文章來源：http://blog.csdn.net/ok138ok/article/details/6317212

本例子，講述在android2.1上完全自已開發一個驅動去控制硬體口並寫應用測試該驅動，通過這樣一個例子，解析Android下的驅動開發流程的應用呼叫流程，可以說是很好的入門引導

要達到的效果：通過android的應用，呼叫驅動程式，在開發板上控制4個LED的亮滅。

一、硬體原理

如上圖，通過4個IO口控制這LED，低電平LED亮，

這4個IO口分別是GPM1, GPM2, GPM3, GPM4,

二、驅動程式

1、在kernel資料夾下的driver目錄，新鍵驅動資料夾

# cd kernel_android_2.6.28.6/drivers

進到開發板的kernel目錄，建驅動資料夾

#mkdir ledtest

2、在/driver/ledtest目錄下，新建leddriver.c ，leddriver.h , Kconfig, Makefile 等4個檔案

leddriver.c

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/init.h>            /* For __init/__exit/... */
#include <linux/module.h>
#include
 
 <mach/hardware.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <plat/gpio-cfg.h>
#include <plat/regs-clock.h>
#include <plat/regs-lcd.h>
#include <plat/regs-gpio.h>
#include <mach/map.h>
#include <linux/gpio.h>
#include <plat/gpio-bank-m.h>
#include
 
 <linux/cdev.h>
#include <linux/fs.h> //for register_chrdev()
#include <linux/device.h>
#include <mach/map.h>
#include "leddriver.h"
#include <linux/miscdevice.h>        /* For MODULE_ALIAS_MISCDEV
                            (WATCHDOG_MINOR) */
#include <linux/watchdog.h>        /* For the watchdog specific items */
#include <linux/fs.h>            /* For file operations */
#define Viberator_MAJOR        97  //主裝置號
#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  請  到的主  裝置  號
static struct cdev *cdev_p;
static int openCnt;
//--全域性變數------------
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<count;i++)
        {
            printk("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)
{
//模組數
  //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;//模組數減1
     printk("GPIO_VIB_release() /n");   
    return 0;
}
static int GPIO_VIB_CTL_init(void)
{
    int ret  = -ENODEV;
   int error ;
    printk("---------------------------------------------- /r/n");
    //初始化埠
        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 /*靜態方式註冊驅動*/
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;
}
//建立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);
}
//建立節點，
device_create(vib_dev_class, NULL, MKDEV(Viberator_MAJOR, 0), NULL, "vib");
// create a point under /dev/class/vib  
//通過上面這兩步，驅動載入後，就會在/dev/class/下面生成vib節點，應用程式可以像操作檔案那樣操作這個節點，通過open ,write,read 等函式操作，詳情可以看後面的應用示例程式。
  return 0;    
#endif
#if 0/* 註冊動態 */
    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;
    //呼叫函式    
        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)
{
    //登出裝置
  //  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檔案

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,unsignedint cmd,unsignedlong 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. staticint GPIO_VIB_CTL_init(void);

Kconfig 檔案

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檔案

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

3、在核心配置裡選單里加入本驅動的配置項

達到的效果是，可以通過核心配置來選擇是否把本驅動編譯進核心裡，也就是出現在make menuconfig 後出來的介面裡，可以參考9.8章<android新增新驅動方法>

1）在arch/arm/Kconfig檔案裡 menu "Device Drivers"與 endmenu之間新增

1. source "drivers/ledtest/Kconfig"

2）在drivers/Kconfig menu "Device Drivers" 和 endmenu之間新增

1. source "drivers/ledtest/Kconfig"

3)修改/drivers/Makefile檔案

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

4、編譯驅動

在kernel目錄下，終端輸入

1. #make menuconfig

“Device Drivers” 下面會看到 “LED test for ARMeasy”，選擇它，

儲存並退出

1. #make

這樣，就會在/drivers/ledtest目錄下得到leddrivr.ko檔案，它就是驅動目標檔案，已級編譯進了zImage 裡了，只要用這個kernel燒錄到開發板，開機就會自動載入本驅動，

PS，如果發現如上編譯，沒有在ledtest目錄下生成leddriver.ko檔案，也就是本根沒有去編譯本驅動，那就把ledtest目錄入到/drivers/misc目錄下，相應的修改misc下面，然後，在makefile裡，不用選直接寫成obj-y += leddriver.o，這樣強制的包含進去編譯。

三、 應用程式（測試驅動）

用C語言寫一個應用，測試上面寫的驅動是否工作正常，這是一般的驅動開發流程

主要有兩個檔案：Android.mk和ledtest.c

1、

在$(YOUR_ANDROID)/external/LEDTEST/目錄編寫ledtest.c檔案，

ledtest.c

1. #include <stdio.h>
2. #include<stdlib.h>
3. #include <fcntl.h>// 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 /目錄編寫Android.mk檔案。這是Android Makefile的標準命名，不要更改。Android.mk檔案的格式和內容可以參考其他已有的Android.mk檔案的寫法，針對helloworld程式的Android.mk檔案內容如下：

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

注意上面LOCAL_SRC_FILES用來指定原始檔；

LOCAL_MODULE指定要編譯的模組的名字，下一步驟編譯時就要用到；

include $(BUILD_EXECUTABLE)表示要編譯成一個可執行檔案，如果想編譯成動態庫則可用BUILD_SHARED_LIBRARY，這些可以在

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

3、 回到Android原始碼頂層目錄進行編譯：

# cd $(YOUR_ANDROID) && make ledtestapp

例如我這裡的實際操作是

#cd android2.1

#make ledtestapp

注意make ledtestapp中的目標名ledtestapp就是上面Android.mk檔案中由LOCAL_MODULE指定的模組名。編譯結果如下

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: <span class="kwrd">out</span>/host/linux-x86/bin/apriori

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

target Executable: ledtestapp (<span class="kwrd">out</span>/target/product/generic/obj/EXECUTABLES/ledtestapp_intermediates/LINKED/ledtestapp)

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

target Strip: ledtestapp (<span class="kwrd">out</span>/target/product/generic/obj/EXECUTABLES/ledtestapp_intermediates/ledtestapp)

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

Install: <span class="kwrd">out</span>/target/product/generic/system/lib/libc.so

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

Install: <span class="kwrd">out</span>/target/product/generic/system/lib/libm.so

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

4、如上面的編譯結果所示，編譯後的可執行檔案存放在

out/target/product/generic/system/bin/目錄 可執行檔案是ledtestapp

5、拷貝ledtestapp可執行檔案到T卡，插入開發板

6、開電，在啟動進入android的過程中，串列埠終端 按回車，進入命令列模式

7、拷貝可執行檔案到根目錄

#cp /sdcard/ledtestapp /   

8、執行程式

#./ledtestapp

通過上面的步驟，可以看到開發板上相應的LED在閉，每秒鐘閃一次！

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