Android驱动例子（LED灯控制）

原文地址：http://www.linuxidc.com/Linux/2011-04/34541.htm

 

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

leddriver.c

1. #include <linux/kernel.h>
2. #include <linux/sched.h>
3. #include <linux/timer.h>
4. #include <linux/init.h>            /* For __init/__exit/... */
5. #include <linux/module.h>
6. #include <mach/hardware.h>
7. #include <asm/io.h>
8. #include <asm/uaccess.h>
9. #include <plat/gpio-cfg.h>
10. #include <plat/regs-clock.h>
11. #include <plat/regs-lcd.h>
12. #include <plat/regs-gpio.h>
13. #include <mach/map.h>
14. #include <linux/gpio.h>
15. #include <plat/gpio-bank-m.h>
16. #include <linux/cdev.h>
17. #include <linux/fs.h> //for register_chrdev()
18. #include <linux/device.h>
19. #include <mach/map.h>
20. #include "leddriver.h"
21. #include <linux/miscdevice.h>        /* For MODULE_ALIAS_MISCDEV
22.                             (WATCHDOG_MINOR) */
23. #include <linux/watchdog.h>        /* For the watchdog specific items */
24. #include <linux/fs.h>            /* For file operations */
25. #define Viberator_MAJOR        97  //?÷éè±?o?
26. #define SCULL_NR_DEVS           4
27. #define SCULL_QUANTUM         4000
28. #define SCULL_QSET             1000
29. //---do as the GIO driver
30. #define DEVCOUNT                4
31. #define GIO_MINOR            2    /* GIO minor no. */
32. static dev_t dev;        //éê ?? μ?μ??÷ éè±? o?
33. static struct cdev *cdev_p;
34. static int openCnt;
35. //--è???±?á?------------
36. int VIB_major  = 97;//we asigment it for test
37. int VIB_minor = 0;
38. int VIB_nr_devs = SCULL_NR_DEVS;
39. int VIB_quantum = SCULL_QUANTUM;
40. int VIB_qset = SCULL_QSET;
41.  
42. static struct class *vib_dev_class;
43. #define GPNCON  S3C64XX_GPNCON
44. #define GPNDAT  S3C64XX_GPNDAT
45. #define GPNPUD  S3C64XX_GPNPUD
46. #define GPMCON S3C64XX_GPMCON
47. #define GPMDAT  S3C64XX_GPMDAT
48. #define GPMPUD S3C64XX_GPMPUD
49.  
50. #define VIB_ON 0x11
51.   #defineVIB_OFF 0x22
52. static const struct file_operations GPIO_Viberator_ctl_ops={
53.     .owner        = THIS_MODULE,
54.     .open    = GPIO_VIB_open,
55.     .read    =GPIO_VIB_read,
56.     .write    =GPIO_VIB_write,
57.     .ioctl     = GPIO_VIB_ioctl,
58.     .release     =GPIO_VIB_release,
59. };
60. ssize_t GPIO_VIB_read(struct file * file,char * buf,size_t count,loff_t * f_ops)
61. {
62.     printk(" GPIO_VIB_read \r\n");
63.     gpio_direction_output(S3C64XX_GPM(3), 0);//
64.     return count ;
65. }
66. ssize_t GPIO_VIB_write (struct file * file,const char * buf, size_t count,loff_t * f_ops)
67. {
68.       printk(" GPIO_VIB_write \r\n");
69.       gpio_direction_output(S3C64XX_GPM(3), 1);//
70.    return count;
71. }
72.  
73. //ssize_t GPIO_VIB_ioctl(struct inode *  inode,struct file * file,unsigned int cmd, long data)
74. static int GPIO_VIB_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
75. {
76.     printk(KERN_ERR"VIB:GPIO_VIB_ioctl --CMD=%x \n",cmd);
77.     switch(cmd)
78.         {
79.            case VIB_ON:
80.             gpio_direction_output(S3C64XX_GPM(1), 0);//
81.             gpio_direction_output(S3C64XX_GPM(2), 0);//
82.             gpio_direction_output(S3C64XX_GPM(3), 0);//
83.             gpio_direction_output(S3C64XX_GPM(4), 1);//
84.             printk(KERN_ERR"VIB:GPIO_VIB_ioctl --VIB_ON\n");
85.             break;
86.          case VIB_OFF:
87.             {
88.             printk(KERN_ERR"VIB:GPIO_VIB_ioctl --VIB_OFF\n");
89.             gpio_direction_output(S3C64XX_GPM(1), 1);//
90.             gpio_direction_output(S3C64XX_GPM(2), 1);//
91.             gpio_direction_output(S3C64XX_GPM(3), 1);//
92.             gpio_direction_output(S3C64XX_GPM(4), 0);//
93.             break;
94.          }
95.          default:break;
96.                 
97.     }
98.         //gpio_free(S3C64XX_GPN(7));
