[置顶] 我的DIY Android之旅--驱动并控制你的Android开发板蜂鸣器

     这些天一直在想Android驱动框架层的实现，本文借助老罗老师的博客和现有通过过分析台湾的Jollen的mokoid 工程代码，并尝试在Android开发板上驱动一个简单的蜂鸣器，来解析Android下驱动的调用。    

 

  HAL架构由Patrick Brady (Google) 在2008 Google  I/O演讲中提出的，如下图。

  其实可以考虑先编写驱动代码，然后使用NDK编译库层的代码，最后在Android应用层来直接完成对硬件驱动层的调用！

 

先编写一个简单的蜂鸣器驱动程序，根据开发板上的硬件IO接口和Android驱动规范，在kernel中的driver目录中新建一个Buzzer文件，新建一个buzzer.c的源文件

#include<linux/init.h>
#include<linux/module.h>
#include<linux/kernel.h>
#include<linux/ioport.h>
#include<linux/fs.h>
#include<asm/io.h>
#include<asm/uaccess.h>

#define DRIVER_AUTHOR "canjianfantasy"
#define DRIVER_DESCRIBLE "buzzer test program"

#define BUZZER_MAJOR 248 //Device Driver Major Number
#define BUZZER_NAME "BUZZER_IO_PORT" //Device Name

#define BUZZER_DRIVER_VERSION "BUZZER IO PORT V0.1" //Device Driver Version

#define BUZZER_ADDRESS 0x88000050 //physical address 
#define BUZZER_ADDRESS_RANGE 0x1000 // I/O region  range

//Glable variable 
static int buzzer_usage = 0;  //if device is already used ?
static unsigned long *buzzer_ioremap ; //io address region


//It is called when program called open() system call

int buzzer_open(struct inode *minode,struct file *mfile)
{
	//if device is already opened 
	if(buzzer_usage != 0)
		return -EBUSY;

	//mapping physical address to virtual address
	buzzer_ioremap = ioremap(BUZZER_ADDRESS,BUZZER_ADDRESS_RANGE);

	//check if it is usable virtual address.
	if(!check_mem_region((unsigned long)buzzer_ioremao,BUZZER_ADDRESS_RANGE))
		{
			//register I/O address region
			request_mem_region((unsigned long)buzzer_ioremap,BUZZER_ADDRESS_RANGE,BUZZER_NAME);
		}
	else 	{
			printk(KERN_WARNING"Can't get I/O region 0x%x\n",(unsigned int)buzzer_ioremap);
		}
	buzzer_usage = 1;
	return 0;
}

//It is called when program called close() system call
int buzzer_release(struct inode *mnode,struct file *mfile)
{
	//Release mapped virtual address
	iounmap(buzzer_ioremap);

	//Release registed I/O memory region
	release_mem_region((unsigned long)buzzer_ioremap,BUZZER_ADDRESS_RANGE);

	buzzer_usage = 0;
 	return  0;

}

//It is called when program calls write() system call
size_t buzzer_write_byte(struct file *inode, const char* gdata, size_t length,
loff_t *off_what)
{
	unsigned char *addr;
	unsigned char c;

	//copy data from gdata to c 
	get_user(c,gdata);

	addr = (unsigned char *)(buzzer_ioremap);
	*addr = c;

	return length;
}

//file operations structure
static struct file_operations buzzer_fops = {
	.owner = THIS_MODULE,
	.open = buzzer_open,
	.write = buzzer_write_byte,
	.release = buzzer_release,
};


// insert module to kernel 
int buzzer_init( void )
{
	int result;
	//Register character device drvier
	result = register_chrdev(BUZZER_MAJOR,BUZZER_NAME,&buzzer_fops);
	
	if(result < 0)
	{
	//registration  failed
	printk(KERN_WARNING "Can't get any major \n");

	return result;
	}
	//print MAJOR_NUMBER
	printk(KERN_WARNING "Init Module ,Buzzer Major number %d \n",BUZZER_MAJOR);

	return 0 ;
}


// remove module from kernel

void buzzer_exit(void)
{

	//Unregister character device driver
	unregister_chardev(BUZZER_MAJOR,BUZZER_NAME);

	printk(KERN_INFO"driver: %s DRIVER EXIT \n",BUZZER_NAME);

}

module_init(buzzer_init);
module_exit(buzzer_exit);

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESCRIPTION);
MODULE_LICENSE("Dual BSD/GPL");

在目录下创建一个Makefile文件，文件内容如下

CC = /usr/local/arm-2009q3/bin/arm-none-linux-gnueabi-gcc

obj-m := buzzer.o

KDIR := /Android/linux-2.6.32

PWD := $(shell pwd)

default :
	$(MAKE) -C $(KDIR) SUBDIRS=$(PWD modules
	rm -f default
clean:
	rm -f *.ko
	rm -f *.o
	rm -f *.mod.*
	rm -f .*.cmd

先运行make clean命令清楚到编译生成的一些工程文件，执行make命令，重新编译驱动程序。将编译生成的buzzer.ko内核镜像文件拷贝出来，adb push buzzer.ko /fpga/moudles

然后插入内核镜像文件到系统中，insmod buzzer.ko,并且装载设备驱动程序，mknod  /dev/buzzer c 248 0

现在就可以在库层直接编写C/C++文件来调用这个驱动程序，这个可以在ubuntu中安装NDK编译环境，新建buzzer文件，编译生成一个库文件，那样就可以直接在应用层使用这个库提供的JNI方法，那样调用会显得更加的简单，当然这个调用方式google并不提倡，我在这里只是想展示这种调用方式而已

构建一个jni工程，新建一个buzzer.c的源文件，内容如下：

#include<errno.h>

#include<android/log.h>

#define LOG_TAG "BuzzerDriver"
//#define LOGW(a) __android_log_write(ANDROID_LOG_WARN,LOG_TAG,a)
#define LOGW(a)  __android_log_write(ANDROID_LOG_WARN,LOG_TAG,a)

jint java_com_fantasy_buzzer_BuzzerActivity_BuzzerControl(JNIEnv *env,jobject thiz,jint value)
{
	int fd,ret;
	int data=value;

	fd=open("/dev/buzzer",O_WRONLY);
	
	if(fd < 0)
	  {     
		LOGW("Android Open Driver buzzer failed!");
		 return -errno;
          }

	ret=write(fd ,&data ,1);
        if(ret < 0)
	   close(fd);

	if(ret == 1)
	  return 0;

进行NDK编译，生成libbuzzer.so，这个库就可以直接在应用层进行调用

 

 在eclipse中编写应用程序直接调用这个库，实现对底层驱动的调用！！

 主要源代码：

package com.fantasy.buzzer;
//@ canjianfantasy 2013.6.22
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;

public class BuzzerActivity extends Activity {
	Button BuzzerButton;
	int BuzzerData =0;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_buzzer);
		
//		BuzzerControl(BuzzerData);
		BuzzerButton =(Button)findViewById(R.id.On);
		
		BuzzerButton.setOnClickListener(new Button.OnClickListener() {
		
			public void onClick(View v) {
				// TODO Auto-generated method stub
				if(BuzzerData == 0){
					BuzzerData = 1;
					BuzzerButton.setText("Buzzer off");
				}
				else{
					BuzzerData = 0;
					BuzzerButton.setText("Buzzer On");
				}
//				BuzzerControl(BuzzerData);
			}
		});
		
	}
	static{
		System.loadLibrary("buzzer");
	}
	public native int BuzzerControl(int Value);
	
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.activity_buzzer, menu);
		return true;
	}

}

整个工程目录：

直接运行，在开发板上查看运行结果。。。