Android 6.0 如何添加完整的系统服务(app-framework-kernel)

最近学习了如何在Android 6.0上添加一个系统服务，APP如何通过新增的系统服务访问底层驱动。
在这学习过程中，收获颇多，并结合学习了《Embeded Android》--Karim Yaghmour 一书中的
Appendix B. Adding Support For New Hardware章节，受益匪浅，讲述了如何添加一个完整的系统
服务（app->framework->kernel）。尽管描述的非常详细，但是基于Android 2.3.7描述的。现在把
书中的opersys例子移植到Android 6.0上，虽然说不上复杂，但由于版本差异，难免会出现许多奇奇
怪怪的问题，甚至版本差异造成了bug出现。特以此移植记录分享学习过程。

主要围绕以下几个步骤添加一个完整的系统服务：
(A) 添加circular-char驱动
(B) 添加opersyshw_qemu HAL
(C) 添加com_android_server_opersys_OpersysService JNI
(D) 添加IOpersysService接口
(E) 添加OpersysService
(F) 添加OpersysManager
(G) 添加系统服务
(H) 注册服务
(I) 更新API
(J) 设置权限
(K) 测试服务
(L) 添加测试APP

(A) 添加circular-char驱动

circular-char是一个简单的字符设备驱动，其实现的功能就是一个简单的FIFO，APP可以通过
read、write来进行读写操作实验，即写数据到FIFO，可以从FIFO读出写入的数据。

kernel/drivers/circular-driver/circular-char.c

  1 #include <linux/module.h>
  2 #include <linux/miscdevice.h>
  3 #include <linux/fs.h>
  4 #include <asm/uaccess.h>
  5 
  6 #define BUF_SIZE 200
  7 
  8 static char buf[BUF_SIZE];
  9 static char *read_ptr;
 10 static char *write_ptr;
 11 
 12 static int device_open(struct inode *inode, struct file *file)
 13 {
 14   printk("device_open called 
");
 15 
 16   return 0;
 17 }
 18 
 19 static int device_release(struct inode *inode, struct file *file)
 20 {
 21   printk("device_release called 
");
 22 
 23   return 0;
 24 }
 25 
 26 static ssize_t device_read(struct file *filp,   /* see include/linux/fs.h   */
 27                char *buffer,    /* buffer to fill with data */
 28                size_t length,   /* length of the buffer     */
 29                loff_t * offset)
 30 {
 31   int chars_read = 0;
 32 
 33   printk("device_read called 
");
 34 
 35   while(length && *read_ptr && (read_ptr != write_ptr)) {
 36     put_user(*(read_ptr++), buffer++);
 37 
 38     printk("Reading %c 
", *read_ptr);
 39 
 40     if(read_ptr >= buf + BUF_SIZE)
 41       read_ptr = buf;
 42 
 43     chars_read++;
 44     length--;
 45   }
 46 
 47   return chars_read;
 48 }
 49 
 50 static ssize_t
 51 device_write(struct file *filp, const char *buff, size_t len, loff_t * off)
 52 {
 53   int i;
 54 
 55   printk("device_write called 
");
 56 
 57   for(i = 0; i < len; i++) {
 58     get_user(*write_ptr, buff++);
 59     printk("Writing %c 
", *write_ptr);
 60     write_ptr++;
 61     if (write_ptr >= buf + BUF_SIZE)
 62       write_ptr = buf;
 63   }
 64 
 65   return len;
 66 }
 67 
 68 static struct file_operations fops = {
 69   .open = device_open,
 70   .release = device_release,
 71   .read = device_read,
 72   .write = device_write,
 73 };
 74 
 75 static struct miscdevice circ_char_misc = {
 76   .minor = MISC_DYNAMIC_MINOR,
 77   .name = "circchar",
 78   .fops = &fops,
 79 };
 80 
 81 int circ_char_enter(void)
 82 {
 83   int retval;
 84 
 85   retval = misc_register(&circ_char_misc);
 86   printk("CIRC Driver got retval %d
", retval);
 87   printk("mmap is %08X
", (int) fops.mmap);
 88 
 89   read_ptr = buf;
 90   write_ptr = buf;
 91 
 92   return 0;
 93 }
 94 
 95 void circ_char_exit(void)
 96 {
 97   misc_deregister(&circ_char_misc);
 98 }
 99 
100 module_init(circ_char_enter);
101 module_exit(circ_char_exit);

