linux device driver —— ioctl

Posted 2020-08-21

实现了应用程序和设备驱动通过ioctl通信。还是对设备驱动没什么感觉，贴一下代码吧。

在Ubuntu 16.04 64bit中测试通过

ioctldemo.c

#include <linux/module.h>
#include <linux/init.h>
#include <linux/stat.h>
#include <linux/types.h>
#include <linux/kdev_t.h>
#include <linux/fs.h>
#include <linux/moduleparam.h>
#include <linux/cdev.h>
#include <asm-generic/uaccess.h>
#include <asm-generic/ioctl.h>
#include <asm-generic/current.h>

#define IOCTLDEMO_MAJOR 0
#define MODULE_NAME "ioctldemo"

#define DEMO_MAGIC ‘m‘
#define DEMO_SIZE  int
#define DEMO_NR_MAX    1
#define MY_IOCTL_READ _IOR(DEMO_MAGIC,1,DEMO_SIZE);

static int ioctldemo_major = IOCTLDEMO_MAJOR;

void ioctldemo_exit(void);
int  ioctldemo_init(void);
long my_unlocked_ioctl(struct file*, unsigned int, unsigned long);
int  my_cdev_open(struct inode*, struct file*);
int  my_cdev_release(struct inode*,struct file*);

MODULE_LICENSE("Dual BSD/GPL");
module_param(ioctldemo_major,int,S_IRUGO);
module_init(ioctldemo_init);
module_exit(ioctldemo_exit);

struct cdev *my_cdev;

static struct file_operations cdev_ops = 
{
    .owner          = THIS_MODULE,
    .open           = my_cdev_open,
    .release        = my_cdev_release,
    .unlocked_ioctl = my_unlocked_ioctl,
};

int __init ioctldemo_init(void)
{
    int ret;
    dev_t devno;
    printk(KERN_NOTICE "=== ioctldemo_init start");
    devno = MKDEV(ioctldemo_major,0);
    if(ioctldemo_major)
    {
        printk(KERN_NOTICE "=== ioctldemo_init try register");
        ret = register_chrdev_region(devno,1,MODULE_NAME);
    }else
    {
        printk(KERN_NOTICE "=== ioctldemo_init auto register");
        ret = alloc_chrdev_region(&devno,0,1,MODULE_NAME);
        ioctldemo_major = MAJOR(devno);
    }
    if(ret < 0)
    {
        printk(KERN_NOTICE "=== ioctldemo_init register fail");
        return ret;
    }

    my_cdev = cdev_alloc();
    my_cdev->owner = THIS_MODULE;
    my_cdev->ops   = &cdev_ops;
    ret = cdev_add(my_cdev,MKDEV(ioctldemo_major,0),1);

    if(ret < 0)
    {
        printk(KERN_NOTICE "=== ioctldemo_init add cdev fail");
        return ret;
    }

    printk(KERN_NOTICE "=== ioctldemo_init finish");
    return 0;
}


void __exit ioctldemo_exit(void)
{
    printk (KERN_NOTICE "=== ioctldemo_exit");
    cdev_del(my_cdev);
    unregister_chrdev_region(MKDEV(ioctldemo_major,0),1);
}

long my_unlocked_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
    int err = 0;
    if(_IOC_TYPE(cmd) != DEMO_MAGIC)
        return -ENOTTY;
    if(_IOC_NR(cmd) > DEMO_NR_MAX)
        return -ENOTTY;
    if(_IOC_DIR(cmd) & _IOC_READ)
        err = !access_ok(VERIFY_WRITE,(void __user*)arg, _IOC_SIZE(cmd));
    if(err)
        return -EFAULT;

    printk(KERN_NOTICE "=== ioctldemo_ioctl current process is: %s, pid is: %d\n",current->comm,current->pid);

    return __put_user(666,(int *)arg);    
}

int my_cdev_open(struct inode *node, struct file *filp)
{
    return 0;
}

int my_cdev_release(struct inode *node, struct file *filp)
{
    return 0;
}

Makefile

ifneq ($(KERNELRELEASE),)
mymodule-objs := ioctldemo    
obj-m := ioctldemo.o  
else
PWD  := $(shell pwd)
KVER ?= $(shell uname -r)
KDIR := /lib/modules/$(KVER)/build
all:
    $(MAKE) -C $(KDIR) M=$(PWD)
clean:           
    rm -rf *.cmd *.o *.mod.c  .tmp_versions *.order *.symvers
endif

install.sh

#!/bin/bash

module="ioctldemo"
device="ioctldemo"
name="ioctldemo"

insmod $module.ko

if [ $? == 1 ]
then 
    exit
fi
major=$(awk "{if(\$2==\"$name\"){print \$1}}"  /proc/devices)

mknod /dev/$device c $major 0

chmod 666 /dev/$device

uninstall.sh

#!/bin/bash
module="ioctldemo"
device="ioctldemo"

file="/dev/$device"

if [ -e $file ]
then    
    rm -rf /dev/$device
    echo ‘rm device‘
fi

echo ‘rm module‘
/sbin/rmmod $module

测试程序：

#include <stdio.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <asm-generic/ioctl.h>
#include <error.h>

#define CMD _IOR(‘m‘,1,int)

int main()
{
    int fd, ret, arg;
    fd = open("/dev/ioctldemo",O_RDWR);
    if(fd < 0)
    {
        puts("open fail");
        return fd;
    }
    ret = ioctl(fd,CMD,&arg);
    if(ret == 0)
        printf("ioctl result :%d",arg);
    else
        perror("ioctl fail");
    close(fd);
    return 0;
}