树莓派4B android 系统添加led灯 Hal 层

本文内容需要用到我上一篇文章做的驱动，可以先看文章https://blog.csdn.net/ange_li/article/details/136759249

一、Hal 层的实现

1.Hal 层的实现一般放在 vendor 目录下，我们在 vendor 目录下创建如下的目录

aosp/vendor/arpi/hardware/interfaces/rbg_led_control_hidl/1.0

接着在aosp/vendor/arpi/hardware/interfaces/rbg_led_control_hidl/1.0 目录下创建Hal文件ILedControl.hal

//定义包名，最后跟一个版本号
package arpi.hardware.rbg_led_control_hidl@1.0;
//定义 hidl 服务对外提供的接口
interface ILedControl {
    //开灯
    openLed(uint32_t red,uint32_t blue,uint32_t green) generates (uint32_t result);
    //读 hello 驱动
    closeLed() generates (uint32_t result);
};

2. hal 文件生成 C++ 源文件

接着我们使用 hidl-gen 命令将我们写的 hal 文件转换为 C++ 文件：

source build/envsetup.sh
lunch rpi4-eng
PACKAGE=arpi.hardware.rbg_led_control_hidl@1.0
LOC=vendor/arpi/hardware/interfaces/rbg_led_control_hidl/1.0/default
hidl-gen -o $LOC -Lc++-impl -rarpi.hardware:vendor/arpi/hardware/interfaces $PACKAGE

接着就会生成一些 C++ 代码：生成下图中的LedControl.h LedControl.cpp

接着修改 LedControl.cpp

// FIXME: your file license if you have one

#include "LedControl.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>

namespace arpi::hardware::rbg_led_control_hidl::implementation {

// Methods from ::arpi::hardware::rbg_led_control_hidl::V1_0::ILedControl follow.
Return<uint32_t> LedControl::openLed(uint32_t red, uint32_t blue, uint32_t green) {
    int fd = open("/dev/led_drv", O_RDWR);
    if (fd == -1){
	printf("can not open file /dev/led_drv\n");
	return  uint32_t { 0 };
    }
    char r[]="red";
    char b[]="blue";
    char g[]="green";
    char cmd[14]="";
    if(red==1){
     	strcat(cmd, r);
    }
    if(blue==1){
     	strcat(cmd, b);
    }
    if(green==1){
     	strcat(cmd, g);
    }
    ::write(fd, cmd, strlen(cmd) +1);
    close(fd);
    return uint32_t {1};
}

Return<uint32_t> LedControl::closeLed() {
    int fd = open("/dev/led_drv", O_RDWR);
    if (fd == -1){
	printf("can not open file /dev/led_drv\n");
	return  uint32_t { 0 };
    }
    char cmd[14]="";
    ::write(fd, cmd, strlen(cmd) +1);
    close(fd);
    return uint32_t {1};
}


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

//ILedControl* HIDL_FETCH_ILedControl(const char* /* name */) {
    //return new LedControl();
//}
//
}  // namespace arpi::hardware::rbg_led_control_hidl::implementation

这里主要是对我们的协议进行实现，实现了对上一节实现的设备文件 /dev/led_drv 的读写。至此我们的 hidl 服务就定义好了

3. 服务端实现

接着我们需要写一个 Server 端来向 HwServiceManager 注册我们的服务。在vendor/arpi/hardware/interfaces/rbg_led_control_hidl/1.0/default 目录下添加 service.cpp(参考上图)

#include <hidl/HidlTransportSupport.h>
#include <utils/Looper.h>
#include <utils/StrongPointer.h>
#include <log/log.h>
#include "LedControl.h"

using android::hardware::configureRpcThreadpool;
using android::hardware::joinRpcThreadpool;
using arpi::hardware::rbg_led_control_hidl::V1_0::ILedControl;
using arpi::hardware::rbg_led_control_hidl::implementation::LedControl;

int main() {
    ALOGD("hello-hidl is starting...");

    configureRpcThreadpool(4, true /* callerWillJoin */);

    android::sp<ILedControl> service = new LedControl();
    android::status_t ret = service->registerAsService();

    if (ret != android::NO_ERROR) {
    }

    joinRpcThreadpool();

    return 0;
    //Passthrough模式
    //return defaultPassthroughServiceImplementation<IHello>(4);
}