kernel/drivers/circular-driver/Kconfig

 1 menuconfig DRIVER_FOR_TEST
 2     bool "Drivers for test"
 3     help
 4       Drivers for test.
 5       If unsure, say no.
 6 
 7 if DRIVER_FOR_TEST
 8 
 9 config CIRCULAR_CHAR
10     tristate "circular-char"
11     help
12       circular-char driver.
13 
14 endif

kernel/drivers/circular-driver/Makefile

1 obj-$(CONFIG_CIRCULAR_CHAR)     += circular-char.o

kernel/drivers/Kconfig

1 ......
2 source "drivers/circular-driver/Kconfig"
3 ......

kernel/drivers/Makefile

1 ......
2 obj-$(CONFIG_DRIVER_FOR_TEST) += circular-driver/
3 ......

kernel/arch/arm/configs/xxx_defconfig

......
CONFIG_DRIVER_FOR_TEST=y
CONFIG_CIRCULAR_CHAR=y
......

驱动已添加到内核，编译烧录到目标板看是否加载成功：

    # ls dev/circchar
    ls dev/circchar
    dev/circchar
    #echo hello > dev/circchar
    echo hello > dev/circchar
    #cat dev/circchar
    dev/circchar
    hello

如果执行以上命令，输出对应得信息，则说明驱动加载成功。

(B) 添加opersyshw_qemu HAL

这里添加一个opersys的HAL层，使应用和驱动分离，hal主要向应用提供open、read、write等几个
接口。

hardware/libhardware/tests/opersyshw/opersyshw_qemu.c

  1 #define  LOG_TAG  "opersyshw_qemu"                                                                                 
  2 #include <cutils/log.h>
  3 #include <cutils/sockets.h>                                                                                        
  4 #include <sys/types.h>                                                                                             
  5 #include <sys/stat.h>                                                                                              
  6 #include <fcntl.h>
  7 #include <hardware/opersyshw.h>                                                                                    
  8 #include <malloc.h>                                                                                                
  9 
 10 #define   OPERSYSHW_DEBUG   1                                                                                      
 11 
 12 #if OPERSYSHW_DEBUG
 13 #  define D(...)   ALOGD(__VA_ARGS__)                                                                              
 14 #else
 15 #  define D(...)   ((void)0)                                                                                       
 16 #endif                                                                                                             
 17 
 18 static int fd = 0;                                                                                                 
 19 
 20 static int opersyshw__read(char* buffer, int length)                                                               
 21 {   
 22     int retval;                                                                                                    
 23     
 24     D("OPERSYS HW - read()for %d bytes called", length);                                                           
 25     
 26     retval = read(fd, buffer, length);    
 27     D("read data from driver: %s", buffer);
 28 
 29     return retval;
 30 }
 31    
 32 static int opersyshw__write(char* buffer, int length)
 33 {
 34     int retval;
 35 
 36     D("OPERSYS HW - write()for %d bytes called", length);
 37 
 38     retval = write(fd, buffer, length);
 39     D("write data to driver: %s", buffer);
 40 
 41     return retval;
 42 }
 43 
 44 static int opersyshw__close(void)
 45 {
 46     if (fd != -1) {
 47         if (!close(fd)) {
 48             return 0;
 49         }
 50     }
 51 
 52     return -1;
 53 }
 54 
 55 static int opersyshw__test(int value)
 56 {
 57     return value;
 58 }
 59 
 60 static int open_opersyshw(const struct hw_module_t* module, char const* name,
 61         struct hw_device_t** device)
 62 {
 63     struct opersyshw_device_t *dev = malloc(sizeof(struct opersyshw_device_t));
 64     if (!dev) {
 65         D("OPERSYS HW failed to malloc memory !!!");
 66         return -1;
 67     }
 68 
 69     memset(dev, 0, sizeof(*dev));
 70 
 71     dev->common.tag = HARDWARE_DEVICE_TAG;
 72     dev->common.version = 0;
 73     dev->common.module = (struct hw_module_t*)module;
 74     dev->read = opersyshw__read;
 75     dev->write = opersyshw__write;
 76     dev->close = opersyshw__close;
 77     dev->test = opersyshw__test;
 78 
 79     *device = (struct hw_device_t*) dev;
 80 
 81     fd = open("/dev/circchar", O_RDWR);
 82     if (fd < 0) {
 83         D("failed to open /dev/circchar!");
 84         return 0;
 85     }
 86 
 87     D("OPERSYS HW has been initialized");
 88 
 89     return 0;
 90 }
 91 
 92 static struct hw_module_methods_t opersyshw_module_methods = {
 93     .open = open_opersyshw,
 94 };
 95 
 96 struct hw_module_t HAL_MODULE_INFO_SYM = {
 97     .tag = HARDWARE_MODULE_TAG,
 98     .version_major = 1,
 99     .version_minor = 0,
100     .id = OPERSYSHW_HARDWARE_MODULE_ID,
101     .name = "Opersys HW Module",
102     .author = "Opersys inc.",
103     .methods = &opersyshw_module_methods,
104 };

