Android 15 AIDL Hal 开发指南 —— 添加硬件访问服务

wj071842154
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1. 定义 AIDL

1.1 创建 aidl 文件 frameworks/base/core/java/android/hardware/hello/IHelloHalManager.aidl：

package android.hardware.hello;

/**
 * {@hide}
 */
interface IHelloHalManager {
    void hellohal_write(String str);
    String hellohal_read();
}

1.2 接着编译：

source build/envsetup.sh
lunch sdk_phone64_x86_64-trunk_staging-eng
make update-api
make -j32

2. 硬件服务 Server 端实现

2.1 在 frameworks/base/services/core/java/com/android/server 目录下添加：

hello/
└── HelloService.java

2.2 其中 HelloService.java 的内容如下：

package com.android.server.hello;

import android.Manifest;
import android.annotation.Nullable;
import android.app.ActivityManager;
import android.content.Context;
import android.hardware.hello.*;
import android.os.Binder;
import android.os.Handler;
import android.os.IBinder;
import android.os.Looper;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.os.Trace;
import android.provider.Settings;
import android.util.Slog;
import android.util.SparseArray;

import com.android.internal.annotations.GuardedBy;
import com.android.internal.annotations.VisibleForTesting;
import com.android.internal.display.BrightnessSynchronizer;
import com.android.internal.util.DumpUtils;
import com.android.internal.util.Preconditions;
import com.android.server.SystemService;

import java.io.FileDescriptor;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import android.annotation.NonNull;
import android.hardware.hello.IHelloHalManager;
import android.hardware.hello.IHelloHal;


public class HelloService extends SystemService {

    // aidl hal 服务
    private IHelloHal mVintfHelloHal = null;
    // SystemServer 中的硬件服务
    private IHelloHalManager mHelloManager = null;

    private final class HelloManagerService extends IHelloHalManager.Stub {

        @Override
        public void hellohal_write( @NonNull String str) throws android.os.RemoteException {
            try {
                if(mVintfHelloHal != null) {
                    mVintfHelloHal.hello_write(str);
                }

            } catch (RemoteException e) {
                throw e.rethrowFromSystemServer();
            }
        }

        @Override
        public String hellohal_read() throws android.os.RemoteException {

            try {
                if(mVintfHelloHal != null) {
                    return mVintfHelloHal.hello_read();
                }
            } catch (RemoteException e) {
                throw e.rethrowFromSystemServer();
            }

            return "";

        }
    }

    public HelloService( Context context ) {
        super(context);
        IBinder binder = Binder.allowBlocking(
                ServiceManager.waitForDeclaredService(IHelloHal.DESCRIPTOR + "/default"));
        if (binder != null) {
            mVintfHelloHal = IHelloHal.Stub.asInterface(binder);
        }

        mHelloManager = new HelloManagerService();

    }

    @Override
    public void onStart() {
        publishBinderService("hello", (IBinder)mHelloManager);
    }

    @Override
    public void onBootPhase(int phase) {
    }
}

2.3 接着在 SystemServer 中添加启动服务的代码：

// 不要忘了导包
    import com.android.server.hello.HelloService;

    private void startBootstrapServices(@NonNull TimingsTraceAndSlog t) {
        // ......
        t.traceBegin("StartHelloHalService");
        mSystemServiceManager.startService(HelloService.class);
        t.traceEnd();
        //......
    }

3. 硬件服务客户端辅助代码实现

3.1 接着创建客户端的接口：

// frameworks/base/core/java/android/hardware/hello/HelloServiceManager.java
package android.hardware.hello;

import android.annotation.SystemService;
import android.compat.annotation.UnsupportedAppUsage;
import android.content.Context;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Singleton;
import android.os.ServiceManager;
import android.annotation.Nullable;

/**
 * { @hide }
 */
public final class HelloServiceManager {

    final Context mContext;

    /*
     * @hide
     */
    public HelloServiceManager (Context systemContext) {
        mContext = systemContext;
    }

    /**
     * @hide 只能系统调用
     */
    public static IHelloHalManager getServerice(){
        return I_HELLOHAL_MANAGER_SINGLETON.get();
    }

    //限制framework中的定义无法被外部应用访问
    @UnsupportedAppUsage
    private static final Singleton<IHelloHalManager> I_HELLOHAL_MANAGER_SINGLETON =
            new Singleton<IHelloHalManager>() {
                @Override
                protected IHelloHalManager create() {
                    final IBinder b= ServiceManager.getService("hello");
                    final IHelloHalManager m = IHelloHalManager.Stub.asInterface(b);
                    return m;
                }
            };


    public void hellohal_write( @Nullable String str){
        try{
            getServerice().hellohal_write(str);
            return;
        }catch (RemoteException e){
            throw e.rethrowFromSystemServer();
        }
    }

    @Nullable
    public String hellohal_read() {
        try{
            return getServerice().hellohal_read();
        }catch (RemoteException e){
            throw e.rethrowFromSystemServer();
        }
    }
}

3.2 接着修改 frameworks/base/core/java/android/app/SystemServiceRegistry.java：

// 不要忘了 import 包
import android.hardware.hello.HelloServiceManager;
static {
    //......
    
    registerService("hello", HelloServiceManager.class,
            new CachedServiceFetcher<HelloServiceManager>() {
                @Override
                public HelloServiceManager createService(ContextImpl ctx)
                        throws ServiceNotFoundException {
                    return new HelloServiceManager(ctx);
                }});  
    //......
    
