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(1, true /*callerWillJoin*/);

    if (hello != nullptr) {
        if (::android::OK != hello->registerAsService()) {
            ALOGE("Error while registering IHello service");
            return 1;
        }
    } else {
        ALOGE("Can't create instance of Hello, nullptr");
    }

    joinRpcThreadpool();

    return 0; // 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 -1;
    }

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

    return 0;
}