android驱动例子（LED灯控制）

--作者：赖玉平（Peter Lai）[email protected]

      本例子，讲述在android2.1上完全自已开发一个驱动去控制硬件口并写应用测试该驱动，通过这样一个例子，解析android下的驱动开发流程的应用调用流程，可以说是很好的入门引导

要达到的效果：通过android的应用，调用驱动程序，在开发板上控制4个LED的亮灭。

一、硬件原理

如上图，通过4个IO口控制这LED，低电平LED亮，

这4个IO口分别是GPM1, GPM2, GPM3, GPM4,

二、驱动程序

1、在kernel文件夹下的driver目录，新键驱动文件夹

# cd kernel_android_2.6.28.6/drivers

进到开发板的kernel目录，建驱动文件夹

#mkdir ledtest

2、在/driver/ledtest目录下，新建leddriver.c ，leddriver.h , Kconfig, Makefile 等4个文件

leddriver.c

#include 
#include 
#include 
#include             /* For __init/__exit/... */
#include 
#include 
#include <asm/io.h>
#include <asm/uaccess.h>
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include  //for register_chrdev()
#include 
#include 
#include "leddriver.h"
#include         /* For MODULE_ALIAS_MISCDEV
                            (WATCHDOG_MINOR) */
#include         /* For the watchdog specific items */
#include             /* For file operations */
#define Viberator_MAJOR        97  //主设备号
#define SCULL_NR_DEVS           4
#define SCULL_QUANTUM         4000
#define SCULL_QSET             1000
//---do as the GIO driver
#define DEVCOUNT                4
#define GIO_MINOR            2    /* GIO minor no. */
static dev_t dev;        //申  请  到的主  设备  号
static struct cdev *cdev_p;
static int openCnt;
//--全局变量------------
int VIB_major  = 97;//we asigment it for test
int VIB_minor = 0;
int VIB_nr_devs = SCULL_NR_DEVS;
int VIB_quantum = SCULL_QUANTUM;
int VIB_qset = SCULL_QSET;

static struct class *vib_dev_class;
#define GPNCON  S3C64XX_GPNCON 
#define GPNDAT  S3C64XX_GPNDAT
#define GPNPUD  S3C64XX_GPNPUD
#define GPMCON S3C64XX_GPMCON
#define GPMDAT  S3C64XX_GPMDAT
#define GPMPUD S3C64XX_GPMPUD

#define VIB_ON 0x11
#define  VIB_OFF 0x22
static const struct file_operations GPIO_Viberator_ctl_ops={
    .owner        = THIS_MODULE,
    .open    = GPIO_VIB_open,
    .read    =GPIO_VIB_read,
    .write    =GPIO_VIB_write,
    .ioctl     = GPIO_VIB_ioctl,
    .release     =GPIO_VIB_release,
};
ssize_t GPIO_VIB_read(struct file * file,char * buf,size_t count,loff_t * f_ops)
{
       char sdas[5]={1,3,8,1,6};
       ssize_t            status = 5;
    unsigned long    missing;
    missing = copy_to_user(buf, sdas, status);
    if (missing == status)
        status = -EFAULT;
    else
        status = status - missing;   
       printk(" GPIO_VIB_read = %d ,count = %d/r/n",status,count);
    gpio_direction_output(S3C64XX_GPM(3), 0);// 
return status ; 
}
ssize_t GPIO_VIB_write (struct file * file,const char * buf, size_t count,loff_t * f_ops)
{
    unsigned long missing;
     char inbuffer[512]={0};
    int i;
     missing = copy_from_user(inbuffer, buf, count);
    printk(" GPIO_VIB_write count = %d missing =%d /r/n",count,missing);
    gpio_direction_output(S3C64XX_GPM(3), 1);// 
    for(i=0;i"Write:inbuffer[%d]=%d /r/n",i,inbuffer[i]);
        } 
return count;
}

