//scull.h
/*
* scull.h -- definitions for the char module
*
* Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
* Copyright (C) 2001 O'Reilly & Associates
*
* The source code in this file can be freely used, adapted,
* and redistributed in source or binary form, so long as an
* acknowledgment appears in derived source files. The citation
* should list that the code comes from the book "Linux Device
* Drivers" by Alessandro Rubini and Jonathan Corbet, published
* by O'Reilly & Associates. No warranty is attached;
* we cannot take responsibility for errors or fitness for use.
*
* $Id: scull.h,v 1.15 2004/11/04 17:51:18 rubini Exp $
*/
#ifndef _SCULL_H_
#define _SCULL_H_
#include <linux/ioctl.h> /* needed for the _IOW etc stuff used later */
#ifndef SCULL_MAJOR
#define SCULL_MAJOR 0 /* dynamic major by default */
#endif
/*
struct cdev {
struct kobject kobj;
struct module *owner; //ËùÊôÄ£¿é
const struct file_operations *ops;
//Îļþ²Ù×÷½á¹¹£¬ÔÚдÇý¶¯Ê±£¬Æä½á¹¹ÌåÄڵĴ󲿷ֺ¯ÊýÒª±»ÊµÏÖ
struct list_head list;
dev_t dev; //É豸ºÅ£¬int ÀàÐÍ£¬¸ß12λΪÖ÷É豸ºÅ£¬µÍ20λΪ´ÎÉ豸ºÅ
unsigned int count;
};
*/
struct scull_dev {
char data[4000];
unsigned int data_size;
struct cdev cdev; /* Char device structure */
};
extern int scull_major; /* main.c */
ssize_t scull_read(struct file *filp, char __user *buf, size_t count,
loff_t *f_pos);
ssize_t scull_write(struct file *filp, const char __user *buf, size_t count,
loff_t *f_pos);
#endif
//scull.c
/*
* main.c -- the bare scull char module
*
* Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
* Copyright (C) 2001 O'Reilly & Associates
*
* The source code in this file can be freely used, adapted,
* and redistributed in source or binary form, so long as an
* acknowledgment appears in derived source files. The citation
* should list that the code comes from the book "Linux Device
* Drivers" by Alessandro Rubini and Jonathan Corbet, published
* by O'Reilly & Associates. No warranty is attached;
* we cannot take responsibility for errors or fitness for use.
*
*/
//#include <linux/config.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/kernel.h> /* printk() */
#include <linux/slab.h> /* kmalloc() */
#include <linux/fs.h> /* everything... */
#include <linux/errno.h> /* error codes */
#include <linux/types.h> /* size_t */
#include <linux/proc_fs.h>
#include <linux/fcntl.h> /* O_ACCMODE */
#include <linux/seq_file.h>
#include <linux/cdev.h>
#include <asm/system.h> /* cli(), *_flags */
#include <asm/uaccess.h> /* copy_*_user */
#include "scull.h" /* local definitions */
#define AUTO_CREATE_DEV_INODE
#ifdef AUTO_CREATE_DEV_INODE
#include <linux/device.h>
struct class *myclass =NULL;
dev_t dev_num;
#endif
/*
* Our parameters which can be set at load time.
