linux设备驱动篇之LED驱动（一）

原帖地址:http://blog.csdn.net/fulinus/article/details/8760993 内核版本：linux-3.0

   在学习LED设备驱动期间经历的问题层出不穷，遇到的问题有以下这些：

1、网上很多的LED驱动几乎都是2.6的内核版本，但是3.0内核和2.6的内核驱动编写有很多地方是不同的在2.6上能运行的设备驱动不一定能在3.0内核上运行。这对于刚刚踏入驱动大门人，急于想了解LED驱动是什么样的，他是怎么工作的，与应用程序又是如何协同工作的呢？对于我们可能第一个要去做的就是去找个例程先跑一跑，了解是怎么回事，增强一些自信和在战略上“藐视”设备驱动的气魄。先介绍一下我的工程结构如下说是，第一个是建立在后面第三个文件s3c_led.c这个LED设备驱动上运行的led运行程序，第二个是Make文件，

[attach]1003[/attach]

我先把可以运行的这个LED驱动贴上来：

（如果你拷贝到你的vim上格式多乱了的话，教你一个快速的方法：在命令行模式下连续按下gg=G这上个字符就能帮你自动调整格式。

你在下面的程序中找到这个nt led[LED_NUM] = {5,6,7,8}; / Four LEDs use GPB5,GPB6,GPB8,GPB10 /，因为我的led是在GPBIO5、6、7、8这个几个端口，结合你自己的情况修改，其他的不用改

/*****

• Copyright: (C) 2012 Guo Wenxue[email]guowenxue@gmail.com[/email]
• All rights reserved.
• Filename: s3c_led.c
• Description: This file
• Version: 1.0.0(07/26/2012~)
• Author: Guo Wenxue [email]guowenxue@gmail.com[/email]
• ChangeLog: 1, Release initial version on "07/26/2012 10:03:40 PM"

• ****/

  include <linux/module.h> / Every Linux kernel module must include this head /

  include <linux/init.h> / Every Linux kernel module must include this head /

  include <linux/kernel.h> / printk() /

  include <linux/fs.h> / struct fops /

  include <linux/errno.h> / error codes /

  include <linux/cdev.h> / cdev_alloc() /

  include <asm/io.h> / ioremap() /

  include <linux/ioport.h> / request_mem_region() /

  include <asm/ioctl.h> / Linux kernel space head file for macro _IO() to generate ioctl command /

  ifndef KERNEL

  include <sys/ioctl.h> / User space head file for macro _IO() to generate ioctl command /

  endif

  //#include <linux/printk.h> / Define log level KERN_DEBUG, no need include here /

  define DRV_AUTHOR "Guo Wenxue [email]guowenxue@gmail.com[/email]"

  define DRV_DESC "S3C24XX LED driver"

  define DEV_NAME "led"

  define LED_NUM 4

  / Set the LED dev major number / //#define LED_MAJOR 79

  ifndef LED_MAJOR

  define LED_MAJOR 0

  endif

  define DRV_MAJOR_VER 1

  define DRV_MINOR_VER 0

  define DRV_REVER_VER 0

  define DISABLE 0

  define ENABLE 1

  define GPIO_INPUT 0x00

  define GPIO_OUTPUT 0x01

  define PLATDRV_MAGIC 0x60

  define LED_OFF _IO (PLATDRV_MAGIC, 0x18)

  define LED_ON _IO (PLATDRV_MAGIC, 0x19)

  define S3C_GPB_BASE 0x56000010

  define GPBCON_OFFSET 0

  define GPBDAT_OFFSET 4

  define GPBUP_OFFSET 8

  define S3C_GPB_LEN 0x10 / 0x56000010~0x56000020 /

int led[LED_NUM] = {5,6,7,8}; / Four LEDs use GPB5,GPB6,GPB8,GPB10 /

static void __iomem *s3c_gpb_membase;

define s3c_gpio_write(val, reg) __raw_writel((val), (reg)+s3c_gpb_membase)

define s3c_gpio_read(reg) __raw_readl((reg)+s3c_gpb_membase)

int dev_count = ARRAY_SIZE(led); int dev_major = LED_MAJOR; int dev_minor = 0; int debug = DISABLE;

static struct cdev *led_cdev;

static int s3c_hw_init(void) { int i; volatile unsigned long gpb_con, gpb_dat, gpb_up;

 if(!request_mem_region(S3C_GPB_BASE, S3C_GPB_LEN, "s3c2440 led"))
 {
     return -EBUSY;
 }

 if( !(s3c_gpb_membase=ioremap(S3C_GPB_BASE, S3C_GPB_LEN)) )
 {
     release_mem_region(S3C_GPB_BASE, S3C_GPB_LEN);
     return -ENOMEM;
 }

 for(i=0; i<dev_count; i++)
 {
     /* Set GPBCON register, set correspond GPIO port as input or output mode  */
     gpb_con = s3c_gpio_read(GPBCON_OFFSET);
     gpb_con &= ~(0x3<<(2*led[i]));   /* Clear the currespond LED GPIO configure register */
     gpb_con |= GPIO_OUTPUT<<(2*led[i]); /* Set the currespond LED GPIO as output mode */
     s3c_gpio_write(gpb_con, GPBCON_OFFSET);

