lv14 ioctl、printk及多个此设备支持 6

发布时间:2024年01月07日

1 ioctl操作实现

对相应设备做指定的控制操作(各种属性的设置获取等等)

long xxx_ioctl (struct file *filp, unsigned int cmd, unsigned long arg);
功能:对相应设备做指定的控制操作(各种属性的设置获取等等)
参数:
    filp:指向open产生的struct file类型的对象,表示本次ioctl对应的那次open
    cmd:用来表示做的是哪一个操作
 ?  arg:和cmd配合用的参数
返回值:成功为0,失败-1

cmd组成

  • dir(direction),ioctl 命令访问模式(属性数据传输方向),占据 2 bit,可以为 IOC_NONE、IOC_READ、IOC_WRITE、IOC_READ | _IOC_WRITE,分别指示了四种访问模式:无数据、读数据、写数据、读写数据

  • type(device type),设备类型,占据 8 bit,在一些文献中翻译为 “幻数” 或者 “魔数”,可以为任意 char 型字符,例如 ‘a’、’b’、’c’ 等等,其主要作用是使 ioctl 命令有唯一的设备标识

  • nr(number),命令编号/序数,占据 8 bit,可以为任意 unsigned char 型数据,取值范围 0~255,如果定义了多个 ioctl 命令,通常

    从 0 开始编号递增

  • size,涉及到 ioctl 函数 第三个参数 arg ,占据 13bit 或者 14bit(体系相关,arm 架构一般为 14 位),指定了 arg 的数据类型及长度,如果在驱动的 ioctl 实现中不检查,通常可以忽略该参数;

#define _IOC(dir,type,nr,size) (((dir)<<_IOC_DIRSHIFT)| \
 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ((type)<<_IOC_TYPESHIFT)| \
 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ((nr)<<_IOC_NRSHIFT)| \
 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ((size)<<_IOC_SIZESHIFT))
//用于解码ioctl数字
/* used to create numbers */
?
// 定义不带参数的 ioctl 命令
#define _IO(type,nr) ? _IOC(_IOC_NONE,(type),(nr),0)
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//定义带读参数的ioctl命令(copy_to_user) size为类型名
#define _IOR(type,nr,size)  _IOC(_IOC_READ,(type),(nr),(_IOC_TYPECHECK(size)))
?
//定义带写参数的 ioctl 命令(copy_from_user) size为类型名
#define _IOW(type,nr,size)  _IOC(_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
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//定义带读写参数的 ioctl 命令 size为类型名
#define _IOWR(type,nr,size) _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
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//用于解码ioctl数字
/* used to decode ioctl numbers */
#define _IOC_DIR(nr) ? ? ?  (((nr) >> _IOC_DIRSHIFT) & _IOC_DIRMASK)
#define _IOC_TYPE(nr) ? ? ? (((nr) >> _IOC_TYPESHIFT) & _IOC_TYPEMASK)
#define _IOC_NR(nr) ? ? (((nr) >> _IOC_NRSHIFT) & _IOC_NRMASK)
#define _IOC_SIZE(nr) ? ?  (((nr) >> _IOC_SIZESHIFT) & _IOC_SIZEMASK)

头文件位置

1.1 示例:

mychar.h

#ifndef MY_CHAR_H
#define MY_CHAR_H

#include <asm/ioctl.h>

#define MY_CHAR_MAGIC 'k'

#define MYCHAR_IOCTL_GET_MAXLEN _IOR(MY_CHAR_MAGIC,1,int*)
#define MYCHAR_IOCTL_GET_CURLEN _IOR(MY_CHAR_MAGIC,2,int*)


#endif

mychar.c

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>

#include "mychar.h"

#define BUF_LEN 100

int major = 11;
int minor = 0;
int mychar_num = 1;

//新建结构体类型
struct mychar_dev
{
	struct cdev mydev;
	char mydef_buf[BUF_LEN];  //相当于结构体的私有变量
	int curlen;          //相当于结构体的私有变量
};

struct mychar_dev gmydev;

int mychar_open(struct inode *pnode, struct file *pfile)
{
	//利用private_data私有变量来指向全局变量结构体地址
	pfile->private_data = (void*)(container_of(pnode->i_cdev,struct mychar_dev,mydev));
    printk("mychar_open is called\n");
    return 0;
}

int mychar_close(struct inode *pnode, struct file *pfile)
{
    printk("mychar_close is called\n");
    return 0;
}


ssize_t mychar_read(struct file *filp, char __user *pbuf, size_t count, loff_t *ppos)
{
	int ret = 0;
	int size = 0;
	//获取全家变量结构体地址
	struct mychar_dev *pmydev = (struct mychar_dev *)filp->private_data;

 	if(count > pmydev->curlen)
	{
		size = pmydev->curlen;
	}
	else
	{
		size = count;
	}

