欢迎来到Doc100.Net免费学习资源知识分享平台!
您的位置:首页 > 程序异常 >

android 驱动开发系列4

更新时间: 2014-01-05 03:20:00 责任编辑: Author_N1

 

Android 驱动开发系列四

 

时隔多日,终于都抽出时间来写blog了。废话不多说,接着上一篇,这里将介绍如何编写HAL层(硬件抽象层)对应的JNI方法。

这里提到的都是在ICS源码里编译的。

 

1、定义JNI层接口

进入到android-4.0.4_r1.2/hardware/libhardware/include/hardware目录,并创建 ttt.h 文件,内容如下:

#ifndef	ANDROID_TTT_INTERFACE_H
#define	ANDROID_TTT_INTERFACE_H
#include <hardware/hardware.h>

__BEGIN_DECLS

// 定义模块ID
#define	HELLO_HARDWARE_MODULE_ID	"ttt"

// 硬件模块结构体
struct ttt_module_t{
    struct hw_module_t common;
};

// hardware interface struct
struct ttt_device_t{
	struct hw_device_t common;
	int fd;
	int(*set_val)(struct ttt_device_t* dev, int val);
	int(*get_val)(struct ttt_device_t* dev, int* val);
};

__END_DECLS


#endif

 

2、实现JNI层接口功能

进入到android-4.0.4_r1.2/frameworks/base/services/jni目录,并创建com_android_server_TTTService.cpp文件,其内容如下:

#define LOG_TAG     "TTTService"

#include "jni.h"
#include "JNIHelp.h"
#include "android_runtime/AndroidRuntime.h"
#include <utils/misc.h>
#include <utils/Log.h>
#include <hardware/hardware.h>
#include <hardware/ttt.h>
#include <stdio.h>

namespace android
{
    struct ttt_device_t* ttt_device = NULL;

    // through the HAL interface to set the register value
    static void ttt_setVal(JNIEnv* env, jobject clazz, jint value){
        int val = value;
        LOGI("TTT JNI: set value %d to device.", val);
        if(!ttt_device){
            LOGI("TTT JNI: device is not open.");
            return;
        }

        ttt_device->set_val(ttt_device, val);
    }

    // through the HAL interface to read the register value
    static jint ttt_getVal(JNIEnv* env, jobject clazz){
        int val = 0;
        if(!ttt_device){
            LOGI("TTT JNI: device is not open.");
            return val;
        }
        ttt_device->get_val(ttt_device, &val);

        LOGI("TTT JNI: get value %d from device.", val);

        return val;
    }

    // through the HAL interface to open the hardware device
    static inline int ttt_device_open(const hw_module_t* module, struct ttt_device_t** device){
        return module->methods->open(module, HELLO_HARDWARE_MODULE_ID, (struct hw_device_t**)device);
    }

    // throught the hardware module ID to load the HAL module and open the device
    static jboolean ttt_init(JNIEnv* env, jclass clazz){
        ttt_module_t* module;

        LOGI("TTT JNI: initializing...");
        if(hw_get_module(HELLO_HARDWARE_MODULE_ID, (const struct hw_module_t**)&module) == 0){
            LOGI("TTT JNI: ttt stub found.");
            if(ttt_device_open(&(module->common), &ttt_device) == 0){
                LOGI("TTT JNI: ttt device is open.");
                return 0;
            }
            LOGE("TTT JNI: failed to open ttt device.");
            return -1;
        }

        LOGE("TTT JNI: failed to get ttt stub module.");
        return -1;
    }

    // JNI methods table
    static const JNINativeMethod method_table[] = {
        {"init_native", "()Z", (void*)ttt_init},
        {"setVal_native", "(I)V", (void*)ttt_setVal},
        {"getVal_native", "()I", (void*)ttt_getVal},
    };

    // regist JNI method
    int register_android_server_TTTService(JNIEnv* env){
        return jniRegisterNativeMethods(env, "com/android/server/TTTService", method_table, NELEM(method_table));
    }
};


 

3、添加JNI初始化调用

修改android-4.0.4_r1.2/frameworks/base/services/jni目录下的 onload.cpp 文件,在 JNI_OnLoad函数中的return之前添加下面一句:

register_android_server_TTTService(env);

同时,在该文件中的namespace中添加下面一句声明:

int register_android_server_TTTService(JNIEnv* env);

 

这样,在系统初始化时,就会调用register_android_server_TTTService方法来加载JNI方法了。

 

