Linux Kernel Driver Program: 7_Real_Device_Driver
neelkanth_surekha#cat Read\ me
This directory contains three files.
1.Driver
2.Make File
3.User Application
Driver is running on kernel space
Makefile is used to build the kernel linux device driver
User application will running on the user space and communicate to driver on kernel space.
neelkanth_surekha#cat driver.c
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kdev_t.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include<linux/slab.h> //kmalloc()
#include<linux/uaccess.h> //copy_to/from_user()
#define mem_size 1024
dev_t dev = 0;
static struct class *dev_class;
static struct cdev dummy_device_cdev;
uint8_t *kernel_buffer;
static int __init dummy_device_driver_init(void);
static void __exit dummy_device_driver_exit(void);
static int dummy_device_open(struct inode *inode, struct file *file);
static int dummy_device_release(struct inode *inode, struct file *file);
static ssize_t dummy_device_read(struct file *filp, char __user *buf, size_t len,loff_t * off);
static ssize_t dummy_device_write(struct file *filp, const char *buf, size_t len, loff_t * off);
static struct file_operations fops =
{
.owner = THIS_MODULE,
.read = dummy_device_read,
.write = dummy_device_write,
.open = dummy_device_open,
.release = dummy_device_release,
};
static int dummy_device_open(struct inode *inode, struct file *file)
{
/*Creating Physical memory*/
if((kernel_buffer = kmalloc(mem_size , GFP_KERNEL)) == 0){
printk(KERN_INFO "Cannot allocate memory in kernel\n");
return -1;
}
printk(KERN_INFO "Device File Opened...!!!\n");
return 0;
}
static int dummy_device_release(struct inode *inode, struct file *file)
{
kfree(kernel_buffer);
printk(KERN_INFO "Device File Closed...!!!\n");
return 0;
}
static ssize_t dummy_device_read(struct file *filp, char __user *buf, size_t len, loff_t *off)
{
copy_to_user(buf, kernel_buffer, mem_size);
printk(KERN_INFO "Data Write : Done!\n");
return mem_size;
}
static ssize_t dummy_device_write(struct file *filp, const char __user *buf, size_t len, loff_t *off)
{
copy_from_user(kernel_buffer, buf, len);
printk(KERN_INFO "Data Read : Done!\n");
return len;
}
static int __init dummy_device_driver_init(void)
{
/*Allocating Major number*/
if((alloc_chrdev_region(&dev, 0, 1, "dummy_device_Dev")) <0){
printk(KERN_INFO "Cannot allocate major number\n");
return -1;
}
printk(KERN_INFO "Major = %d Minor = %d \n",MAJOR(dev), MINOR(dev));
/*Creating cdev structure*/
cdev_init(&dummy_device_cdev,&fops);
dummy_device_cdev.owner = THIS_MODULE;
dummy_device_cdev.ops = &fops;
/*Adding character device to the system*/
if((cdev_add(&dummy_device_cdev,dev,1)) < 0){
printk(KERN_INFO "Cannot add the device to the system\n");
goto r_class;
}
/*Creating struct class*/
if((dev_class = class_create(THIS_MODULE,"dummy_device_class")) == NULL){
printk(KERN_INFO "Cannot create the struct class\n");
goto r_class;
}
/*Creating device*/
if((device_create(dev_class,NULL,dev,NULL,"dummy_driver_device")) == NULL){
printk(KERN_INFO "Cannot create the Device 1\n");
goto r_device;
}
printk(KERN_INFO "Device Driver Insert...Done!!!\n");
return 0;
r_device:
class_destroy(dev_class);
r_class:
unregister_chrdev_region(dev,1);
return -1;
}
void __exit dummy_device_driver_exit(void)
{
device_destroy(dev_class,dev);
class_destroy(dev_class);
cdev_del(&dummy_device_cdev);
unregister_chrdev_region(dev, 1);
printk(KERN_INFO "Device Driver Remove...Done!!!\n");
}
module_init(dummy_device_driver_init);
module_exit(dummy_device_driver_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Neelkanth <www.neelkanth.13@gmail.com>");
MODULE_DESCRIPTION("A simple device driver");
MODULE_VERSION("0:1.0");
neelkanth_surekha#cat test_app.c [User space application code]
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int8_t write_buf[1024];
int8_t read_buf[1024];
int main()
{
int fd;
char option;
printf("*********************************\n");
chmod("/dev/dummy_driver_device", 0777);
fd = open("/dev/dummy_driver_device", O_RDWR);
if(fd < 0) {
printf("Cannot open device file...\n");
return 0;
}
while(1) {
printf("****Please Enter the Option******\n");
printf(" 1. Write \n");
printf(" 2. Read \n");
printf(" 3. Exit \n");
printf("*********************************\n");
scanf(" %c", &option);
printf("Your Option = %c\n", option);
switch(option) {
case '1':
printf("Enter the string to write into driver :");
scanf(" %[^\t\n]s", write_buf);
printf("Data Writing ...");
write(fd, write_buf, strlen(write_buf)+1);
printf("Done!\n");
break;
case '2':
printf("Data Reading ...");
read(fd, read_buf, 1024);
printf("Done!\n\n");
printf("Data = %s\n\n", read_buf);
break;
case '3':
close(fd);
exit(1);
break;
default:
printf("Enter Valid option = %c\n",option);
break;
}
}
close(fd);
}
neelkanth_surekha#cat Makefile
obj-m += driver.o
KDIR = /lib/modules/$(shell uname -r)/build
all:
make -C $(KDIR) M=$(shell pwd) modules
clean:
make -C $(KDIR) M=$(shell pwd) clean