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android驱动例子（LED灯控制）

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08/22
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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
  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<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

  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 <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. 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！