宋宝华 《Linux设备驱动开发详解》示例代码之second设备

second.c代码

#include <linux/module.h>#include <linux/fs.h>#include <linux/types.h>#include <linux/sched.h>#include <linux/cdev.h>#include <linux/init.h>#include <linux/timer.h>#include <asm/io.h>#include <asm/system.h>#include <asm/uaccess.h>#defineSECOND_MAJOR252staticintsecond_major = SECOND_MAJOR;structsecond_dev{structcdevcdev;atomic_tcounter;structtimer_lists_timer;};structsecond_dev*second_devp;staticvoidsecond_timer_handle(unsigned long arg){mod_timer(&second_devp->s_timer, jiffies + HZ);atomic_inc(&second_devp->counter);printk(KERN_NOTICE "current jiffies is %ld\n", jiffies);}intsecond_open(struct inode *inode, struct file *filp){init_timer(&second_devp->s_timer);second_devp->s_timer.function = &second_timer_handle;second_devp->s_timer.expires  = jiffies + HZ;add_timer(&second_devp->s_timer);atomic_set(&second_devp->counter, 0);return 0;}intsecond_release(struct inode *inode, struct file *filp){del_timer(&second_devp->s_timer);return 0;}staticssize_tsecond_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos){int counter;counter = atomic_read(&second_devp->counter);if(put_user(counter, (int *)buf))return -EFAULT;elsereturn sizeof(unsigned int);return 0;}staticconststructfile_operations second_fops = {.owner=THIS_MODULE,.open=second_open,.release=second_release,.read=second_read,};static voidsecond_setup_cdev(struct second_dev *dev,int index ){int err;int devno = MKDEV(second_major, index);cdev_init(&dev->cdev, &second_fops);dev->cdev.owner = THIS_MODULE;dev->cdev.ops = &second_fops;err=cdev_add(&dev->cdev, devno, 1);if(err)printk(KERN_ALERT "Error setup the second device");}intsecond_init(void){intret;dev_tdevno = MKDEV(second_major, 0);if(second_major)ret = register_chrdev_region(devno, 1, "second");else{ret = alloc_chrdev_region(&devno, 0, 1, "second" );second_major = MAJOR(devno);}if( ret < 0)return ret;second_devp = kmalloc(sizeof(struct second_dev), GFP_KERNEL);if(!second_devp){ret = -ENOMEM;goto fail_malloc;}memset(second_devp, 0 ,sizeof(struct second_dev));second_setup_cdev(second_devp, 0);return 0;fail_malloc:unregister_chrdev_region(devno, 1);return ret;}voidsecond_exit(void){cdev_del(&second_devp->cdev);kfree(second_devp);unregister_chrdev_region(MKDEV(second_major, 0), 1);}MODULE_AUTHOR("BG2BKK");MODULE_LICENSE("Dual BSD/GPL");module_init(second_init);module_exit(second_exit);

makefile

KERNEL_DIR := /lib/modules/$(shell uname -r)/buildPWD:= $(shell pwd)obj-m := second.odefault:$(MAKE) -C $(KERNEL_DIR) SUBDIRS=$(PWD) modulestest: test.cgcc $< -o $@.o  -gclean:rm -rf *.o *.ko *~ *.order *.symvers *.markers *.mod.c

测试代码

/*======================================================================    A test program to access /dev/second    This example is to help understand kernel timer         The initial developer of the original code is Baohua Song    <[e-mail]>. All Rights Reserved.======================================================================*/#include <sys/types.h>#include <sys/stat.h>#include <stdio.h>#include <fcntl.h>#include <unistd.h>#include <sys/time.h>main(){  int fd;  int counter = 0;  int old_counter = 0;    /*打开/dev/second设备文件*/  fd = open("/dev/second", O_RDONLY);  if (fd !=  - 1)  {    while (1)    {      read(fd,&counter, sizeof(unsigned int));//读目前经历的秒数      if(counter!=old_counter)      {      printf("seconds after open /dev/second :%d\n",counter);      old_counter = counter;      }    }      }  else  {    printf("Device open failure\n");  }}

测试脚本

1 load_scull.sh

#!/bin/sh/sbin/insmod second.komknod /dev/second c 252 0

2 unload_scull.sh

#!/bin/sh/sbin/rmmod second.korm /dev/second -f

3 test.sh

#!/bin/shmake cleanmake make testsudo ./unload_scullsudo ./load_scullsudo ./test.o