1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * Sample kfifo byte stream 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 byte stream fifo. |
16 | */ |
17 | |
18 | /* fifo size in elements (bytes) */ |
19 | #define FIFO_SIZE 32 |
20 | |
21 | /* name of the proc entry */ |
22 | #define PROC_FIFO "bytestream-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 | #ifdef DYNAMIC |
40 | static struct kfifo test; |
41 | #else |
42 | static DECLARE_KFIFO(test, unsigned char, FIFO_SIZE); |
43 | #endif |
44 | |
45 | static const unsigned char expected_result[FIFO_SIZE] = { |
46 | 3, 4, 5, 6, 7, 8, 9, 0, |
47 | 1, 20, 21, 22, 23, 24, 25, 26, |
48 | 27, 28, 29, 30, 31, 32, 33, 34, |
49 | 35, 36, 37, 38, 39, 40, 41, 42, |
50 | }; |
51 | |
52 | static int __init testfunc(void) |
53 | { |
54 | unsigned char buf[6]; |
55 | unsigned char i, j; |
56 | unsigned int ret; |
57 | |
58 | printk(KERN_INFO "byte stream fifo test start\n" ); |
59 | |
60 | /* put string into the fifo */ |
61 | kfifo_in(&test, "hello" , 5); |
62 | |
63 | /* put values into the fifo */ |
64 | for (i = 0; i != 10; i++) |
65 | kfifo_put(&test, i); |
66 | |
67 | /* show the number of used elements */ |
68 | printk(KERN_INFO "fifo len: %u\n" , kfifo_len(&test)); |
69 | |
70 | /* get max of 5 bytes from the fifo */ |
71 | i = kfifo_out(&test, buf, 5); |
72 | printk(KERN_INFO "buf: %.*s\n" , i, buf); |
73 | |
74 | /* get max of 2 elements from the fifo */ |
75 | ret = kfifo_out(&test, buf, 2); |
76 | printk(KERN_INFO "ret: %d\n" , ret); |
77 | /* and put it back to the end of the fifo */ |
78 | ret = kfifo_in(&test, buf, ret); |
79 | printk(KERN_INFO "ret: %d\n" , ret); |
80 | |
81 | /* skip first element of the fifo */ |
82 | printk(KERN_INFO "skip 1st element\n" ); |
83 | kfifo_skip(&test); |
84 | |
85 | /* put values into the fifo until is full */ |
86 | for (i = 20; kfifo_put(&test, i); i++) |
87 | ; |
88 | |
89 | printk(KERN_INFO "queue len: %u\n" , kfifo_len(&test)); |
90 | |
91 | /* show the first value without removing from the fifo */ |
92 | if (kfifo_peek(&test, &i)) |
93 | printk(KERN_INFO "%d\n" , i); |
94 | |
95 | /* check the correctness of all values in the fifo */ |
96 | j = 0; |
97 | while (kfifo_get(&test, &i)) { |
98 | printk(KERN_INFO "item = %d\n" , i); |
99 | if (i != expected_result[j++]) { |
100 | printk(KERN_WARNING "value mismatch: test failed\n" ); |
101 | return -EIO; |
102 | } |
103 | } |
104 | if (j != ARRAY_SIZE(expected_result)) { |
105 | printk(KERN_WARNING "size mismatch: test failed\n" ); |
106 | return -EIO; |
107 | } |
108 | printk(KERN_INFO "test passed\n" ); |
109 | |
110 | return 0; |
111 | } |
112 | |
113 | static ssize_t fifo_write(struct file *file, const char __user *buf, |
114 | size_t count, loff_t *ppos) |
115 | { |
116 | int ret; |
117 | unsigned int copied; |
118 | |
119 | if (mutex_lock_interruptible(&write_access)) |
120 | return -ERESTARTSYS; |
121 | |
122 | ret = kfifo_from_user(&test, buf, count, &copied); |
123 | |
124 | mutex_unlock(lock: &write_access); |
125 | if (ret) |
126 | return ret; |
127 | |
128 | return 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_access)) |
138 | return -ERESTARTSYS; |
139 | |
140 | ret = kfifo_to_user(&test, buf, count, &copied); |
141 | |
142 | mutex_unlock(lock: &read_access); |
143 | if (ret) |
144 | return ret; |
145 | |
146 | return copied; |
147 | } |
148 | |
149 | static const struct proc_ops fifo_proc_ops = { |
150 | .proc_read = fifo_read, |
151 | .proc_write = fifo_write, |
152 | .proc_lseek = noop_llseek, |
153 | }; |
154 | |
155 | static int __init example_init(void) |
156 | { |
157 | #ifdef DYNAMIC |
158 | int ret; |
159 | |
160 | ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); |
161 | if (ret) { |
162 | printk(KERN_ERR "error kfifo_alloc\n" ); |
163 | return ret; |
164 | } |
165 | #else |
166 | INIT_KFIFO(test); |
167 | #endif |
168 | if (testfunc() < 0) { |
169 | #ifdef DYNAMIC |
170 | kfifo_free(&test); |
171 | #endif |
172 | return -EIO; |
173 | } |
174 | |
175 | if (proc_create(PROC_FIFO, mode: 0, NULL, proc_ops: &fifo_proc_ops) == NULL) { |
176 | #ifdef DYNAMIC |
177 | kfifo_free(&test); |
178 | #endif |
179 | return -ENOMEM; |
180 | } |
181 | return 0; |
182 | } |
183 | |
184 | static void __exit example_exit(void) |
185 | { |
186 | remove_proc_entry(PROC_FIFO, NULL); |
187 | #ifdef DYNAMIC |
188 | kfifo_free(&test); |
189 | #endif |
190 | } |
191 | |
192 | module_init(example_init); |
193 | module_exit(example_exit); |
194 | MODULE_LICENSE("GPL" ); |
195 | MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>" ); |
196 | |