Embedded LINUX driver learning 4. Character device driver programming (3) Driver registration and uninstallation of user space implementation code

Note: In this example, the generated driver module is the file mychrdev.ko, and all executions are performed on the lower computer

1. Register the driver module:

insmod mychrdev.ko

2. View the registered main device number

cat  /proc/devices 
     Character devices:
      1 mem
      5 /dev/tty
      5 /dev/console
      5 /dev/ptmx
      ........
      244 myfile_cdev     //主设备号244
      ........

Three, create a character device file based on the major device number

3.1 Method 1: Created by bash

mknod /dev/mychrdev0 c 244 0
mknod /dev/mychrdev1 c 244 1
mknod /dev/mychrdev2 c 244 2
mknod /dev/mychrdev3 c 244 3
#命令说明：
#      Usage: mknod [-m MODE] NAME TYPE MAJOR MINOR
#      TYPE:
#        b       Block device
#        c or u  Character device
#        p       Named pipe (MAJOR and MINOR are ignored)
#

Method 2: Create by writing code in C language, see Appendix A for the code, take the compiled file name: mychrdev_reg as an example:

./mychrdev_reg 244 4 mychrdev
#命令说明：
#      Usage:comm MAJOR minorct chrdev_name

Four unload the driver module

rmmod mychrdev.ko

Attached A

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
int main(int argc , char * argv[]){
    
    
    //对命令行输入的参数做判断
    if (argc !=4){
    
    
        printf("参数错误:\n");
        printf("         comm <major> <minorct> <name>\n");
        return -1;
    }
    unsigned long int i = 0;
    dev_t dev_num;//定义设备号
    dev_t major = strtoul(argv[1],NULL,0); 将主设备号转为整数型
    int minorct = strtoul(argv[2],NULL,0);//将次设备号数量由字符型转为整形
    int path_name_len;
    char path_name[128] = "/dev/";//定义初始化保存设备名称的字符数组
    char buf[4];//用于保存字符设备名称最后一位，即整形转为字符型的内容
    strcat(path_name,argv[3]);//strcat(3)
    path_name_len = strlen(path_name);   
    for(; i<minorct ;i++){
    
    
        dev_num = makedev(major,i);//见帮忙手册mknod(2) makedev(3)
        sprintf(buf,"%d",i);//sprintf(3)
        strcat(path_name,buf);//为字符设备名称加编号
        mknod(path_name,S_IFCHR,dev_num);//创建字符设备
        path_name[path_name_len] = '\0';
    }
    return 0;
}