内核版本：linux-3.0
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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，
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<guowenxue@gmail.com> * All rights reserved.** Filename: s3c_led.c* Description: This file* * Version: 1.0.0(07/26/2012~)* Author: Guo Wenxue <guowenxue@gmail.com>* 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 <guowenxue@gmail.com>"#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); 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.oKERNELDIR := ~/kernel/linux-3.0-fulinux/PWD := $(shell pwd)modules: $(MAKE) -C $(KERNELDIR) M=$(PWD) modulesmodules_install: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules_installclean: 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<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 <fulinux@sina.com>* ChangeLog: 1, Release initial version on "2013年04月04日 14时19分53秒"* ********************************************************************************/#include <stdio.h>#include <stdlib.h>#include <unistd.h>#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
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
routeadd 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
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
我的led主设备号是253,
创建一个设备节点：
mknod /dev/led c 253 0
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：
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：
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
编译后送到开发板中
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：-（
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下 篇：linux设备驱动篇之LED驱动（二）http://blog.csdn.net/sonbai/article/details/8761796
PC 平 台：ubuntu12.10
开 发 板：tq2440fl2440
内核版本：linux-3.0
作 者：fulinux
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所有欺骗中，自欺是最为严重的
