1.在用户空间中有个字符数组，要求在内核空间打印，用dmesg查看。（ioctl实现）

        zy.h，封装一个发送用的命令码

#ifndef __LED_H__
#define __LED_H__
#define UACCESS_BUF _IOW('a',1,char [128])
#endif

        zy.c 申请并自动创建设备结点，在mydev_ioctl函数中确认命令码并接受字符数组信息存储在kbuf中，同时打印kbuf信息。

#include 
#include 
#include
#include
#include
#include
#include"zy.h"
#define CNAME "zy"
int major;
struct class* cls;
struct device* dev;
char kbuf[128]={};
int mydev_open (struct inode *inode, struct file *file)
{return 0;
}
int mydev_close (struct inode *inode, struct file *file)
{return 0;
}long mydev_ioctl (struct file *file, unsigned int cmd,unsigned long arg)
{int ret;if(cmd==UACCESS_BUF){ret=copy_from_user(kbuf,(void*)arg,sizeof(kbuf));if(ret){printk("copy from user error\n");return EIO;}printk("kbuf = %s\n",kbuf);}return 0;
}
const struct file_operations fops={.open=mydev_open,.release=mydev_close,.unlocked_ioctl=mydev_ioctl,};static int __init demo_init(void)
{major=register_chrdev(0,CNAME,&fops);if(major<0){printk("register_chrdev error\n");return major;}printk("major=%d\n",major);cls=class_create(THIS_MODULE,CNAME);if(IS_ERR(cls)){return PTR_ERR(cls);}//提交设备结点信息dev=device_create(cls,NULL,MKDEV(major,0),NULL,CNAME);if(IS_ERR(dev)){return PTR_ERR(dev);}return 0;    
}static void __exit demo_exit(void)
{device_destroy(cls,MKDEV(major,0));class_destroy(cls);unregister_chrdev(major,CNAME);
}
module_init(demo_init);
module_exit(demo_exit);
MODULE_LICENSE("GPL");

        test.c 打开驱动文件并发送字符数组

#include
#include
#include
#include
#include
#include
#include
#include
#include "zy.h"
int main(int argc, char const *argv[])
{char buf[128]={"You have an ambitious nature and may make a name for yourself"};int fd=-1;fd=open("/dev/zy",O_RDWR);if(-1==fd){perror("open error");return -1;}ioctl(fd,UACCESS_BUF,buf);return 0;
}

makefile：编译工具

ARCH?=x86
NAME?=zy
ifeq ($(ARCH),x86)KERNEDIR:=/lib/modules/$(shell uname -r)/build
elseKERNEDIR:=/home/ubuntu/linux-5.10.61
endif
PWD:=$(shell pwd)
all:make -C $(KERNEDIR) M=$(PWD) modules
clean:make -C $(KERNEDIR) M=$(PWD) clean
obj-m:=$(NAME).o

实验结果截图

 二：将结构题传递到内核空间，在内核空间打印，把值+10后传递会用户空间打印。

        zy2.h：封装结构体和发送接收两个命令码。

#ifndef __LED_H__
#define __LED_H__
typedef struct {int width;int high;
}image_t;
#define struct_send _IOW('a',1,image_t)
#define struct_recv _IOR('a',1,image_t)
#endif

        zy2.c：在接收后打印，然后加10返回用户空间

#include 
#include 
#include
#include
#include
#include
#include"zy2.h"
#define CNAME "zy2"
int major;
struct class* cls;
struct device* dev;
image_t kimage;
int mydev_open (struct inode *inode, struct file *file)
{return 0;
}
int mydev_close (struct inode *inode, struct file *file)
{return 0;
}long mydev_ioctl (struct file *file, unsigned int cmd,unsigned long arg)
{int ret;if(cmd==struct_send){ret=copy_from_user(&kimage,(void*)arg,sizeof(image_t));if(ret){printk("copy from user error\n");return EIO;}printk("width=%d\nhigh=%d\n",kimage.width,kimage.high);kimage.width+=10;kimage.high+=10;}else if(cmd==struct_recv){ret=copy_to_user((void*)arg,&kimage,sizeof(image_t));if(ret){printk("copy to user error\n");return EIO;}}return 0;
}
const struct file_operations fops={.open=mydev_open,.release=mydev_close,.unlocked_ioctl=mydev_ioctl,};static int __init demo_init(void)
{major=register_chrdev(0,CNAME,&fops);if(major<0){printk("register_chrdev error\n");return major;}printk("major=%d\n",major);cls=class_create(THIS_MODULE,CNAME);if(IS_ERR(cls)){return PTR_ERR(cls);}//提交设备结点信息dev=device_create(cls,NULL,MKDEV(major,0),NULL,CNAME);if(IS_ERR(dev)){return PTR_ERR(dev);}return 0;    
}static void __exit demo_exit(void)
{device_destroy(cls,MKDEV(major,0));class_destroy(cls);unregister_chrdev(major,CNAME);
}
module_init(demo_init);
module_exit(demo_exit);
MODULE_LICENSE("GPL");

        test2.c：发送接收并打印

#include
#include
#include
#include
#include
#include
#include
#include
#include "zy2.h"
int main(int argc, char const *argv[])
{image_t image={20,40};int fd=-1;fd=open("/dev/zy2",O_RDWR);if(-1==fd){perror("open error");return -1;}ioctl(fd,struct_send,&image);ioctl(fd,struct_recv,&image);printf("width=%d\nhigh=%d\n",image.width,image.high);close(fd);return 0;
}

makefile：编译工具

ARCH?=x86
NAME?=zy2
ifeq ($(ARCH),x86)KERNEDIR:=/lib/modules/$(shell uname -r)/build
elseKERNEDIR:=/home/ubuntu/linux-5.10.61
endif
PWD:=$(shell pwd)
all:make -C $(KERNEDIR) M=$(PWD) modules
clean:make -C $(KERNEDIR) M=$(PWD) clean
obj-m:=$(NAME).o

结果截图