キャラクタドライバ(実践)
1. scull.h
2 scull.c
3 Makefile
4コンパイル
Lenovo:~/LDD$make//ファイルがあるディレクトリの下
Lenovo:~/LDD$ insmod ./scull.ko//makeの後にkoファイルを生成し、insmodの後にノードを確立してからアプリケーションに読み書きアクセスされます.
cat/proc/devices//ファイルにscullのプライマリ・デバイス番号が表示されます
root@caoyin-Lenovo:/home/caoyin/LDD# sudo su root@caoyin-Lenovo:/home/caoyin/LDD# mknod/dev/scull0 c 250 0 root@caoyin-Lenovo:/home/caoyin/LDD# mknod/dev/scull1 c 250 1 root@caoyin-Lenovo:/home/caoyin/LDD# mknod/dev/scull2 c 250 2 root@caoyin-Lenovo:/home/caoyin/LDD# mknod/dev/scull3 c 250 3 root@caoyin-Lenovo:/home/caoyin/LDD# chgrp staff/dev/scull[0-3] root@caoyin-Lenovo:/home/caoyin/LDD# chmod 664/dev/scull[0-3]
/devの下にscull 0-scull 3端末が先に生成されます
5試験手順scull_test.c
実行:
root@caoyin-Lenovo:/home/caoyin/LDD# gcc scull_test.c -o scull_test.o root@caoyin-Lenovo:/home/caoyin/LDD# sudo ./scull_test.o
結果:
Write 8 bytes to scull/nWrite 8 bytes to scull/nWrite 8 bytes to scull/nRead 8 bytes from scull/nRead 8 bytes from scull/nRead 8 bytes from scull/nRead Hello, C
#ifndef _SCULL_H_
#define _SCULL_H_
#ifndef SCULL_MAJOR
#define SCULL_MAJOR 0 /* dynamic major by default */
#endif
#ifndef SCULL_NR_DEVS
#define SCULL_NR_DEVS 4 /* scull0 through scull3 */
#endif
#ifndef SCULL_QUANTUM
#define SCULL_QUANTUM 4000
#endif
#ifndef SCULL_QSET
#define SCULL_QSET 1000
#endif
/*
* Representation of scull quantum sets.
*/
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 */
};
/*
* The different configurable parameters
*/
extern int scull_major; /* main.c */
extern int scull_nr_devs;
extern int scull_quantum;
extern int scull_qset;
#endif /* _SCULL_H_ */
2 scull.c
#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 */
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("victorsummer");
MODULE_LICENSE("Dual BSD/GPL");
struct scull_dev *scull_devices; /* allocated in scull_init_module */
/*
* Empty out the scull device; must be called with the device
* semaphore held.
*/
int scull_trim(struct scull_dev *dev)
{
struct scull_qset *next, *dptr;
int qset = dev->qset; /* "dev" is not-null */
int i;
for (dptr = dev->data; dptr; dptr = next) { /* all the list items */
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;
}
/*
* 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;
scull_trim(dev); /* ignore errors */
up(&dev->sem);
}
return 0; /* success */
}
int scull_release(struct inode *inode, struct file *filp)
{
return 0;
}
/*
* Follow the list
*/
struct scull_qset *scull_follow(struct scull_dev *dev, int n)
{
struct scull_qset *qs = dev->data;
/* Allocate first qset explicitly if need be */
if (! qs) {
qs = dev->data = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);
if (qs == NULL)
return NULL; /* Never mind */
memset(qs, 0, sizeof(struct scull_qset));
}
/* Then follow the list */
while (n--) {
if (!qs->next) {
qs->next = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);
if (qs->next == NULL)
return NULL; /* Never mind */
memset(qs->next, 0, sizeof(struct scull_qset));
}
qs = qs->next;
continue;
}
return qs;
}
/*
* 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;
struct scull_qset *dptr; /* the first listitem */
int quantum = dev->quantum, qset = dev->qset;
int itemsize = quantum * qset; /* how many bytes in the listitem */
int item, s_pos, q_pos, rest;
ssize_t retval = 0;
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
if (*f_pos >= dev->size)
goto out;
if (*f_pos + count > dev->size)
count = dev->size - *f_pos;
/* find listitem, qset index, and offset in the quantum */