	//将内核空间中的数据复制到用户空间
	ret = copy_to_user(pbuf,pmydev->mydef_buf,size);
	if(ret)
	{
	
		printk("copy_to_user failed\n");
		return -1;
	}
	//读完之后把后面的内容再拷贝过来,同时更新curlen
	memcpy(pmydev->mydef_buf,pmydev->mydef_buf+size,pmydev->curlen - size);
	pmydev->curlen = pmydev->curlen - size;

	return size;

}

ssize_t mychar_write (struct file *filp, const char __user *pbuf, size_t count, loff_t *ppos)
{

	int size = 0;
	int ret  = 0;
	//获取全家变量结构体地址
	struct mychar_dev *pmydev = (struct mychar_dev *)filp->private_data;

	if(count > BUF_LEN - pmydev->curlen)
	{
		size = BUF_LEN - pmydev->curlen;
	}
	else
	{
		size = count;
	}

	//将用户空间中的数据复制到内核空间中
	ret = copy_from_user(pmydev->mydef_buf + pmydev->curlen, pbuf, size);
	if(ret)
	{
		printk("copy_from_user failed\n");
		return -1;
	}
    //更新curlen
	pmydev->curlen = pmydev->curlen + size;
	return size;
}

long mychar_ioctl(struct file *filp, unsigned int cmd,unsigned long arg)
{
    int __user *pret = (int *)arg;
	int maxlen = BUF_LEN;
	int ret = 0;
	struct mychar_dev *pmydev = (struct mychar_dev *)filp->private_data;

	switch(cmd)
	{
		case MYCHAR_IOCTL_GET_MAXLEN:
			ret = copy_to_user(pret,&maxlen,sizeof(int));
			if(ret)
			{
				printk("copy_to_user MAXLEN failed\n");
				return -1;
			}
			break;
		case MYCHAR_IOCTL_GET_CURLEN:
			ret = copy_to_user(pret,&pmydev->curlen,sizeof(int));
			if(ret)
			{
				printk("copy_to_user CURLEN failed\n");
				return -1;
			}
			break;
		default:
			printk("The cmd is unknow\n");
			return -1;
	}
	return 0;
}

//结构体初始化:部分变量赋值初始化
struct file_operations myops = {
    .owner = THIS_MODULE,
    .open = mychar_open,
    .release = mychar_close,
	.read = mychar_read,
	.write = mychar_write,
	.unlocked_ioctl = mychar_ioctl
};

int mychar_init(void)
{
    int ret = 0;
    dev_t devno = MKDEV(major, minor);

    /* 申请设备号 */
    ret = register_chrdev_region(devno, mychar_num, "mychar");
    if (ret) {
        ret = alloc_chrdev_region(&devno, minor, mychar_num, "mychar");
        if (ret) {
            printk("get devno failed\n");
            return -1;
        }
		major = MAJOR(devno); // 容易遗漏,注意
    }

    /* 给struct cdev对象指定操作函数集 */
    cdev_init(&gmydev.mydev, &myops);

    /* 将 struct cdev对象添加到内核对应的数据结构里 */
    gmydev.mydev.owner = THIS_MODULE;
    cdev_add(&gmydev.mydev, devno, mychar_num);

    return 0;
}

void __exit mychar_exit(void)
{
    dev_t devno = MKDEV(major, minor);

    cdev_del(&gmydev.mydev);

    unregister_chrdev_region(devno, mychar_num);
}

//表示支持GPL的开源协议
MODULE_LICENSE("GPL");

module_init(mychar_init);
module_exit(mychar_exit);

Makefile

ifeq ($(KERNELRELEASE),)

ifeq ($(ARCH),arm)
KERNELDIR ?= /home/linux/Linux_4412/kernel/linux-3.14
ROOTFS ?= /opt/4412/rootfs
else
KERNELDIR ?= /lib/modules/$(shell uname -r)/build
endif
PWD := $(shell pwd)


modules:
	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules

modules_install:
	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules INSTALL_MOD_PATH=$(ROOTFS) modules_install

clean:
	rm -rf  *.o  *.ko  .*.cmd  *.mod.*  modules.order  Module.symvers   .tmp_versions

else
CONFIG_MODULE_SIG=n
obj-m += mychar.o

endif

testmychar_app.c

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>

#include "mychar.h"
#include <stdio.h>


int main(int argc,char *argv[])
{
	int fd = -1;
	char buf[8] = "";
	int max = 0;
	int cur = 0;

	if(argc < 2)
	{
		printf("The argument is too few\n");
		return 1;
	}

	fd = open(argv[1],O_RDWR);
	if(fd < 0)
	{
		printf("open %s failed\n",argv[1]);
		return 2;
	}

	ioctl(fd,MYCHAR_IOCTL_GET_MAXLEN,&max);
	printf("max len is %d\n",max);

	write(fd,"hello",6);

	ioctl(fd,MYCHAR_IOCTL_GET_CURLEN,&cur);
	printf("cur len is %d\n",cur);

	read(fd,buf,8);
	printf("buf=%s\n",buf);

	close(fd);
	fd = -1;
	return 0;
}

?编译执行,测试获取设备参数

?