hardware/libhardware/include/hardware/opersyshw.h

 1 #ifndef ANDROID_OPERSYSHW_INTERFACE_H
 2 #define ANDROID_OPERSYSHW_INTERFACE_H
 3 
 4 #include <stdint.h>
 5 #include <sys/cdefs.h>
 6 #include <sys/types.h>
 7 
 8 #include <hardware/hardware.h>
 9     
10 __BEGIN_DECLS
11 
12 #define OPERSYSHW_HARDWARE_MODULE_ID "opersyshw"
13 
14 struct opersyshw_device_t {
15     struct hw_device_t common;
16 
17     int (*read)(char* buffer, int length);
18     int (*write)(char* buffer, int length);
19     int (*close)(void);
20     int (*test)(int value);
21 };
22 
23 __END_DECLS
24 
25 #endif // ANDROID_OPERSYSHW_INTERFACE_H

hardware/libhardware/tests/opersyshw/Android.mk

 1 LOCAL_PATH := $(call my-dir)
 2     
 3 # HAL module implemenation, not prelinked and stored in
 4 # hw/<GPS_HARDWARE_MODULE_ID>.<ro.hardware>.so
 5 include $(CLEAR_VARS)
 6 LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hw
 7 LOCAL_CFLAGS += $(common_flags)
 8 LOCAL_LDLIBS += -llog
 9 LOCAL_C_INCLUDES := hardware/libhardware
10 LOCAL_SHARED_LIBRARIES := liblog libcutils libhardware
11 LOCAL_SRC_FILES := opersyshw_qemu.c
12 LOCAL_MODULE := opersyshw.$(TARGET_BOARD_PLATFORM)
13 LOCAL_MODULE_TAGS := optional
14 include $(BUILD_SHARED_LIBRARY)

编译之后看看是否错误，是否生成.so文件，在源码根目录下：

    # find ./out/ -name 'opersyshw.*.so'
    ......
    ./out/target/product/<project>/system/lib/hw/opersyshw.sc8830.so
    ......

