HIDL学习笔记

2022-09-23 10:37:10

一、HIDL简单介绍

HIDL是Android8.0新出的一个技能，以service和client的方式实现hal接口，目的是想使Android系统和BSP解绑，使系统升级更加方便。HIDL的使用方法一般是先提供.hal文件，然后使用hidl-gen工具生成框架源文件和Android.bp编译工具文件，之后填充生成的源文件和定制Android.bp编译文件。

二、修改源HIDL文件添加hal接口

以Qucomm蓝牙模块额外提供BT MAC地址访问接口为例进行机介绍

[ubuntu @fm]$ tree

.

├── 1.0

│   ├── Android.bp

│   ├── Android.mk

│   ├── hidl-gen.sh

│   ├── IFmHciCallbacks.hal

│   ├── IFmHci.hal

│   └── types.hal

└── Android.bp

1.修改提供.hal文件

# cat vendor/qcom/proprietaryinterfaces/fm/1.0/IFmHci.hal

package vendor.qti.hardware.fm@1.0;

interface IFmHci {

     sendHciCommand(HciPacket command);

+    getBluetoothMacAddress() generates (MacRet mret); //添加这个接口，MacRet (void)类型

};

# cat vendor/qcom/proprietaryinterfaces/fm/1.0/types.hal

package vendor.qti.hardware.fm@1.0;

struct MacRet {     //添加这个结构体

   uint8_t mac0;    //写成数组测试不行，hidl不自持吧。

   uint8_t mac1;

   uint8_t mac2;

   uint8_t mac3;

   uint8_t mac4;

   uint8_t mac5;

   int8_t ret;

};

2.重新生成1.0目录下的Android.bp和Android.mk
这两个文件是hidl-gen根据hal文件自动生成的，用户不要去改。因为hal文件变了，因此需要重新生成。

# rm 1.0/Android.mk

# rm 1.0/Android.bp

# hidl-gen -Landroidbp -r vendor.qti.hardware:vendor/qcom/proprietary/interfaces -r android.hidl:system/libhidl/transport vendor.qti.hardware.fm@1.0

# hidl-gen -Lmakefile -r vendor.qti.hardware:vendor/qcom/proprietary/interfaces -r android.hidl:system/libhidl/transport vendor.qti.hardware.fm@1.0    //一般情况下只需要重新生成Android.bp就可以了。

3.生成hal文件中新添加函数的C++代码实现框架
可以根据hal文件生成cpp文件，然后从新生成的cpp文件中拷贝出getBluetoothMacAddress的cpp实现框架，然后将其拷贝到原cpp文件中。注意，需要在指定在一个临时的目录中生成C++实现框架文件，以免将已经存在原来的C++文件覆盖掉。
# hidl-gen -o tmp_dir -Lc++-impl -r vendor.qti.hardware:vendor/qcom/proprietary/interfaces -r android.hidl:system/libhidl/transport vendor.qti.hardware.fm@1.0
此时会在tmp_dir中生成FmHci.cpp文件和FmHci.h文件,拷贝这两个文件中getBluetoothMacAddress()到原来的C++实现文件的对应位置

# cat FmHci.h

struct FmHci : public IFmHci {

    ...

    Return<void> getBluetoothMacAddress(getBluetoothMacAddress_cb _hidl_cb) override; //拷贝过来

    ...

};

# cat FmHci.cpp

Return<void> FmHci::getBluetoothMacAddress(getBluetoothMacAddress_cb _hidl_cb) { //参数是个回调函数

    bool ret;

    MacRet mret; //这里不需要加struct

    ret = BluetoothAddress::GetLocalAddress((uint8_t *)&mret);

    if (ret == true) {

        mret.ret = true;

    } else {

        memset(&mret, , sizeof(mret));

        mret.ret = false;

    }

     _hidl_cb(mret); //给回调函数传参，回调的函数来自client

     return Void();

}

4.收尾工作
(1)使用using导入使用的元素
FmHci.h中：
using android::hardware::bluetooth::V1_0::implementation::BluetoothAddress; //导入FmHci.cpp文件中使用到的BluetoothAddress::GetLocalAddress()所在的类。
(2)添加头文件搜索路径
在Android.mk中：

LOCAL_C_INCLUDES += vendor/qcom/proprietary/qmi-framework/inc

LOCAL_C_INCLUDES += vendor/qcom/proprietary/qmi/inc

LOCAL_C_INCLUDES += vendor/qcom/proprietary/bt/hci_qcomm_init

若此时能编译成功，则Service端添加的这个hal接口就添加好了。

5.编写测试程序进行验证
一般测试程序放在/external/tools目录下，也可以放在hal实现目录下的vts目录下
(1)编写测试cpp文件

//[ubuntu @btaddr_test]$ cat btaddr_client.cpp

#include <stdio.h>

#include <android/hardware/btaddr/1.0/IBtaddr.h>

#include <android/hardware/btaddr/1.0/types.h>

using ::android::hardware::btaddr::V1_0::IBtaddr;

using ::android::hardware::btaddr::V1_0::MacRet;

using namespace std;

