1/*
2 * Sample kfifo int type implementation
3 *
4 * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
5 *
6 * Released under the GPL version 2 only.
7 *
8 */
9
10#include <linux/init.h>
11#include <linux/module.h>
12#include <linux/proc_fs.h>
13#include <linux/mutex.h>
14#include <linux/kfifo.h>
15
16/*
17 * This module shows how to create a int type fifo.
18 */
19
20/* fifo size in elements (ints) */
21#define FIFO_SIZE	32
22
23/* name of the proc entry */
24#define	PROC_FIFO	"int-fifo"
25
26/* lock for procfs read access */
27static DEFINE_MUTEX(read_lock);
28
29/* lock for procfs write access */
30static DEFINE_MUTEX(write_lock);
31
32/*
33 * define DYNAMIC in this example for a dynamically allocated fifo.
34 *
35 * Otherwise the fifo storage will be a part of the fifo structure.
36 */
37#if 0
38#define DYNAMIC
39#endif
40
41#ifdef DYNAMIC
42static DECLARE_KFIFO_PTR(test, int);
43#else
44static DEFINE_KFIFO(test, int, FIFO_SIZE);
45#endif
46
47static const int expected_result[FIFO_SIZE] = {
48	 3,  4,  5,  6,  7,  8,  9,  0,
49	 1, 20, 21, 22, 23, 24, 25, 26,
50	27, 28, 29, 30, 31, 32, 33, 34,
51	35, 36, 37, 38, 39, 40, 41, 42,
52};
53
54static int __init testfunc(void)
55{
56	int		buf[6];
57	int		i, j;
58	unsigned int	ret;
59
60	printk(KERN_INFO "int fifo test start\n");
61
62	/* put values into the fifo */
63	for (i = 0; i != 10; i++)
64		kfifo_put(&test, i);
65
66	/* show the number of used elements */
67	printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
68
69	/* get max of 2 elements from the fifo */
70	ret = kfifo_out(&test, buf, 2);
71	printk(KERN_INFO "ret: %d\n", ret);
72	/* and put it back to the end of the fifo */
73	ret = kfifo_in(&test, buf, ret);
74	printk(KERN_INFO "ret: %d\n", ret);
75
76	/* skip first element of the fifo */
77	printk(KERN_INFO "skip 1st element\n");
78	kfifo_skip(&test);
79
80	/* put values into the fifo until is full */
81	for (i = 20; kfifo_put(&test, i); i++)
82		;
83
84	printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));
85
86	/* show the first value without removing from the fifo */
87	if (kfifo_peek(&test, &i))
88		printk(KERN_INFO "%d\n", i);
89
90	/* check the correctness of all values in the fifo */
91	j = 0;
92	while (kfifo_get(&test, &i)) {
93		printk(KERN_INFO "item = %d\n", i);
94		if (i != expected_result[j++]) {
95			printk(KERN_WARNING "value mismatch: test failed\n");
96			return -EIO;
97		}
98	}
99	if (j != ARRAY_SIZE(expected_result)) {
100		printk(KERN_WARNING "size mismatch: test failed\n");
101		return -EIO;
102	}
103	printk(KERN_INFO "test passed\n");
104
105	return 0;
106}
107
108static ssize_t fifo_write(struct file *file, const char __user *buf,
109						size_t count, loff_t *ppos)
110{
111	int ret;
112	unsigned int copied;
113
114	if (mutex_lock_interruptible(&write_lock))
115		return -ERESTARTSYS;
116
117	ret = kfifo_from_user(&test, buf, count, &copied);
118
119	mutex_unlock(&write_lock);
120
121	return ret ? ret : copied;
122}
123
124static ssize_t fifo_read(struct file *file, char __user *buf,
125						size_t count, loff_t *ppos)
126{
127	int ret;
128	unsigned int copied;
129
130	if (mutex_lock_interruptible(&read_lock))
131		return -ERESTARTSYS;
132
133	ret = kfifo_to_user(&test, buf, count, &copied);
134
135	mutex_unlock(&read_lock);
136
137	return ret ? ret : copied;
138}
139
140static const struct file_operations fifo_fops = {
141	.owner		= THIS_MODULE,
142	.read		= fifo_read,
143	.write		= fifo_write,
144	.llseek		= noop_llseek,
145};
146
147static int __init example_init(void)
148{
149#ifdef DYNAMIC
150	int ret;
151
152	ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
153	if (ret) {
154		printk(KERN_ERR "error kfifo_alloc\n");
155		return ret;
156	}
157#endif
158	if (testfunc() < 0) {
159#ifdef DYNAMIC
160		kfifo_free(&test);
161#endif
162		return -EIO;
163	}
164
165	if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) {
166#ifdef DYNAMIC
167		kfifo_free(&test);
168#endif
169		return -ENOMEM;
170	}
171	return 0;
172}
173
174static void __exit example_exit(void)
175{
176	remove_proc_entry(PROC_FIFO, NULL);
177#ifdef DYNAMIC
178	kfifo_free(&test);
179#endif
180}
181
182module_init(example_init);
183module_exit(example_exit);
184MODULE_LICENSE("GPL");
185MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");
186