Linux 2.6驱动开发－－字符设备驱动实例

驱动代码

#include <linux/module.h> #include <linux/fs.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/types.h> #include <linux/errno.h> #include <linux/fcntl.h> #define MY_DEVICE_NAME "mydevice" #define MY_DEVICE_MAJOR 240 int device_open(struct inode * inode,struct file *flip) { int num=MINOR(inode->i_rdev); printk("My device open ->minor: %d/n",num); return 0; } ssize_t device_read(struct file * filp,char * buf,size_t count,loff_t *f_ops ) { printk("My device read ->buf : %08X count %08X/n",buf,count); return 0; } ssize_t device_write(struct file * filp,const char * buf,size_t count,loff_t *f_ops) { printk("My device wirte ->buf : %08X count %08X/n",buf,count); return 0; } int device_close(struct inode *inode,struct file *flip) { printk("My device close/n"); return 0; } struct file_operations my_device_fops = { .owner=THIS_MODULE, .read=device_read, .open=device_open, .write=device_write, .release=device_close, }; int mydevice_init(void) { int ret; printk("call my device/n"); ret=register_chrdev(MY_DEVICE_MAJOR,MY_DEVICE_NAME,&my_device_fops); if(ret<0) { printk("Regist device error/n"); return ret; } return 0; } void mydevice_exit(void) { printk("call my device release/n"); unregister_chrdev(MY_DEVICE_MAJOR,MY_DEVICE_NAME); } module_init (mydevice_init); module_exit(mydevice_exit); MODULE_LICENSE("Dual BSD/GPL"); 

 

Makefile文件

 

#KVER = /usr/src/linux-source-2.6.38

KVER = /lib/modules/`uname -r`/build

CURDIR = $(shell pwd)

# Kernel modules

obj-m := my_device.o

 

build: kernel_modules

 

kernel_modules:

$(MAKE) -C $(KVER) M=$(CURDIR) modules

 

clean:

$(MAKE) -C $(KVER) M=$(CURDIR) clean

 

 

测试代码

#include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <sys/ioctl.h> #include <fcntl.h> #include <unistd.h> #define DEVICE_NAME "/dev/yming_device" int main() { int dev; int ret; dev=open(DEVICE_NAME,O_RDWR|O_NDELAY); printf("dev : %d/n",dev); if(dev<0) { printf("can not open the device %s/n",DEVICE_NAME); return -1; } read(dev,0x30,0x31); write(dev,0x41,0x42); close(dev); printf("the program is over/n"); return 0; } 

 

然后gcc call_test.c -o call_test

 

sudo insmod#加载驱动

然后创建字符设备

sudo mknod /dev/yming_device c 240 32

分别表示设备文件名，设备类型，主设备号，次设备号

 

运行call_test,然后使用命令查看驱动的运行信息

dmesg | tail

如下

[ 1190.544602] keyboard: can't emulate rawmode for keycode 240

[ 1190.544620] keyboard: can't emulate rawmode for keycode 240

[ 1521.351828] exe (1755): /proc/1755/oom_adj is deprecated, please use /proc/1755/oom_score_adj instead.

[ 6359.871814] call my device

[ 7014.893799] call my device release

[ 7283.765009] call my device

[ 7289.153601] My device open ->minor: 32

[ 7289.153663] My device read ->buf : 00000030   count 00000031

[ 7289.153667] My device wirte ->buf : 00000041   count 00000042

[ 7289.153671] My device close

注，注意应用程序对设备的操作权限，可以使用命令

chmod 777 /dev/yming_device 给所有用户以读写权限