}

3.3 接着编译：

source build/envsetup.sh
lunch sdk_phone64_x86_64-trunk_staging-eng
make update-api
make -j32

4. App 访问硬件服务

简单起见，这里我们直接在 Launcher 中加访问硬件服务的代码。

// packages/apps/Launcher3/src/com/android/launcher3/Launcher.java

// 不要忘了导包
import android.hardware.hello.HelloServiceManager;

    protected void onCreate(Bundle savedInstanceState) {

        HelloServiceManager manager = (HelloServiceManager) getSystemService("hello");
        manager.hellohal_write("nihao");
    }

5. Selinux 配置

5.1 在 system/sepolicy/prebuilts/api/34.0/private/service.te  system/sepolicy/private/service.te system/sepolicy/prebuilts/api/202404/private/service.te中添加：

hello_service, app_api_service, ephemeral_app_api_service, system_server_service, service_manager_type;

5.2 在 system/sepolicy/prebuilts/api/34.0/private/service_contexts system/sepolicy/prebuilts/api/202404/private/service_contexts system/sepolicy/private/service_contexts 中添加：

hello                                     u:object_r:hello_service:s0

5.3 在 system/sepolicy/prebuilts/api/34.0/private/system_app.te system/sepolicy/prebuilts/api/202404/private/system_app.te和 system/sepolicy/private/system_app.te：

allow system_app hello_service:service_manager find;

5.4 在/system/sepolicy/build/soong/service_fuzzer_bindings.go文件中添加如下代码

       "hello":                                  []string{},
       "*":                                      EXCEPTION_NO_FUZZER,
    }
)

6. 编译运行

6.1 接着编译

source build/envsetup.sh
lunch sdk_phone64_x86_64-trunk_staging-eng
make update-api
make -j32

6.2 查看日志

wj071842154@wj071842154:~/android/aosp$ adb logcat | grep hello
09-25 22:52:49.781     0     0 I init    : Parsing file /vendor/etc/init/android.hardware.hello.rc...
09-25 22:52:54.518     0     0 I init    : starting service 'vendor.hellohal-default'...
09-25 22:52:54.523     0     0 I init    : ... started service 'vendor.hellohal-default' has pid 335
09-25 22:52:54.462   335   335 D HelloHalImpl: HelloHalImpl instance =android.hardware.hello.IHelloHal/default  sde =0x74aba1271450 
09-25 22:52:54.590     0     0 I servicemanager: Caller(pid=335,uid=0,sid=u:r:hal_hellohal_default:s0) Found android.hardware.hello.IHelloHal/default in device VINTF manifest.
09-25 22:53:43.380   622   622 I SystemServiceManager: Starting com.android.server.hello.HelloService
09-25 22:53:43.485     0     0 I servicemanager: Caller(pid=622,uid=1000,sid=u:r:system_server:s0) Found android.hardware.hello.IHelloHal/default in device VINTF manifest.
09-25 22:53:43.496   622   622 D SystemServerTiming: OnBootPhase_480_com.android.server.hello.HelloService
09-25 22:53:43.496   622   622 V SystemServerTiming: OnBootPhase_480_com.android.server.hello.HelloService took to complete: 0ms
09-25 22:53:44.038   622   622 D SystemServerTiming: OnBootPhase_500_com.android.server.hello.HelloService
09-25 22:53:44.038   622   622 V SystemServerTiming: OnBootPhase_500_com.android.server.hello.HelloService took to complete: 0ms
09-25 22:53:44.309   622   622 D SystemServerTiming: OnBootPhase_520_com.android.server.hello.HelloService
09-25 22:53:44.309   622   622 V SystemServerTiming: OnBootPhase_520_com.android.server.hello.HelloService took to complete: 0ms
09-25 22:53:45.950   622   622 D SystemServerTiming: OnBootPhase_550_com.android.server.hello.HelloService
09-25 22:53:45.950   622   622 V SystemServerTiming: OnBootPhase_550_com.android.server.hello.HelloService took to complete: 0ms
09-25 22:53:47.493   622   622 D SystemServerTiming: OnBootPhase_600_com.android.server.hello.HelloService
09-25 22:53:47.493   622   622 V SystemServerTiming: OnBootPhase_600_com.android.server.hello.HelloService took to complete: 0ms
09-25 22:53:48.895   622   622 D SystemServerTimingAsync: ssm.onStartUser-0_com.android.server.hello.HelloService
09-25 22:53:48.895   622   622 V SystemServerTimingAsync: ssm.onStartUser-0_com.android.server.hello.HelloService took to complete: 0ms
09-25 22:54:01.207   622   656 D ActivityManagerTiming: OnBootPhase_1000_com.android.server.hello.HelloService
09-25 22:54:01.207   622   656 V ActivityManagerTiming: OnBootPhase_1000_com.android.server.hello.HelloService took to complete: 0ms
09-25 22:54:03.877   622   665 D SystemServerTimingAsync: ssm.onUnlockingUser-0_com.android.server.hello.HelloService
09-25 22:54:03.877   622   665 V SystemServerTimingAsync: ssm.onUnlockingUser-0_com.android.server.hello.HelloService took to complete: 0ms
09-25 22:54:05.118   622   665 D SystemServerTimingAsync: ssm.onUnlockedUser-0_com.android.server.hello.HelloService
09-25 22:54:05.118   622   665 V SystemServerTimingAsync: ssm.onUnlockedUser-0_com.android.server.hello.HelloService took to complete: 0ms
09-25 22:54:10.247   622  1758 D SystemServerTimingAsync: ssm.onCompletedEventUser-0_{|Unlocked|}_com.android.server.hello.HelloService
    09-25 22:54:10.248   622  1758 V SystemServerTimingAsync: ssm.onCompletedEventUser-0_{|Unlocked|}_com.android.server.hello.HelloService took to complete: 1ms

AIDL Hal 开发指南8 —— 添加硬件访问服务

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