/* * complete.c -- the writers awake the readers * * Copyright (C) 2003 Alessandro Rubini and Jonathan Corbet * Copyright (C) 2003 O'Reilly & Associates * * The source code in this file can be freely used, adapted, * and redistributed in source or binary form, so long as an * acknowledgment appears in derived source files.  The citation * should list that the code comes from the book "Linux Device * Drivers" by Alessandro Rubini and Jonathan Corbet, published * by O'Reilly & Associates.   No warranty is attached; * we cannot take responsibility for errors or fitness for use. * * $Id: complete.c,v 1.2 2004/09/26 07:02:43 gregkh Exp $ */#include <linux/module.h>#include <linux/init.h>#include <linux/sched.h>  /* current and everything */#include <linux/kernel.h> /* printk() */#include <linux/fs.h>     /* everything... */#include <linux/types.h>  /* size_t */#include <linux/completion.h>MODULE_LICENSE("Dual BSD/GPL");static int complete_major = 0;DECLARE_COMPLETION(comp);ssize_t complete_read (struct file *filp, char __user *buf, size_t count, loff_t *pos){	printk(KERN_DEBUG "process %i (%s) going to sleep\n",			current->pid, current->comm);	wait_for_completion(&comp);	printk(KERN_DEBUG "awoken %i (%s)\n", current->pid, current->comm);	return 0; /* EOF */}ssize_t complete_write (struct file *filp, const char __user *buf, size_t count,		loff_t *pos){	printk(KERN_DEBUG "process %i (%s) awakening the readers...\n",			current->pid, current->comm);	complete(&comp);	return count; /* succeed, to avoid retrial */}struct file_operations complete_fops = {	.owner = THIS_MODULE,	.read =  complete_read,	.write = complete_write,};int complete_init(void){	int result;	/*	 * Register your major, and accept a dynamic number	 */	result = register_chrdev(complete_major, "complete", &complete_fops);	if (result < 0)		return result;	if (complete_major == 0)		complete_major = result; /* dynamic */	return 0;}void complete_cleanup(void){	unregister_chrdev(complete_major, "complete");}module_init(complete_init);module_exit(complete_cleanup);