android hidl简单实例1

刚接触android 的hidl，项目中要用到，就尝试写了一个简单的实例。

一、定义HIDL接口文件

1.进入hardware/interfaces/目录下建立新的接口文件

首先建立对应的文件夹：android/hardware/interfaces/sample/1.0/default

接着在android/hardware/interfaces/sample/1.0/目录创建接口描述文件ISample.hal

android/hardware/interfaces/sample/1.0/ISample.hal内容如下：

package android.hardware.sample@1.0;interface ISample {helloWorld(string name) generates (string result);init();
};

2.通过hidl-gen工具（源码中编译生成hidl-gen）生成Sample.cpp，Sample.h ,Android.bp文件。步骤如下：

1.source build/envsetup.sh
2.lunch 9            （根据自己的项目选）
3.export PACKAGE=android.hardware.sample@1.0      //设置变量
4.export LOC=hardware/interfaces/sample/1.0/default/   //设置变量生成目录的所在地
5.hidl-gen -o $LOC -Lc++-impl -randroid.hardware:hardware/interfaces -randroid.hidl:system/libhidl/transport $PACKAGE//在hardware/interfaces/sample/1.0/default/生成Sample.cpp和Sample.h
6.hidl-gen -o $LOC -Landroidbp-impl -randroid.hardware:hardware/interfaces -randroid.hidl:system/libhidl/transport $PACKAGE
//在hardware/interfaces/sample/1.0/default/生成Android.bp
7.在android目录下执行 ./hardware/interfaces/update-makefiles.sh在hardware/interfaces/sample/1.0/目录下生成Android.bp

这时文件目录结构如下

@user-virtual-machine:~/android/hardware/interfaces/sample$ ls 1.0/
Android.bp default ISample.hal
@user-virtual-machine:~/android/hardware/interfaces/sample$ ls 1.0/default/
Android.bp Sample.cpp Sample.h

生成的代码如下：

3.android/hardware/interfaces/sample/1.0/default/Sample.h

去掉注释．采用直通模式

//extern "C" ISample* HIDL_FETCH_ISample(const char* name);

android/hardware/interfaces/sample/1.0/default/Sample.h内容如下#ifndef ANDROID_HARDWARE_SAMPLE_V1_0_SAMPLE_H
#define ANDROID_HARDWARE_SAMPLE_V1_0_SAMPLE_H#include <android/hardware/sample/1.0/ISample.h>
#include <hidl/MQDescriptor.h>
#include <hidl/Status.h>namespace android {
namespace hardware {
namespace sample {
namespace V1_0 {
namespace implementation {using ::android::hardware::hidl_array;
using ::android::hardware::hidl_memory;
using ::android::hardware::hidl_string;
using ::android::hardware::hidl_vec;
using ::android::hardware::Return;
using ::android::hardware::Void;
using ::android::sp;struct Sample : public ISample {// Methods from ::android::hardware::sample::V1_0::ISample follow.Return<void> helloWorld(const hidl_string& name, helloWorld_cb _hidl_cb) override;Return<void> init() override;// Methods from ::android::hidl::base::V1_0::IBase follow.};// FIXME: most likely delete, this is only for passthrough implementationsextern "C" ISample* HIDL_FETCH_ISample(const char* name);}  // namespace implementation
}  // namespace V1_0
}  // namespace sample
}  // namespace hardware
}  // namespace android#endif  // ANDROID_HARDWARE_SAMPLE_V1_0_SAMPLE_H

4.android/hardware/interfaces/sample/1.0/default/Sample.cpp

//ISample* HIDL_FETCH_ISample(const char* /* name */) {
//    return new Sample();
//}

去掉上面的注释

android/hardware/interfaces/sample/1.0/default/Sample.cpp内容如下#include "Sample.h"
namespace android {
namespace hardware {
namespace sample {
namespace V1_0 {
namespace implementation {// Methods from ::android::hardware::sample::V1_0::ISample follow.
Return<void> Sample::helloWorld(const hidl_string& name, helloWorld_cb _hidl_cb) {// TODO implementreturn Void();
}Return<void> Sample::init() {// TODO implementreturn Void();
}// Methods from ::android::hidl::base::V1_0::IBase follow.ISample* HIDL_FETCH_ISample(const char* /* name */) {return new Sample();
}
//
}  // namespace implementation
}  // namespace V1_0
}  // namespace sample
}  // namespace hardware
}  // namespace android