2 printk

//日志级别
#define KERN_EMERG  "<0>"   /* system is unusable           */
#define KERN_ALERT  "<1>"   /* action must be taken immediately */
#define KERN_CRIT   "<2>"   /* critical conditions          */
#define KERN_ERR    "<3>"   /* error conditions         */
?
#define KERN_WARNING    "<4>"   /* warning conditions           */
?
#define KERN_NOTICE "<5>"   /* normal but significant condition */
#define KERN_INFO   "<6>"   /* informational            */
#define KERN_DEBUG  "<7>"   /* debug-level messages         */
?
用法:printk(KERN_INFO"....",....)
 ? ?
 ? ?printk(KERN_INFO"Hello World"); =====> printk("<6>""Hello World") ====> printk("<6>Hello World")
 ?

dmesg --level=emerg,alert,crit,err,warn,notice,info,debug?

(dmesg中7个级别对应printk中7个级别)

#define HELLO_DEBUG
#undef PDEBUG
#ifdef HELLO_DEBUG
#define PDEBUG(fmt, args...) printk(KERN_DEBUG fmt, ##args)
#else
#define PDEBUG(fmt, args...)
#endif

3 多个次设备的支持

  • linux支持一个具体的设备同时占用1个主设备号多个次设备号的情况(这种情况主要是根据cdev_add中参数来决定的,一般是1,需要多个次设备号改写参数)
  • 另一种情况是针对一份驱动代码对应多个同类次设备(主设备号一样,次设备不一样的设备)

本节讲得是第二个情况,必须有一个struct cdev来代表它

  • cdev_init
  • cdev.owner赋值
  • cdev_add

以上三个操作对每个具体设备都要进行

3.1 示例

multimychar.c

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>

#include "mychar.h"

#define BUF_LEN 100
#define MYCHAR_DEV_CNT 3

int major = 11;
int minor = 0;
int mychar_num = MYCHAR_DEV_CNT; //支持多个设备

//新建结构体类型
struct mychar_dev
{
	struct cdev mydev;
	char mydef_buf[BUF_LEN];  //相当于结构体的私有变量
	int curlen;          //相当于结构体的私有变量
};

struct mychar_dev gmydev_arr[MYCHAR_DEV_CNT];  //多个设备实现:创建结构体数组


int mychar_open(struct inode *pnode, struct file *pfile)
{
	//利用private_data私有变量来指向全局变量结构体地址
	pfile->private_data = (void*)(container_of(pnode->i_cdev,struct mychar_dev,mydev));
    printk("mychar_open is called\n");
    return 0;
}

int mychar_close(struct inode *pnode, struct file *pfile)
{
    printk("mychar_close is called\n");
    return 0;
}


ssize_t mychar_read(struct file *filp, char __user *pbuf, size_t count, loff_t *ppos)
{
	int ret = 0;
	int size = 0;
	//获取全家变量结构体地址
	struct mychar_dev *pmydev = (struct mychar_dev *)filp->private_data;

 	if(count > pmydev->curlen)
	{
		size = pmydev->curlen;
	}
	else
	{
		size = count;
	}

	//将内核空间中的数据复制到用户空间
	ret = copy_to_user(pbuf,pmydev->mydef_buf,size);
	if(ret)
	{
	
		printk("copy_to_user failed\n");
		return -1;
	}
	//读完之后把后面的内容再拷贝过来,同时更新curlen
	memcpy(pmydev->mydef_buf,pmydev->mydef_buf+size,pmydev->curlen - size);
	pmydev->curlen = pmydev->curlen - size;

	return size;

}

ssize_t mychar_write (struct file *filp, const char __user *pbuf, size_t count, loff_t *ppos)
{

	int size = 0;
	int ret  = 0;
	//获取全家变量结构体地址
	struct mychar_dev *pmydev = (struct mychar_dev *)filp->private_data;

	if(count > BUF_LEN - pmydev->curlen)
	{
		size = BUF_LEN - pmydev->curlen;
	}
	else
	{
		size = count;
	}

