager::getInstance() {if (!sInstance) {sInstance = new ImwManager();}return sInstance;
}Return<void> ImwManager::onCreate()
{ALOGW("onCreate\n");return Void();
}Return<void> ImwManager::onInitStart()
{ALOGW("onInitStart\n");return Void();
}Return<void> ImwManager::onInitCompleted()
{ALOGW("onInitCompleted\n");return Void();
}Return<void> ImwManager::onStart()
{ALOGW("onStart\n");return Void();
}Return<void> ImwManager::onSystemAppStart()
{ALOGW("onSystemAppStart\n");return Void();
}Return<void> ImwManager::onBootanimationExit()
{ALOGW("onBootanimationExit\n");return Void();
}Return<void> ImwManager::onBootCompleted()
{ALOGW("onBootCompleted\n");return Void();
}Return<void> ImwManager::onReboot()
{ALOGW("onReboot\n");return Void();
}Return<void> ImwManager::onRecovery()
{ALOGW("onRecovery\n");return Void();
}Return<void> ImwManager::onSleep()
{ALOGW("onSleep\n");return Void();
}Return<void> ImwManager::onShutdown()
{ALOGW("onShutdown\n");return Void();
}ImwManager *ImwManager::sInstance = nullptr;}  // namespace implementation
}  // namespace V1_0
}  // namespace imw
}  // namespace hardware
}  // namespace isolution
}  // namespace vendor

添加rc文件：

rc 是 “runcom” 的缩写，这个术语最初来源于 Unix 系统，在早期的系统中使用了一个叫做 “runcom” 的目录，用于存放启动时需要运行的一些脚本和配置文件。

在实现了 serivce 和 impl 代码后需要添加 rc 文件，文件名为 vendor.isolution.hardware.imw@1.0-service.rc

service imw-hal-1-0 /vendor/bin/hw/vendor.isolution.hardware.imw@1.0-serviceclass haluser rootgroup root media system graphics input bluetooth shell drmrpc media_rw audio