[root@bogon 桌面]#
gedit mycdev_globalmem.c#include
#include
#include
#include
#include
#include
MODULE_AUTHOR("Me");
MODULE_LICENSE("GPL");
#define GLOBALMEM_SIZE 0x1000
#define GLOBALMEM_MAJOR 256
static int globalmem_major = GLOBALMEM_MAJOR;
struct globalmem_dev
{
struct cdev cdev; /*cdev 结构体*/
unsigned char mem[255]; /*全局内存*/
};
struct globalmem_dev *globalmem_devp; /*定义设备变量*/
/*文件打开函数*/
static 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*/
filp->private_data = globalmem_devp;
return 0;
}
/*globalmem设备驱动的读函数*/
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;
/*从内核空间向用户空间写数据*/
if (copy_to_user(buf, (void*)(dev->mem + p), count))
{
ret = -EFAULT;
}
else
{
*ppos += count;
ret = count;
printk(KERN_INFO "read %u bytes(s) from %u\n", count, p);
}
return ret;
}
static ssize_t globalmem_write(struct file *fp, const char __user *buf, size_t size, loff_t *pos)
{
return size;
}
static int globalmem_release(struct inode *inode, struct file *fp)
{
return 0;
}
static const struct file_operations globalmem_fops =
{
.owner = THIS_MODULE,
.read = globalmem_read,
.write = globalmem_write,
.open = globalmem_open,
.release = globalmem_release,
};
/*初始化并添加cdev结构体的函数*/
static void globalmem_setup_cdev(struct globalmem_dev *dev, int index)
{
int ret;
int devno = MKDEV(globalmem_major, index);
cdev_init(&dev->cdev, &globalmem_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &globalmem_fops;
ret = cdev_add(&dev->cdev, devno, 1);
if(ret){
printk("adding globalmem error");
}
}
/*模块初始化函数*/
int globalmem_init(void)
{
int result;
dev_t devno=MKDEV(globalmem_major,0);
if(globalmem_major) /*globalmem_major为给定的全局变量,见后面的程序清单*/
{
result=register_chrdev_region(devno,1,"globalmem");
}
else
{
result=alloc_chrdev_region(&devno,0,1,"globalmem");
globalmem_major=MAJOR(devno);
}
if(result<0){
printk("register globalmem failed..\n");
return result;
}else{
printk("register globalmem success..\n");
}
globalmem_devp=kmalloc(sizeof(struct globalmem_dev),GFP_KERNEL);
if(!globalmem_devp)
{
result=-ENOMEM;
goto fail_malloc;
}
memset(globalmem_devp,0,sizeof(struct globalmem_dev));
memcpy(globalmem_devp->mem, "This is mycdev_globalmem!", sizeof(struct globalmem_dev));
globalmem_setup_cdev(globalmem_devp,0);
return 0;
fail_malloc:
unregister_chrdev_region(devno,1);
return result;
}
/*模块退出函数*/
static void __exit globalmem_exit(void)
{
cdev_del(&globalmem_devp->cdev); /*释放struct cdev*/
kfree(globalmem_devp); /*释放分配为给 struct globalmem_dev的内存*/
unregister_chrdev_region(MKDEV(globalmem_major,0), 1); /*释放devno*/
}
module_init(globalmem_init);
module_exit(globalmem_exit);
[root@bogon 桌面]# gedit Makefile
obj-m:=mycdev_globalmem.o
PWD:=$(shell pwd)
CUR_PATH:=$(shell uname -r)
KERNEL_PATH:=/usr/src/kernels/$(CUR_PATH)
all:
make -C $(KERNEL_PATH) M=$(PWD) modules
clean:
make -C $(KERNEL_PATH) M=$(PWD) clean
[root@bogon 桌面]# gedit mycdev_globalmem_test.c
#include
#include
#include
#include
#include
#define GLOBALMEM_SIZE 0x1000
int main()
{
int testdev;
int i, ret;
char buf[GLOBALMEM_SIZE];
testdev = open("/dev/mycdev_globalmem", O_RDWR);
if (-1 == testdev) {
printf("cannot open file.\n");
exit(1);
}
if (ret = read(testdev, buf, GLOBALMEM_SIZE) <0) {
printf("read error!\n");
exit(1);
}
printf("%s\n", buf);
close(testdev);
return 0;
}
[root@bogon 桌面]# make
[root@bogon 桌面]# insmod mycdev_globalmem.ko
[root@bogon 桌面]# cat /proc/devices
[root@bogon 桌面]# mknod /dev/mycdev_globalmem c 256 0
[root@bogon 桌面]# chmod 777 /dev/mycdev_globalmem
[root@bogon 桌面]# gcc mycdev_globalmem_test.c -o mycdev_globalmem_test
[root@bogon 桌面]# ./mycdev_globalmem_test
[root@bogon 桌面]# dmesg
阅读(1573) | 评论(0) | 转发(0) |