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Android11+ AIDL：专为提升应用性能而生！ 原创 saltfish saltfish Android系统攻城狮 在小说阅读器读本章 去阅读 在小说阅读器中沉浸阅读 点击下方👇关注 Android系统攻城狮每日充电：OS+MultiMedia学习之旅1.前言学习理念：一次理解一个知识点难度：★★★★☆源码环境：Android 12硬件环境：SDM845阅读时间：1.5分钟接着上一篇Android HAL发展历程：探索HAL到HIDL四个阶段的演进过程文章，我们已经介绍了HAL到HIDL发展的历程。Android11版本开始，AIDL引入实现HAL同样的功能，可以调用HAL，也可以直接和内核驱动通信。下面看一下HIDL和AIDL通信过程，AIDL比起传统通信方式有哪些优点？接着实现一个AIDL实现用例，读者可以和上一篇文章HIDL实现服务做一个对比，看看它们之间的差异在哪里？1.先看一个HIDL模式通信路线图：图一2.再看一个AIDL模式通信路线图：图二通过图一和图二比较，就能知道谷歌为什么要在Android 10以后逐渐去除HIDL通信模式。AIDL优势很明显，它在应用端直接获取AIDL Service后，可以直接给AIDL的服务端发送IPC通信，在服务端直接调用HAL的API或者直接通过open("/dev/xxx")与驱动通信。与传统的AIDL比起来，中间少了两三个通信环节，效率会显著提升。下面写一个AIDL使用Binder IPC通信的例子。2.AIDL客户端1.创建aidl接口# mkdir -p hardware/interfaces/invcase/aidl/android/hardware/invcase# emacs IInvcase.aidlpackage android.hardware.invcase; @VintfStabilityinterface IInvcase { String getChars(); void putChars(in String msg);}2.创建Android.bp# cd hardware/interfaces/invcase/aidl# emacs Android.bpaidl_interface { name: "android.hardware.invcase", vendor: true, srcs: ["android/hardware/invcase/*.aidl"], stability: "vintf", owner: "vqtrong", backend: { cpp: { enabled: false, }, java: { sdk_version: "module_current", }, },}3.编译与配置1.执行以下命令：编译报错# mmm hardware/interfaces/invcase/aidl 2.执行以下操作后，再编译aidl# m android.hardware.invcase-update-api -j12 3.再编译aidl# mmm hardware/interfaces/invcase/aidl 4.将invacase模块配置编译到系统# emacs build/make/target/product/base_vendor.mkPRODUCT_PACKAGES += android.hardware.invcase 到此AIDL客户端创建完成，接下来创建AIDL Server端。3.AIDL Server端1.AIDL对应Server端头文件实现# emacs hardware/interfaces/invcase/aidl/default/Invcase.h#pragma once#include <aidl/android/hardware/invcase/BnInvcase.h>namespace aidl {namespace android {namespace hardware {namespace invcase { class Invcase : public BnInvcase { public: //AIDL：String getChars(); ndk::ScopedAStatus getChars(std::string* _aidl_return); //AIDL：void putChars(in String msg); ndk::ScopedAStatus putChars(const std::string& in_msg);};} } } } 2.AIDL对应Server端c++实现# emacs hardware/interfaces/invcase/aidl/default/Invcase.cpp#define LOG_TAG "Invcase" #include <utils/Log.h>#include <iostream>#include <fstream>#include "Invcase.h" namespace aidl { namespace android { namespace hardware { namespace invcase { //String getChars(); ndk::ScopedAStatus Invcase::getChars(__unused std::string* _aidl_return) { std::string str = "I am from HAL layer"; *_aidl_return = str; ALOGE("%s, %s(), line = %d, HAL: send_to_app: %s",__FILE__,__FUNCTION__,__LINE__,str.c_str()); return ndk::ScopedAStatus::ok(); } //void putChars(in String msg); ndk::ScopedAStatus Invcase::putChars(__unused const std::string& in_msg) { ALOGE("%s, %s(), line = %d, HAL: recive_from_app = %s",__FILE__,__FUNCTION__,__LINE__,in_msg.c_str()); return ndk::ScopedAStatus::ok(); } } } } } 在Invcase::getChars和Invcase::putChars函数中添加对驱动程序的访问即可。在这里我只是写了打印语句。到这里AIDL的Server端也实现完成，我们要将实现的内容注册成一个AIDL服务，可以通过Binder完成IPC通信。4.创建AIDL IPC通信1.注册AIDL服务# emacs hardware/interfaces/invcase/aidl/default/service.cpp#define LOG_TAG "Invcase"#include <android-base/logging.h>#include <android/binder_manager.h>#include <android/binder_process.h>#include <binder/ProcessState.h>#include <binder/IServiceManager.h>#include "Invcase.h"using aidl::android::hardware::invcase::Invcase;using std::string_literals::operator""s; int main() { android::ProcessState::initWithDriver("/dev/vndbinder"); ABinderProcess_setThreadPoolMaxThreadCount(0); ABinderProcess_startThreadPool(); std::shared_ptr<Invcase> invcase = ndk::SharedRefBase::make<Invcase>(); const std::string name = Invcase::descriptor + "/default"s; ALOGE("%s, %s(), line = %d, descriptor = %s, name = %s,",__FILE__,__FUNCTION__,__LINE__,Invcase::descriptor,name.c_str()); if(AServiceManager_addService(invcase->asBinder().get(), name.c_str()) != STATUS_OK) { ALOGE("Failed to register IInvcase service"); return -1; } ALOGE("IInvcase service starts to join s
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