LDD3 scull内存驱动程序改写
对于第三章的内容，所用设备数据结构有点复杂，从数据操作中解脱出来应该更好理解。
1、只建立一个设备scull
2、将数据区域直接改成一个1000的字符数组
3、实现功能：open，close，read，write，llseek
红色字体为改动的地方:
头文件源码
#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
#ifndef SCULL_NR_DEVS
#define SCULL_NR_DEVS 1 /* scull */
#endif
#ifndef SCULL_P_NR_DEVS
#define SCULL_P_NR_DEVS 1 /* scullpipe0 through scullpipe3 */
#endif
/*
* The pipe device is a simple circular buffer. Here its default size
*/
#ifndef SCULL_P_BUFFER
#define SCULL_P_BUFFER 4000
#endif
/*
* Representation of scull quantum sets.
*/
#define Data_Len 1000
struct scull_dev {
char data[Data_Len];
struct semaphore sem; /* mutual exclusion semaphore */
struct cdev cdev; /* Char device structure */
};
/*
* The different configurable parameters
*/
extern int scull_major; /* main.c */
extern int scull_nr_devs;
/*
* Prototypes for shared functions
*/
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);
loff_t scull_llseek(struct file *filp, loff_t off, int whence);
主文件源码：
/*
* 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 */
/*
* Our parameters which can be set at load time.
*/
int scull_major = SCULL_MAJOR;
int scull_minor = 0;
int scull_nr_devs = SCULL_NR_DEVS; /* number of bare scull devices */
module_param(scull_major, int, S_IRUGO);
module_param(scull_minor, int, S_IRUGO);
module_param(scull_nr_devs, int, S_IRUGO);
MODULE_AUTHOR("Alessandro Rubini, Jonathan Corbet");
MODULE_LICENSE("Dual BSD/GPL");
struct scull_dev *scull_devices; /* allocated in scull_init_module */
/*
* Open and close
*/
int scull_open(struct inode *inode, struct file *filp)
{
struct scull_dev *dev; /* device information */
dev = container_of(inode->i_cdev, struct scull_dev, cdev);
filp->private_data = dev; /* for other methods */
/* now trim to 0 the length of the device if open was write-only */
if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) {
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
up(&dev->sem);
}
return 0; /* success */
}
int scull_release(struct inode *inode, struct file *filp)
{
return 0;
}
/*
* Data management: read and write
*/
ssize_t scull_read(struct file *filp, char __user *buf, size_t count,
loff_t *f_pos)
{
struct scull_dev *dev = filp->private_data;
ssize_t retval = 0;
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
if((*f_pos)>= Data_Len)
goto out;
if(((*f_pos)+count)>= Data_Len)
{
count= Data_Len-(*f_pos);
}
if (copy_to_user(buf, dev->data, count))
{
retval = -EFAULT;
goto out;
}
(*f_pos)+=count;
retval= count;
out:
up(&dev->sem);
return retval;
}
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;
ssize_t retval = -ENOMEM; /* value used in "goto out" statements */
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
if((*f_pos+count)>=Data_Len)
{
count= Data_Len-(*f_pos);
}
if (copy_from_user(&(dev->data[*f_pos]), buf, count)) {
retval = -EFAULT;
goto out;
}
*f_pos += count;
retval = count;
out:
up(&dev->sem);
return retval;
}
/*
* The "extended" operations -- only seek
*/
loff_t scull_llseek(struct file *filp, loff_t off, int whence)
{
struct scull_dev *dev = filp->private_data;
loff_t newpos;
switch(whence) {
case 0: /* SEEK_SET */
newpos = off;
break;
case 1: /* SEEK_CUR */
newpos = filp->f_pos + off;
break;
case 2: /* SEEK_END */
newpos = Data_Len;
break;
default: /* can't happen */
return -EINVAL;
}
if (newpos < 0) return -EINVAL;
filp->f_pos = newpos;
return newpos;
}
struct file_operations scull_fops = {
.owner = THIS_MODULE,
.llseek = scull_llseek,
.read = scull_read,
.write = scull_write,
.ioctl = NULL,// 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)
{
int i;
dev_t devno = MKDEV(scull_major, scull_minor);
/* Get rid of our char dev entries */
if (scull_devices) {
for (i = 0; i < scull_nr_devs; i++) {
cdev_del(&scull_devices[i].cdev);
}
kfree(scull_devices);
}
/* cleanup_module is never called if registering failed */
unregister_chrdev_region(devno, scull_nr_devs);
}
/*
* Set up the char_dev structure for this device.
*/
static void scull_setup_cdev(struct scull_dev *dev, int index)
{
int err, devno = MKDEV(scull_major, scull_minor + index);
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%d", err, index);
}
int scull_init_module(void)
{
int result, i;
dev_t dev = 0;
/*
* Get a range of minor numbers to work with, asking for a dynamic
* major unless directed otherwise at load time.
*/
if (scull_major) {
dev = MKDEV(scull_major, scull_minor);
result = register_chrdev_region(dev, scull_nr_devs, "scull");
} else {
result = alloc_chrdev_region(&dev, scull_minor, scull_nr_devs,
"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(scull_nr_devs * sizeof(struct scull_dev), GFP_KERNEL);
if (!scull_devices) {
result = -ENOMEM;
goto fail; /* Make this more graceful */
}
memset(scull_devices, 0, scull_nr_devs * sizeof(struct scull_dev));
/* Initialize each device. */
init_MUTEX(scull_devices->sem);
scull_setup_cdev(scull_devices, 0);
return 0; /* succeed */
fail:
scull_cleanup_module();
return result;
}
module_init(scull_init_module);
module_exit(scull_cleanup_module);
测试程序：
#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#define Scull_Device "/dev/scull"
#define Data_Num 100
int main(void)
{
int fscull;
int bytesize=0;
char buff[Data_Num]="i am here ,ericjiang";
fscull=open(Scull_Device,O_RDWR);
if(fscull== -1)
{
perror("open scull device fail!/n");
return -1;
}
sleep(5);
bytesize=write(fscull,buff,strlen(buff));
printf("write data byte==%d/n",bytesize);
buff[0]='a';
buff[1]='a';
buff[2]='a';
buff[3]='a';
buff[4]='a';
buff[5]='a';
buff[6]='a';
buff[7]='a';
buff[8]='a';
buff[9]='a';
lseek(fscull,0,SEEK_SET);
bytesize=read(fscull,buff,5);
sleep(5);
printf("read data byte==%d/n",bytesize);
printf("str==%s/n",buff);
close(fscull);
return 0;
}
试验：
make
insmod scull.ko //插入模块
mknod /dev/scull c 253 0 //建立节点
gcc -o scull_test scull_test.c //编译测试程序
./scull_test //测试
write data byte==20
read data byte==5
str==i am aaaaa ericjiang