#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 */
MODULE_AUTHOR("Alessandro Rubini, Jonathan Corbet");
MODULE_LICENSE("Dual BSD/GPL");
struct scull_dev *scull_devices;
int scull_major = 188; /*主设备号*/
int scull_minor = 0;
int scull_nr_devs = SCULL_NR_DEVS; /*scull0--scull3*/
int scull_quantum = SCULL_QUANTUM; /*一个4000量子有4000字节(数组)*/
int scull_qset = SCULL_QSET; /*一个scull_qset中有1000个量子数组的指针*/
int scull_trim(struct scull_dev *dev)
{
struct scull_qset *next, *dptr;
int qset = dev->qset; /* "dev" 非空 */
int i;
for (dptr = dev->data; dptr; dptr = next) { /* 遍历所有链表项 */
if (dptr->data) {
for (i = 0; i < qset; i++)
kfree(dptr->data[i]); /*data[]中的元素是量子(含有4000个整型量)指针*/
kfree(dptr->data); /*释放掉量子指针空间*/
dptr->data = NULL;
}
next = dptr->next; /* 找下一个 scull_qset */
kfree(dptr); /*释放掉前一个 scull_qset 空间*/
}
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); /*获得设备属性结构体的指针*/
filp->private_data = dev; /* 以后会用到这个指针 */
/* 如果以只写的方法打开设备,那么将这个内存设备的内存长度截断为0 */
if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) {
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
scull_trim(dev);
up(&dev->sem);
}
return 0;
}
int scull_release(struct inode *inode, struct file *filp)
{
return 0;
}
/*读和写都需要用到*/
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; /* Never mind */
memset(qs, 0, sizeof(struct scull_qset));
}
/* 沿链表前行 */
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;
}
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;
int qset = dev->qset;
int itemsize = quantum * qset; /*一个scull_qset可存储的总数据量*/
int item, s_pos, q_pos, rest;
ssize_t retval = 0;
if (down_interruptible (&dev->sem)) /*不允许多进程同时读*/
return (-ERESTARTSYS);
if (*f_pos >= dev->size) /*已经没有什么东西可读,返回0*/
goto out;
if (*f_pos + count > dev->size) /*把剩下的数据返回给用户,尽管要求的count大于这个数*/
count = dev->size - *f_pos;
item = (long)*f_pos / itemsize; /* 经过的scull_qset数 */
rest = (long)*f_pos % itemsize;
s_pos = rest / quantum; /* 在scull_qset中经过的量子数 */
q_pos = rest % quantum; /* 在一个量子中的位置 */
dptr = scull_follow (dev, item);
/*无数据读*/
if (dptr == NULL || !dptr->data || !dptr->data[s_pos])
goto out;
/*读取该量子的数据直到结尾*/
if (count > quantum - q_pos)
count = quantum - q_pos;
/*将数据返回给用户态*/
if (copy_to_user (buf, dptr->data[s_pos] + q_pos, count)) {
retval = -EFAULT;
goto out;
}
*f_pos += count; /* 更新文件读位置 */
retval = count; /* 返回读到的字节数 */
out:
up (&dev->sem); /*释放信号量*/
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; /* 在"goto out" 中使用 */
if (down_interruptible(&dev->sem)) /*不允许多进程同时写*/
return -ERESTARTSYS;
/* 在量子集中寻找链表项, qset 索引以及偏移量 */
item = (long)*f_pos / itemsize; /* 经过的scull_qset数 */
rest = (long)*f_pos % itemsize;
s_pos = rest / quantum; /* 在scull_qset中经过的量子数 */
q_pos = rest % quantum; /* 在一个量子中的位置 */
/* 沿链表前行,直到正确的位置 */
dptr = scull_follow(dev, item);
if (dptr == NULL)
goto out;
if (!dptr->data) { /*分配到了一个scull_qset结构(前面的scull_qset刚好都用完所以需要再分配一个)*/
dptr->data = kmalloc(qset * sizeof(char *), GFP_KERNEL); /*分配指针数组*/
if (!dptr->data)
goto out; /*分配失败*/
memset(dptr->data, 0, qset * sizeof(char *)); /*分配成功并初始化*/
}
if (!dptr->data[s_pos]) {
dptr->data[s_pos] = kmalloc(quantum, GFP_KERNEL); /*分配量子集空间*/
if (!dptr->data[s_pos])
goto out;
}
/* 将数据写入该量子集,直到结尾,尽管用户态传来要写大于该量子剩余空间的参数count */
if (count > quantum - q_pos)
count = quantum - q_pos;
if (copy_from_user(dptr->data[s_pos]+q_pos, buf, count)) { /*用户态数据写入*/
retval = -EFAULT;
goto out;
}
*f_pos += count; /*调整文件位置*/
retval = count; /*返回写成功的字节数*/
/* 更新存储的数据数 */
if (dev->size < *f_pos)
dev->size = *f_pos;
out:
up(&dev->sem);
return retval;
}
/*系统调用和驱动程序之间的桥梁*/
struct file_operations scull_fops = {
.owner = THIS_MODULE,
.read = scull_read,
.write = scull_write,
.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); /*退出时对已分配内存空间回收*/
cdev_del(&scull_devices[i].cdev); /*卸载字符设备*/
}
kfree(scull_devices); /*释放每个设备属性结构体空间*/
}
unregister_chrdev_region(devno, scull_nr_devs); /*释放设备号*/
}
