Root/samples/kfifo/record-example.c

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

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