我们的服务端需要在开机时启动，vendor/arpi/hardware/interfaces/rbg_led_control_hidl/1.0/default 目录下创建arpi.hardware.rbg_led_control_hidl@1.0-service.rc 文件

service vendor_rbg_led_control_hidl_service /vendor/bin/hw/arpi.hardware.rbg_led_control_hidl@1.0-service
	class hal
	user system
	group system

接着我们需要添加 VINTF 对象，对于注册到 hwservicemanager 的服务都需要添加一个 VINTF 对象。对于编码来说 VINTF 对象就是一个 xml 文件，vendor/arpi/hardware/interfaces/rbg_led_control_hidl/1.0/default 目录下创建arpi.hardware.rbg_led_control_hidl@1.0-service.xml

<manifest version="1.0" type="device">
  <hal format="hidl">
        <name>arpi.hardware.rbg_led_control_hidl</name>
        <transport>hwbinder</transport>
        <version>1.0</version>
        <interface>
            <name>ILedControl</name>
            <instance>default</instance>
        </interface>
    </hal>
</manifest>

4 生成 Android.bp

hidl-gen -o $LOC -Landroidbp-impl -rarpi.hardware:vendor/arpi/hardware/interfaces $PACKAGE

该命令会在vendor/arpi/hardware/interfaces/rbg_led_control_hidl/1.0/default 目录下创建Android.bp

简单修改该文件：

// FIXME: your file license if you have one

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: "arpi.hardware.rbg_led_control_hidl@1.0-impl",
    relative_install_path: "hw",
    // FIXME: this should be 'vendor: true' for modules that will eventually be
    // on AOSP.
    proprietary: true,
    srcs: [
        "LedControl.cpp",
    ],
    shared_libs: [
        "libhidlbase",
        "libhidltransport",
        "libutils",
        "arpi.hardware.rbg_led_control_hidl@1.0",
        "liblog",
    ],
}

cc_binary {
    name: "arpi.hardware.rbg_led_control_hidl@1.0-service",
    init_rc: ["arpi.hardware.rbg_led_control_hidl@1.0-service.rc"],
    vintf_fragments: ["arpi.hardware.rbg_led_control_hidl@1.0-service.xml"],
    defaults: ["hidl_defaults"],
    relative_install_path: "hw",
    vendor: true,
    srcs: ["service.cpp", "LedControl.cpp"],
    shared_libs: [
        "arpi.hardware.rbg_led_control_hidl@1.0",
        "libhardware",
        "libhidlbase",
        "libhidltransport",
        "libutils",
        "liblog",
    ],
}

生成的库里面有一个依赖 arpi.hardware.rbg_led_control_hidl@1.0，接着我们来生成这个库对应的 Android.bp：

在vendor/arpi/hardware/interfaces/下创建update-makefiles.sh

#!/bin/bash

source $ANDROID_BUILD_TOP/system/tools/hidl/update-makefiles-helper.sh

do_makefiles_update \
  "arpi.hardware:vendor/arpi/hardware/interfaces"

接着执行：

./vendor/arpi/hardware/interfaces/update-makefiles.sh

结果生成文件aosp/vendor/arpi/hardware/interfaces/rbg_led_control_hidl/Android.bp

// This file is autogenerated by hidl-gen -Landroidbp.

hidl_interface {
    name: "arpi.hardware.rbg_led_control_hidl@1.0",
    root: "arpi.hardware",
    system_ext_specific: true,
    srcs: [
        "ILedControl.hal",
    ],
    interfaces: [
        "android.hidl.base@1.0",
    ],
    gen_java: true,
}

这个过程会生成一些so 库。

随后在aosp/vendor/arpi/hardware/interfaces下创建Android.bp （告诉编译系统包名与路径的映射关系）

hidl_package_root {
    name: "arpi.hardware",
    path: "vendor/arpi/hardware/interfaces",
}

