来自：http://xianzilu.spaces.live.com/blog/cns!4201FDC93932DDAF!211.entry我写驱动的时候总希望能找到一个样例参考一下，可惜网上的例子基本找不到。还好友善之臂的文档里有些例子，但是说的很不详细，要是直接输入会有很多的编译错误。我的这个例子是一个控制LED的例子，用Linux就控制LED，当然是相当的弱智的哈哈。我用的是S3C2410，LED连接在GPB7~10上，灌电流方式驱动，IO配置寄存器GPBCON的物理地址0x56000010，IO数据寄存器GPBDAT的物理地址0x56000014。程序中的几个关键点，在我昨天的BLOG中有叙述。首先编写一个叫做leds_test.c的文件，内容如下：#include <linux/config.h>#include <linux/fs.h>#include <linux/module.h>#include <linux/errno.h>#include <linux/kernel.h>#include <linux/init.h>//Please configure your kernel first to use the following headers,because the directory "asm" is a short cut to your arch’s "asm"directory.//So do the headers in the "hardware" sub directory.#include <asm/io.h> //This header is for ioremap(), iounmap().#include <asm/uaccess.h> //This header is for get_user(), put_user().#define NAME "led_test"MODULE_AUTHOR("Lu Xianzi <cosine@126.com>"); //Thisline and the following4 lines can be omitted.MODULE_DESCRIPTION("LED Test Driver");MODULE_LICENSE("GPL");module_param(major, int, 0);MODULE_PARM_DESC(major, "Major device number");static int major = 231; //Define device majorunsigned long * pREG; //Definition of register base.static ssize_t led_test_write(struct file *file, const char __user *data,size_t len, loff_t *ppos){char buf[256];size_t i;for (i = 0; i < len && i < 254; i++)if (get_user(buf[i], data + i))return -EFAULT;buf[i] = ‘/0’;printk("LED Test – write: user_data %s/n", buf);return (len < 255 ? len : 255);}static ssize_t led_test_read(struct file *file, char __user *buf,size_t len, loff_t *ppos){char rbuf[4];size_t i;long tmp;tmp = * (volatile unsigned long *)(pREG + 1);rbuf[0] = tmp % 256;rbuf[1] = (tmp >> 8) % 256;rbuf[2] = (tmp >> 16) % 256;rbuf[3] = (tmp >> 24) % 256;if (len > 4)return 0;for (i = 0; i < len && i < 4; i++)if (put_user(rbuf[i], buf + i))return -EFAULT;printk("LED Test – read/n");return (len < 4 ? len : 4);}static int led_test_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg){unsigned long tmp;printk("LED Test – ioctl: param %u %lu/n", cmd, arg);switch (cmd){case 0:case 1:if (arg > 3)return -EINVAL;if (!cmd)* (volatile unsigned long *)(pREG + 1) |= (0x80 << arg);else* (volatile unsigned long *)(pREG + 1) &= ~(0x80 << arg);tmp = * (volatile unsigned long *)pREG;printk("GPBCON = 0x%lx/n", tmp);tmp = * (volatile unsigned long *)(pREG + 1);printk("GPBDAT = 0x%lx/n", tmp);break;default:return -EINVAL;}return 1;}static int led_test_open(struct inode *inode, struct file *file){unsigned m = iminor(inode);if (m > 63)return -EINVAL;printk("LED Test driver opened!/n");return nonseekable_open(inode, file);}static int led_test_release(struct inode *inode, struct file *file){printk("LED Test driver released!/n");return 0;}static struct file_operations led_test_fops = {.owner = THIS_MODULE,.ioctl = led_test_ioctl,.write = led_test_write,.read = led_test_read,.open = led_test_open,.release = led_test_release,};static int __init led_test_init(void){int ret;unsigned long tmp;printk("LXZ LED Test Driver./n");ret = register_chrdev(major, NAME, &led_test_fops);if (ret < 0) {printk("Unable to register character device!