IOCTL: usage example
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ioctl is used in communication with modules of Linux.
Module:
#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() #include <linux/ioctl.h> #define WR_VALUE _IOW(‘a‘,‘a‘,int32_t*) #define RD_VALUE _IOR(‘a‘,‘b‘,int32_t*) int32_t value = 0; dev_t dev = 0; static struct class *dev_class; static struct cdev etx_cdev; static int __init etx_driver_init(void); static void __exit etx_driver_exit(void); static int etx_open(struct inode *inode, struct file *file); static int etx_release(struct inode *inode, struct file *file); static ssize_t etx_read(struct file *filp, char __user *buf, size_t len,loff_t * off); static ssize_t etx_write(struct file *filp, const char *buf, size_t len, loff_t * off); static long etx_ioctl(struct file *file, unsigned int cmd, unsigned long arg); static struct file_operations fops = { .owner = THIS_MODULE, .read = etx_read, .write = etx_write, .open = etx_open, .unlocked_ioctl = etx_ioctl, .release = etx_release, }; static int etx_open(struct inode *inode, struct file *file) { printk(KERN_INFO "Device File Opened...!!!\n"); return 0; } static int etx_release(struct inode *inode, struct file *file) { printk(KERN_INFO "Device File Closed...!!!\n"); return 0; } static ssize_t etx_read(struct file *filp, char __user *buf, size_t len, loff_t *off) { printk(KERN_INFO "Read Function\n"); return 0; } static ssize_t etx_write(struct file *filp, const char __user *buf, size_t len, loff_t *off) { printk(KERN_INFO "Write function\n"); return 0; } static long etx_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { switch(cmd) { case WR_VALUE: copy_from_user(&value ,(int32_t*) arg, sizeof(value)); printk(KERN_INFO "Value = %d\n", value); break; case RD_VALUE: copy_to_user((int32_t*) arg, &value, sizeof(value)); break; } return 0; } static int __init etx_driver_init(void) { /*Allocating Major number*/ if((alloc_chrdev_region(&dev, 0, 1, "etx_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(&etx_cdev,&fops); etx_cdev.owner = THIS_MODULE; etx_cdev.ops = &fops; /*Adding character device to the system*/ if((cdev_add(&etx_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,"etx_class")) == NULL){ printk(KERN_INFO "Cannot create the struct class\n"); goto r_class; } /*Creating device*/ if((device_create(dev_class,NULL,dev,NULL,"etx_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 etx_driver_exit(void) { device_destroy(dev_class,dev); class_destroy(dev_class); cdev_del(&etx_cdev); unregister_chrdev_region(dev, 1); printk(KERN_INFO "Device Driver Remove...Done!!!\n"); } module_init(etx_driver_init); module_exit(etx_driver_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("EmbeTronicX <[email protected] or [email protected]>"); MODULE_DESCRIPTION("A simple device driver"); MODULE_VERSION("1.5");
User space
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include<sys/ioctl.h> #define WR_VALUE _IOW(‘a‘,‘a‘,int32_t*) #define RD_VALUE _IOR(‘a‘,‘b‘,int32_t*) int main() { int fd; int32_t value, number; printf("*********************************\n"); printf("*******WWW.EmbeTronicX.com*******\n"); printf("\nOpening Driver\n"); fd = open("/dev/etx_device", O_RDWR); if(fd < 0) { printf("Cannot open device file...\n"); return 0; } printf("Enter the Value to send\n"); scanf("%d",&number); printf("Writing Value to Driver\n"); ioctl(fd, WR_VALUE, (int32_t*) &number); printf("Reading Value from Driver\n"); ioctl(fd, RD_VALUE, (int32_t*) &value); printf("Value is %d\n", value); printf("Closing Driver\n"); close(fd); }
In case of Makefile is needed:
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
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