注意Android.mk中的$(TARGET_BOARD_PLATFORM)，这里是sc8830，不同的平台会有差异

(C) 添加com_android_server_opersys_OpersysService JNI

JNI接口主要是为了Java（app）调用C/C++。

frameworks/base/services/core/jni/com_android_server_opersys_OpersysService.cpp

  1 #define LOG_TAG "OpersysServiceJNI"
  2 
  3 #include "jni.h"
  4 #include "JNIHelp.h"
  5 #include "android_runtime/AndroidRuntime.h"
  6 
  7 #include <utils/misc.h>
  8 #include <utils/Log.h>
  9 #include <hardware/hardware.h>
 10 #include <hardware/opersyshw.h>
 11 
 12 #include <stdio.h>
 13 
 14 namespace android
 15 {
 16 
 17 opersyshw_device_t* opersyshw_dev;
 18 
 19 static jint init_native(JNIEnv *env, jobject /* clazz */)
 20 {
 21     int err;
 22     hw_module_t* module;
 23     opersyshw_device_t* dev = NULL;
 24 
 25     //ALOGI("init_native()"); 
 26 
 27     err = hw_get_module(OPERSYSHW_HARDWARE_MODULE_ID, (hw_module_t const**)&module);
 28     if (err == 0) {
 29         if (module->methods->open(module, "", ((hw_device_t**) &dev)) != 0) {
 30             ALOGE("Can't open opersys module!!!");
 31             return 0;
 32         }
 33     } else {
 34         ALOGE("Can't get opersys module!!!");
 35         return 0;
 36     }
 37 
 38     return (jint)dev;
 39 }
 40 
 41 static void finalize_native(JNIEnv *env, jobject /* clazz */, int ptr)
 42 {
 43     opersyshw_device_t* dev = (opersyshw_device_t*)ptr;
 44 
 45     //ALOGI("finalize_native()");
 46 
 47     if (dev == NULL) {
 48         return;
 49     }
 50 
 51     dev->close();
 52 
 53     free(dev);
 54 }
 55 
 56 static int read_native(JNIEnv *env, jobject /* clazz */, int ptr, jbyteArray buffer)
 57 {
 58     opersyshw_device_t* dev = (opersyshw_device_t*)ptr;
 59     jbyte* real_byte_array;
 60     int length;
 61 
 62     //ALOGI("read_native()");
 63 
 64     real_byte_array = env->GetByteArrayElements(buffer, NULL);
 65 
 66     if (dev == NULL) {
 67         return 0;
 68     }
 69 
 70     length = dev->read((char*) real_byte_array, env->GetArrayLength(buffer));
 71 
 72     ALOGI("read data from hal: %s", (char *)real_byte_array);
 73 
 74     env->ReleaseByteArrayElements(buffer, real_byte_array, 0);
 75 
 76     return length;
 77 }
 78 
 79 static int write_native(JNIEnv *env, jobject /* clazz */, int ptr, jbyteArray buffer)
 80 {
 81     opersyshw_device_t* dev = (opersyshw_device_t*)ptr;
 82     jbyte* real_byte_array;
 83     int length;
 84 
 85     //ALOGI("write_native()");
 86 
 87     real_byte_array = env->GetByteArrayElements(buffer, NULL);
 88 
 89     if (dev == NULL) {
 90         return 0;
 91     }
 92 
 93     length = dev->write((char*) real_byte_array, env->GetArrayLength(buffer));
 94 
 95     ALOGI("write data to hal: %s", (char *)real_byte_array);
 96 
 97     env->ReleaseByteArrayElements(buffer, real_byte_array, 0);
 98 
 99     return length;
100 }
101 
102 
103 static int test_native(JNIEnv *env, jobject /* clazz */, int ptr, int value)
104 {
105     opersyshw_device_t* dev = (opersyshw_device_t*)ptr;
106 
107     if (dev == NULL) {
108         return 0;
109     }
110 
111     ALOGI("test_native()");
112 
113     return dev->test(value);
114 }
115 
116 static JNINativeMethod method_table[] = {
117     { "init_native", "()I", (void*)init_native },
118     { "finalize_native", "(I)V", (void*)finalize_native },
119     { "read_native", "(I[B)I", (void*)read_native },
120     { "write_native", "(I[B)I", (void*)write_native },
121     { "test_native", "(II)I", (void*)test_native}
122 };
123 
124 int register_android_server_opersys_OpersysService(JNIEnv *env)
125 {
126     return jniRegisterNativeMethods(env, "com/android/server/opersys/OpersysService",
127             method_table, NELEM(method_table));
128 
129 };

