1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * Sample dynamic sized record fifo implementation |
4 | * |
5 | * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net> |
6 | */ |
7 | |
8 | #include <linux/init.h> |
9 | #include <linux/module.h> |
10 | #include <linux/proc_fs.h> |
11 | #include <linux/mutex.h> |
12 | #include <linux/kfifo.h> |
13 | |
14 | /* |
15 | * This module shows how to create a variable sized record fifo. |
16 | */ |
17 | |
18 | /* fifo size in elements (bytes) */ |
19 | #define FIFO_SIZE 128 |
20 | |
21 | /* name of the proc entry */ |
22 | #define PROC_FIFO "record-fifo" |
23 | |
24 | /* lock for procfs read access */ |
25 | static DEFINE_MUTEX(read_access); |
26 | |
27 | /* lock for procfs write access */ |
28 | static DEFINE_MUTEX(write_access); |
29 | |
30 | /* |
31 | * define DYNAMIC in this example for a dynamically allocated fifo. |
32 | * |
33 | * Otherwise the fifo storage will be a part of the fifo structure. |
34 | */ |
35 | #if 0 |
36 | #define DYNAMIC |
37 | #endif |
38 | |
39 | /* |
40 | * struct kfifo_rec_ptr_1 and STRUCT_KFIFO_REC_1 can handle records of a |
41 | * length between 0 and 255 bytes. |
42 | * |
43 | * struct kfifo_rec_ptr_2 and STRUCT_KFIFO_REC_2 can handle records of a |
44 | * length between 0 and 65535 bytes. |
45 | */ |
46 | |
47 | #ifdef DYNAMIC |
48 | struct kfifo_rec_ptr_1 test; |
49 | |
50 | #else |
51 | typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest; |
52 | |
53 | static mytest test; |
54 | #endif |
55 | |
56 | static const char *expected_result[] = { |
57 | "a" , |
58 | "bb" , |
59 | "ccc" , |
60 | "dddd" , |
61 | "eeeee" , |
62 | "ffffff" , |
63 | "ggggggg" , |
64 | "hhhhhhhh" , |
65 | "iiiiiiiii" , |
66 | "jjjjjjjjjj" , |
67 | }; |
68 | |
69 | static int __init testfunc(void) |
70 | { |
71 | char buf[100]; |
72 | unsigned int i; |
73 | unsigned int ret; |
74 | struct { unsigned char buf[6]; } hello = { "hello" }; |
75 | |
76 | printk(KERN_INFO "record fifo test start\n" ); |
77 | |
78 | kfifo_in(&test, &hello, sizeof(hello)); |
79 | |
80 | /* show the size of the next record in the fifo */ |
81 | printk(KERN_INFO "fifo peek len: %u\n" , kfifo_peek_len(&test)); |
82 | |
83 | /* put in variable length data */ |
84 | for (i = 0; i < 10; i++) { |
85 | memset(buf, 'a' + i, i + 1); |
86 | kfifo_in(&test, buf, i + 1); |
87 | } |
88 | |
89 | /* skip first element of the fifo */ |
90 | printk(KERN_INFO "skip 1st element\n" ); |
91 | kfifo_skip(&test); |
92 | |
93 | printk(KERN_INFO "fifo len: %u\n" , kfifo_len(&test)); |
94 | |
95 | /* show the first record without removing from the fifo */ |
96 | ret = kfifo_out_peek(&test, buf, sizeof(buf)); |
97 | if (ret) |
98 | printk(KERN_INFO "%.*s\n" , ret, buf); |
99 | |
100 | /* check the correctness of all values in the fifo */ |
101 | i = 0; |
102 | while (!kfifo_is_empty(&test)) { |
103 | ret = kfifo_out(&test, buf, sizeof(buf)); |
104 | buf[ret] = '\0'; |
105 | printk(KERN_INFO "item = %.*s\n" , ret, buf); |
106 | if (strcmp(buf, expected_result[i++])) { |
107 | printk(KERN_WARNING "value mismatch: test failed\n" ); |
108 | return -EIO; |
109 | } |
110 | } |
111 | if (i != ARRAY_SIZE(expected_result)) { |
112 | printk(KERN_WARNING "size mismatch: test failed\n" ); |
113 | return -EIO; |
114 | } |
115 | printk(KERN_INFO "test passed\n" ); |
116 | |
117 | return 0; |
118 | } |
119 | |
120 | static ssize_t fifo_write(struct file *file, const char __user *buf, |
121 | size_t count, loff_t *ppos) |
122 | { |
123 | int ret; |
124 | unsigned int copied; |
125 | |
126 | if (mutex_lock_interruptible(&write_access)) |
127 | return -ERESTARTSYS; |
128 | |
129 | ret = kfifo_from_user(&test, buf, count, &copied); |
130 | |
131 | mutex_unlock(lock: &write_access); |
132 | if (ret) |
133 | return ret; |
134 | |
135 | return 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_access)) |
145 | return -ERESTARTSYS; |
146 | |
147 | ret = kfifo_to_user(&test, buf, count, &copied); |
148 | |
149 | mutex_unlock(lock: &read_access); |
150 | if (ret) |
151 | return ret; |
152 | |
153 | return copied; |
154 | } |
155 | |
156 | static const struct proc_ops fifo_proc_ops = { |
157 | .proc_read = fifo_read, |
158 | .proc_write = fifo_write, |
159 | .proc_lseek = noop_llseek, |
160 | }; |
161 | |
162 | static int __init example_init(void) |
163 | { |
164 | #ifdef DYNAMIC |
165 | int ret; |
166 | |
167 | ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); |
168 | if (ret) { |
169 | printk(KERN_ERR "error kfifo_alloc\n" ); |
170 | return ret; |
171 | } |
172 | #else |
173 | INIT_KFIFO(test); |
174 | #endif |
175 | if (testfunc() < 0) { |
176 | #ifdef DYNAMIC |
177 | kfifo_free(&test); |
178 | #endif |
179 | return -EIO; |
180 | } |
181 | |
182 | if (proc_create(PROC_FIFO, mode: 0, NULL, proc_ops: &fifo_proc_ops) == NULL) { |
183 | #ifdef DYNAMIC |
184 | kfifo_free(&test); |
185 | #endif |
186 | return -ENOMEM; |
187 | } |
188 | return 0; |
189 | } |
190 | |
191 | static void __exit example_exit(void) |
192 | { |
193 | remove_proc_entry(PROC_FIFO, NULL); |
194 | #ifdef DYNAMIC |
195 | kfifo_free(&test); |
196 | #endif |
197 | } |
198 | |
199 | module_init(example_init); |
200 | module_exit(example_exit); |
201 | MODULE_LICENSE("GPL" ); |
202 | MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>" ); |
203 | |