1/*
2 * Sample dynamic sized record fifo 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 variable sized record fifo.
18 */
19
20/* fifo size in elements (bytes) */
21#define FIFO_SIZE	128
22
23/* name of the proc entry */
24#define	PROC_FIFO	"record-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/*
42 * struct kfifo_rec_ptr_1 and  STRUCT_KFIFO_REC_1 can handle records of a
43 * length between 0 and 255 bytes.
44 *
45 * struct kfifo_rec_ptr_2 and  STRUCT_KFIFO_REC_2 can handle records of a
46 * length between 0 and 65535 bytes.
47 */
48
49#ifdef DYNAMIC
50struct kfifo_rec_ptr_1 test;
51
52#else
53typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest;
54
55static mytest test;
56#endif
57
58static const char *expected_result[] = {
59	"a",
60	"bb",
61	"ccc",
62	"dddd",
63	"eeeee",
64	"ffffff",
65	"ggggggg",
66	"hhhhhhhh",
67	"iiiiiiiii",
68	"jjjjjjjjjj",
69};
70
71static int __init testfunc(void)
72{
73	char		buf[100];
74	unsigned int	i;
75	unsigned int	ret;
76	struct { unsigned char buf[6]; } hello = { "hello" };
77
78	printk(KERN_INFO "record fifo test start\n");
79
80	kfifo_in(&test, &hello, sizeof(hello));
81
82	/* show the size of the next record in the fifo */
83	printk(KERN_INFO "fifo peek len: %u\n", kfifo_peek_len(&test));
84
85	/* put in variable length data */
86	for (i = 0; i < 10; i++) {
87		memset(buf, 'a' + i, i + 1);
88		kfifo_in(&test, buf, i + 1);
89	}
90
91	/* skip first element of the fifo */
92	printk(KERN_INFO "skip 1st element\n");
93	kfifo_skip(&test);
94
95	printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
96
97	/* show the first record without removing from the fifo */
98	ret = kfifo_out_peek(&test, buf, sizeof(buf));
99	if (ret)
100		printk(KERN_INFO "%.*s\n", ret, buf);
101
102	/* check the correctness of all values in the fifo */
103	i = 0;
104	while (!kfifo_is_empty(&test)) {
105		ret = kfifo_out(&test, buf, sizeof(buf));
106		buf[ret] = '\0';
107		printk(KERN_INFO "item = %.*s\n", ret, buf);
108		if (strcmp(buf, expected_result[i++])) {
109			printk(KERN_WARNING "value mismatch: test failed\n");
110			return -EIO;
111		}
112	}
113	if (i != ARRAY_SIZE(expected_result)) {
114		printk(KERN_WARNING "size mismatch: test failed\n");
115		return -EIO;
116	}
117	printk(KERN_INFO "test passed\n");
118
119	return 0;
120}
121
122static ssize_t fifo_write(struct file *file, const char __user *buf,
123						size_t count, loff_t *ppos)
124{
125	int ret;
126	unsigned int copied;
127
128	if (mutex_lock_interruptible(&write_lock))
129		return -ERESTARTSYS;
130
131	ret = kfifo_from_user(&test, buf, count, &copied);
132
133	mutex_unlock(&write_lock);
134
135	return ret ? ret : copied;
136}
137
138static ssize_t fifo_read(struct file *file, char __user *buf,
139						size_t count, loff_t *ppos)
140{
141	int ret;
142	unsigned int copied;
143
144	if (mutex_lock_interruptible(&read_lock))
145		return -ERESTARTSYS;
146
147	ret = kfifo_to_user(&test, buf, count, &copied);
148
149	mutex_unlock(&read_lock);
150
151	return ret ? ret : copied;
152}
153
154static const struct file_operations fifo_fops = {
155	.owner		= THIS_MODULE,
156	.read		= fifo_read,
157	.write		= fifo_write,
158	.llseek		= noop_llseek,
159};
160
161static int __init example_init(void)
162{
163#ifdef DYNAMIC
164	int ret;
165
166	ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
167	if (ret) {
168		printk(KERN_ERR "error kfifo_alloc\n");
169		return ret;
170	}
171#else
172	INIT_KFIFO(test);
173#endif
174	if (testfunc() < 0) {
175#ifdef DYNAMIC
176		kfifo_free(&test);
177#endif
178		return -EIO;
179	}
180
181	if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) {
182#ifdef DYNAMIC
183		kfifo_free(&test);
184#endif
185		return -ENOMEM;
186	}
187	return 0;
188}
189
190static void __exit example_exit(void)
191{
192	remove_proc_entry(PROC_FIFO, NULL);
193#ifdef DYNAMIC
194	kfifo_free(&test);
195#endif
196}
197
198module_init(example_init);
199module_exit(example_exit);
200MODULE_LICENSE("GPL");
201MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");
202