编写字符驱动程序 - 读取cmos中的时间

来源：互联网发布：win10网络授权编辑：程序博客网时间：2024/06/05 02:47

要求：该驱动程序主设备文件名为：/dev/cmos ，主设备号位 211 ，次设备号为0

cmos.c

#include <linux/init.h>#include <linux/kernel.h>#include <linux/fs.h>#include <linux/cdev.h>#include <linux/types.h>#include <linux/slab.h> //kmalloc()#include <asm/uaccess.h> //copy_from_user#include <linux/pci.h>#include <linux/module.h>#include <asm/io.h> MODULE_LICENSE("GPL") ;#define device_name "cmos"#define cmos_major 211#define cmos_minor 0#define CMOS_READ(addr) ({outb(0x80|addr,0x70);inb(0x71);}) #define BCD_TO_BIN(val) ((val)=((val)&15)+((val)>>4)*10) static int cmos_open(struct inode *inode, struct file *file){    return 0;}static int cmos_release(struct inode *inode, struct file *file){    return 0;}static ssize_t cmos_read(struct file *file, char *buf,size_t count, loff_t *ppos){    char d[6]; //yy/mm/dd/hh/min/sec    int i;    printk("cmos driver:read\n");    d[0] = CMOS_READ(9);    d[1] = CMOS_READ(8);    d[2] = CMOS_READ(7);    d[3] = CMOS_READ(4);    d[4] = CMOS_READ(2);    d[5] = CMOS_READ(0);    for(i=0;i<6;i++)        BCD_TO_BIN(d[i]);    if(count > 6)        count = 6;    copy_to_user(buf,d,count);    return count;}static struct file_operations cmos_fops = {    owner:THIS_MODULE, /* Owner *///<linux/fs.h>    open:cmos_open, /* Open method */    read:cmos_read,    release:cmos_release, /* Release method */}; static int __init cmos_init(void){    printk("CMOS Driver Initialized.\n");    register_chrdev(cmos_major , device_name,&cmos_fops) ;    return 0;}static void __exit cmos_exit(void){    printk("exit\n");    unregister_chrdev(cmos_major , device_name) ;}module_init(cmos_init) ;module_exit(cmos_exit) ;

cmostest.c

#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <fcntl.h>char buf[6];int main(int argc,char **argv){int fd;int ret;if((fd=open("/dev/cmos",O_RDWR))<0){printf("cmos driver open fail\n");return -1;}ret=read(fd,buf,6);if(ret == -1){printf("read fail\n");return -1;}printf("CMOS tell me the time is:20%02d/%02d/%02d %02d:%02d:%02d\n",buf[0],buf[1],buf[2],buf[3],buf[4],buf[5]);close(fd);return 0;}

Makefile:

ifneq ($(KERNELRELEASE),)obj-m := cmos.oelseKERNELDIR ?= /lib/modules/$(shell uname -r)/buildPWD := $(shell pwd)default:$(MAKE) -C $(KERNELDIR) M=$(PWD) modulesclean:rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.crm -rf Module.* modules.*endif

加载模块并查看调试信息

查看创建的设备驱动

运行测试程序

卸载驱动模块，检查模块驱动设备是否没有了

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