//ssize_t GPIO_VIB_ioctl(struct inode *  inode,struct file * file,unsigned int cmd, long data)
static int GPIO_VIB_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
    printk(KERN_ERR"VIB:GPIO_VIB_ioctl --CMD=%x /n",cmd);
    switch(cmd)
        {
           case VIB_ON:
            gpio_direction_output(S3C64XX_GPM(1), 0);// 
            gpio_direction_output(S3C64XX_GPM(2), 0);// 
            gpio_direction_output(S3C64XX_GPM(3), 0);// 
            gpio_direction_output(S3C64XX_GPM(4), 1);// 
            printk(KERN_ERR"VIB:GPIO_VIB_ioctl --VIB_ON/n");
            break;
         case VIB_OFF:
            {
            printk(KERN_ERR"VIB:GPIO_VIB_ioctl --VIB_OFF/n");
            gpio_direction_output(S3C64XX_GPM(1), 1);// 
            gpio_direction_output(S3C64XX_GPM(2), 1);// 
            gpio_direction_output(S3C64XX_GPM(3), 1);// 
            gpio_direction_output(S3C64XX_GPM(4), 0);// 
            break;
         }
         default:break;
                
    }
        //gpio_free(S3C64XX_GPN(7));
}
ssize_t GPIO_VIB_open(struct inode * inode,struct file * file)
{
//模块数
  //MOD_INC_USE_COUNT;
  printk("GPIO_VIB_open() /n");   
  return 0;
}
ssize_t GPIO_VIB_release(struct inode * inode, struct file * file)
{
   // MOD_DEC_USE_COUNT;//模块数减1
     printk("GPIO_VIB_release() /n");   
    return 0;
}
static int GPIO_VIB_CTL_init(void)
{
    int ret  = -ENODEV;
   int error ;
    printk("---------------------------------------------- /r/n");
    //初始化端口
        s3c_gpio_cfgpin(S3C64XX_GPM(1), S3C_GPIO_SFN(1));//GPM1 output
        s3c_gpio_cfgpin(S3C64XX_GPM(2), S3C_GPIO_SFN(1));//GPM2 output
        s3c_gpio_cfgpin(S3C64XX_GPM(3), S3C_GPIO_SFN(1));//GPM3 output
        s3c_gpio_cfgpin(S3C64XX_GPM(4), S3C_GPIO_SFN(1));//GPM4 output
#if 1 /*静态方式注册驱动*/
ret = register_chrdev(Viberator_MAJOR, "viberator", &GPIO_Viberator_ctl_ops);
if (ret < 0) {
    printk(KERN_ERR "VIB: unable to get major %d/n", ret);
    return ret;
}
//创建class
vib_dev_class = class_create(THIS_MODULE, "viberator");
if (IS_ERR(vib_dev_class)) {
    unregister_chrdev(Viberator_MAJOR, "capi20");
    return PTR_ERR(vib_dev_class);
}
//创建节点，
device_create(vib_dev_class, NULL, MKDEV(Viberator_MAJOR, 0), NULL, "vib");
// create a point under /dev/class/vib  
//通过上面这两步，驱动加载后，就会在/dev/class/下面生成vib节点，应用程序可以像操作文件那样操作这个节点，通过open ,write,read 等函数操作，详情可以看后面的应用示例程序。
  return 0;    
#endif
#if 0/* 注册动态 */
    if ((error = alloc_chrdev_region(&dev, 0, DEVCOUNT, "vibrate")) < 0)
        {
        printk(KERN_ERR
               "VIB: Couldn't alloc_chrdev_region, error=%d/n",
               error);
        return 1;
    }
         printk("dev = %d  /n",dev);
    cdev_p = cdev_alloc();
    cdev_p->ops = &GPIO_Viberator_ctl_ops;
    error = cdev_add(cdev_p, dev, DEVCOUNT);
    if (error) {
        printk(KERN_ERR
               "VIB: Couldn't cdev_add, error=%d/n", error);
        return 1;
    }

    vib_dev_class = class_create(THIS_MODULE, "vib-dev");
    if (IS_ERR(vib_dev_class)) {
        res = PTR_ERR(vib_dev_class);
        goto out_unreg_class;
    }
    return 0;
#endif
out_unreg_class:
    class_destroy(vib_dev_class);
return 1;
}