frameworks/base/services/core/jni/onload.cpp

 1 ......
 2 namespace android {
 3 ......
 4 int register_android_server_opersys_OpersysService(JNIEnv* env);
 5 ......
 6 };
 7 
 8 ....
 9 
10 extern "C" jint JNI_OnLoad(JavaVM* vm, void* /* reserved */)
11 {
12 ......
13 register_android_server_opersys_OpersysService(env);
14 ......
15 }

frameworks/base/services/core/jni/Android.mk

1 ......
2 LOCAL_SRC_FILES += 
3 ......
4 $(LOCAL_REL_DIR)/com_android_server_opersys_OpersysService.cpp 
5 ......

(D) 添加IOpersysService接口

IOpersysService主要用于实现一个进程间通信的接口，其内部机制就是通过Binder实现进程间通信的，
即客户端与服务端(OpersysService)分别处于不同的进程中，客户端和服务端之间不能够直接相互访问，
之间必须通过Binder传递。

frameworks/base/core/java/android/opersys/IOpersysService.aidl

1 interface IOpersysService {
2 /**
3 * {@hide}
4 */
5 String read(int maxLength);
6 int write(String mString);
7 }

frameworks/base/Android.mk

1 ......
2 LOCAL_SRC_FILES += 
3 ......
4 core/java/android/opersys/IOpersysService.aidl 
5 ......

其中，aidl文件主要用于生成同名的.java文件IOpersysService.java，IOpersysService.java主要实现
了一些Binder相关的设置和相关接口。
编译后，会在out目录下生成：

out/target/common/obj/JAVA_LIBRARIES/framework_intermediates/src/core/java/android/opersys/IOpersysService.java

(E) 添加OpersysService

OpersysService主要充当一个服务端（server），直接调用native如：

private static native int init_native();
private static native void finalize_native(int ptr);
private static native int read_native(int ptr, byte[] buffer);
private static native int write_native(int ptr, byte[] buffer);
private static native int test_native(int ptr, int value);

这些方法对应的是frameworks/base/services/core/jni/com_android_server_opersys_OpersysService.cpp
对应的同名函数，视觉上就像Java直接调用了C/C++一样。

frameworks/base/services/core/java/com/android/server/opersys/OpersysService.java

 1 package com.android.server.opersys;
 2 
 3 import android.content.Context;
 4 import android.os.Handler;
 5 import android.opersys.IOpersysService;
 6 import android.os.Looper;
 7 import android.os.Message;
 8 import android.os.Process;
 9 import android.util.Slog;
10 import android.os.RemoteException;
11 
12 public class OpersysService extends IOpersysService.Stub {
13     private static final String TAG = "OpersysService";
14     private Context mContext;
15     private int mNativePointer;
16 
17     public OpersysService(Context context) {
18         super();
19         mContext = context;
20         Slog.i(TAG, "Opersys Service started");
21 
22         mNativePointer = init_native();
23 
24         Slog.i(TAG, "test() returns " + test_native(mNativePointer, 20));
25     }
26 
27     protected void finalize() throws Throwable {
28         finalize_native(mNativePointer);
29         super.finalize();
30     }    
31     
32     public String read(int maxLength) throws RemoteException
33     {
34         int length;
35         byte[] buffer = new byte[maxLength];
36 
37         length = read_native(mNativePointer, buffer);
38 
39         try {
40             return new String(buffer, 0, length, "UTF-8");
41         } catch (Exception e) {
42             Slog.e(TAG, "read buffer error!");
43             return null;
44         }
45     }
46 
47     public int write(String mString) throws RemoteException
48     {
49         byte[] buffer = mString.getBytes();
50 
51         return write_native(mNativePointer, buffer);
52     }
53 
54     private static native int init_native();
55     private static native void finalize_native(int ptr);
56     private static native int read_native(int ptr, byte[] buffer);
57     private static native int write_native(int ptr, byte[] buffer);
58     private static native int test_native(int ptr, int value);
59 }