item = (long)*f_pos / itemsize;
rest = (long)*f_pos % itemsize;
s_pos = rest / quantum; q_pos = rest % quantum;
/* follow the list up to the right position (defined elsewhere) */
dptr = scull_follow(dev, item);
if (dptr == NULL || !dptr->data || ! dptr->data[s_pos])
goto out; /* don't fill holes */
/* read only up to the end of this quantum */
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;
}
*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; /* value used in "goto out" statements */
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
/* find listitem, qset index and offset in the quantum */
item = (long)*f_pos / itemsize;
rest = (long)*f_pos % itemsize;
s_pos = rest / quantum; q_pos = rest % quantum;
/* follow the list up to the right position */
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;
}
/* write only up to the end of this quantum */
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;
/* update the size */
if (dev->size < *f_pos)
dev->size = *f_pos;
out:
up(&dev->sem);
return retval;
}
struct file_operations scull_fops = {
.owner = THIS_MODULE,
.llseek = NULL,
.read = scull_read,
.write = scull_write,
.ioctl = NULL,
.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++) {
scull_trim(scull_devices + 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. */
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);
}
/* At this point call the init function for any friend device */
dev = MKDEV(scull_major, scull_minor + scull_nr_devs);
return 0; /* succeed */
fail:
scull_cleanup_module();
return result;
}
module_init(scull_init_module);
module_exit(scull_cleanup_module);
3 Makefile
KERNELDIR = /usr/src/linux-headers-2.6.35-30-generic /* */
PWD := $(shell pwd)
obj-m := scull.o
modules:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules // Tab
4コンパイル
Lenovo:~/LDD$make//ファイルがあるディレクトリの下
Lenovo:~/LDD$ insmod ./scull.ko//makeの後にkoファイルを生成し、insmodの後にノードを確立してからアプリケーションに読み書きアクセスされます.
cat/proc/devices//ファイルにscullのプライマリ・デバイス番号が表示されます
root@caoyin-Lenovo:/home/caoyin/LDD# sudo su root@caoyin-Lenovo:/home/caoyin/LDD# mknod/dev/scull0 c 250 0 root@caoyin-Lenovo:/home/caoyin/LDD# mknod/dev/scull1 c 250 1 root@caoyin-Lenovo:/home/caoyin/LDD# mknod/dev/scull2 c 250 2 root@caoyin-Lenovo:/home/caoyin/LDD# mknod/dev/scull3 c 250 3 root@caoyin-Lenovo:/home/caoyin/LDD# chgrp staff/dev/scull[0-3] root@caoyin-Lenovo:/home/caoyin/LDD# chmod 664/dev/scull[0-3]
/devの下にscull 0-scull 3端末が先に生成されます
5試験手順scull_test.c
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int main()
{
char *write_buffer = "Hello, Character driver!";
char *read_buffer = malloc(sizeof(char*)*30);
int scull_fd = 0;
int code, back = 0;
// write data to scull
scull_fd = open("/dev/scull1", O_WRONLY);
while(*write_buffer != '\0')
{
code = write(scull_fd , write_buffer , 8);
printf("Write %d bytes to scull/n", code);
write_buffer += code;
}
close(scull_fd);
// read data from scull
scull_fd = open("/dev/scull1", O_RDONLY);
while((code = read(scull_fd , read_buffer , 8)) != 0)
{
printf("Read %d bytes from scull/n", code);
read_buffer += code;
back += code;
}
read_buffer -= back;
printf("Read %s from scull /n", read_buffer);
close(scull_fd);
exit(0);
return 0;
}
実行:
root@caoyin-Lenovo:/home/caoyin/LDD# gcc scull_test.c -o scull_test.o root@caoyin-Lenovo:/home/caoyin/LDD# sudo ./scull_test.o
結果:
Write 8 bytes to scull/nWrite 8 bytes to scull/nWrite 8 bytes to scull/nRead 8 bytes from scull/nRead 8 bytes from scull/nRead 8 bytes from scull/nRead Hello, C