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5bf2b193 SS |
1 | /* |
2 | * Sample kfifo byte stream 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 byte stream fifo. | |
18 | */ | |
19 | ||
20 | /* fifo size in elements (bytes) */ | |
21 | #define FIFO_SIZE 32 | |
22 | ||
23 | /* name of the proc entry */ | |
24 | #define PROC_FIFO "bytestream-fifo" | |
25 | ||
26 | /* lock for procfs read access */ | |
27 | static DEFINE_MUTEX(read_lock); | |
28 | ||
29 | /* lock for procfs write access */ | |
30 | static 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 | |
42 | static struct kfifo test; | |
43 | #else | |
44 | static DECLARE_KFIFO(test, unsigned char, FIFO_SIZE); | |
45 | #endif | |
46 | ||
a25effa4 | 47 | static const unsigned char expected_result[FIFO_SIZE] = { |
2aaf2092 AR |
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 | ||
5bf2b193 SS |
54 | static int __init testfunc(void) |
55 | { | |
56 | unsigned char buf[6]; | |
2aaf2092 | 57 | unsigned char i, j; |
5bf2b193 SS |
58 | unsigned int ret; |
59 | ||
60 | printk(KERN_INFO "byte stream fifo test start\n"); | |
61 | ||
62 | /* put string into the fifo */ | |
63 | kfifo_in(&test, "hello", 5); | |
64 | ||
65 | /* put values into the fifo */ | |
66 | for (i = 0; i != 10; i++) | |
498d319b | 67 | kfifo_put(&test, i); |
5bf2b193 SS |
68 | |
69 | /* show the number of used elements */ | |
70 | printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); | |
71 | ||
72 | /* get max of 5 bytes from the fifo */ | |
73 | i = kfifo_out(&test, buf, 5); | |
74 | printk(KERN_INFO "buf: %.*s\n", i, buf); | |
75 | ||
76 | /* get max of 2 elements from the fifo */ | |
77 | ret = kfifo_out(&test, buf, 2); | |
78 | printk(KERN_INFO "ret: %d\n", ret); | |
79 | /* and put it back to the end of the fifo */ | |
80 | ret = kfifo_in(&test, buf, ret); | |
81 | printk(KERN_INFO "ret: %d\n", ret); | |
82 | ||
5ddf8391 AR |
83 | /* skip first element of the fifo */ |
84 | printk(KERN_INFO "skip 1st element\n"); | |
85 | kfifo_skip(&test); | |
86 | ||
5bf2b193 | 87 | /* put values into the fifo until is full */ |
498d319b | 88 | for (i = 20; kfifo_put(&test, i); i++) |
5bf2b193 SS |
89 | ; |
90 | ||
91 | printk(KERN_INFO "queue len: %u\n", kfifo_len(&test)); | |
92 | ||
a25effa4 AR |
93 | /* show the first value without removing from the fifo */ |
94 | if (kfifo_peek(&test, &i)) | |
95 | printk(KERN_INFO "%d\n", i); | |
96 | ||
2aaf2092 AR |
97 | /* check the correctness of all values in the fifo */ |
98 | j = 0; | |
99 | while (kfifo_get(&test, &i)) { | |
a25effa4 | 100 | printk(KERN_INFO "item = %d\n", i); |
2aaf2092 AR |
101 | if (i != expected_result[j++]) { |
102 | printk(KERN_WARNING "value mismatch: test failed\n"); | |
103 | return -EIO; | |
104 | } | |
105 | } | |
106 | if (j != ARRAY_SIZE(expected_result)) { | |
107 | printk(KERN_WARNING "size mismatch: test failed\n"); | |
108 | return -EIO; | |
109 | } | |
110 | printk(KERN_INFO "test passed\n"); | |
5bf2b193 SS |
111 | |
112 | return 0; | |
113 | } | |
114 | ||
115 | static ssize_t fifo_write(struct file *file, const char __user *buf, | |
116 | size_t count, loff_t *ppos) | |
117 | { | |
118 | int ret; | |
119 | unsigned int copied; | |
120 | ||
121 | if (mutex_lock_interruptible(&write_lock)) | |
122 | return -ERESTARTSYS; | |
123 | ||
124 | ret = kfifo_from_user(&test, buf, count, &copied); | |
125 | ||
126 | mutex_unlock(&write_lock); | |
127 | ||
128 | return ret ? ret : copied; | |
129 | } | |
130 | ||
131 | static ssize_t fifo_read(struct file *file, char __user *buf, | |
132 | size_t count, loff_t *ppos) | |
133 | { | |
134 | int ret; | |
135 | unsigned int copied; | |
136 | ||
137 | if (mutex_lock_interruptible(&read_lock)) | |
138 | return -ERESTARTSYS; | |
139 | ||
140 | ret = kfifo_to_user(&test, buf, count, &copied); | |
141 | ||
142 | mutex_unlock(&read_lock); | |
143 | ||
144 | return ret ? ret : copied; | |
145 | } | |
146 | ||
147 | static const struct file_operations fifo_fops = { | |
148 | .owner = THIS_MODULE, | |
149 | .read = fifo_read, | |
150 | .write = fifo_write, | |
6038f373 | 151 | .llseek = noop_llseek, |
5bf2b193 SS |
152 | }; |
153 | ||
154 | static int __init example_init(void) | |
155 | { | |
156 | #ifdef DYNAMIC | |
157 | int ret; | |
158 | ||
159 | ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); | |
160 | if (ret) { | |
161 | printk(KERN_ERR "error kfifo_alloc\n"); | |
162 | return ret; | |
163 | } | |
164 | #else | |
165 | INIT_KFIFO(test); | |
166 | #endif | |
2aaf2092 AR |
167 | if (testfunc() < 0) { |
168 | #ifdef DYNAMIC | |
169 | kfifo_free(&test); | |
170 | #endif | |
171 | return -EIO; | |
172 | } | |
5bf2b193 SS |
173 | |
174 | if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { | |
175 | #ifdef DYNAMIC | |
176 | kfifo_free(&test); | |
177 | #endif | |
178 | return -ENOMEM; | |
179 | } | |
180 | return 0; | |
181 | } | |
182 | ||
183 | static void __exit example_exit(void) | |
184 | { | |
185 | remove_proc_entry(PROC_FIFO, NULL); | |
186 | #ifdef DYNAMIC | |
187 | kfifo_free(&test); | |
188 | #endif | |
189 | } | |
190 | ||
191 | module_init(example_init); | |
192 | module_exit(example_exit); | |
193 | MODULE_LICENSE("GPL"); | |
194 | MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); |