(F) 添加OpersysManager

OpersysManager主要用于管理OpersysService，实例化了IOpersysService，在注册服务的
时候就是实例化了一个OpersysManager，APP(客户端)获取服务getService时也是获得这个对象，通过这个对象，APP就

可以调用该服务的相关接口（API）了

frameworks/base/core/java/android/opersys/OpersysManager.java

 1 package android.opersys;
 2 
 3 import android.content.Context;
 4 import android.os.RemoteException;
 5 import android.opersys.IOpersysService;
 6 import android.util.Slog;
 7 
 8 public class OpersysManager
 9 {
10     private static final String TAG = "OpersysManager";
11 
12     public String read(int maxLength) {
13         try {
14             return mService.read(maxLength);
15         } catch (RemoteException e) {
16             Slog.e(TAG, "read error!");
17             return null;
18         }
19     }
20 
21     public int write(String mString) {
22         try {
23             return mService.write(mString);
24         } catch (RemoteException e) {
25             Slog.e(TAG, "write error!");
26             return 0;
27         }    
28     }
29 
30     public OpersysManager(Context context, IOpersysService service) {
31         mService = service;
32     }
33 
34     IOpersysService mService;
35 }

(G) 添加系统服务addService

实现了OpersysService的各种接口之后，需要向SystemServer添加服务

frameworks/base/services/java/com/android/server/SystemServer.java

 1 ......
 2 import com.android.server.opersys.OpersysService;
 3     ......
 4 private void startOtherServices() {
 5     ......
 6     OpersysService opersys = null;
 7     ......
 8     if (mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL) { 
 9         ......
10         try {
11             Slog.i(TAG, "Opersys Service");
12             opersys = new OpersysService(context);                                                             
13             Slog.i(TAG, "Add Opersys Service");
14             ServiceManager.addService(Context.OPERSYS_SERVICE, opersys);                                       
15             Slog.i(TAG, "Opersys Service Succeed!");                                                           
16         } catch (Throwable e) {
17             Slog.e(TAG, "Failure starting OpersysService Service", e);                                         
18         }
19         ......
20     }
21 }

frameworks/base/core/java/android/content/Context.java

 1 ......
 2     @StringDef({
 3         ......
 4         OPERSYS_SERVICE,
 5         ......
 6     })
 7     ......
 8     /**
 9      * Use with {@link #getSystemService} to retrieve a
10      * {@link android.opersys.OpersysManager} for using Opersys Service.
11      *
12      * @see #getSystemService
13      */
14     public static final String OPERSYS_SERVICE = "opersys";
15     ......

(H) 注册服务

frameworks/base/core/java/android/app/SystemServiceRegistry.java

 1 ......
 2 import android.opersys.OpersysManager;
 3 import android.opersys.IOpersysService;
 4 ......
 5 final class SystemServiceRegistry {
 6     ......
 7     static {
 8         ......
 9         registerService(Context.OPERSYS_SERVICE, OpersysManager.class,
10                 new CachedServiceFetcher<OpersysManager>() {
11             @Override
12             public OpersysManager createService(ContextImpl ctx) {
13                 IBinder b = ServiceManager.getService(Context.OPERSYS_SERVICE);
14                 IOpersysService service = IOpersysService.Stub.asInterface(b);
15                 if (service == null) {
16                     return null;
17                 }
18                 return new OpersysManager(ctx, service);
19             }});
20         ......
21     }
22     ......
23 }
24 ......

到这里，主要工作都要完成了，貌似可以直接可以编译进行测试了。但是实际上还有些东西需要
设置，如编译设置，SeLinux安全设置等。

(I) 更新API

在前面添加和注册了服务之后，需要更新一下API才能正常编译。

frameworks/data-binding/compiler/src/main/resources/api-versions.xml

1 ......
2 <field name="OPERSYS_SERVICE" />
3 ......