99. }
100. ssize_t GPIO_VIB_open(struct inode * inode,struct file * file)
101. {
102. //?￡?éêy
103.   //MOD_INC_USE_COUNT;
104.   printk("GPIO_VIB_open() \n");   
105.   return 0;
106. }
107. ssize_t GPIO_VIB_release(struct inode * inode, struct file * file)
108. {
109.    // MOD_DEC_USE_COUNT;//?￡?éêy??
110.      printk("GPIO_VIB_release() \n");   
111.     return 0;
112. }
113. static int GPIO_VIB_CTL_init(void)
114. {
115.     int ret  = -ENODEV;
116.    int error ;
117.     printk("---------------------------------------------- \r\n");
118.     //3?ê??ˉ???ú
119.         s3c_gpio_cfgpin(S3C64XX_GPM(1), S3C_GPIO_SFN(1));//GPM1 output
120.         s3c_gpio_cfgpin(S3C64XX_GPM(2), S3C_GPIO_SFN(1));//GPM2 output
121.         s3c_gpio_cfgpin(S3C64XX_GPM(3), S3C_GPIO_SFN(1));//GPM3 output
122.         s3c_gpio_cfgpin(S3C64XX_GPM(4), S3C_GPIO_SFN(1));//GPM4 output
123. #if 1 /*?2ì?·?ê?×￠2á?y?ˉ*/
124. ret = register_chrdev(Viberator_MAJOR, "viberator", &GPIO_Viberator_ctl_ops);
125. if (ret < 0) {
126.     printk(KERN_ERR "VIB: unable to get major %d\n", ret);
127.     return ret;
128. }
129. //′′?¨\uc1class
130. vib_dev_class = class_create(THIS_MODULE, "viberator");
131. if (IS_ERR(vib_dev_class)) {
132.     unregister_chrdev(Viberator_MAJOR, "capi20");
133.     return PTR_ERR(vib_dev_class);
134. }
135. //′′?¨?úμ?￡?
136. device_create(vib_dev_class, NULL, MKDEV(Viberator_MAJOR, 0), NULL, "vib");
137. // create a point under /dev/class/vib  
138. //í¨1yé????aá?2?￡??y?ˉ?ó??oó￡??í?á?ú/dev/class/????éú3é\uc1vib?úμ?￡?ó|ó?3ìDò?éò???2ù×÷???t???ù2ù×÷?a???úμ?￡?í¨1y\uc1open ,write,read μèoˉêy2ù×÷￡??ê?é?éò??′oó??μ?ó|ó?ê?ày3ìDò?￡
139.   return 0;    
140. #endif
141. #if 0/* ×￠2á?ˉì?*/
142.     if ((error = alloc_chrdev_region(&dev, 0, DEVCOUNT, "vibrate")) < 0)
143.         {
144.         printk(KERN_ERR
145.                "VIB: Couldn't alloc_chrdev_region, error=%d\n",
146.                error);
147.         return 1;
148.     }
149.          printk("dev = %d  \n",dev);
150.     cdev_p = cdev_alloc();
151.     cdev_p->ops = &GPIO_Viberator_ctl_ops;
152.     error = cdev_add(cdev_p, dev, DEVCOUNT);
153.     if (error) {
154.         printk(KERN_ERR
155.                "VIB: Couldn't cdev_add, error=%d\n", error);
156.         return 1;
157.     }
158.  
159.     vib_dev_class = class_create(THIS_MODULE, "vib-dev");
160.     if (IS_ERR(vib_dev_class)) {
161.         res = PTR_ERR(vib_dev_class);
162.         goto out_unreg_class;
163.     }
164.     return 0;
165. #endif
166. out_unreg_class:
167.     class_destroy(vib_dev_class);
168. return 1;
169. }
170.  
171. static int __init S3C6410_VIB_init(void)
172. {
173.     int ret = -ENODEV;
174.     //μ÷ó?oˉêy   
175.         printk(KERN_ERR "Auly: S3C6410_VIB_init---\n");
176.     ret = GPIO_VIB_CTL_init();
177.     if(ret)
178.         {
179.         printk(KERN_ERR "Auly: S3C6410_VIB_init--Fail !!!\n");
180.         return ret;
181.     }
182.     return 0;
183. }
184. static void __exit cleanup_GPIO_VIB(void)
185. {
186.     //×￠?úéè±?
187.   //  devfs_unregister_chrdev(Viberator_MAJOR,"gpio_vib_ctl");
188. #if 0
189.       cdev_del(cdev_p);
190.     unregister_chrdev_region(dev, DEVCOUNT);
191.     class_destroy(vib_dev_class);
192. #endif
193. device_destroy(vib_dev_class, MKDEV(Viberator_MAJOR, 0));
194. class_destroy(vib_dev_class);
195. unregister_chrdev(Viberator_MAJOR, "viberator");
196. }
197. MODULE_LICENSE("GPL");
198. MODULE_DESCRIPTION("Peter first driver");
199. MODULE_ALIAS_CHARDEV(Viberator_MAJOR, 0);
200.  
201. module_init(S3C6410_VIB_init);
202. 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,const char * 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.  
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。

、 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！