MacRet g_mret;

IBtaddr::getBluetoothMacAddress_cb get_mac_addr(android::hardware::btaddr::V1_0::MacRet mret)

{

    g_mret = mret;

    return nullptr;

}

int main()

{

    android::sp<IBtaddr> service = IBtaddr::getService();

    if (service == nullptr){

        printf("SFL: Failed to get service\n");

        return -;

    }

    service->getBluetoothMacAddress(get_mac_addr);

    printf("MAC=0x%x 0x%x 0x%x 0x%x 0x%x 0x%x\n", g_mret.mac0, g_mret.mac1, g_mret.mac2, g_mret.mac3, g_mret.mac4, g_mret.mac5);

    return ;

}

(2)编写Android.bp

//[ubuntu @btaddr_test]$ cat Android.bp

cc_binary {

    name: "btaddr_test",

    vendor: true,

    srcs: ["btaddr_client.cpp"],

    cflags: ["-Wall"],

    shared_libs: [

        "liblog",

        "libutils",

        "libhidltransport",

        "android.hardware.btaddr@1.0",

        "libhidlbase",

        "libbase",

    ],

}

(3)将测试程序btaddr_test安装到文件系统
在device/qcom/common/base.mk中添加
XX_TEST_APPS += demo_client //XX_TEST_APPS环境变量里面的所有可执行程序都会被编译进文件系统

然后就可以重新烧录验证了。

三、独立实现HIDL文件

1.实现.hal文件

/media/ubuntu/work/g6pa_mount/G6PA_NEW/LINUX/android/hardware/interfaces/btaddr

[hardware/interfaces/btaddr: @btaddr]$ tree

.

├── 1.0

    ├── IBtaddr.hal

    └── types.hal

//# cat 1.0/IBtaddr.hal

package android.hardware.btaddr@1.0;

interface IBtaddr {

    getBluetoothMacAddress() generates (MacRet mret);

};

//# cat 1.0/types.hal

package android.hardware.btaddr@1.0;

struct MacRet {

   uint8_t mac0;

   uint8_t mac1;

   uint8_t mac2;

   uint8_t mac3;

   uint8_t mac4;

   uint8_t mac5;

   int8_t ret;

};

2.由hal文件生成C++实现文件

# hidl-gen -o hardware/interfaces/btaddr/1.0/default -Lc++-impl -randroid.hardware:hardware/interfaces -randroid.hidl:system/libhidl/transport android.hardware.btaddr@1.0

会在1./default下生成Btaddr.cpp 和Btaddr.h

# hidl-gen -o hardware/interfaces/btaddr/1.0/default -Landroidbp-impl -randroid.hardware:hardware/interfaces -randroid.hidl:system/libhidl/transport android.hardware.btaddr@1.0

会在1./default下生成Android.bp

# ./hardware/interfaces/update-makefiles.sh

会在btaddr下生成Android.bp .0下生成Android.bp和Android.mk

此时：

[ubuntu @btaddr]$ tree

.

├── 1.0

│   ├── Android.bp

│   ├── Android.mk

│   ├── default

│   │   ├── Android.bp

│   │   ├── Btaddr.cpp

│   │   └── Btaddr.h

│   ├── IBtaddr.hal

│   └── types.hal

└── Android.bp

3.实现生成C++文件

//[ubuntu @btaddr]$ cat 1.0/default/Btaddr.cpp

#define LOG_TAG "android.hardware.btaddr@1.0-impl"

#include <string.h>

#include <errno.h>

#include "Btaddr.h"

namespace android {

namespace hardware {

namespace btaddr {

namespace V1_0 {

namespace implementation {

// Methods from IBtaddr follow.

Return<void> Btaddr::getBluetoothMacAddress(getBluetoothMacAddress_cb _hidl_cb) {

    MacRet mret;

    mret.ret = ;

    mret.mac0 = 0x11;

    mret.mac1 = 0x22;

    mret.mac2 = 0x33;

    mret.mac3 = 0x44;

    mret.mac4 = 0x55;

    mret.mac5 = 0x66;

    _hidl_cb(mret);

    return Void();

}

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

IBtaddr* HIDL_FETCH_IBtaddr(const char* /* name */) {

    return new Btaddr();

}

}  // namespace implementation

}  // namespace V1_0

}  // namespace btaddr

}  // namespace hardware

}  // namespace android

//[ubuntu @btaddr]$ cat 1.0/default/Btaddr.h

#ifndef ANDROID_HARDWARE_BTADDR_V1_0_BTADDR_H

#define ANDROID_HARDWARE_BTADDR_V1_0_BTADDR_H

#include <android/hardware/btaddr/1.0/IBtaddr.h>

#include <hidl/MQDescriptor.h>

#include <hidl/Status.h>

namespace android {

namespace hardware {

namespace btaddr {

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;

using ::android::hardware::btaddr::V1_0::IBtaddr;

using ::android::hardware::btaddr::V1_0::MacRet;

struct Btaddr : public IBtaddr {

    // Methods from IBtaddr follow.

