
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_LDLIBS :=-llog
LOCAL_MODULE    := touch
LOCAL_SRC_FILES := touch.cpp
include $(BUILD_SHARED_LIBRARY)

2. Application.mk

APP_ABI := all #编译所有平台

3. touch.cpp (文件名和Android.mk 的 MODULE匹配， JNI里面的语法知识不做介绍)


#include<android/log.h>
#include <jni.h>
#include <fcntl.h>
 
#define TAG "TOUCH-JNI" // 这个是自定义的LOG的标识
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG,TAG ,__VA_ARGS__)
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,TAG ,__VA_ARGS__)
#define LOGW(...) __android_log_print(ANDROID_LOG_WARN,TAG ,__VA_ARGS__)
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,TAG ,__VA_ARGS__)
#define LOGF(...) __android_log_print(ANDROID_LOG_FATAL,TAG ,__VA_ARGS__)
 
#define IOCTL_GET_DRIVER_VERSION   0x80084300
#define IOCTL_GET_DEVICE_TYPE      0x80084301
 
extern "C"
{
    jstring Java_com_morgen_touch_MainActivity_getStringFromJni(JNIEnv* jni, jobject obj) {
        return jni->NewStringUTF("Hello jni!");
    }
 
    jlong Java_com_morgen_touch_MainActivity_ioctl(JNIEnv* jni, jobject obj, jint code, jlong arg) {
        char path[30] = "/proc/icn85xx_tool";
        int fd = 0;
 
        LOGE("code:0x%x arg:0x%x", code, arg);
 
        fd = open(path, O_RDWR);
        if (fd < 0) {
            LOGE("Open file failed");
            return -1;
        }
 
        switch (code) {
        case IOCTL_GET_DRIVER_VERSION:
        case IOCTL_GET_DEVICE_TYPE:
            ioctl(fd, code, &arg);//注意这里是核心代码
            LOGE("arg:0x%x", arg);
            break;
        default:
            LOGE("CTLCODE was not right");
        }
 
        close(fd);
        LOGE("ioctl successfully");
        return arg;
    }
}//extern "C"

4.到这里基本的jni层相关代码都配置OK了，接下来编译

a.打开命令窗口进入jni目录，输入ndk-build，

b.如下图，可以看到相关平台的so文件都已经编译成功

c.编译好了之后so文件在jni同级目录的libs目录下 (libtouch.so以生成)

d.到这里就为应用层app调用jni so库文件做好了准备

应用层app demo实现

使用android studio创建默认工程

1.创建好的工程目录如下（怎么创建android demo工程这里就不赘述了，只需要创建一个空壳应用就好）：

2.将ndk编译好的libs目录拷贝到touch工程中的main目录下，如上图

引用libtouch.so库文件

1.在app工程目录下的build.gradle文件中添加 ndk和sourceSets.main这两个代码段


android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"
    defaultConfig {
        applicationId "com.morgen.touch"
        minSdkVersion 15
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        ndk {                               //1.添加ndk模块名
            moduleName "touch"
        }
    }
    sourceSets.main{                        //2.添加jni lib目录
        jni.srcDirs=[]
        jniLibs.srcDir "src/main/libs"
    }
}

3.然后在MainActivity中载入touch模块

4.然后在onCreate中调用

5.MainActivity完整代码如下（到这里，引用和调用都以完成）：


package com.morgen.touch;
 
import android.os.Bundle;
import com.google.android.material.bottomnavigation.BottomNavigationView;
import androidx.appcompat.app.AppCompatActivity;
import androidx.annotation.NonNull;
import android.util.Log;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
 
import java.io.File;
 
public class MainActivity extends AppCompatActivity {
    private TextView mTextMessage;
    private Button mButton;
 
    static {
        System.loadLibrary("touch");
    }
    public native long ioctl(int a, long b);
 
    private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
            = new BottomNavigationView.OnNavigationItemSelectedListener() {
 
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()) {
                case R.id.navigation_home:
                    mTextMessage.setText(R.string.title_home);
                    return true;
                case R.id.navigation_dashboard:
                    mTextMessage.setText(R.string.title_dashboard);
                    return true;
                case R.id.navigation_notifications:
                    mTextMessage.setText(R.string.title_notifications);
                    return true;
            }
            return false;
        }
    };
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        BottomNavigationView navView = findViewById(R.id.nav_view);
        mTextMessage = findViewById(R.id.message);
        navView.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
        mButton = findViewById(R.id.button);
 
        mButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                long arg = 0;
                Log.e("TOUCH-APP", "0x" + Long.toHexString(ioctl(0x80084300, arg)));
                Log.e("TOUCH-APP", "0x" + Long.toHexString(ioctl(0x80084301, arg)));
                Log.e("TOUCH-APP", "0x" + Long.toHexString(ioctl(0x80084302, arg)));
                Log.e("TOUCH-APP", "0x" + Long.toHexString(ioctl(0x80084303, arg)));
                Log.e("TOUCH-APP", "0x" + Long.toHexString(ioctl(0x80084304, arg)));
                Log.e("TOUCH-APP", "0x" + Long.toHexString(ioctl(0xc0084310, arg)));
                Log.e("TOUCH-APP", "0x" + Long.toHexString(ioctl(0xc0084320, arg)));
                Log.e("TOUCH-APP", "0x" + Long.toHexString(ioctl(0xc0084321, arg)));
            }
        });
    }
}