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); /*字符设备初始化函数*/
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &scull_fops;
err = cdev_add (&dev->cdev, devno, 1); /*加载字符设备*/
/* 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;
dev = MKDEV(scull_major, scull_minor); /*根据已知的主设备号和次设备号生成dev_t类型设备号*/
result = register_chrdev_region(dev, scull_nr_devs, "scull"); /*注册字符设备*/
if (result < 0) {
printk(KERN_WARNING "scull: can't get major %d\n", scull_major);
return result;
}
/* 每个设备都有一个描述其属性的结构体 */
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));
/* 对每个设备进行初始化 */
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); /*在初始化每个设备时要先给它加个互斥型信号量*/
scull_setup_cdev(&scull_devices[i], i);
}
return 0; /* 初始化成功 */
fail:
scull_cleanup_module();
return result;
}
module_init(scull_init_module);
module_exit(scull_cleanup_module);
#define SCULL_QUANTUM 4000
#define SCULL_QSET 1000
#define SCULL_NR_DEVS 4
struct scull_qset {
void **data;
struct scull_qset *next;
};
struct scull_dev {
struct scull_qset *data; /* 第一个量子集指针 */
int quantum; /* 量子个数 */
int qset; /* 量子指针数组大小 */
unsigned long size; /* 存储的数据数 */
struct semaphore sem; /* 互斥型信号量 */
struct cdev cdev; /* 字符设备结构体*/
};
obj-m := scull.o
default:
make -C /lib/modules/`uname -r`/build M=`pwd` modules
#!/bin/sh
device="scull"
rmmod scull.ko
rm -f /dev/${device}[0-3]
mknod /dev/${device}0 c 188 0
mknod /dev/${device}1 c 188 1
mknod /dev/${device}2 c 188 2
mknod /dev/${device}3 c 188 3
insmod ./scull.ko $* || exit 1
# sh mknode.sh
# ll > /dev/scull0
# ll > /dev/scull1
# cat /dev/scull0
总用量 120
drwxr-xr-x 3 beyes beyes 4096 2010-09-24 12:40 ./
drwxr-xr-x 4 beyes beyes 4096 2010-09-23 23:31 ../
-rw-r--r-- 1 beyes beyes 82 2010-09-18 11:55 Makefile
-rw-r--r-- 1 beyes beyes 222 2010-09-23 23:31 mknode.sh
-rw-r--r-- 1 beyes beyes 61 2010-09-23 23:30 modules.order
-rw-r--r-- 1 beyes beyes 0 2010-09-18 15:51 Module.symvers
-rw-r--r-- 1 beyes beyes 8254 2010-09-23 23:03 scull.c
-rw-r--r-- 1 beyes beyes 479 2010-09-18 23:55 scull.h
-rw-r--r-- 1 root root 7224 2010-09-23 23:30 scull.ko
-rw-r--r-- 1 root root 331 2010-09-23 23:30 .scull.ko.cmd
-rw-r--r-- 1 beyes beyes 1163 2010-09-18 17:12 scull.mod.c
-rw-r--r-- 1 root root 2780 2010-09-23 23:30 scull.mod.o
-rw-r--r-- 1 root root 23122 2010-09-23 23:30 .scull.mod.o.cmd
-rw-r--r-- 1 root root 5083 2010-09-23 23:30 scull.o
-rw-r--r-- 1 root root 24895 2010-09-23 23:30 .scull.o.cmd
drwxr-xr-x 2 root root 4096 2010-09-23 23:30 .tmp_versions/
# cat /dev/scull1
总用量 120
drwxr-xr-x 3 beyes beyes 4096 2010-09-24 12:40 ./
drwxr-xr-x 4 beyes beyes 4096 2010-09-23 23:31 ../
-rw-r--r-- 1 beyes beyes 82 2010-09-18 11:55 Makefile
-rw-r--r-- 1 beyes beyes 222 2010-09-23 23:31 mknode.sh
-rw-r--r-- 1 beyes beyes 61 2010-09-23 23:30 modules.order
-rw-r--r-- 1 beyes beyes 0 2010-09-18 15:51 Module.symvers
-rw-r--r-- 1 beyes beyes 8254 2010-09-23 23:03 scull.c
-rw-r--r-- 1 beyes beyes 479 2010-09-18 23:55 scull.h
-rw-r--r-- 1 root root 7224 2010-09-23 23:30 scull.ko
-rw-r--r-- 1 root root 331 2010-09-23 23:30 .scull.ko.cmd
-rw-r--r-- 1 beyes beyes 1163 2010-09-18 17:12 scull.mod.c
-rw-r--r-- 1 root root 2780 2010-09-23 23:30 scull.mod.o
-rw-r--r-- 1 root root 23122 2010-09-23 23:30 .scull.mod.o.cmd
-rw-r--r-- 1 root root 5083 2010-09-23 23:30 scull.o
-rw-r--r-- 1 root root 24895 2010-09-23 23:30 .scull.o.cmd
drwxr-xr-x 2 root root 4096 2010-09-23 23:30 .tmp_versions/
# cp scull.c /dev/scull2
# cat /dev/scull2
#define SCULL_QUANTUM 4000
#define SCULL_QSET 1000
#define SCULL_NR_DEVS 4
struct scull_qset {
void **data;
struct scull_qset *next;
};
struct scull_dev {
struct scull_qset *data; /* 第一个量子集指针 */
int quantum; /* 量子个数 */
int qset; /* 量子指针数组大小 */
unsigned long size; /* 存储的数据数 */
struct semaphore sem; /* 互斥型信号量 */
struct cdev cdev; /* 字符设备结构体*/
};
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