Basic Char driver for kernel version 4.15.0

In the post, Example Char driver, the code for a basic charchater driver is given along with the steps to insert it into the kernel and create a char device. #include <linux/module.h> #include <linux/kernel.h> #include <linux/fs.h> // required for various structures related to files liked fops. #include <linux/uaccess.h> // required for copy_from and copy_to user functions #include <linux/semaphore.h> #include <linux/cdev.h> static int Major; dev_t dev_no,dev; struct device1 { char array[100]; struct semaphore sem; }char_arr; int open(struct inode *inode, struct file *filp) { printk(KERN_INFO "Inside open \n"); if(down_interruptible(&char_arr.sem)) { printk(KERN_INFO " could not hold semaphore"); return -1; } return 0; } int release(struct inode *inode, struct file *filp) { printk (KERN_INFO "Inside close \n"); printk(KERN_INFO "Releasing semaphore"); up(&char_arr.sem); return 0; } ssize_t read(struct file *filp, char *buff, size_t count, loff_t *offp) { unsigned long ret; printk("Inside read \n"); ret = copy_to_user(buff, char_arr.array, count); return ret; } ssize_t write(struct file *filp, const char *buff, size_t count, loff_t *offp) { unsigned long ret; printk(KERN_INFO "Inside write \n"); ret = copy_from_user(char_arr.array, buff, count); return count; } struct file_operations fops = { read: read, write: write, open: open, release: release }; struct cdev *kernel_cdev; int char_arr_init (void) { int ret; kernel_cdev = cdev_alloc(); kernel_cdev->ops = &fops; kernel_cdev->owner = THIS_MODULE; printk (" Inside init module\n"); ret = alloc_chrdev_region( &dev_no , 0, 1,"chr_arr_dev"); if (ret < 0) { printk("Major number allocation is failed\n"); return ret; } Major = MAJOR(dev_no); dev = MKDEV(Major,0); sema_init(&char_arr.sem,1); printk (" The major number for your device1 is %d\n", Major); ret = cdev_add( kernel_cdev,dev,1); if(ret < 0 ) { printk(KERN_INFO "Unable to allocate cdev"); return ret; } return 0; } void char_arr_cleanup(void) { printk(KERN_INFO " Inside cleanup_module\n"); cdev_del(kernel_cdev); unregister_chrdev_region(Major, 1); } MODULE_LICENSE("GPL"); module_init(char_arr_init); module_exit(char_arr_cleanup); The following is the updated code for the same driver tested for the kernel version 4.15.0.To test the working of the driver please use the code given in post User access for example driver