现在对linux设备驱动还没有什么认识,跟着书上敲了一个字符驱动,这里把代码贴一下.
测试环境是 Ubuntu 16.04 64bit
驱动程序:
#include <linux/fs.h>#include <linux/module.h>#include <linux/init.h>#include <linux/cdev.h>#include <linux/uaccess.h>#define CDEVDEMO_MAJOR 0#define BUFFER_SIZE 512static int cdevdemo_major = CDEVDEMO_MAJOR;static char msgbuff[BUFFER_SIZE];void cdevdemo_exit(void);int cdevdemo_init(void);MODULE_LICENSE("Dual BSD/GPL");module_param(cdevdemo_major,int,S_IRUGO);
//注册初始化方法module_init(cdevdemo_init);
//注册退出方法module_exit(cdevdemo_exit);struct cdev *my_cdev;ssize_t cdev_write(struct file *, const char __user *, size_t, loff_t *);ssize_t cdev_read (struct file *, char __user *, size_t, loff_t *);int cdev_open (struct inode *,struct file *);int cdev_release (struct inode *,struct file *);struct file_operations my_fops = { .owner = THIS_MODULE, .open = cdev_open, .release = cdev_release, .read = cdev_read, .write = cdev_write,};void init_cdev(void){ int ret; my_cdev = cdev_alloc(); my_cdev->owner = THIS_MODULE; my_cdev->ops = &my_fops; //添加字符设备 ret = cdev_add(my_cdev,MKDEV(cdevdemo_major,),); ) { printk(KERN_NOTICE "=== cdev_add fail"); } printk(KERN_NOTICE "=== init_cdev finish");}int __init cdevdemo_init(void){ int ret; dev_t devno; printk(KERN_NOTICE "=== cdevdemo_init 0"); devno = MKDEV(cdevdemo_major,); if(cdevdemo_major) { printk(KERN_NOTICE "=== cdevdemo_init try register"); ret = register_chrdev_region(devno,,"cdevdemo"); }else { printk(KERN_NOTICE "=== cdevdemo_init auto register"); ret = alloc_chrdev_region(&devno,,,"cdevdemo"); cdevdemo_major = MAJOR(devno); } ) { printk(KERN_NOTICE "=== cdevdemo_init register fail"); return ret; } init_cdev(); printk(KERN_NOTICE "=== cdevdemo_init finish"); ;}void __exit cdevdemo_exit(void){ printk (KERN_NOTICE "=== cdevdemo_exit"); //去除字符设备 cdev_del(my_cdev); unregister_chrdev_region(MKDEV(cdevdemo_major,),);}ssize_t cdev_write(struct file *filp, const char __user *buf, size_t count, loff_t *offp){ int ret; printk(KERN_NOTICE "=== cdev_write"); ret = copy_from_user(msgbuff,buf,count%BUFFER_SIZE); ) { printk(KERN_NOTICE "=== cdev_write copy_from_user fail %d",ret); return -EFAULT; } msgbuff[count] = '-'; msgbuff[count+] = '-'; msgbuff[count+] = 'k'; msgbuff[count+] = 'e'; msgbuff[count+] = 'r'; msgbuff[count+] = 'n'; msgbuff[count+] = 'e'; msgbuff[count+] = 'l'; msgbuff[count+] = '\0'; printk(KERN_NOTICE "--- cdev_write : %s",msgbuff); return count%BUFFER_SIZE;}ssize_t cdev_read (struct file *filp, char __user *buf, size_t count, loff_t *offp){ int ret; printk(KERN_NOTICE "=== cdev_read"); ret = copy_to_user(buf,msgbuff,count%BUFFER_SIZE); ) { printk(KERN_NOTICE "=== cdev_read copy_to_user fail %d",ret); return -EFAULT; } printk(KERN_NOTICE "--- cdev_read :%s",msgbuff); return count%BUFFER_SIZE;}int cdev_open (struct inode *inode,struct file *filp){ printk(KERN_NOTICE "=== cdev_open"); ;}int cdev_release (struct inode *inode,struct file *filp){ printk(KERN_NOTICE "=== cdev_release"); ;}
Makefile
ifneq ($(KERNELRELEASE),)mymodule-objs := cdevobj-m := cdev.oelsePWD := $(shell pwd)KVER ?= $(shell uname -r)KDIR := /lib/modules/$(KVER)/buildall: $(MAKE) -C $(KDIR) M=$(PWD)clean: rm -rf *.cmd *.o *.mod.c *.ko .tmp_versionsendif
install.sh
#!/bin/bashmodule="cdev"device="cdev"name="cdevdemo"insmod $module.ko ]then exitfimajor=$(awk "{if(\$2==\"$name\"){print \$1}}" /proc/devices) /dev/$device
uninstall.sh
#!/bin/bashmodule="cdev"device="cdev"file="/dev/$device"if [ -e $file ]then rm -rf /dev/$device echo 'rm device'fiecho 'rm module'/sbin/rmmod $module
测试程序
#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <unistd.h>#include <stdio.h>int main(void){ int fd,ret; ] = "hello I'm from user"; ] = {}; fd = open("/dev/cdev",O_RDWR); ) { puts("open fail"); ; } ret = write(fd,buff,strlen(buff)); printf("write ret :%d\n",ret); ret = read(fd,rbuff,); printf("read ret :%d\n%s",ret,rbuff); ;}
运行结果:
write ret :read ret :hello I'm from user--kernel
