globalmem设备代码分析

驱动程序代码：

#include<linux/module.h>

#include<linux/types.h>
#include<linux/fs.h>
#include<linux/errno.h>
#include<linux/mm.h>
#include<linux/sched.h>
#include<linux/init.h>
#include<linux/cdev.h>
#include<linux/slab.h>
#include<linux/kdev_t.h>
#include<linux/device.h>
#include <asm/io.h>
#include<asm/system.h>
#include<asm/uaccess.h>

#define DEVICE_NAME "globalmem"
#define GLOBALMEM_SIZE 0x1000 /*全局内存最大4K字节*/
#define MEM_CLEAR 0x1 /*清0全局内存*/
#define GLOBALMEM_MAJOR 241 /*预设的globalmem的主设备号*/

static int globalmem_major = GLOBALMEM_MAJOR;

/*globalmem设备结构体*/
struct globalmem_dev
{
struct cdev cdev; /*cdev结构体*/
unsigned char mem[GLOBALMEM_SIZE];/*全局内存*/
};

struct globalmem_dev *globalmem_devp; /*设备结构体指针*/

static struct class *globalmem0_class;
static struct class *globalmem1_class;

/*文件打开函数*/
int globalmem_open(struct inode *inode, struct file *filp)
{
/*将设备结构体指针赋值给文件私有数据指针*/
struct globalmem_dev *dev;

dev = container_of(inode->i_cdev,struct globalmem_dev,cdev);
filp->private_data = dev;
return 0;
}

/*文件释放函数*/
int globalmem_release(struct inode *inode, struct file *filp)
{
return 0;
}

/* ioctl设备控制函数 */
static int globalmem_ioctl(struct inode *inodep, struct file *filp, unsigned
int cmd, unsigned long arg)
{
struct globalmem_dev *dev = filp->private_data;/*获得设备结构体指针*/

switch (cmd)
{
case MEM_CLEAR:
memset(dev->mem, 0, GLOBALMEM_SIZE);
printk(KERN_INFO "globalmem is setto zero\n");
break;

default:
return - EINVAL;
}
return 0;
}

/*读函数*/
static ssize_t globalmem_read(struct file *filp, char __user *buf, size_t size,
loff_t *ppos)
{
unsigned long p = *ppos;
unsigned int count = size;
int ret = 0;
struct globalmem_dev *dev = filp->private_data; /*获得设备结构体指针*/

/*分析和获取有效的写长度*/
if (p >= GLOBALMEM_SIZE)
return count ? - ENXIO: 0;
if (count > GLOBALMEM_SIZE - p)
count = GLOBALMEM_SIZE - p;

/*内核空间->用户空间*/
if (copy_to_user(buf, (void*)(dev->mem +p), count))
{
ret = - EFAULT;
}
else
{
*ppos += count;
ret = count;

printk(KERN_INFO "read %d bytes(s)from %d\n", count, p);
}
return ret;
}

/*写函数*/
static ssize_t globalmem_write(struct file *filp, const char __user *buf,
size_t size, loff_t *ppos)
{
unsigned long p = *ppos;
unsigned int count = size;
int ret = 0;
struct globalmem_dev *dev = filp->private_data; /*获得设备结构体指针*/

/*分析和获取有效的写长度*/
if (p >= GLOBALMEM_SIZE)
return count ? - ENXIO: 0;
if (count > GLOBALMEM_SIZE - p)
count = GLOBALMEM_SIZE - p;

/*用户空间->内核空间*/
if (copy_from_user(dev->mem + p, buf,count))
ret = - EFAULT;
else
{
*ppos += count;
ret = count;
printk(KERN_INFO "written %d bytes(s)from %d\n", count, p);
}

return ret;
}

/* seek文件定位函数 */
static loff_t globalmem_llseek(struct file *filp, loff_t offset, int orig)
{
loff_t ret = 0;
switch (orig)
{
case 0: /*相对文件开始位置偏移*/
if (offset < 0)
{
ret = - EINVAL;
break;
}
if ((unsigned int)offset >GLOBALMEM_SIZE)
{
ret = - EINVAL;
break;
}
filp->f_pos = (unsigned int)offset;
ret = filp->f_pos;
break;

case 1: /*相对文件当前位置偏移*/
if ((filp->f_pos + offset) >GLOBALMEM_SIZE)
{
ret = - EINVAL;
break;
}
if ((filp->f_pos + offset) < 0)
{
ret = - EINVAL;
break;
}
filp->f_pos += offset;
ret = filp->f_pos;
break;

default:
ret = - EINVAL;
break;
}
return ret;
}

/*文件操作结构体*/
static const struct file_operations globalmem_fops =
{
.owner = THIS_MODULE,
.llseek = globalmem_llseek,
.read = globalmem_read,
.write = globalmem_write,
//.ioctl = globalmem_ioctl,
.unlocked_ioctl = globalmem_ioctl,
.compat_ioctl = globalmem_ioctl,
.open = globalmem_open,
.release = globalmem_release,
};

