1 /*
2 * complete.c -- the writers awake the readers
3 *
4 * Copyright (C) 2003 Alessandro Rubini and Jonathan Corbet
5 * Copyright (C) 2003 O'Reilly & Associates
6 *
7 * The source code in this file can be freely used, adapted,
8 * and redistributed in source or binary form, so long as an
9 * acknowledgment appears in derived source files. The citation
10 * should list that the code comes from the book "Linux Device
11 * Drivers" by Alessandro Rubini and Jonathan Corbet, published
12 * by O'Reilly & Associates. No warranty is attached;
13 * we cannot take responsibility for errors or fitness for use.
14 *
15 * $Id: complete.c,v 1.2 2004/09/26 07:02:43 gregkh Exp $
16 */
17
18 #include <linux/module.h>
19 #include <linux/init.h>
20
21 #include <linux/sched.h> /* current and everything */
22 #include <linux/kernel.h> /* printk() */
23 #include <linux/fs.h> /* everything... */
24 #include <linux/types.h> /* size_t */
25 #include <linux/completion.h>
26
27 MODULE_LICENSE("Dual BSD/GPL");
28
29 static int complete_major = 0;
30
31 DECLARE_COMPLETION(comp);
32
33 ssize_t complete_read (struct file *filp, char __user *buf, size_t count, loff_t *pos)
34 {
35 printk(KERN_DEBUG "process %i (%s) going to sleep\n",
36 current->pid, current->comm);
37 wait_for_completion(&comp);
38 printk(KERN_DEBUG "awoken %i (%s)\n", current->pid, current->comm);
39 return 0; /* EOF */
40 }
41
42 ssize_t complete_write (struct file *filp, const char __user *buf, size_t count,
43 loff_t *pos)
44 {
45 printk(KERN_DEBUG "process %i (%s) awakening the readers...\n",
46 current->pid, current->comm);
47 complete(&comp);
48 return count; /* succeed, to avoid retrial */
49 }
50
51
52 struct file_operations complete_fops = {
53 .owner = THIS_MODULE,
54 .read = complete_read,
55 .write = complete_write,
56 };
57
58
59 int complete_init(void)
60 {
61 int result;
62
63 /*
64 * Register your major, and accept a dynamic number
65 */
66 result = register_chrdev(complete_major, "complete", &complete_fops);
67 if (result < 0)
68 return result;
69 if (complete_major == 0)
70 complete_major = result; /* dynamic */
71 return 0;
72 }
73
74 void complete_cleanup(void)
75 {
76 unregister_chrdev(complete_major, "complete");
77 }
78
79 module_init(complete_init);
80 module_exit(complete_cleanup);
81
82
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