5.上面大部分都是通过hidl工具生成的，下面完善一下接口代码。

android/hardware/interfaces/sample/1.0/default/Sample.cpp#include "Sample.h"
#define LOG_TAG "xingchen"
#include <log/log.h>
namespace android {
namespace hardware {
namespace sample {
namespace V1_0 {
namespace implementation {// Methods from ::android::hardware::sample::V1_0::ISample follow.
Return<void> Sample::helloWorld(const hidl_string& name, helloWorld_cb _hidl_cb) {// TODO implementchar buf[128];::memset(buf,0,128);::snprintf(buf,128,"Hello World,%s",name.c_str());hidl_string result(buf);_hidl_cb(result);//ALOGI("xingchen helloWorld Sample:: ___%s__",__fun__);ALOGI("xingchen helloWorld Sample::----");return Void();
}Return<void> Sample::init() {// TODO implement//ALOGI("xingchen Sample:: ___%s__",__fun__);ALOGI("xingchen Sample::---");return Void();
}// Methods from ::android::hidl::base::V1_0::IBase follow.ISample* HIDL_FETCH_ISample(const char* /* name */) {return new Sample();
}
//
}  // namespace implementation
}  // namespace V1_0
}  // namespace sample
}  // namespace hardware
}  // namespace android

6.android/hardware/interfaces/sample/1.0/default/Android.bp

android/hardware/interfaces/sample/1.0/default/Android.bp内容如下cc_library_shared {// FIXME: this should only be -impl for a passthrough hal.// In most cases, to convert this to a binderized implementation, you should:// - change '-impl' to '-service' here and make it a cc_binary instead of a//   cc_library_shared.// - add a *.rc file for this module.// - delete HIDL_FETCH_I* functions.// - call configureRpcThreadpool and registerAsService on the instance.// You may also want to append '-impl/-service' with a specific identifier like// '-vendor' or '-<hardware identifier>' etc to distinguish it.name: "android.hardware.sample@1.0-impl",relative_install_path: "hw",// FIXME: this should be 'vendor: true' for modules that will eventually be// on AOSP.proprietary: true,srcs: ["Sample.cpp",],shared_libs: ["libhidlbase","libhidltransport","libhardware","libutils","liblog","android.hardware.sample@1.0",],
}

7.到这里基本上代码就写完了，大部分都是生成的,下面开始编译.

 mmm hardware/interfaces/sample/1.0/default/ 生成库文件
/vendor/lib64/hw/android.hardware.sample@1.0-impl.so
/vendor/lib/hw/android.hardware.sample@1.0-impl.so
/system/lib64/android.hardware.sample@1.0.so
/system/lib/android.hardware.sample@1.0.so

二、构建binder service

1.现在有了库，我们还需要构建binder通信服务．

文件名：hardware/interfaces/sample/1.0/default/android.hardware.sample@1.0-service.rc
代码
service sample_service /vendor/bin/hw/android.hardware.sample@1.0-serviceclass haluser systemgroup systemseclabel u:r:init:s0   //我的android9.0的环境关闭了selinux所以加上这行

2.设定sample_service服务．接下来完善服务代码：

文件路径：android/hardware/interfaces/sample/1.0/default/service.cpp
代码：
#define LOG_TAG "android.hardware.sample@1.0-service"#include <android/hardware/sample/1.0/ISample.h>
#include <hidl/LegacySupport.h> //need log libusing android::hardware::sample::V1_0::ISample;
using android::hardware::defaultPassthroughServiceImplementation;int main()
{return defaultPassthroughServiceImplementation<ISample>();
}

3.在Android.bp中添加对服务器的编译：

文件路径：android/hardware/interfaces/sample/1.0/default/Android.bp
在文件最后面加上以下代码
cc_binary {name: "android.hardware.sample@1.0-service",defaults: ["hidl_defaults"],proprietary: true,relative_install_path: "hw",srcs: ["service.cpp"],init_rc: ["android.hardware.sample@1.0-service.rc"],shared_libs: ["libhidlbase","libhidltransport","libhardware","libutils","liblog","android.hardware.sample@1.0",],
}