接着创建aosp/vendor/arpi/hardware/interfaces/current.txt

ecf0cea3adff3da5319d360d2e86c3a4b336aa64e798f1fc4eb3dc2abbd6905f arpi.hardware.rbg_led_control_hidl@1.0::ILedControl

再执行一遍 update-makefiles.sh，这个时候就会发现提示 hash 值不正确了，同时会给出正确的 hash 值，我们把正确的 hash 值替换到 current.txt 即可。

5 test客户端编写

vendor/arpi/hardware/interfaces/rbg_led_control_hidl/1.0/default 目录下创建test文件夹

Android.bp

cc_binary {
    name: "rbg_led_control_hidl_test",
    srcs: ["rbg_led_control_hidl_test.cpp"],
    vendor: true,
    shared_libs: [
        "liblog",
        "arpi.hardware.rbg_led_control_hidl@1.0",
        "libhidlbase",
        "libhidltransport",
        "libhwbinder",
        "libutils",
    ],
}

#include <arpi/hardware/rbg_led_control_hidl/1.0/ILedControl.h>
#include <hidl/LegacySupport.h>

#define LOG_TAG "rbg_led_control_hidl"
#include <log/log.h>

using android::sp;
using arpi::hardware::rbg_led_control_hidl::V1_0::ILedControl;
using android::hardware::Return;
using android::hardware::hidl_string;

int main(){
    android::sp<ILedControl> hw_device = ILedControl::getService();
    if (hw_device == nullptr) {
              ALOGD("failed to get rbg_led_control_hidl");
              return -1;
        }
    ALOGD("success to rbg_led_control_hidl....");
   
    hw_device->openLed(1,0,0);
  
    return 0;
}

上面测试代码可以点亮led 红灯

6 selinux 配置

在aosp/device/arpi/rpi4/sepolicy 目录下

device.te 中添加如下内容:

type led_drv_t, dev_type;

hwservice.te：

type rbg_led_control_hidl_hwservice, hwservice_manager_type;

rbg_led_control_hidl.te：

# type rbg_led_control_hidl, domain;



type rbg_led_control_hidl, domain;
type rbg_led_control_hidl_exec, exec_type, vendor_file_type, file_type;

init_daemon_domain(rbg_led_control_hidl);
add_hwservice(rbg_led_control_hidl, rbg_led_control_hidl_hwservice)
hwbinder_use(rbg_led_control_hidl)


allow rbg_led_control_hidl hidl_base_hwservice:hwservice_manager { add };
allow rbg_led_control_hidl led_drv_t:chr_file { open read write };
binder_call(rbg_led_control_hidl,hwservicemanager)
get_prop(rbg_led_control_hidl,hwservicemanager_prop)

hwservice_contexts：

arpi.hardware.rbg_led_control_hidl::ILedControl      u:object_r:rbg_led_control_hidl_hwservice:s0

rbg_led_control_hidl_test.te：

type  rbg_led_control_hidl_test, domain;
type  rbg_led_control_hidl_test_exec, exec_type, vendor_file_type, file_type;

domain_auto_trans(shell, rbg_led_control_hidl_test_exec, rbg_led_control_hidl_test);

get_prop(rbg_led_control_hidl_test, hwservicemanager_prop);
allow rbg_led_control_hidl_test rbg_led_control_hidl_hwservice:hwservice_manager find;
hwbinder_use(rbg_led_control_hidl_test);

file_contexts：

/dev/led_drv                    u:object_r:led_drv_t:s0
/vendor/bin/hw/arpi\.hardware\.rbg_led_control_hidl@1\.0-service    u:object_r:rbg_led_control_hidl_exec:s0

7 编译执行

接着在aosp/device/arpi/rpi4/rpi4.mk 加入程序

PRODUCT_PACKAGES += \
    arpi.hardware.rbg_led_control_hidl@1.0-service \
    rbg_led_control_hidl_test \
    arpi.hardware.rbg_led_control_hidl@1.0-impl \

 source build/envsetup.sh
 lunch rpi4-eng
 make ramdisk systemimage vendorimage

最后测试（点亮led）：

rbg_led_control_hidl_test &