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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 | |
47 | static const unsigned char expected_result[FIFO_SIZE] = { |
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 | |
54 | static int __init testfunc(void) |
55 | { |
56 | unsigned char buf[6]; |
57 | unsigned char i, j; |
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++) |
67 | kfifo_put(&test, &i); |
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 | |
83 | /* skip first element of the fifo */ |
84 | printk(KERN_INFO "skip 1st element\n"); |
85 | kfifo_skip(&test); |
86 | |
87 | /* put values into the fifo until is full */ |
88 | for (i = 20; kfifo_put(&test, &i); i++) |
89 | ; |
90 | |
91 | printk(KERN_INFO "queue len: %u\n", kfifo_len(&test)); |
92 | |
93 | /* show the first value without removing from the fifo */ |
94 | if (kfifo_peek(&test, &i)) |
95 | printk(KERN_INFO "%d\n", i); |
96 | |
97 | /* check the correctness of all values in the fifo */ |
98 | j = 0; |
99 | while (kfifo_get(&test, &i)) { |
100 | printk(KERN_INFO "item = %d\n", i); |
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"); |
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, |
151 | .llseek = noop_llseek, |
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 |
167 | if (testfunc() < 0) { |
168 | #ifdef DYNAMIC |
169 | kfifo_free(&test); |
170 | #endif |
171 | return -EIO; |
172 | } |
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>"); |
195 |
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