     /* Set GPBUP register, set correspond GPIO port pull up resister as enable or disable  */
     gpb_up = s3c_gpio_read(GPBUP_OFFSET);
     //gpb_up &= ~(0x1<<led[i]); /* Enable pull up resister */
     gpb_up |= (0x1<<led[i]);  /* Disable pull up resister */
     s3c_gpio_write(gpb_up, GPBUP_OFFSET);

     /* Set GPBDAT register, set correspond GPIO port power level as high level or low level */
     gpb_dat = s3c_gpio_read(GPBDAT_OFFSET);
     //gpb_dat &= ~(0x1<<led[i]); /* This port set to low level, then turn LED on */
     gpb_dat |= (0x1<<led[i]);  /* This port set to high level, then turn LED off */
     s3c_gpio_write(gpb_dat, GPBDAT_OFFSET);
 }

 return 0;

}

static void turn_led(int which, unsigned int cmd) { volatile unsigned long gpb_dat;

 gpb_dat = s3c_gpio_read(GPBDAT_OFFSET);

[p=30, 2, left][/p] if(LED_ON == cmd) { gpb_dat &= ~(0x1<<led[which]); / Turn LED On / } else if(LED_OFF == cmd) { gpb_dat |= (0x1<<led[which]); / Turn LED off / }

 s3c_gpio_write(gpb_dat, GPBDAT_OFFSET);

}

static void s3c_hw_term(void) { int i; volatile unsigned long gpb_dat;

 for(i=0; i<dev_count; i++)
 {
     gpb_dat = s3c_gpio_read(GPBDAT_OFFSET);
     gpb_dat |= (0x1<<led[i]);  /* Turn LED off */
     s3c_gpio_write(gpb_dat, GPBDAT_OFFSET);
 }

 release_mem_region(S3C_GPB_BASE, S3C_GPB_LEN);
 iounmap(s3c_gpb_membase);

}

static int led_open(struct inode inode, struct file file) { int minor = iminor(inode);

 file->private_data = (void *)minor;

 printk(KERN_DEBUG "/dev/led%d opened.\n", minor);
 return 0;

}

static int led_release(struct inode inode, struct file file) { printk(KERN_DEBUG "/dev/led%d closed.\n", iminor(inode));

 return 0;

}

static void print_help(void) { printk("Follow is the ioctl() commands for %s driver:\n", DEV_NAME); //printk("Enable Driver debug command: %u\n", SET_DRV_DEBUG); printk("Turn LED on command : %u\n", LED_ON); printk("Turn LED off command : %u\n", LED_OFF);

 return;

}

static long led_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { int which = (int)file->private_data;

 switch (cmd)
 {
     case LED_ON:

         turn_led(which, LED_ON);
         break;

     case LED_OFF:
         turn_led(which, LED_OFF);
         break;

     default:
         printk(KERN_ERR "%s driver don't support ioctl command=%d\n", DEV_NAME, cmd);
         print_help();
         break;
 }

 return 0;

}

static struct file_operations led_fops = { .owner = THIS_MODULE, .open = led_open, .release = led_release, .unlocked_ioctl = led_ioctl, };

static int __init s3c_led_init(void) { int result; dev_t devno;

 if( 0 != s3c_hw_init() )
 {
     printk(KERN_ERR "s3c2440 LED hardware initialize failure.\n");
     return -ENODEV;
 }

 /*  Alloc the device for driver */
 if (0 != dev_major) /*  Static */
 {
     devno = MKDEV(dev_major, 0);
     result = register_chrdev_region (devno, dev_count, DEV_NAME);
 }
 else
 {
     result = alloc_chrdev_region(&devno, dev_minor, dev_count, DEV_NAME);
     dev_major = MAJOR(devno);
 }

 /*  Alloc for device major failure */
 if (result < 0)
 {
     printk(KERN_ERR "S3C %s driver can't use major %d\n", DEV_NAME, dev_major);
     return -ENODEV;
 }
 printk(KERN_DEBUG "S3C %s driver use major %d\n", DEV_NAME, dev_major);

 if(NULL == (led_cdev=cdev_alloc()) )
 {
     printk(KERN_ERR "S3C %s driver can't alloc for the cdev.\n", DEV_NAME);
     unregister_chrdev_region(devno, dev_count);
     return -ENOMEM;
 }

s3c_led.c

 led_cdev->owner = THIS_MODULE;
 cdev_init(led_cdev, &led_fops);

 result = cdev_add(led_cdev, devno, dev_count);
 if (0 != result)
 {
     printk(KERN_INFO "S3C %s driver can't reigster cdev: result=%d\n", DEV_NAME, result);
     goto ERROR;
 }

 printk(KERN_ERR "S3C %s driver[major=%d] version %d.%d.%d installed successfully!\n",
         DEV_NAME, dev_major, DRV_MAJOR_VER, DRV_MINOR_VER,DRV_REVER_VER);
 return 0;

