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Stefani Seibold5bf2b192010-08-10 18:03:39 -07001/*
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
Andrea Righia25effa2010-08-19 14:13:30 -070058static 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
Stefani Seibold5bf2b192010-08-10 18:03:39 -070071static 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
Andrea Righia25effa2010-08-19 14:13:30 -070091 /* skip first element of the fifo */
92 printk(KERN_INFO "skip 1st element\n");
93 kfifo_skip(&test);
94
Stefani Seibold5bf2b192010-08-10 18:03:39 -070095 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
Andrea Righia25effa2010-08-19 14:13:30 -0700102 /* check the correctness of all values in the fifo */
103 i = 0;
Stefani Seibold5bf2b192010-08-10 18:03:39 -0700104 while (!kfifo_is_empty(&test)) {
105 ret = kfifo_out(&test, buf, sizeof(buf));
Andrea Righia25effa2010-08-19 14:13:30 -0700106 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 }
Stefani Seibold5bf2b192010-08-10 18:03:39 -0700112 }
Andrea Righia25effa2010-08-19 14:13:30 -0700113 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");
Stefani Seibold5bf2b192010-08-10 18:03:39 -0700118
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};
159
160static int __init example_init(void)
161{
162#ifdef DYNAMIC
163 int ret;
164
165 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
166 if (ret) {
167 printk(KERN_ERR "error kfifo_alloc\n");
168 return ret;
169 }
170#else
171 INIT_KFIFO(test);
172#endif
Andrea Righia25effa2010-08-19 14:13:30 -0700173 if (testfunc() < 0) {
174#ifdef DYNAMIC
175 kfifo_free(&test);
176#endif
177 return -EIO;
178 }
Stefani Seibold5bf2b192010-08-10 18:03:39 -0700179
180 if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) {
181#ifdef DYNAMIC
182 kfifo_free(&test);
183#endif
184 return -ENOMEM;
185 }
186 return 0;
187}
188
189static void __exit example_exit(void)
190{
191 remove_proc_entry(PROC_FIFO, NULL);
192#ifdef DYNAMIC
193 kfifo_free(&test);
194#endif
195}
196
197module_init(example_init);
198module_exit(example_exit);
199MODULE_LICENSE("GPL");
200MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");