编译运行安装touch应用

1.安装后的应用

2.点击按钮运行，同时抓取logcat log（如下图），这里可以看到app层和jni层的log都有打印出来，但是有没有被底层识别呢，接下来我们再看底层设备驱动的简单实现


130|root@msm8994:/ # logcat | grep TOUCH
E/TOUCH-JNI(14217): code:0x80084300 arg:0x0
E/TOUCH-JNI(14217): arg:0x10310
E/TOUCH-JNI(14217): ioctl successfully
E/TOUCH-APP(14217): 0x10310
E/TOUCH-JNI(14217): code:0x80084301 arg:0x0
E/TOUCH-JNI(14217): arg:0x991110
E/TOUCH-JNI(14217): ioctl successfully
E/TOUCH-APP(14217): 0x991110
E/TOUCH-JNI(14217): code:0x80084302 arg:0x0
E/TOUCH-JNI(14217): arg:0x212
E/TOUCH-JNI(14217): ioctl successfully
E/TOUCH-APP(14217): 0x212
E/TOUCH-JNI(14217): code:0x80084303 arg:0x0
E/TOUCH-JNI(14217): arg:0x61702cf
E/TOUCH-JNI(14217): ioctl successfully
E/TOUCH-APP(14217): 0x61702cf
E/TOUCH-JNI(14217): code:0x80084304 arg:0x0
E/TOUCH-JNI(14217): arg:0x120020
E/TOUCH-JNI(14217): ioctl successfully
E/TOUCH-APP(14217): 0x120020
E/TOUCH-JNI(14217): code:0xc0084310 arg:0x0
E/TOUCH-JNI(14217): arg:0x0
E/TOUCH-JNI(14217): ioctl successfully
E/TOUCH-APP(14217): 0x0
E/TOUCH-JNI(14217): code:0xc0084320 arg:0x0
E/TOUCH-JNI(14217): arg:0x0
E/TOUCH-JNI(14217): ioctl successfully
E/TOUCH-APP(14217): 0x0
E/TOUCH-JNI(14217): code:0xc0084321 arg:0x0
E/TOUCH-JNI(14217): arg:0x0
E/TOUCH-JNI(14217): ioctl successfully
E/TOUCH-APP(14217): 0x0

设备驱动程序ioctl实现关键代码

1.代码如下：


static long tool_ioctl(struct file *file, unsigned int cmd,
        unsigned long arg)
{
    struct ts_data *data;
    struct device *dev;
 
    pr_info("ioctl, cmd=0x%08x, arg=0x%08lx", cmd, arg);
 
    data = file->private_data;
    if (data == NULL) {
        pr_err("IOCTL with private data = NULL");
        return -EFAULT;
    }
 
    switch (cmd) {
    case IOCTL_GET_DRIVER_VERSION:
        return put_user(CTS_DRIVER_VERSION_CODE,
                (unsigned int __user *)arg);
    case IOCTL_GET_DEVICE_TYPE:
        return put_user(dev->hwdata->hwid,
                (unsigned int __user *)arg);
    }
 
    return -ENOTSUPP;
}
static int tool_open(struct inode *inode, struct file *file)
{
    file->private_data = PDE_DATA(inode);
    return 0;
}
static struct file_operations tool_fops = {
    .owner = THIS_MODULE,
    .llseek = no_llseek,
    .open  = tool_open,
    .unlocked_ioctl = tool_ioctl,
};

2.这时候抓取kernel log如下（cat dev/kmsg）：

这里可以看到应用层传下来的cmd，底层设备驱动已经接收到了，这就说明从app-jni-kernel的ioctl功能已经实现


<I>Tool ioctl, cmd=0x80084300, arg=0x7fd4dc4508                                      
<I>Tool ioctl, cmd=0x80084301, arg=0x7fd4dc4508
<I>Tool ioctl, cmd=0x80084302, arg=0x7fd4dc4508
<I>Tool ioctl, cmd=0x80084303, arg=0x7fd4dc4508
<I>Tool ioctl, cmd=0x80084304, arg=0x7fd4dc4508

======== 完 =========

到这里，从应用层到JNI层再到kernel层，功能实现OK，这就是上层应用来控制底层设备的大概逻辑。

以上，如有错误欢迎大家指出，共同进步，谢谢！

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