static int __init S3C6410_VIB_init(void)
{
    int ret = -ENODEV;
    //调用函数    
        printk(KERN_ERR "Auly: S3C6410_VIB_init---/n");
    ret = GPIO_VIB_CTL_init();
    if(ret)
        {
        printk(KERN_ERR "Auly: S3C6410_VIB_init--Fail !!!/n");
        return ret;
    }
    return 0;
}
static void __exit cleanup_GPIO_VIB(void)
{
    //注销设备
  //  devfs_unregister_chrdev(Viberator_MAJOR,"gpio_vib_ctl");
 #if 0 
      cdev_del(cdev_p);
    unregister_chrdev_region(dev, DEVCOUNT);
    class_destroy(vib_dev_class);
#endif 
device_destroy(vib_dev_class, MKDEV(Viberator_MAJOR, 0));
class_destroy(vib_dev_class);
unregister_chrdev(Viberator_MAJOR, "viberator");
}
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Peter first driver");
MODULE_ALIAS_CHARDEV(Viberator_MAJOR, 0);

module_init(S3C6410_VIB_init);
module_exit(cleanup_GPIO_VIB);

leddriver.h文件

leddriver.h文件

1. ssize_t GPIO_VIB_read(struct file * file,char * buf,size_t count,loff_t * f_ops);
2. ssize_t GPIO_VIB_write (struct file * file,constchar * buf, size_t count,loff_t * f_ops);
3. static int GPIO_VIB_ioctl(struct inode *inode,struct file *file,unsigned int cmd,unsigned long arg);
4. ssize_t GPIO_VIB_open(struct inode * inode,struct file * file);
5. ssize_t GPIO_VIB_release(struct inode * inode,struct file * file);
6. static int GPIO_VIB_CTL_init(void);

Kconfig 文件

Kconfig 文件

1. config LEDTEST
2.   tristate "LED test for ARMeasy"
3.   default n
4.   help
5.   this is a LED driver for ARMEASY with S3C6410

Makefile文件

Makefile文件

1. obj-$(CONFIG_LEDTEST)+=leddriver.o

3、在内核配置里菜单里加入本驱动的配置项

达到的效果是，可以通过内核配置来选择是否把本驱动编译进内核里，也就是出现在make menuconfig 后出来的界面里，可以参考9.8章

1）在arch/arm/Kconfig文件里 menu "Device Drivers"与 endmenu之间添加

1. source "drivers/ledtest/Kconfig"

2）在drivers/Kconfig menu "Device Drivers" 和 endmenu之间添加

1. source "drivers/ledtest/Kconfig"

3)修改/drivers/Makefile文件

1. Obj-$(CONFIG_LEDTEST) +=ledtest/

4、编译驱动

在kernel目录下，终端输入

1. #make menuconfig

“Device Drivers” 下面会看到 “LED test for ARMeasy”，选择它，

保存并退出

1. #make

这样，就会在/drivers/ledtest目录下得到leddrivr.ko文件，它就是驱动目标文件，已级编译进了zImage 里了，只要用这个kernel烧录到开发板，开机就会自动加载本驱动，

PS，如果发现如上编译，没有在ledtest目录下生成leddriver.ko文件，也就是本根没有去编译本驱动，那就把ledtest目录入到/drivers/misc目录下，相应的修改misc下面，然后，在makefile里，不用选直接写成obj-y += leddriver.o，这样强制的包含进去编译。

三、 应用程序（测试驱动）

用C语言写一个应用，测试上面写的驱动是否工作正常，这是一般的驱动开发流程

主要有两个文件：Android.mk和ledtest.c

1、

在$(YOUR_ANDROID)/external/LEDTEST/目录编写ledtest.c文件，

ledtest.c

ledtest.c

1. #include
2. #include
3. #include // contact the open(),close(),read(),write() and so on!
4.   #define DEVICE_NAME"/dev/vib"//device point
5. #define LED_ON     0x11
6. #define LED_OFF     0x22
7. int main(int argc,char **argv)
8. {   
9.     int fd;
10.     int ret;
11.     char *i;
12.     printf("\n start gpio_led_driver test \r\n");
13.     fd = open(DEVICE_NAME,O_RDWR);//Open device ,get the handle
14.     printf("fd = %d \n",fd);
15.     if(fd == -1) //open fail
16.     {
17.       printf("open device %s error \n",DEVICE_NAME);
18.     }
19.     else
20.     {
21.         while(1)
22.         {
23.           ioctl(fd,LED_OFF); //call the output function to off LEDs
24.           sleep(1);//wait 1 second
25.           ioctl(fd,LED_ON);
26.           sleep(1);
27.         }
28.         ret = close(fd); //close device
29.         printf("ret = %d \n",ret);
30.         printf("close gpio_led test \n");
31.     }
32.   return 0;
33. }

