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
testfunc(void)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
fifo_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)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 if (ret)
135 return ret;
136
137 return copied;
138 }
139
fifo_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)140 static ssize_t fifo_read(struct file *file, char __user *buf,
141 size_t count, loff_t *ppos)
142 {
143 int ret;
144 unsigned int copied;
145
146 if (mutex_lock_interruptible(&read_lock))
147 return -ERESTARTSYS;
148
149 ret = kfifo_to_user(&test, buf, count, &copied);
150
151 mutex_unlock(&read_lock);
152 if (ret)
153 return ret;
154
155 return copied;
156 }
157
158 static const struct file_operations fifo_fops = {
159 .owner = THIS_MODULE,
160 .read = fifo_read,
161 .write = fifo_write,
162 .llseek = noop_llseek,
163 };
164
example_init(void)165 static int __init example_init(void)
166 {
167 #ifdef DYNAMIC
168 int ret;
169
170 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
171 if (ret) {
172 printk(KERN_ERR "error kfifo_alloc\n");
173 return ret;
174 }
175 #else
176 INIT_KFIFO(test);
177 #endif
178 if (testfunc() < 0) {
179 #ifdef DYNAMIC
180 kfifo_free(&test);
181 #endif
182 return -EIO;
183 }
184
185 if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) {
186 #ifdef DYNAMIC
187 kfifo_free(&test);
188 #endif
189 return -ENOMEM;
190 }
191 return 0;
192 }
193
example_exit(void)194 static void __exit example_exit(void)
195 {
196 remove_proc_entry(PROC_FIFO, NULL);
197 #ifdef DYNAMIC
198 kfifo_free(&test);
199 #endif
200 }
201
202 module_init(example_init);
203 module_exit(example_exit);
204 MODULE_LICENSE("GPL");
205 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");
206