在源码目录下：

 # make update-api -j16

编译通过后，会自动更新以下两个文件
frameworks/base/api/current.txt

......
field public static final java.lang.String OPERSYS_SERVICE = "opersys";
......
package android.opersys {

  public abstract interface IOpersysService implements android.os.IInterface {
    method public abstract int write(java.lang.String) throws android.os.RemoteException;
  }

  public static abstract class IOpersysService.Stub extends android.os.Binder implements android.opersys.IOpersysService {
    ctor public IOpersysService.Stub();
    method public android.os.IBinder asBinder();
    method public static android.opersys.IOpersysService asInterface(android.os.IBinder);
    method public boolean onTransact(int, android.os.Parcel, android.os.Parcel, int) throws android.os.RemoteException;
  }

  public class OpersysManager {
    ctor public OpersysManager(android.content.Context, android.opersys.IOpersysService);
    method public java.lang.String read(int);
    method public int write(java.lang.String);
  }

}
......

frameworks/base/api/system-current.txt更新同上

(J) 设置权限

external/sepolicy/service.te

1 ......
2 type opersys_service, app_api_service, system_server_service, service_manager_type;
3 ......

external/sepolicy/service_contexts

1 ......
2 opersys                                   u:object_r:opersys_service:s0
3 ......

device/<manufacturer>/<chip>/common/sepolicy/device.te

1 ......
2 type circchar_device, dev_type;
3 ......

device/<manufacturer>/<chip>/common/sepolicy/file_contexts

1 ......
2 /dev/circchar        u:object_r:circchar_device:s0
3 ......

device/<manufacturer>/<chip>/common/sepolicy/system_server.te

1 ......
2 allow system_server circchar_device:chr_file { open read write ioctl };
3 ......

system/core/rootdir/ueventd.rc

1 ......
2 /dev/circchar         0660   system     system
3 ......

(K) 测试服务

完成以上步骤后，全编译一次，烧录后，可先通过命令测试一下服务是否正常启动：

    # service check opersys
    service check opersys
    Service opersys：found
    # service list 
    service list
    ......
    24      opersys: [android.opersys.IOpersysService]
    ......
    # service call opersys 2 s16 "Hello, World!"
    service call opersys 2 s16 "Hello, World!"
    Result: Parcel(00000000 0000000d    '........')
    # service call opersys 1 i32 20
    service call opersys 1 i32 20
    Result: Parcel(
    0x00000000: 00000000 0000000d 00650048 006c006c '........H.e.l.l.'
    0x00000010: 002c006f 00570020 0072006f 0064006c 'o.,. .W.o.r.l.d.'
    0x00000020: 00000021                            '!...            ')

执行以上命令得到对应的结果后，说明服务启动正常。接下来就可以在APP上使用了。

(L) 添加测试APP

这个APP的功能是，当用户打开APP时，APP会获得OpersysService服务，然后向这个服务发送
“Hello Opersys”，然后从这个服务读回。

packages/apps/HelloOpersysInternal/src/com/opersys/hellointernal/HelloOpersysInternalActivity.java

 1 package com.opersys.hellointernal;                                                                                 
 2                                                                                                                    
 3 import android.app.Activity;                                                                                       
 4 import android.os.Bundle;                                                                                          
 5 import android.util.Log;                                                                                           
 6 import android.os.ServiceManager;   // Will only work in AOSP                                                      
 7 //import android.opersys.IOpersysService;  // Interface "hidden" in SDK                                            
 8 import android.opersys.OpersysManager;                                                                             
 9 import android.content.Context;                                                                                    
10                                                                                                                    
11 public class HelloOpersysInternalActivity extends Activity {                                                       
12     private static final String DTAG = "HelloOpersysInternal";                                                     
13                                                                                                                    
14     /** Called when the activity is first created. */                                                              
15     @Override                                                                                                      
16     public void onCreate(Bundle savedInstanceState) {                                                              
17         super.onCreate(savedInstanceState);                                                                        
18         setContentView(R.layout.main);                                                                             
19                                                                                                                    
20         //IOpersysService om = IOpersysService.Stub.asInterface(ServiceManager.getService("opersys"));             
21                                                                                                                    
22         OpersysManager om = (OpersysManager)getSystemService(Context.OPERSYS_SERVICE);                             
23         try {                                                                                                      
24             Log.d(DTAG, "Going to write to the "opersys" service");                                              
25             om.write("Hello Opersys");                                                                             
26             Log.d(DTAG, "Service returned: " + om.read(20));                                                       
27         }                                                                                                          
28         catch (Exception e) {                                                                                      
29             Log.d(DTAG, "FAILED to call service");                                                                 
30             e.printStackTrace();
31         }
32     }
33 }