ERROR: printk(KERN_ERR "S3C %s driver installed failure.\n", DEV_NAME); cdev_del(led_cdev); unregister_chrdev_region(devno, dev_count); return result; }

static void __exit s3c_led_exit(void) { dev_t devno = MKDEV(dev_major, dev_minor);

 s3c_hw_term();

 cdev_del(led_cdev);
 unregister_chrdev_region(devno, dev_count);

 printk(KERN_ERR "S3C %s driver version %d.%d.%d removed!\n",
         DEV_NAME, DRV_MAJOR_VER, DRV_MINOR_VER,DRV_REVER_VER);

 return ;

}

/ These two functions defined in <linux/init.h> / module_init(s3c_led_init); module_exit(s3c_led_exit);

module_param(debug, int, S_IRUGO); module_param(dev_major, int, S_IRUGO);

MODULE_AUTHOR(DRV_AUTHOR); MODULE_DESCRIPTION(DRV_DESC); MODULE_LICENSE("GPL");

2、makefile文件的它要和你的内核一起才能工作，这里是linux-3.0，你进入linux-3.0目录后要先make一下才能在led目录下make,makefile文件代码如下所示，你有没有看到绿色的一行，你把它指定到你的内核目录就行，我的目录是home/fulinux/kernel/linux-3.0-fulinux/，所以是这样设置的

obj-m := s3c_led.o KERNELDIR := ~/kernel/linux-3.0-fulinux/ PWD := $(shell pwd) modules: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules modules_install: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install clean: rm -rf .o ~core .depend ..cmd .ko .mod.c .tmp_versions odule* $(TARGET)

3、应用程序代码如下，编译的时候是没有用makefile文件的，你只需要用arm-linux-gcc -o led_test led_test.c命令或者你的编译器的绝对路径，我的是

/opt/buildroot-2012.08/arm920t/usr/bin/arm-linux-gcc -o led_test led_test.c

/*****

• Copyright: (C) 2013 fulinux
• All rights reserved.
• Filename: led_test.c
• Description: This file is used to test led
• Version: 1.0.0(2013年04月04日~)
• Author: fulinux [email]fulinux@sina.com[/email]
• ChangeLog: 1, Release initial version on "2013年04月04日 14时19分53秒"

• ****/

  include

  include

  include

  include <sys/ioctl.h>

  include <asm/ioctl.h> / Linux kernel space head file for macro _IO() to generate ioctl command /

  ifndef KERNEL

  include <sys/ioctl.h> / User space head file for macro _IO() to generate ioctl command /

  endif

  define PLATDRV_MAGIC 0x60

  define LED_OFF _IO (PLATDRV_MAGIC, 0x18)

  define LED_ON _IO (PLATDRV_MAGIC, 0x19)

  int main(int argc, char **argv) { int on; int led_no; int fd;

  fd = open("/dev/led", 0); if (fd < 0) { fd = open("/dev/led", 0); } if (fd < 0) { perror("open device led"); exit(1); } ioctl(fd, LED_ON, 0); close(fd); return 0; }

4、编译完成后通过你的方式将s3c_led.ko 和led_test这两个执行文件送到开发板上，我是通过tftp服务器

tftp -gr s3c_led.ko 192.168.1.4

tftp -gr led_test 192.168.1.4

[attach]1004[/attach]

将文件送到开发板上的。

如果你的开发板网络没有配置好，输入如下命令：

ifconfig eth0 192.168.1.3 netmask 255.255.255.0

route add default gw 192.168.1.1

5、在开发板里执行：

insmod s3c_led.ko

然后显示如下信息说明安装成功 [attach]1005[/attach]

6、好了到了这里不要以为就可以运行led_test了，其实还没。你要先为驱动创建一个设备节点，怎么创建呢，先看下设备驱动的主设备号 [attach]1006[/attach]

我的led主设备号是253,

创建一个设备节点：

mknod /dev/led c 253 0

[attach]1007[/attach]

7、修改一下应用程序的权限，记住在PC上改变权限不行，要在开发板里改变

chmod 777 led_test

如果不修改权限会有出现如下信息： [attach]1008[/attach]

8、最后执行运行程序

./led_test

你就会看到你的开发板上的LED亮了：-）

后话：

上面的程序执行后你会看到只有第一盏灯是亮着的，如果要想让第二盏灯亮，分析一下代码： [attach]1009[/attach]

看一下高亮的地方，前面我们指定的次设备号（minor）是0，第二盏灯对应的次设备号是1，同时你要在应用程序里修改如下 [attach]1010[/attach]

编译后送到开发板中

[attach]1011[/attach]

就会发现开发板亮了第二个灯，这个应用程序很简陋，要继续优化才行：-（

[attach]1007[/attach]