2、在$(YOUR_ANDROID)/external/ LEDTEST /目录编写Android.mk文件。这是Android Makefile的标准命名，不要更改。Android.mk文件的格式和内容可以参考其他已有的Android.mk文件的写法，针对helloworld程序的Android.mk文件内容如下：

Android.mk

1.  
2. LOCAL_PATH:= $(call my-dir)
3. include $(CLEAR_VARS)
4. LOCAL_SRC_FILES:= \/par     hello.c
5. LOCAL_MODULE := ledtestapp
6. include $(BUILD_EXECUTABLE)

注意上面LOCAL_SRC_FILES用来指定源文件；

LOCAL_MODULE指定要编译的模块的名字，下一步骤编译时就要用到；

include $(BUILD_EXECUTABLE)表示要编译成一个可执行文件，如果想编译成动态库则可用BUILD_SHARED_LIBRARY，这些可以在

$(YOUR_ANDROID)/build/core/config.mk查到。

3、 回到Android源代码顶层目录进行编译：

# cd $(YOUR_ANDROID) && make ledtestapp

例如我这里的实际操作是

#cd android2.1

#make ledtestapp

注意make ledtestapp中的目标名ledtestapp就是上面Android.mk文件中由LOCAL_MODULE指定的模块名。编译结果如下

make ledtestapp

============================================

PLATFORM_VERSION_CODENAME=REL

PLATFORM_VERSION=2.1-update1

TARGET_PRODUCT=generic

TARGET_BUILD_VARIANT=eng

TARGET_SIMULATOR=

TARGET_BUILD_TYPE=release

TARGET_ARCH=arm

HOST_ARCH=x86

HOST_OS=linux

HOST_BUILD_TYPE=release

BUILD_ID=ECLAIR

============================================

/bin/bash: line 0: cd: sdk/layoutopt/app/src/resources: No such file or directory

target thumb C: ledtestapp <= external/LEDTEST/ledtest.c

Install: out/host/linux-x86/bin/apriori

Install: out/host/linux-x86/bin/soslim

target Executable: ledtestapp (out/target/product/generic/obj/EXECUTABLES/ledtestapp_intermediates/LINKED/ledtestapp)

target Non-prelinked: ledtestapp (out/target/product/generic/symbols/system/bin/ledtestapp)

target Strip: ledtestapp (out/target/product/generic/obj/EXECUTABLES/ledtestapp_intermediates/ledtestapp)

Install: out/target/product/generic/system/lib/libdl.so

Install: out/target/product/generic/system/lib/libc.so

Install: out/target/product/generic/system/lib/libstdc++.so

Install: out/target/product/generic/system/lib/libm.so

Install: out/target/product/generic/system/bin/ledtestapp

4、如上面的编译结果所示，编译后的可执行文件存放在

out/target/product/generic/system/bin/目录 可执行文件是ledtestapp

5、拷贝ledtestapp可执行文件到T卡，插入开发板

6、开电，在启动进入android的过程中，串口终端 按回车，进入命令行模式

7、拷贝可执行文件到根目录

#cp /sdcard/ledtestapp /   

8、执行程序

#./ledtestapp

通过上面的步骤，可以看到开发板上相应的LED在闭，每秒钟闪一次！

  推荐使用 著名开源项目：树莓派3 卡片电脑，我个人觉得挺不错的，也非常的便宜，

 介绍看这里

 http://www.superpi.org/chanpin/superpi3/superpi3.htm

 

 

后语：近来老发现有网站盗用我的博客文章，又不注明出处，很不尊重我的劳动果实，所以设计了以上签名，做成图片，望理解！