LDD3《Linux设备驱动》中的最简单的字符设备驱动实现与测试
源代码如下：
#include <linux/config.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
//#include "scull.h"
#define SCULL_MAJOR 0 /* dynamic major by default */
#define SCULL_NR_DEVS 4 /* scull0 through scull3 */
#define SCULL_P_NR_DEVS 4 /* scullpipe0 through scullpipe3 */
#define SCULL_QUANTUM 4000
#define SCULL_QSET 1000
struct scull_qset {
void **data;
struct scull_qset *next;
};
struct scull_dev {
struct scull_qset *data; /* Pointer to first quantum set */
int quantum; /* the current quantum size */
int qset; /* the current array size */
unsigned long size; /* amount of data stored here */
unsigned int access_key; /* used by sculluid and scullpriv */
struct semaphore sem; /* mutual exclusion semaphore */
struct cdev cdev; /* Char device structure */
};
int scull_major = SCULL_MAJOR;
int scull_minor = 0;
int scull_nr_devs = SCULL_NR_DEVS;
int scull_quantum = SCULL_QUANTUM;
int scull_qset = SCULL_QSET;
module_param(scull_major, int, S_IRUGO);
module_param(scull_minor, int, S_IRUGO);
module_param(scull_nr_devs,int, S_IRUGO);
module_param(scull_quantum, int, S_IRUGO);
module_param(scull_qset,int,S_IRUGO);
MODULE_AUTHOR("BG2BKK");
MODULE_LICENSE("Dual BSD/GPL");
struct scull_dev *scull_devices;
int scull_trim(struct scull_dev *dev)
{
struct scull_qset *next,*dptr;
int qset = dev->qset;
int i;
for(dptr = dev->data; dptr;dptr = next)
{
if(dptr->data){
for (i=0;i<qset;i++)
kfree(dptr->data[i]);
kfree(dptr->data);
dptr->data = NULL;
}
next = dptr->next;
kfree(dptr);
}
dev->size = 0;
dev->quantum = scull_quantum;
dev->qset = scull_qset;
dev->data = NULL;
return 0;
}
int scull_open(struct inode *inode, struct file *filp)
{
struct scull_dev *dev;
dev = container_of(inode->i_cdev,struct scull_dev, cdev);
filp->private_data = dev;
if((filp->f_flags & O_ACCMODE) == O_WRONLY){
scull_trim(dev);
}
return 0;
}
int scull_release(struct inode *inode,struct file *filp)
{
printk(KERN_ALERT "scullrelease\n");
return 0;
}
struct scull_qset *scull_follow(struct scull_dev *dev,int n)
{
struct scull_qset *qs = dev->data;
if(!qs)
{
qs = dev->data = kmalloc(sizeof(struct scull_qset),GFP_KERNEL);
if(qs == NULL)
return NULL;
memset(qs,0,sizeof(struct scull_qset));
}
while(n--)
{
if( !qs->next ){
qs->next = kmalloc(sizeof(struct scull_qset),GFP_KERNEL);
if(qs->next == NULL)
return NULL;
memset(qs->next, 0 ,sizeof(struct scull_qset));
}
qs = qs->next;
continue;
}
return qs;
}
ssize_t scull_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
struct scull_dev *dev = filp->private_data;
struct scull_qset *dptr;
int quantum = dev->quantum, qset = dev->qset;
int itemsize = quantum*qset;
int item,s_pos,q_pos,rest;
ssize_t retval = 0;
if(down_interruptible(&dev->sem))
return -ERESTARTSYS;
// printk("f_pos= %d\n",*f_pos);
// printk("count= %d\n",count);
if( *f_pos >= dev->size)
goto out;
if( *f_pos + count > dev->size)
count = dev->size - *f_pos;
item = (long)*f_pos / itemsize;
rest = (long)*f_pos % itemsize;
s_pos = rest / quantum;
q_pos = rest % quantum;
dptr = scull_follow(dev,item);
if(dptr == NULL || !dptr->data || !dptr->data[s_pos])
goto out;
if(count > quantum - q_pos)
count = quantum - q_pos;
if(copy_to_user(buf, dptr->data[s_pos] + q_pos, count)){
retval = -EFAULT;
goto out;
}
// printk("read scull: %d\n",count);
*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;
struct scull_qset *dptr;
int quantum = dev->quantum,qset = dev->qset;
