android hidl

1、定义.hal接口文件，如：

在vendor/sprd/interface中新建目录hello，其中定义好hidl接口，如：

 package vendor.sprd.hardware.hello@1.0;

 interface IHello {

     helloWorld(string name) generates (string result);

 };

2、利用hidl-gen工具生成通信框架及业务类模板

# PACKAGE=vendor.sprd.hardware.hello@1.0
# LOC=vendor/sprd/interfaces/hello/1.0/default/
# hidl-gen -o $LOC -Lc++-impl -r vendor.sprd.hardware:vendor/sprd/interfaces -r android.hidl:system/libhidl/transport $PACKAGE
# hidl-gen -o $LOC -Landroidbp-impl -r vendor.sprd.hardware:vendor/sprd/interfaces -r android.hidl:system/libhidl/transport $PACKAGE

这样在default下，可见新生成Hello.cpp  Hello.h文件，此为我们将要实现的业务逻辑类

 struct Hello : public IHello {
     // Methods from ::vendor::sprd::hardware::hello::V1_0::IHello follow.
     Return<void> helloWorld(const hidl_string& name, helloWorld_cb _hidl_cb) override;

     // Methods from ::android::hidl::base::V1_0::IBase follow.

 };

 // FIXME: most likely delete, this is only for passthrough implementations
 // extern "C" IHello* HIDL_FETCH_IHello(const char* name);

在Hello.cpp中实现之

3、运行业务逻辑，上面的Hello.cpp代码需要在进程中运行，所以需要新建一个

创建文件service.cpp、vendor.sprd.hardware.hello@1.0-service.rc，

上面的业务类可以编译成so加载到此进程中，也可以把代码直接编译成bin文件运行。这里采取前者

bp文件如下：

 1 cc_binary {
 2     name: "vendor.sprd.hardware.hello@1.0-service",
 3     init_rc: ["vendor.sprd.hardware.hello@1.0-service.rc"],
 4     relative_install_path: "hw",
 5     vendor: true,
 6
 7     srcs: [
 8         "Hello.cpp",
 9         "service.cpp"
10     ],
11
12     shared_libs: [
13         "libcutils",
14         "liblog",
15         "libhidlbase",
16         "libhidltransport",
17         "libhardware",
18         "libutils",
19         "vendor.sprd.hardware.hello@1.0",
20     ],
21 }

sevice.cpp：

 int main() {
     ALOGD("Hello hidl main()...");

     android::sp<IHello> hello = new Hello();

     configureRpcThreadpool(, true /*callerWillJoin*/);

     if (hello != nullptr) {
         if (::android::OK != hello->registerAsService()) {
             ALOGE("Error while registering IHello service");
             return ;
         }
     } else {
         ALOGE("Can't create instance of Hello, nullptr");
     }

     joinRpcThreadpool();

     return ; // should never get here
 }

4、至此，命令行下启动vendor.sprd.hardware.hello@1.0-service可执行文件，即可运行该hidl服务

5、测试文件：

 int main() {
     int ret;

     android::sp<IHello> service = IHello::getService();
     if (service == nullptr) {
         printf("Failed to get service\n");
         return -;
     }

     service->helloWorld("Trump", [&](hidl_string result) {
             printf("%s\n", result.c_str());
         });

     return ;
 }