4.android/hardware/interfaces/sample/1.0/default/如下

为了让服务器被客户端访问到，还需要在device/autochips/ac8257_demo/manifest.xml（不同厂商路径不同）添加如下：

      <hal format="hidl"><name>android.hardware.sample</name><transport>hwbinder</transport><version>1.0</version><interface><name>ISample</name><instance>default</instance></interface></hal>

5.mmm编译生成库文件和service文件

 mmm hardware/interfaces/sample/1.0/default/ 生成库文件和service文件
/vendor/lib64/hw/android.hardware.sample@1.0-impl.so
/vendor/lib/hw/android.hardware.sample@1.0-impl.so
/system/lib64/android.hardware.sample@1.0.so
/system/lib/android.hardware.sample@1.0.so
/vendor/etc/init/android.hardware.sample@1.0-service.rc (在out目录删除文件，项目全编的时候不会生成)
/vendor/bin/hw/android.hardware.sample@1.0-service(在out目录删除文件，项目全编的时候不会生成)

6.修改build/make/target/product/vndk/28.txt和 build/make/target/product/vndk/current.txt

添加如下，记得按照字母排列顺序位置添加

+VNDK-core: android.hardware.sample@1.0.so

三、添加测试程序

/hardware/interfaces/sample/client/helloworld.cpp

文件路径：/hardware/interfaces/sample/client/helloworld.cpp
代码：
#include <android/hardware/sample/1.0/ISample.h>
#include <hidl/Status.h>
#include <hidl/LegacySupport.h>
#include <utils/misc.h>
#include <hidl/HidlSupport.h>
#include <stdio.h>using android::hardware::sample::V1_0::ISample;
using android::sp;
using android::hardware::hidl_string;int main()
{android::sp<ISample> service = ISample::getService();if(service == nullptr){printf("xingchen Failed to get service\n");return -1;}printf("xingchen succeed to get service\n");service->init();return 0;}

/hardware/interfaces/sample/client/Android.mk

文件路径：/hardware/interfaces/sample/client/Android.mk
代码：
LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)
LOCAL_PROPRIETARY_MODULE := true
LOCAL_MODULE := helloworld
LOCAL_SRC_FILES := helloworld.cpp
LOCAL_SHARED_LIBRARIES := \liblog \libhidlbase \libutils \android.hardware.sample@1.0 \include $(BUILD_EXECUTABLE)

四、把上面的service，rc和client端的可执行文件helloworld打包进固件.

/device/autochips/ac8257/device.mk文件中加入代码PRODUCT_PACKAGES += helloworld
PRODUCT_PACKAGES += \android.hardware.sample@1.0-impl \android.hardware.sample@1.0-service

五、全编整个工程并烧入机器。

在全编之前可以把out目录下的上面mmm出来的文件删除,确保全编的时候相关文件可以一起编译出来。

cd out/target/product/ac8257_demo/
find ./system -name "*android.hardware.sample*" | xargs rm -rf
find ./vendor -name "*android.hardware.sample*" | xargs rm -rf

/vendor/lib64/hw/android.hardware.sample@1.0-impl.so
/vendor/lib/hw/android.hardware.sample@1.0-impl.so
/system/lib64/android.hardware.sample@1.0.so
/system/lib/android.hardware.sample@1.0.so
/vendor/etc/init/android.hardware.sample@1.0-service.rc
/vendor/bin/hw/android.hardware.sample@1.0-service (服务端)
/vendor/bin/helloworld   (客户端)

六、启动机器 ps - A | grep android.hardware.sample@1.0-service 发现server已经起来了

logcat -s xingchen & 然后执行客户端helloworld

客户端已经成功调用服务器的接口.

七、遇到的问题

1. 在调试的时候手动执行/vendor/bin/hw/android.hardware.sample@1.0-service出现

CANNOT LINK EXECTABLE ...... :library ......;错误

原因是在hardware/interfaces/sample/1.0/default/Android.bp中加入了"android.hardware.sample@1.0-impl"导致的，删除即可。

cc_binary {name: "android.hardware.sample@1.0-service",defaults: ["hidl_defaults"],proprietary: true,relative_install_path: "hw",srcs: ["service.cpp"],init_rc: ["android.hardware.sample@1.0-service.rc"],shared_libs: ["libhidlbase","libhidltransport","libhardware","libutils","liblog","android.hardware.sample@1.0","android.hardware.sample@1.0-impl", //加入这行导致,删除即可，网上参考，想不到这个地方是个坑],
}

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