/n");return ret;}pREG = ioremap(0x56000010, 0x20);printk("Virtual addr base = 0x%lx/n", (unsigned long)pREG);tmp = * (volatile unsigned long *)pREG;printk("GPBCON = 0x%lx/n", tmp);tmp = * (volatile unsigned long *)(pREG + 1);printk("GPBDAT = 0x%lx/n", tmp);printk("Seting LED Test Driver…/n");* (volatile unsigned long *)pREG = 0x155555;* (volatile unsigned long *)(pREG + 1) = 0xfff;tmp = * (volatile unsigned long *)pREG;printk("GPBCON = 0x%lx/n", tmp);tmp = * (volatile unsigned long *)(pREG + 1);printk("GPBDAT = 0x%lx/n", tmp);printk("LED Test Driver initiated./n");return 0;}static void __exit led_test_cleanup(void){int ret;iounmap(pREG);ret = unregister_chrdev(major, NAME);if (ret < 0)printk("Unable to register character device!/n");else printk("LED Test Driver unloaded!");}module_init(led_test_init);module_exit(led_test_cleanup);在驱动程序的目录下建立一个名为“Makefile”的文件，其内容只有一行：obj-m := leds_test.o值得说明的是，编译模块的make file的文件名必须是Makefile，而不能是makefile编译之，我的linux内核存在/home/lxz/linux-2.6.11.7，所以编译命令为make -k -C /home/lxz/linux-2.6.11.7 SUBDIRS=$PWD modules//或者使用如下模板：ifneq ($(KERNELRELEASE),) obj-m := helloworld.o else KERNELDIR ?= /lib/modules/$(shell uname -r)/build #直接指定为绝对路径即可 PWD := $(shell pwd) default: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules endif 关于GNU make工具扩展的说明 在上面的Makefile中使用了 obj-m := 这个赋值语句的含义说明要使用目标文件helloworld.o建立一个模块，最后生成 的模块的名字就是helloworld.ko，如果你有一个名为module.ko的模块依赖于两个文件 file1.o和file2.o，那么我们可以使用module-obj扩展，如下所示 obj-m := module.o module-objs := file1.o file2.o //编译后生成几个文件，其中leds_test.ko是我们需要的驱动模块。然后在另外一个目录中编写一个叫做leds.c的文件，其内容如下#include <stdio.h>#include <fcntl.h>int main(int argc, char **argv){int fd;int on, led_no;char buf[256] = {"1234567890"};unsigned long tmp;if(argc != 3 || sscanf(argv[1], "%d", &led_no) != 1 ||sscanf(argv[2], "%d", &on) != 1 || on < 0 || on > 1 || led_no< 0 || led_no >3){fprintf(stderr, "Usage: leds led_no 0|1/n");exit(1);}fd = open("/dev/leds", O_RDWR);if (fd < 0){perror("open device leds");exit(1);}ioctl(fd, on, led_no);write(fd, buf, 10);read(fd, buf, 4);tmp = buf[0] + (buf[1] << 8) + (buf[2] << 16) + (buf[3] << 24);printf("User program read: GPBDAT = 0x%lx/n", tmp);close(fd);return 0;}编译之，输入arm-linux-gcc -o leds leds.c然后把生成的leds_test.ko和leds这2个文件拷贝到你的文件系统中，如/home下，启动Linux。之后的过程如下：/ # cd /home/home # insmod leds_test.koLxz LED Test Driver.Virtual addr base = 0xc485e010GPBCON = 0x44555GPBDAT = 0x540Seting LED Test Driver…GPBCON = 0x155555GPBDAT = 0x7ffLED Test Driver initiated./home # mknod /dev/leds c 231 0/home # ./leds 0 1LED Test driver opened!LED Test – ioctl: param 1 0GPBCON = 0x155555GPBDAT = 0x77fLED Test – write: user_data 1234567890LED Test – readUser proLED Test driver released!gram read: GPBDAT = 0x77f/home #这里有个非常有趣的事情，你会发现内核的printk函数比客户程序的printf函数打印时出现一些混乱，我想应该是因为Linux不是一个实时系统，内核和用户程序分时执行的结果。如果要卸载驱动模块，如下：/ # rmmod leds_testLED Test Driver unloaded!//注：我再用busybox1.14.2+armgcc4.3.2的时候，发现只能不带ko来rmmod，带了ko反而不好用。不知道为什么。另外如果ko不是放到/lib/modules/2.xxx，rmmod还有提示，奇怪。知道的大侠请指教一下。
因为有梦，所以勇敢出发，选择出发，便只顾风雨兼程。
