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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 */ |
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 | /* |
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 |
50 | struct kfifo_rec_ptr_1 test; |
51 | |
52 | #else |
53 | typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest; |
54 | |
55 | static mytest test; |
56 | #endif |
57 | |
58 | static 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 | |
71 | static 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 | |
122 | static 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 | |
138 | static 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 | |
154 | static const struct file_operations fifo_fops = { |
155 | .owner = THIS_MODULE, |
156 | .read = fifo_read, |
157 | .write = fifo_write, |
158 | .llseek = noop_llseek, |
159 | }; |
160 | |
161 | static 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 | |
190 | static void __exit example_exit(void) |
191 | { |
192 | remove_proc_entry(PROC_FIFO, NULL); |
193 | #ifdef DYNAMIC |
194 | kfifo_free(&test); |
195 | #endif |
196 | } |
197 | |
198 | module_init(example_init); |
199 | module_exit(example_exit); |
200 | MODULE_LICENSE("GPL"); |
201 | MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); |
202 |
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