用C程序测试随内核加载的驱动

    在前面内核驱动加载成功后就可以尝试用程序的方式测试该驱动了。
1、进入android源代码路径（注意不是内核源代码路径）
2、cd external
3、mkdir hello
4、cd hello
5、创建hello.c

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#define DEVICE_NAME "/dev/hello"
int main(int argc, char** argv)
{
    int fd = -1;
    int val = 0;
    fd = open(DEVICE_NAME, O_RDWR);
    if(fd == -1) {
        printf("Failed to open device %s.\n", DEVICE_NAME);
        return -1;
    }

    printf("Read original value:\n");
    read(fd, &val, sizeof(val));
    printf("%d.\n\n", val);
    val = 5;
    printf("Write value %d to %s.\n\n", val, DEVICE_NAME);
        write(fd, &val, sizeof(val));

    printf("Read the value again:\n");
        read(fd, &val, sizeof(val));
        printf("%d.\n\n", val);
    close(fd);
    return 0;
}

6、创建Android.mk

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE := hello
LOCAL_SRC_FILES := $(call all-subdir-c-files)
include $(BUILD_EXECUTABLE)

7、回到android源代码根路径
8、make hello
9、make snod
10、cd 安卓源代码路径/out/target/product/generic
11、emulator -image system.img -data userdata.img -ramdisk ramdisk.img -sdcard dcard.img -kernel 安卓内核源代码路径/kernel/goldfish/arch/arm/boot/zImage -avd a_avd&
12、验证结果

adb shell
cd /system/bin
./hello