TQ210搭载Android4.0.3系统构建之ADC从驱动到HAL到JNI到应用程序(HAL篇)

   其实ADC的HAL层和BEEP、LED的就HAL层很像，所以注释就很少了，详情见BEEP、LED的HAL层

   直接上源码吧

   adc_under_hal.h

    

#ifndef __ADC_UNDER_H
#define __ADC_UNDER_H

#include <hardware/hardware.h>
#include <stdint.h>
#include <sys/cdefs.h>

__BEGIN_DECLS //采用C语言的方式编译和连接变量与函数
#define ADC_UNDER_ID "adc_unders"

static struct adc_hw_module_t
{
	struct hw_module_t common;
};

static struct adc_hw_device_t
{
	struct hw_device_t common;
	int (*read)(struct adc_hw_device_t *device);
};

__END_DECLS
#endif

adc_under_hal.c

#include <hardware/hardware.h>
#include <hardware/adc_under_hal.h>
#include <android/log.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>

#define DEVICE_NAME "/dev/adc_unders"  //设备文件

int fd=-1;

int adc_open()  //打开设备文件
{
	fd=open(DEVICE_NAME,O_RDWR);
	if(fd<0)
		{
			__android_log_print(ANDROID_LOG_DEBUG, "msg", "can not open fd,fd=%d.
",fd);
			return -1;
	       }
	__android_log_print(ANDROID_LOG_DEBUG,"msg", "open fd success,fd=%d
",fd);
	return 0;
}

int adc_read(struct adc_hw_device_t *dev)  //读取adc数据
{
	int data=0,ret;
	if(fd==-1) return -1;
	ret=read(fd,&data,sizeof(&data));
	if(ret<0) __android_log_print(ANDROID_LOG_DEBUG,"msg", "can not read data from kernel.
");
	return data;
}

int adc_close(struct hw_device_t *dev)
{
	if(fd!=-1)
		{
			close(fd);
			if(dev) free(dev);
		}
	return 0;
}

int adc_init(struct hw_module_t *module,const char *id,struct hw_device_t **device) //adc的初始化函数，将设备带回给device
{
	struct adc_hw_device_t *dev;
	dev=(struct adc_hw_device_t *)malloc(sizeof(struct adc_hw_device_t));
	if(dev==NULL)
		{
		__android_log_print(ANDROID_LOG_DEBUG, "msg", "can not alloc mem.
");
		return -1;
		}
	memset(dev,0,sizeof(*dev));  
	dev->common.tag=HARDWARE_DEVICE_TAG; //初始化设备信息
	dev->common.version=1;
	dev->common.module=module;
	dev->common.close=(int (*)(struct hw_device_t *))adc_close;

	*device=(struct hw_device_t *)&dev->common;

	dev->read=adc_read;

	if(adc_open()==-1)  //打开设备文件
		{
			free(dev);
			dev=NULL;
			return -1;
		}
	return 0;
	
}

static struct hw_module_methods_t adc_module_methods_t=
{
	open:adc_init
};


const struct adc_hw_module_t HAL_MODULE_INFO_SYM=  //模块的入口，HMI符号
{
	common:
			{
				tag:HARDWARE_MODULE_TAG,
				version_major:1,
				version_minor:0,
				id:ADC_UNDER_ID, //组成模块名称的ID
				name:"adc stub",
				author:"undergrowth",
				methods:&adc_module_methods_t,
			}

};

编译文件 Android.mk

LOCAL_PATH	:=$(call my-dir)
include $(CLEAR_VARS)
LOCAL_PRELINK_MODULE	:=false
LOCAL_SHARED_LIBRARIES	:=libutils 
LOCAL_SRC_FILES 	:=adc_under_hal.c
LOCAL_MODULE		:=adc_unders.$(TARGET_BOARD_PLATFORM)
LOCAL_MODULE_PATH	:=$(LOCAL_PATH)
LOCAL_MODULE_TAGS	:=optional
include $(BUILD_SHARED_LIBRARY)