02.03.Character Device Registration Initialization

Hello Kernel compile successfully on linux kernel 5.8.11

But during installation we have low memory Issue in / dirctory

[niranjan@localhost libraryManagementSystem-V2]$ df -h
Filesystem      Size  Used Avail Use% Mounted on
devtmpfs        3.8G     0  3.8G   0% /dev
tmpfs           3.8G  554M  3.3G  15% /dev/shm
tmpfs           3.8G  2.3M  3.8G   1% /run
/dev/sda13       48G   47G     0 100% /
tmpfs           3.8G   53M  3.8G   2% /tmp
/dev/sda17      9.6G  5.3G  3.8G  59% /var
/dev/sda19      4.8G  318M  4.2G   7% /opt
/dev/sda12      1.9G  253M  1.6G  14% /boot
/dev/sda11      999M   21M  978M   3% /boot/efi
/dev/sda15       39G   31G  5.9G  84% /home
/dev/sda18      4.8G   20M  4.5G   1% /temp
/dev/sda14       48G   53M   46G   1% /usr/local
tmpfs           773M   44K  773M   1% /run/user/42
tmpfs           773M  148K  773M   1% /run/user/1000

How to resolve low memory issue?

sir,

this error is recurring while doing 

make 

Makefile

Hi sir ,

I run application with driver as below step-

step 1- Compile Application & driver successfully

step 2- insmod kernel driver success. and major id 237 for this driver

step 3 -check dmesg print as per expected & create mknode for major no 237

step 4 -run appliactoon & select openDev choice

step 5 - check dmesg print but not opendriver print not present

step 6 - rmove kernel module driver & check dmesg print as per expected.

Application open Dev File-

void* openDev(void *arg)
{
        int *fd;
        printf("%s : Begin..\n",__func__);
        fd = (int *)arg;
        if(fd)
        {
                printf("%s : Already open File\n",__func__);
                return arg;
        }
        fd = (int *)malloc(sizeof(int));
        if(!fd)
        {
                perror("Error in malloc()");
                (fptr[EXIT_FUNC])((void *)"failure");
        }

        *fd = open("arnavDev",O_WRONLY);
       if(*fd == -1)
       {
                perror("Error in open()");
                (fptr[EXIT_FUNC])((void *)"failure");
        }

        printf("%s : open node file fd: %d\n",__func__, *fd);

        printf("%s : End\n",__func__);
        return (void *)fd;
}

---------------Driver Module file------

1. fileOpr.h

struct file_operations fopr=
{
        open:   openDev,
        release:releaseDev
};
~             ____________

2. declearation.h

#ifndef DEV_NAME
#define DEV_NAME "arnavDriver"
#endif
#ifndef DEV_MAJOR_NUM
#define DEV_MAJOR_NUM 0
#endif
#ifndef DEV_MINOR_NUM
#define DEV_MINOR_NUM 0
#endif
#ifndef DEV_NO_DEVICE
#define DEV_NO_DEVICE 1
#endif
/* Stucture Driver*/
typedef struct qset
{
        struct qset *next;
        void **data;
}Qset;
typedef struct dev
{
        Qset *qset;
        struct cdev chDev;
}Dev;

MODULE_LICENSE("GPL");
extern unsigned int majorNum, minorNum;
extern uint noOfDevice;
extern dev_t deviceId, devNo;
extern Dev *devN;
int openDev(struct inode *, struct file *);
int releaseDev(struct inode *, struct file *);

____________________

3. init.c#include"headers.h"
#include"declearations.h"
#include"fileOpr.h"

unsigned int majorNum, minorNum;
uint noOfDevice ;
dev_t deviceId, devNo;
struct file_operations fops;
Dev *devN;
module_param(noOfDevice, uint, S_IRUGO);

static int __init initFn(void)
{
        int ret, i;
        printk(KERN_INFO "Hello Kernel! New Driver Initilize. Driveyyr here forever !\n");
        majorNum = DEV_MAJOR_NUM;
        minorNum = DEV_MINOR_NUM;
        //noOfDevice = DEV_NO_DEVICE;

        ret = alloc_chrdev_region(&deviceId, minorNum, noOfDevice, DEV_NAME);
        if(ret == -1)
        {
                printk(KERN_ERR "Error Found! alloc_chrdev_region Failure\n");
                return -1;
        }
        majorNum = MAJOR(deviceId);
        minorNum = MINOR(deviceId);
        printk(KERN_INFO "Major num = %d\n",majorNum);
        printk(KERN_INFO "Minor num = %d\n",majorNum);
        printk(KERN_INFO "No Of Device = %d\n",noOfDevice);
        devN =(Dev*)kmalloc(sizeof(Dev)*noOfDevice, GFP_KERNEL);
        if(!devN)
        {
                printk(KERN_ERR "Error Found! kmalloc ailure\n");
                return -1;
        }
        for(i=0; i< noOfDevice; i++)
        {
                cdev_init(&devN[i].chDev, &fops);
                devN[i].chDev.ops = &fops;
                devNo = MKDEV(majorNum, i);
                ret = cdev_add(&devN[i].chDev, devNo, 1);
                if(ret == -1)
                {
                              printk(KERN_ERR "Error! %d cdev_add() failure\n",i);
                        return -1;
                }
                printk(KERN_INFO " Major No=%d Minor No=%d\n",MAJOR(devNo), MINOR(devNo));
        }
        printk(KERN_INFO "cdev_add()! Successfully added driver!\n");


        return 0;
}

module_init(initFn);