Description of Linux device driver development by Song Baohua

The drive of a general character device is transformed into a misc device. The MISC device is not as troublesome as a character device. In the future, try to replace the scull. c driver with a misc device.

#include <linux/fs.h>

#include <linux/kernel.h>#include <linux/cdev.h>#include <linux/module.h>#include <linux/slab.h>#include <linux/gfp.h>#include <asm/uaccess.h>#include <linux/miscdevice.h>#define SCULL_NAME"scull"#define MAX_DATA0x1000struct scull_dev {struct miscdevice misc_scull;char data[MAX_DATA];struct semaphore sem;};MODULE_LICENSE("Dual BSD/GPL");MODULE_AUTHOR("BG2BKK");structscull_dev *scull_devp;intscull_open(struct inode *inode, struct file *filp){printk(KERN_ALERT "open the scull device\n");return 0;}intscull_release(struct inode *inode, struct file *filp){printk(KERN_ALERT "close the scull device\n");return 0;}ssize_tscull_read(struct file *filp, char __user *buf, size_t count, loff_t *f_ops){unsigned longp = *f_ops;unsigned intcnt = count;int ret = 0;if(down_interruptible(&scull_devp->sem))return -ERESTARTSYS;if(copy_to_user(buf, scull_devp->data,cnt)){ret = -EFAULT;} else {*f_ops += cnt;ret = cnt;printk(KERN_ALERT "read %u bytes from %lu\n",cnt, p);}up(&scull_devp->sem);printk(KERN_ALERT "read %d bytes\n",count);return ret;}ssize_t scull_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_ops){unsigned long p = *f_ops;unsigned int cnt = count;int ret = 0;if(down_interruptible(&scull_devp->sem))return -ERESTARTSYS;if(copy_from_user(scull_devp->data,buf, cnt))ret = -EFAULT;else {*f_ops += cnt;ret = cnt;printk(KERN_ALERT "written %u bytes from %lu\n",cnt, p);}up(&scull_devp->sem);printk(KERN_ALERT "write %d bytes\n",count);return ret;}structfile_operations scull_fops = {.owner=THIS_MODULE,.open=scull_open,.release=scull_release,.write=scull_write,.read=scull_read,};intscull_init(void){int result;scull_devp = kmalloc(sizeof(struct scull_dev), GFP_KERNEL);if(!scull_devp){printk(KERN_ALERT "fialed to malloc a device\n");result = -ENOMEM;goto fail_malloc;}memset(scull_devp, 0 , sizeof(struct scull_dev));scull_devp->misc_scull.name=SCULL_NAME;scull_devp->misc_scull.minor=MISC_DYNAMIC_MINOR;scull_devp->misc_scull.fops=&scull_fops;result = misc_register(&scull_devp->misc_scull);if(result){printk(KERN_ALERT "failed to register a misc device\n");result = -1;goto fail_register;}init_MUTEX(&scull_devp->sem);printk(KERN_ALERT "init scull device\n");return 0;fail_register:kfree(scull_devp);scull_devp = NULL;fail_malloc:return result;}voidscull_cleanup(void){misc_deregister(&scull_devp->misc_scull);kfree(scull_devp);scull_devp = NULL;printk(KERN_ALERT "clean scull device\n");}module_init(scull_init);module_exit(scull_cleanup);

Test code

Test. c

/************************************************************************* *fileName:    test.c *description: test the myscull.c *author:      Hzc *create time: 2007-04-20 *modify info: -*************************************************************************/#include <stdio.h>#include <fcntl.h>#include <sys/ioctl.h>#include <sys/types.h>/* device path */char path[] = "/dev/scull";char buf[10];char rbuf[10];int i;int t = 1;intmain (){  int f = open (path, O_RDWR);   for (i = 0; i < 10; i++)    {      buf[i] = i;      printf("buf[%d] = %d\n",i,buf[i]);    }printf("write %d bytes\n",write (f, buf, 10));//  close (f);//////  f = open (path, O_RDONLY);// if (f == -1)//    {//      printf ("device open error 2!\n");//      return 1;//    }  printf ("Read the string from device...\n");printf("read %d bytes\n",read (f, rbuf, 10));  for (i = 0; i < 10; i++)    {      printf ("%d\n", rbuf[i]);    }  close (f);}

Makefile

#KERNEL_DIR := /home/huang/linux-2.6.18/KERNEL_DIR := /lib/modules/$(shell uname -r)/buildPWD:= $(shell pwd)obj-m := scull.odefault:$(MAKE) -C $(KERNEL_DIR) M=$(PWD) modulestest: test.cgcc $< -o $@.o  -gclean:rm -rf *.o *.ko *~ *.order *.symvers *.markers *.mod.c

Test script

1 load_scull.sh

#!/bin/sh/sbin/insmod scull.ko

2 unload_scull.sh

#!/bin/sh/sbin/rmmod scull.ko

3 test. Sh

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