/*初始化并注册cdev*/
static void globalmem_setup_cdev(struct globalmem_dev *dev, int index)
{
int err, devno = MKDEV(globalmem_major,index);

/*
cdev_init(&dev->cdev, &globalmem_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &globalmem_fops;
*/

cdev_init(&dev->cdev, &globalmem_fops);
dev->cdev.owner = THIS_MODULE;

err = cdev_add(&dev->cdev, devno, 1);
if (err)
printk(KERN_NOTICE "Error %d addingLED%d", err, index);
}

/*设备驱动模块加载函数*/
int globalmem_init(void)
{
int result;
dev_t devno = MKDEV(globalmem_major, 0);

/* 申请设备号*/
if (globalmem_major)
result = register_chrdev_region(devno, 2,DEVICE_NAME);
else /* 动态申请设备号 */
{
result = alloc_chrdev_region(&devno, 0,2, DEVICE_NAME);
globalmem_major = MAJOR(devno);
}
if (result < 0)
return result;

/* 动态申请2个设备结构体的内存*/
globalmem_devp = kmalloc(2*sizeof(struct globalmem_dev), GFP_KERNEL);
if (!globalmem_devp) /*申请失败*/
{
result = - ENOMEM;
goto fail_malloc;
}
memset(globalmem_devp, 0, 2*sizeof(struct globalmem_dev));

globalmem_setup_cdev(&globalmem_devp[0],0);
globalmem_setup_cdev(&globalmem_devp[1],1);

//注册一个类，使mdev可以在/dev/下面建立设备节点
globalmem0_class =class_create(THIS_MODULE, "globalmem0");
if( IS_ERR(globalmem0_class) )
{
printk(KERN_NOTICE, "creatglobalmem0_class failed!");
return -1;
}

//创建一个设备节点，节点名字为globalmem0
device_create(globalmem0_class, NULL,MKDEV(globalmem_major, 0), NULL, "globalmem0");
printk(KERN_NOTICE, "globalmem0initialized!");

globalmem1_class =class_create(THIS_MODULE, "globalmem1");
if( IS_ERR(globalmem1_class) )
{
printk(KERN_NOTICE, "creatglobalmem1_class failed!");
return -1;
}

//创建一个设备节点，节点名字为globalmem1
device_create(globalmem1_class, NULL,MKDEV(globalmem_major, 1), NULL, "globalmem1");
printk(KERN_NOTICE, "globalmem1initialized!");

return 0;

fail_malloc:
unregister_chrdev_region(devno,2);
return result;
}

/*模块卸载函数*/
void globalmem_exit(void)
{
cdev_del(&(globalmem_devp[0].cdev));
cdev_del(&(globalmem_devp[1].cdev)); /*注销cdev*/
kfree(globalmem_devp); /*释放设备结构体内存*/
unregister_chrdev_region(MKDEV(globalmem_major, 0), 2); /*释放设备号*/
class_destroy(globalmem0_class);
class_destroy(globalmem1_class);
}

MODULE_AUTHOR("SongBaohua");
MODULE_LICENSE("GPL");
//MODULE_LICENSE("DualBSD/GPL");

module_param(globalmem_major,int, S_IRUGO);

module_init(globalmem_init);

module_exit(globalmem_exit);

用户空间测试程序代码：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include<linux/fcntl.h>

int main()
{
int fd;
char buf1[]="testglobalmen data!";//写入memdev设备的内容
char buf_read[4096]; //memdev设备的内容读入到该buf中

if((fd=open("/dev/globalmem0",O_RDWR))==-1)//打开memdev设备
{
printf("open globalmem0 WRONG！\n");
return 0;
}

int count = 0;
while(count<=100)
{
printf("openglobalmem0 SUCCESS!\n");
printf("buf is %s\n",buf1);
write(fd,buf1,sizeof(buf1));//把buf中的内容写入memdev设备
lseek(fd,0,SEEK_SET); //把文件指针重新定位到文件开始的位置
read(fd,buf_read,sizeof(buf1));//把memdev设备中的内容读入到buf_read中
printf("buf_read is %s\n",buf_read);
count++;
}

close(fd);
return 0;
}

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