android驱动例子（LED灯控制）

2022-02-15 22:14:55

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 <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<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

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

Kconfig 文件

Kconfig 文件

config LEDTEST
tristate "LED test for ARMeasy"
default n
help
this is a LED driver for ARMEASY with S3C6410

Makefile文件

Makefile文件

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<android添加新驱动方法>

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

source "drivers/ledtest/Kconfig"

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

source "drivers/ledtest/Kconfig"

3)修改/drivers/Makefile文件

Obj-$(CONFIG_LEDTEST) +=ledtest/

4、编译驱动

在kernel目录下，终端输入

#make menuconfig

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

保存并退出

#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

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>// contact the open(),close(),read(),write() and so on!
#define DEVICE_NAME"/dev/vib"//device point
#define LED_ON 0x11
#define LED_OFF 0x22
int main(int argc,char **argv)
{
int fd;
int ret;
char *i;
printf("\n start gpio_led_driver test \r\n");
fd = open(DEVICE_NAME,O_RDWR);//Open device ,get the handle
printf("fd = %d \n",fd);
if(fd == -1) //open fail
{
printf("open device %s error \n",DEVICE_NAME);
}
else
{
while(1)
{
ioctl(fd,LED_OFF); //call the output function to off LEDs
sleep(1);//wait 1 second
ioctl(fd,LED_ON);
sleep(1);
}
ret = close(fd); //close device
printf("ret = %d \n",ret);
printf("close gpio_led test \n");
}
return 0;
}

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

LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_SRC_FILES:= \/par hello.c
LOCAL_MODULE := ledtestapp
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: <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！

码农公寓

一、硬件原理

二、驱动程序

三、 应用程序（测试驱动）

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三、应用程序（测试驱动）