*/
/*
MAJOR(dev_t dev)
MINOR(dev_t dev)
MKDEV(int major,int minor) //ͨ¹ýÖ÷´ÎÉ豸ºÅÀ´Éú³Édev_t
ÒÔÉϺêµ÷ÓÃÔÚÄÚºËÔ´ÂëÖÐÈç´Ë¶¨Ò壺
#define MINORBITS 20
#define MINORMASK ((1U << MINORBITS) - 1)
//(1<<20 -1) ´Ë²Ù×÷ºó£¬MINORMASKºêµÄµÍ20λΪ1£¬¸ß12λΪ0
#define MAJOR(dev) ((unsigned int) ((dev) >> MINORBITS))
#define MINOR(dev) ((unsigned int) ((dev) & MINORMASK))
#define MKDEV(ma,mi) (((ma) << MINORBITS) | (mi))
*/
int scull_major = SCULL_MAJOR;
int scull_minor = 0;
module_param(scull_major, int, S_IRUGO);
module_param(scull_minor, int, S_IRUGO);
MODULE_AUTHOR("Alessandro Rubini, Jonathan Corbet");
MODULE_LICENSE("Dual BSD/GPL");
struct scull_dev *scull_devices; /* allocated in scull_init_module */
int scull_open(struct inode *inode, struct file *filp)
{
struct scull_dev *dev; /* device information */
/*container_of()Èý¸ö²ÎÊýΪ:1½á¹¹Ìå³ÉÔ±µÄµØÖ·£¬2ÊǽṹÌåÀàÐÍ£¬3ÊǽṹÌåµÄ³ÉÔ±£¬¼´2²ÎÊýÖеijÉÔ±*/
/*×îÖÕ»ñµÃinodeÖбäÁ¿cdevµÄµØÖ·*/
dev = container_of(inode->i_cdev, struct scull_dev, cdev);
filp->private_data = dev; /* for other methods */
/*
ÔÚsturct fileÖУ¬private_dataÊÇvoid *µÄÖ¸ÕëÀàÐÍ
scullÀïÃæ¾ÍÊÇÓÃÕâ¸öÖ¸ÕëÖ¸ÏòÓû§ÉêÇëµÄÄÚ´æÇøÓò
*/
return 0; /* success */
}
int scull_release(struct inode *inode, struct file *filp)
{
return 0;
}
ssize_t scull_read(struct file *filp, char __user *buf, size_t count,
loff_t *f_pos)
{
struct scull_dev *dev = filp->private_data;
unsigned long ret;
void *start;
start = dev->data;
if(dev->data_size < count)
count = dev->data_size;
ret =copy_to_user(buf, start, count);
return count;
}
ssize_t scull_write(struct file *filp, const char __user *buf, size_t count,
loff_t *f_pos)
{
struct scull_dev *dev = filp->private_data;
void *start;
unsigned long ret;
start = dev->data;
if(count > 4000)
count = 4000 - 1;
ret = copy_from_user(start, buf, count);
dev->data_size = count;
return count;
}
struct file_operations scull_fops = {
.owner = THIS_MODULE,
// .llseek = scull_llseek,
.read = scull_read,
.write = scull_write,
// .ioctl = scull_ioctl,
.open = scull_open,
.release = scull_release,
};
/*
* Finally, the module stuff
*/
/*
* The cleanup function is used to handle initialization failures as well.
* Thefore, it must be careful to work correctly even if some of the items
* have not been initialized
*/
void scull_cleanup_module(void)
{
dev_t devno = MKDEV(scull_major, scull_minor);
/*
void cdev_del(struct cdev *);//×¢ÏúÉ豸£¬Í¨³£·¢ÉúÔÚÇý¶¯Ä£¿éµÄжÔغ¯ÊýÖÐ
*/
#ifdef AUTO_CREATE_DEV_INODE
class_device_destroy(myclass,dev_num);
class_destroy(myclass);
#endif
cdev_del(&scull_devices->cdev);
kfree(scull_devices);
/* cleanup_module is never called if registering failed */
unregister_chrdev_region(devno, 1);
}
/*
* Set up the char_dev structure for this device.
*/
static void scull_setup_cdev(struct scull_dev *dev)
{
int err, devno = MKDEV(scull_major, scull_minor);
/*
void cdev_init(struct cdev *, const struct file_operations *);
//³õʼ»¯£¬½¨Á¢cdevºÍfile_operation Ö®¼äµÄÁ¬½Ó
*/
cdev_init(&dev->cdev, &scull_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &scull_fops;
err = cdev_add (&dev->cdev, devno, 1);
/* Fail gracefully if need be */
if (err)
printk(KERN_NOTICE "Error %d adding scull", err);
}
int scull_init_module(void)
{
int result;
dev_t dev = 0;
/*
* Get a range of minor numbers to work with, asking for a dynamic
* major unless directed otherwise at load time.