	//将用户空间中的数据复制到内核空间中
	ret = copy_from_user(pmydev->mydef_buf + pmydev->curlen, pbuf, size);
	if(ret)
	{
		printk("copy_from_user failed\n");
		return -1;
	}
    //更新curlen
	pmydev->curlen = pmydev->curlen + size;
	return size;
}

long mychar_ioctl(struct file *filp, unsigned int cmd,unsigned long arg)
{
    int __user *pret = (int *)arg;
	int maxlen = BUF_LEN;
	int ret = 0;
	struct mychar_dev *pmydev = (struct mychar_dev *)filp->private_data;

	switch(cmd)
	{
		case MYCHAR_IOCTL_GET_MAXLEN:
			ret = copy_to_user(pret,&maxlen,sizeof(int));
			if(ret)
			{
				printk("copy_to_user MAXLEN failed\n");
				return -1;
			}
			break;
		case MYCHAR_IOCTL_GET_CURLEN:
			ret = copy_to_user(pret,&pmydev->curlen,sizeof(int));
			if(ret)
			{
				printk("copy_to_user CURLEN failed\n");
				return -1;
			}
			break;
		default:
			printk("The cmd is unknow\n");
			return -1;
	}
	return 0;
}

//结构体初始化:部分变量赋值初始化
struct file_operations myops = {
    .owner = THIS_MODULE,
    .open = mychar_open,
    .release = mychar_close,
	.read = mychar_read,
	.write = mychar_write,
	.unlocked_ioctl = mychar_ioctl
};

int mychar_init(void)
{
    int ret = 0;
	int i = 0;
    dev_t devno = MKDEV(major, minor);

    /* 申请设备号 */
    ret = register_chrdev_region(devno, mychar_num, "mychar");
    if (ret) {
        ret = alloc_chrdev_region(&devno, minor, mychar_num, "mychar");
        if (ret) {
            printk("get devno failed\n");
            return -1;
        }
		major = MAJOR(devno); // 容易遗漏,注意
    }

	for(i = 0;i < MYCHAR_DEV_CNT;i++)
	{
		devno = MKDEV(major,minor+i);  //设备号需要重新组合
		/* 给struct cdev对象指定操作函数集 */
		cdev_init(&gmydev_arr[i].mydev, &myops);

		/* 将 struct cdev对象添加到内核对应的数据结构里 */
		gmydev_arr[i].mydev.owner = THIS_MODULE;
		cdev_add(&gmydev_arr[i].mydev, devno, 1);   //这里需要填1
 	}

    return 0;
}

void __exit mychar_exit(void)
{
    dev_t devno = MKDEV(major, minor);
	int i = 0;
	for(i = 0; i< MYCHAR_DEV_CNT; i ++)
	{
		cdev_del(&gmydev_arr[i].mydev);
	}
	
    unregister_chrdev_region(devno, mychar_num);
}

//表示支持GPL的开源协议
MODULE_LICENSE("GPL");

module_init(mychar_init);
module_exit(mychar_exit);

mychar.h(未修改)

#ifndef MY_CHAR_H
#define MY_CHAR_H

#include <asm/ioctl.h>

#define MY_CHAR_MAGIC 'k'

#define MYCHAR_IOCTL_GET_MAXLEN _IOR(MY_CHAR_MAGIC,1,int*)
#define MYCHAR_IOCTL_GET_CURLEN _IOR(MY_CHAR_MAGIC,2,int*)


#endif

testmychar_app.c(维修工)

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>

#include "mychar.h"
#include <stdio.h>


int main(int argc,char *argv[])
{
	int fd = -1;
	char buf[8] = "";
	int max = 0;
	int cur = 0;

	if(argc < 2)
	{
		printf("The argument is too few\n");
		return 1;
	}

	fd = open(argv[1],O_RDWR);
	if(fd < 0)
	{
		printf("open %s failed\n",argv[1]);
		return 2;
	}

	ioctl(fd,MYCHAR_IOCTL_GET_MAXLEN,&max);
	printf("max len is %d\n",max);

	write(fd,"hello",6);

	ioctl(fd,MYCHAR_IOCTL_GET_CURLEN,&cur);
	printf("cur len is %d\n",cur);

	read(fd,buf,8);
	printf("buf=%s\n",buf);

	close(fd);
	fd = -1;
	return 0;
}

Makefile

ifeq ($(KERNELRELEASE),)

ifeq ($(ARCH),arm)
KERNELDIR ?= /home/linux/Linux_4412/kernel/linux-3.14
ROOTFS ?= /opt/4412/rootfs
else
KERNELDIR ?= /lib/modules/$(shell uname -r)/build
endif
PWD := $(shell pwd)


modules:
	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules

modules_install:
	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules INSTALL_MOD_PATH=$(ROOTFS) modules_install

clean:
	rm -rf  *.o  *.ko  .*.cmd  *.mod.*  modules.order  Module.symvers   .tmp_versions

else
CONFIG_MODULE_SIG=n
obj-m += mychar.o

endif

编译运行

?

文章来源:https://blog.csdn.net/m0_60718520/article/details/135438084
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