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virtualcdev.c
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229 lines (201 loc) · 5.29 KB
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#include<linux/module.h>
#include<linux/cdev.h>
#include<linux/device.h>
#include<linux/types.h>
#include<linux/kernel.h>
#include<linux/fs.h>
#include<linux/init.h>
#include<linux/delay.h>
#include<asm/uaccess.h>
#include<asm/io.h>
#include<asm/system.h>
#include<linux/mm.h>
#include<linux/slab.h>
#define GLOBALMEM_SIZE 0x1000
#define DEVICE_NAME "virtualcdev" /* 加载模块后，执行”cat /proc/devices”命令看到的设备名称 */
#define VIRTUALCDEV_MAJOR 0 /* 主设备号 */
#define MEM_CLEAR 0x1 /* 清零全局内存 */
static int major = VIRTUALCDEV_MAJOR;
static struct class *virtualcdev_class;
struct device *virtualcdev_device;
/* globalmem设备结构体 */
struct virtualcdev_dev
{
struct cdev cdev; /* cdev结构体 */
unsigned char mem[GLOBALMEM_SIZE]; /* 全局内存 */
};
struct virtualcdev_dev *virtualcdev_devp; /* 设备结构体指针 */
/* 应用程序对设备文件/dev/virtualcdev执行open(...)时，
* 就会调用virtualcdev_open函数
*/
static int virtualcdev_open(struct inode *inode, struct file *filp)
{
filp->private_data = virtualcdev_devp;
return 0;
}
static int virtualcdev_release(struct inode *inode, struct file *filp)
{
return 0;
}
static long virtualcdev_ioctl(struct inode *inodep, struct file *filp, unsigned int cmd, unsigned long arg)
{
struct virtualcdev_dev *devp = filp->private_data; /* 获得设备结构体指针 */
switch(cmd)
{
case MEM_CLEAR:
memset(devp->mem, 0, GLOBALMEM_SIZE);
printk(KERN_INFO "globalmem is set to zero\n");
break;
default:
return -EINVAL;
}
return 0;
}
static ssize_t virtualcdev_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 virtualcdev_dev *devp = filp->private_data; /* 获得设备结构体指针 */
if(p >= GLOBALMEM_SIZE)
return 0;
if(count > GLOBALMEM_SIZE - p)
count = GLOBALMEM_SIZE - p;
if(copy_to_user(buf, (void *)(devp->mem + p), count))
{
ret = -EFAULT;
}
else
{
*ppos += count;
ret = count;
}
return ret;
}
static ssize_t virtualcdev_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 virtualcdev_dev *devp = filp->private_data;
if(p >= GLOBALMEM_SIZE)
return 0;
if(count > GLOBALMEM_SIZE - p)
count = GLOBALMEM_SIZE - p;
if(copy_from_user(devp->mem + p, buf, count))
ret = -EFAULT;
else
{
*ppos += count;
ret = count;
printk(KERN_INFO "written %u bytes(s) from %lu\n", count, p);
}
return ret;
}
/* seek文件定位函数 */
static loff_t virtualcdev_llseek(struct file *filp, loff_t offset, int orig)
{
loff_t ret = 0;
switch(orig)
{
case 0: /* 相对文件开始位置位移 */
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) < 0)
{
ret = -EINVAL;
break;
}
if((filp->f_pos + offset) > GLOBALMEM_SIZE)
{
ret = -EINVAL;
break;
}
filp->f_pos += offset;
ret = filp->f_pos;
break;
default:
ret = -EINVAL;
break;
}
return ret;
}
/* 这个结构是字符设备驱动程序的核心
* 当应用程序操作设备文件时所调用的open、read、write等函数，
* 最终会调用这个结构中指定的对应函数
*/
static struct file_operations virtualcdev_fops = {
.owner = THIS_MODULE, /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */
.open = virtualcdev_open,
.read = virtualcdev_read,
.write = virtualcdev_write,
.llseek = virtualcdev_llseek,
.release = virtualcdev_release,
.unlocked_ioctl = virtualcdev_ioctl
};
/*
* 执行insmod命令时就会调用这个函数
*/
static int __init virtualcdev_init(void)
{
dev_t devno = MKDEV(major, 0);
if(major)
major = register_chrdev_region(devno, 1, "virtualcdev");
else
{
major = alloc_chrdev_region(&devno, 0, 1, "virtualcdev");
major = MAJOR(devno);
}
virtualcdev_class = class_create(THIS_MODULE, "virtualcdev");
virtualcdev_device = device_create(virtualcdev_class, 0, MKDEV(major, 0),
0, "%s", DEVICE_NAME);
if (IS_ERR(virtualcdev_device)) {
printk("device create err\n");
}
if(major < 0)
return major;
virtualcdev_devp = kmalloc(sizeof(struct virtualcdev_dev), GFP_KERNEL);
if(!virtualcdev_devp)
{
major = -ENOMEM;
goto fail_malloc;
}
memset(virtualcdev_devp, 0, sizeof(struct virtualcdev_dev));
cdev_init(&(virtualcdev_devp->cdev), &virtualcdev_fops);
virtualcdev_devp->cdev.owner = THIS_MODULE;
cdev_add(&(virtualcdev_devp->cdev), devno, 1);
return 0;
fail_malloc: unregister_chrdev_region(devno, 1);
return major;
}
/*
* 执行rmmod命令时就会调用这个函数
*/
static void __exit virtualcdev_exit(void)
{
device_destroy(virtualcdev_class, MKDEV(major, 0));
class_destroy(virtualcdev_class);
cdev_del(&virtualcdev_devp->cdev);
kfree(virtualcdev_devp);
unregister_chrdev_region(MKDEV(major, 0), 1);
}
/* 这两行指定驱动程序的初始化函数和卸载函数 */
module_init(virtualcdev_init);
module_exit(virtualcdev_exit);
/* 描述驱动程序的一些信息 */
MODULE_AUTHOR("author");
MODULE_VERSION("0.1.0");
MODULE_DESCRIPTION("virtualcdev Driver");
MODULE_LICENSE("GPL");