*/
/*
ÔÚ×¢²áʱӦ¸ÃÏȵ÷Óãºint register_chrdev_region(dev_t from,unsigned count,const char *name)º¯ÊýΪÆä·ÖÅäÉ豸ºÅ£¬´Ëº¯Êý¿ÉÓãº
int alloc_chrdev_region(dev_t *dev,unsigned baseminor,unsigned count,const char *name)º¯Êý´úÌ棬ËûÃÇÖ®¼äµÄÇø±ðÔÚÓÚ£º
register_chrdev_region()ÓÃÓÚÒÑÖªÉ豸ºÅʱ£¬ÁíÒ»¸öÓÃÓÚ¶¯Ì¬ÉêÇ룬ÆäÓŵãÔÚÓÚ²»»áÔì³ÉÉ豸ºÅÖظ´µÄ³åÍ»¡£
ÔÚ×¢ÏúÖ®ºó£¬Ó¦µ÷Óãºvoid unregister_chrdev_region(dev_t from,unsigned count)º¯ÊýÊÍ·ÅÔÏÈÉêÇëµÄÉ豸ºÅ¡£
ËûÃÇÖ®¼äµÄ˳Ðò¹ØϵÈçÏ£º
register_chrdev_region()££>cdev_add() //´Ë¹ý³ÌÔÚ¼ÓÔØÄ£¿éÖÐ
cdev_del()-->unregister_chrdev_region() //´Ë¹ý³ÌÔÚжÔØÄ£¿éÖÐ
*/
if (scull_major) {
dev = MKDEV(scull_major, scull_minor);
result = register_chrdev_region(dev, 1, "scull");
} else {
/*
¶¯Ì¬·ÖÅä:
Int alloc_chrdev_region(dev_t *dev,unsigned int firstminor,unsigned int count,char *name);
Firstminor : ͨ³£Îª0;
*dev:´æ·Å·µ»ØµÄÉ豸ºÅ;
*/
result = alloc_chrdev_region(&dev, scull_minor, 1,
"scull");
scull_major = MAJOR(dev);
}
if (result < 0) {
printk(KERN_WARNING "scull: can't get major %d\n", scull_major);
return result;
}
/*
* allocate the devices -- we can't have them static, as the number
* can be specified at load time
*/
scull_devices = kmalloc(sizeof(struct scull_dev), GFP_KERNEL);
if (!scull_devices) {
result = -ENOMEM;
goto fail; /* Make this more graceful */
}
memset(scull_devices, 0, sizeof(struct scull_dev));
/* Initialize each device. */
#ifdef AUTO_CREATE_DEV_INODE
dev_num = dev;
myclass = class_create(THIS_MODULE,"scull");
class_device_create(myclass,NULL,dev_num,NULL,"scull0");
#endif
scull_setup_cdev(scull_devices);
return 0; /* succeed */
fail:
scull_cleanup_module();
return result;
}
module_init(scull_init_module);
module_exit(scull_cleanup_module);
//makefile
obj-m := scull.o
PWD := $(shell pwd)
KVER := $(shell uname -r)
KDIR := /lib/modules/$(KVER)/build
all:
$(MAKE) -C $(KDIR) M=$(PWD) modules
clean:
rm -f *.o *.ko *.mod.c .hello*
//test sample
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <error.h>
#include <fcntl.h>
#include <sys/types.h>
#include <string.h>
#define MAXLEN 100
#define DEV_PATH "/dev/scull0"
int main(void)
{
int fd,len;
char inbuf[MAXLEN];
char outbuf[MAXLEN]="scull dev test";
char tmp_buf[MAXLEN];
int i;
for(i=0;i<10;i++)
{
fd=open(DEV_PATH,O_WRONLY);
if(fd < 0)
{
perror("open device");
exit(EXIT_FAILURE);
}
memset(tmp_buf,0,MAXLEN);
sprintf(tmp_buf,"%d",i);
strcat(outbuf, tmp_buf);
len = write(fd,outbuf,strlen(outbuf)+1);
if(len < 0)
{
perror("write device");
close(fd);
exit(EXIT_FAILURE);
}
printf("write device %d bytes ok\n",len);
close(fd);
sleep(1);
fd=open(DEV_PATH,O_RDONLY);
if(fd < 0)
{
perror("open device");
exit(EXIT_FAILURE);
}
memset(inbuf,0,MAXLEN);
len = read(fd,inbuf,len);
if(len < 0)
{
perror("read device");
close(fd);
exit(EXIT_FAILURE);
}
printf("read device ok\n");
printf("%s\n",inbuf);
}
}
//gcc -o scull_test scull_test.c
来源：https://www.cnblogs.com/image-eye/archive/2011/08/19/2145929.html