lv14 ioctl、printk及多个此设备支持 6

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opencmd：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)

//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)))

//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)))

//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 100int 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curlenmemcpy(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curlenpmydev->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) modulesmodules_install:$(MAKE) -C $(KERNELDIR) M=$(PWD) modules INSTALL_MOD_PATH=$(ROOTFS) modules_installclean:rm -rf  *.o  *.ko  .*.cmd  *.mod.*  modules.order  Module.symvers   .tmp_versionselse
CONFIG_MODULE_SIG=n
obj-m += mychar.oendif

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 3int 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curlenmemcpy(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curlenpmydev->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) modulesmodules_install:$(MAKE) -C $(KERNELDIR) M=$(PWD) modules INSTALL_MOD_PATH=$(ROOTFS) modules_installclean:rm -rf  *.o  *.ko  .*.cmd  *.mod.*  modules.order  Module.symvers   .tmp_versionselse
CONFIG_MODULE_SIG=n
obj-m += mychar.oendif

编译运行