1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
|
// SPDX-License-Identifier: GPL-2.0-only
/*
* Sample kfifo byte stream implementation
*
* Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/mutex.h>
#include <linux/kfifo.h>
/*
* This module shows how to create a byte stream fifo.
*/
/* fifo size in elements (bytes) */
#define FIFO_SIZE 32
/* name of the proc entry */
#define PROC_FIFO "bytestream-fifo"
/* lock for procfs read access */
static DEFINE_MUTEX(read_access);
/* lock for procfs write access */
static DEFINE_MUTEX(write_access);
/*
* define DYNAMIC in this example for a dynamically allocated fifo.
*
* Otherwise the fifo storage will be a part of the fifo structure.
*/
#if 0
#define DYNAMIC
#endif
#ifdef DYNAMIC
static struct kfifo test;
#else
static DECLARE_KFIFO(test, unsigned char, FIFO_SIZE);
#endif
static const unsigned char expected_result[FIFO_SIZE] = {
3, 4, 5, 6, 7, 8, 9, 0,
1, 20, 21, 22, 23, 24, 25, 26,
27, 28, 29, 30, 31, 32, 33, 34,
35, 36, 37, 38, 39, 40, 41, 42,
};
static int __init testfunc(void)
{
unsigned char buf[6];
unsigned char i, j;
unsigned int ret;
printk(KERN_INFO "byte stream fifo test start\n");
/* put string into the fifo */
kfifo_in(&test, "hello", 5);
/* put values into the fifo */
for (i = 0; i != 10; i++)
kfifo_put(&test, i);
/* show the number of used elements */
printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
/* get max of 5 bytes from the fifo */
i = kfifo_out(&test, buf, 5);
printk(KERN_INFO "buf: %.*s\n", i, buf);
/* get max of 2 elements from the fifo */
ret = kfifo_out(&test, buf, 2);
printk(KERN_INFO "ret: %d\n", ret);
/* and put it back to the end of the fifo */
ret = kfifo_in(&test, buf, ret);
printk(KERN_INFO "ret: %d\n", ret);
/* skip first element of the fifo */
printk(KERN_INFO "skip 1st element\n");
kfifo_skip(&test);
/* put values into the fifo until is full */
for (i = 20; kfifo_put(&test, i); i++)
;
printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));
/* show the first value without removing from the fifo */
if (kfifo_peek(&test, &i))
printk(KERN_INFO "%d\n", i);
/* check the correctness of all values in the fifo */
j = 0;
while (kfifo_get(&test, &i)) {
printk(KERN_INFO "item = %d\n", i);
if (i != expected_result[j++]) {
printk(KERN_WARNING "value mismatch: test failed\n");
return -EIO;
}
}
if (j != ARRAY_SIZE(expected_result)) {
printk(KERN_WARNING "size mismatch: test failed\n");
return -EIO;
}
printk(KERN_INFO "test passed\n");
return 0;
}
static ssize_t fifo_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
int ret;
unsigned int copied;
if (mutex_lock_interruptible(&write_access))
return -ERESTARTSYS;
ret = kfifo_from_user(&test, buf, count, &copied);
mutex_unlock(&write_access);
if (ret)
return ret;
return copied;
}
static ssize_t fifo_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
int ret;
unsigned int copied;
if (mutex_lock_interruptible(&read_access))
return -ERESTARTSYS;
ret = kfifo_to_user(&test, buf, count, &copied);
mutex_unlock(&read_access);
if (ret)
return ret;
return copied;
}
static const struct proc_ops fifo_proc_ops = {
.proc_read = fifo_read,
.proc_write = fifo_write,
.proc_lseek = noop_llseek,
};
static int __init example_init(void)
{
#ifdef DYNAMIC
int ret;
ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
if (ret) {
printk(KERN_ERR "error kfifo_alloc\n");
return ret;
}
#else
INIT_KFIFO(test);
#endif
if (testfunc() < 0) {
#ifdef DYNAMIC
kfifo_free(&test);
#endif
return -EIO;
}
if (proc_create(PROC_FIFO, 0, NULL, &fifo_proc_ops) == NULL) {
#ifdef DYNAMIC
kfifo_free(&test);
#endif
return -ENOMEM;
}
return 0;
}
static void __exit example_exit(void)
{
remove_proc_entry(PROC_FIFO, NULL);
#ifdef DYNAMIC
kfifo_free(&test);
#endif
}
module_init(example_init);
module_exit(example_exit);
MODULE_DESCRIPTION("Sample kfifo byte stream implementation");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");
|