int itemsize = quantum * qset;
int item,s_pos,q_pos,rest;
ssize_t retval = -ENOMEM;
if(down_interruptible(&dev->sem))
return -ERESTARTSYS;
item = (long)*f_pos / itemsize;
rest = (long)*f_pos % itemsize;
s_pos = rest / quantum;
q_pos = rest % quantum;
dptr = scull_follow(dev, item);
if(dptr == NULL)
goto out;
if(!dptr->data){
dptr->data = kmalloc(qset * sizeof(char *),GFP_KERNEL);
if(!dptr->data)
goto out;
memset(dptr->data, 0, qset*sizeof(char *));
}
if(!dptr->data[s_pos])
{
dptr->data[s_pos] = kmalloc(quantum, GFP_KERNEL);
if(!dptr->data[s_pos])
goto out;
}
if(count > quantum - q_pos)
count = quantum - q_pos;
if(copy_from_user(dptr->data[s_pos] + q_pos, buf,count)){
retval = -EFAULT;
goto out;
}
*f_pos += count;
retval = count;
if(dev->size < *f_pos)
dev->size = *f_pos;
out:
up(&dev->sem);
return retval;
}
int scull_ioctl(struct inode *inode,struct file *filp,unsigned int cmd,unsigned long arg)
{
return 0;
}
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:
newpos = off;
break;
case 1:
newpos = filp->f_pos + off;
break;
case 2:
newpos = dev->size + off;
break;
default:
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 = scull_ioctl,
.open = scull_open,
.release= scull_release,
};
void scull_cleanup_module(void)
{
int i;
dev_t devno = MKDEV(scull_major,scull_minor);
if(scull_devices){
for(i=0; i<scull_nr_devs;i++)
{
scull_trim(scull_devices + i);
cdev_del(&scull_devices[i].cdev);
}
kfree(scull_devices);
}
#ifdef SCULL_DEBUG
// scull_remove_proc();
#endif
unregister_chrdev_region(devno,scull_nr_devs);
// scull_p_cleanup();
// scull_access_cleanup();
}
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);
if(err)
printk(KERN_NOTICE "Error %d adding scull%d",err,index);
}
int scull_init_module(void)
{
int result,i;
dev_t dev=0;
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;
}
printk(KERN_ALERT "hello scull major %d\n minor %d\n",scull_major,scull_minor);
scull_devices = kmalloc(scull_nr_devs * sizeof(struct scull_dev),GFP_KERNEL);
if(!scull_devices){
result = -ENOMEM;
goto fail;
}
memset(scull_devices, 0,scull_nr_devs*sizeof(struct scull_dev));
for(i=0; i< scull_nr_devs; i++){
scull_devices[i].quantum = scull_quantum;
scull_devices[i].qset = scull_qset;
init_MUTEX(&scull_devices[i].sem);
scull_setup_cdev(&scull_devices[i],i);
}
dev=MKDEV(scull_major,scull_minor+scull_nr_devs);
// dev += scull_p_init(dev);
// dev += scull_access_init(dev);
#ifdef SCULL_DEBUG
scull_create_proc();
#endif
return 0;
fail:
scull_cleanup_module();
return result;
}
module_init(scull_init_module);
module_exit(scull_cleanup_module)
测试代码如下
/*************************************************************************
*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/sculldev";
int buf[40];
int rbuf[40];
int i;
int t=1;
int main()
{
int f = open(path, O_WRONLY);
if (f == -1)
{
printf("device open error!\n");
return 1;
}
printf("Input a string to write device \n");
//scanf("%s", buf);
for(i=0;i<40;i++)
{
buf[i]=i;
write(f, buf+i,1 ); /* device wirte */
}
close(f);
f= open(path,O_RDONLY);
printf("Read the string from device...\n");
if (f == -1)
{
printf("device open error!\n");
return 1;
}
for(i=0;i<40;i++)
{
read(f, rbuf+i, 1); /* device wirte */
}
for(i=0;i<40;i++)
{
printf("%d\t",rbuf[i]);
if((i+1)%10 == 0) printf("\n");
}
close(f);
}
驱动加载脚本如下：
#!/bin/sh insmod scull.ko mknod /dev/sculldev c 252 0驱动卸载脚本如下：
#!/bin/sh rmmod scull.ko rm /dev/sculldev