    Return<void> getBluetoothMacAddress(getBluetoothMacAddress_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" IBtaddr* HIDL_FETCH_IBtaddr(const char* name);

}  // namespace implementation

}  // namespace V1_0

}  // namespace btaddr

}  // namespace hardware

}  // namespace android

#endif  // ANDROID_HARDWARE_BTADDR_V1_0_BTADDR_H

4.添加service.cpp和启动此service的android.hardware.btaddr@1.0-service.rc文件

//[ubuntu @btaddr]# cat 1.0/default/service.cpp

[ubuntu @btaddr]$ cat 1.0/default/service.cpp

#define LOG_TAG "android.hardware.btaddr@1.0-service"

#include <android-base/logging.h>

#include <hidl/HidlTransportSupport.h>

#include <android/hardware/btaddr/1.0/IBtaddr.h>

#include <hidl/LegacySupport.h>

#include "Btaddr.h"

using android::hardware::configureRpcThreadpool;

using android::hardware::joinRpcThreadpool;

using android::hardware::btaddr::V1_0::implementation::Btaddr;

int main()

{

    configureRpcThreadpool(, true);

    Btaddr addr;

    auto status = addr.registerAsService();

    CHECK_EQ(status, android::OK) << "Failed to register btaddr HAL implementation";

    joinRpcThreadpool();

    return ;

}

[ubuntu @btaddr]# cat 1.0/default/android.hardware.btaddr@1.0-service.rc

service btaddr-hal-- /vendor/bin/hw/android.hardware.btaddr@1.0-service

    class core

    user root

    group root

5.修改编译service的Android.bp

[ubuntu @btaddr]# cat 1.0/default/Android.bp

cc_binary {

    name: "android.hardware.btaddr@1.0-service",

    vendor: true,

    relative_install_path: "hw",

    init_rc: ["android.hardware.btaddr@1.0-service.rc"],

    srcs: [

        "Btaddr.cpp",

        "service.cpp",

    ],

    cflags: [

        "-Wall",

    ],

    shared_libs: [

        "libhidlbase",

        "libhidltransport",

        "libutils",

        "android.hardware.btaddr@1.0",

        "liblog",

        "libutils",

        "libbase",

    ],

}

在btaddr下mm，若能build过，Service端就实现好了

6.将编译出的service可执行程序编译进文件系统
在/device/$(Vender)/$(Product)/$(Product).mk中添加: PRODUCT_PACKAGES += android.hardware.btaddr@1.0-service

7.将这个hwservice注册到系统(这样getService()才能找到它) 在/device/$(Vender)/$(Product)/manifest.xml中添加:

<hal format="hidl">

    <name>android.hardware.btaddr</name>

    <transport>hwbinder</transport>

    <version>1.0</version>

    <interface>

        <name>IBtaddr</name>

        <instance>default</instance>

    </interface>

</hal>

8.添加selinux权限
在device/qcom/sepolicy/common/hwservice_contexts中添加：

android.hardware.btaddr::IBtaddr     u:object_r:hal_btaddr_hwservice:s0

android.hardware.btaddr::MacRet      u:object_r:hal_btaddr_hwservice:s0

在device/qcom/sepolicy/common/hwservice.te中添加：

type hal_btaddr_hwservice, hwservice_manager_type;

在device/qcom/sepolicy/msm8996/file_contexts中添加：

/(vendor|system/vendor)/bin/hw/android.hardware.btaddr@1.0-service    u:object_r:hal_btaddr_default_exec:s0

添加文件：device/qcom/sepolicy/msm8996/hal_btaddr_default.te

# cat device/qcom/sepolicy/msm8996/hal_btaddr_default.te 

type hal_btaddr_default, domain;

type hal_btaddr_default_exec, exec_type, vendor_file_type, file_type;

allow hal_btaddr_default sysfs:file rw_file_perms;

allow hal_btaddr_default hwservicemanager_prop:file r_file_perms;

allow hal_btaddr_default hwservicemanager:binder { transfer call };

allow hal_btaddr_default hal_btaddr_hwservice:binder call;

allow hal_btaddr_default hal_btaddr_hwservice:hwservice_manager { add find };

allow hal_btaddr_default hidl_base_hwservice:hwservice_manager add;

init_daemon_domain(hal_btaddr_default)

在/device/qcom/sepolicy/msm8996/hwservicemanager.te中添加：

allow hwservicemanager hal_btaddr_default:process getattr;

allow hwservicemanager hal_btaddr_default:binder { transfer call };

allow hwservicemanager hal_btaddr_default:file r_file_perms;

allow hwservicemanager hal_btaddr_default:dir search;

重新编译系统进行验证。

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