packages/apps/HelloOpersysInternal/res/layout/main.xml

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:layout_width="fill_parent"
 4     android:layout_height="fill_parent"
 5     android:orientation="vertical" >
 6 
 7     <TextView
 8         android:layout_width="fill_parent"
 9         android:layout_height="wrap_content"
10         android:text="@string/hello" />
11 
12 </LinearLayout>

packages/apps/HelloOpersysInternal/res/values/strings.xml

1 <?xml version="1.0" encoding="utf-8"?>
2 <resources>
3 
4     <string name="hello">Hello World, HelloOpersysInternalActivity!</string>
5     <string name="app_name">HelloOpersysInternal</string>
6 
7 </resources>

packages/apps/HelloOpersysInternal/AndroidManifest.xml

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
 3     package="com.opersys.hellointernal"
 4     android:versionCode="1"
 5     android:versionName="1.0" >
 6 
 7     <uses-sdk android:minSdkVersion="10" />
 8 
 9     <application
10         android:icon="@drawable/ic_launcher"
11         android:label="@string/app_name" >
12         <activity
13             android:label="@string/app_name"
14             android:name=".HelloOpersysInternalActivity" >
15             <intent-filter >
16                 <action android:name="android.intent.action.MAIN" />
17 
18                 <category android:name="android.intent.category.LAUNCHER" />
19             </intent-filter>
20         </activity>
21     </application>
22 
23 </manifest>

packages/apps/HelloOpersysInternal/Android.mk

 1 LOCAL_PATH:= $(call my-dir)
 2 include $(CLEAR_VARS)
 3 
 4 LOCAL_MODULE_TAGS := optional
 5     
 6 LOCAL_SRC_FILES := $(call all-java-files-under, src)
 7 
 8 LOCAL_PACKAGE_NAME := HelloOpersysInternal
 9 
10 include $(BUILD_PACKAGE)

vendor/sprd/open-source/common_packages.mk

1 PRODUCT_PACKAGES += 
2 ......
3 HelloOpersysInternal
4 ......

到这里，已经完成了所有步骤，全编译烧录之后，打开HelloOpersysInternalAPP，再打开
logcat，可以看到以下信息：

01-01 08:07:56.137  3729  3729 D HelloOpersysInternal: Going to write to the "opersys" service

01-01 08:07:56.140  1272  3082 D opersyshw_qemu: OPERSYS HW - write()for 13 bytes called

01-01 08:07:56.140  1272  3082 D opersyshw_qemu: write data to driver: Hello Opersys

01-01 08:07:56.140  1272  3082 I OpersysServiceJNI: write data to hal: Hello Opersys

01-01 08:07:56.142  1272  3032 D opersyshw_qemu: OPERSYS HW - read()for 20 bytes called

01-01 08:07:56.142  1272  3032 D opersyshw_qemu: read data from driver: Hello Opersys

01-01 08:07:56.142  1272  3032 I OpersysServiceJNI: read data from hal: Hello Opersys

01-01 08:07:56.143  3729  3729 D HelloOpersysInternal: Service returned: Hello Opersys

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原文地址：https://www.cnblogs.com/hackfun/p/7418902.html