4、添加编译JNI的配置

修改android-4.0.4_r1.2/frameworks/base/services/jni目录下的 Android.mk 文件,在 LOCAL_SRC_FILES 变量中添加下面一行:

    com_android_server_TTTService.cpp \

这里是添加编译配置。


5、开始编译

root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# . build/envsetup.sh 
including device/moto/stingray/vendorsetup.sh
including device/moto/wingray/vendorsetup.sh
including device/samsung/crespo4g/vendorsetup.sh
including device/samsung/crespo/vendorsetup.sh
including device/samsung/maguro/vendorsetup.sh
including device/samsung/smdkc110/vendorsetup.sh
including device/samsung/smdkv210/vendorsetup.sh
including device/samsung/torospr/vendorsetup.sh
including device/samsung/toro/vendorsetup.sh
including device/samsung/tuna/vendorsetup.sh
including device/ti/panda/vendorsetup.sh
including sdk/bash_completion/adb.bash
root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2#
root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# mmm frameworks/base/services/jni
============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=4.0.4
TARGET_PRODUCT=full
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=arm
TARGET_ARCH_VARIANT=armv7-a
HOST_ARCH=x86
HOST_OS=linux
HOST_BUILD_TYPE=release
BUILD_ID=IMM76I
============================================
make:进入目录'/home/brantyou/workspace/android-4.0.4_r1.2'
target thumb C++: libandroid_servers <= frameworks/base/services/jni/com_android_server_HelloService.cpp
target thumb C++: libandroid_servers <= frameworks/base/services/jni/com_android_server_TTTService.cpp
target thumb C++: libandroid_servers <= frameworks/base/services/jni/onload.cpp
make: *** 没有规则可以创建“out/target/product/generic/obj/SHARED_LIBRARIES/libandroid_servers_intermediates/LINKED/libandroid_servers.so”需要的目标“out/target/product/generic/obj/lib/libsystem_server.so”。 停止。
make:离开目录“/home/brantyou/workspace/android-4.0.4_r1.2”
root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# 

矮油~~~这里出错了,提示没有找到 libsystem_server.so 文件。
执行下面的命令,生成 libsystem_server.so 文件:

root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# make libsystem_server

生成之后的提示:

Install: out/target/product/generic/system/lib/libvorbisidec.so
Install: out/target/product/generic/system/lib/libstagefright_yuv.so
Install: out/target/product/generic/system/lib/libdrmframework.so
Install: out/target/product/generic/system/lib/libchromium_net.so
Install: out/target/product/generic/system/lib/libstagefright_amrnb_common.so
Install: out/target/product/generic/system/lib/libstagefright_enc_common.so
Install: out/target/product/generic/system/lib/libstagefright_avc_common.so
Install: out/target/product/generic/system/lib/libstagefright.so
Install: out/target/product/generic/system/lib/libstagefright_omx.so
Install: out/target/product/generic/system/lib/libmediaplayerservice.so
Install: out/target/product/generic/system/lib/libinput.so
Install: out/target/product/generic/system/lib/libsystem_server.so
root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# 

好了,这个问题解决了,我们继续编译这个JNI。

root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# mmm frameworks/base/services/jni
============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=4.0.4
TARGET_PRODUCT=full
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=arm
TARGET_ARCH_VARIANT=armv7-a
HOST_ARCH=x86
HOST_OS=linux
HOST_BUILD_TYPE=release
BUILD_ID=IMM76I
============================================
make:进入目录'/home/brantyou/workspace/android-4.0.4_r1.2'
target SharedLib: libandroid_servers (out/target/product/generic/obj/SHARED_LIBRARIES/libandroid_servers_intermediates/LINKED/libandroid_servers.so)
target Symbolic: libandroid_servers (out/target/product/generic/symbols/system/lib/libandroid_servers.so)
target Strip: libandroid_servers (out/target/product/generic/obj/lib/libandroid_servers.so)
Install: out/target/product/generic/system/lib/libandroid_servers.so
make:离开目录“/home/brantyou/workspace/android-4.0.4_r1.2”
root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2#

很好,这一次已经顺利的编译完了。


下面我们需要重新打包这个 system.img,包我们编写的JNI方法包含进去:

root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# make snod
============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=4.0.4
TARGET_PRODUCT=full
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=arm
TARGET_ARCH_VARIANT=armv7-a
HOST_ARCH=x86
HOST_OS=linux
HOST_BUILD_TYPE=release
BUILD_ID=IMM76I
============================================
make snod: ignoring dependencies
Target system fs image: out/target/product/generic/system.img
out/target/product/generic/system.img total size is 44107008
root@brantyou-ubuntu:~/workspace/android-4.0.4_r1.2# 

这样就成功的把我们编写的JNI打包到 system.img中了。

 

这章到此结束,下一章将介绍,如何基于JNI接口编写对应的服务和编写对应的Android程序来访问服务。

上一篇:上一篇
下一篇:下一篇

 

随机推荐程序问答结果

 

 

如对文章有任何疑问请提交到问题反馈,或者您对内容不满意,请您反馈给我们DOC100.NET论坛发贴求解。
DOC100.NET资源网,机器学习分类整理更新日期::2014-01-05 03:20:00
如需转载,请注明文章出处和来源网址:http://www.doc100.net/bugs/t/20941/
本文WWW.DOC100.NET DOC100.NET版权所有。