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5bf2b193 SS |
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 int __init testfunc(void) | |
48 | { | |
49 | unsigned char buf[6]; | |
50 | unsigned char i; | |
51 | unsigned int ret; | |
52 | ||
53 | printk(KERN_INFO "byte stream fifo test start\n"); | |
54 | ||
55 | /* put string into the fifo */ | |
56 | kfifo_in(&test, "hello", 5); | |
57 | ||
58 | /* put values into the fifo */ | |
59 | for (i = 0; i != 10; i++) | |
60 | kfifo_put(&test, &i); | |
61 | ||
62 | /* show the number of used elements */ | |
63 | printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); | |
64 | ||
65 | /* get max of 5 bytes from the fifo */ | |
66 | i = kfifo_out(&test, buf, 5); | |
67 | printk(KERN_INFO "buf: %.*s\n", i, buf); | |
68 | ||
69 | /* get max of 2 elements from the fifo */ | |
70 | ret = kfifo_out(&test, buf, 2); | |
71 | printk(KERN_INFO "ret: %d\n", ret); | |
72 | /* and put it back to the end of the fifo */ | |
73 | ret = kfifo_in(&test, buf, ret); | |
74 | printk(KERN_INFO "ret: %d\n", ret); | |
75 | ||
76 | /* put values into the fifo until is full */ | |
77 | for (i = 20; kfifo_put(&test, &i); i++) | |
78 | ; | |
79 | ||
80 | printk(KERN_INFO "queue len: %u\n", kfifo_len(&test)); | |
81 | ||
82 | /* print out all values in the fifo */ | |
83 | while (kfifo_get(&test, &i)) | |
84 | printk("%d ", i); | |
85 | printk("\n"); | |
86 | ||
87 | return 0; | |
88 | } | |
89 | ||
90 | static ssize_t fifo_write(struct file *file, const char __user *buf, | |
91 | size_t count, loff_t *ppos) | |
92 | { | |
93 | int ret; | |
94 | unsigned int copied; | |
95 | ||
96 | if (mutex_lock_interruptible(&write_lock)) | |
97 | return -ERESTARTSYS; | |
98 | ||
99 | ret = kfifo_from_user(&test, buf, count, &copied); | |
100 | ||
101 | mutex_unlock(&write_lock); | |
102 | ||
103 | return ret ? ret : copied; | |
104 | } | |
105 | ||
106 | static ssize_t fifo_read(struct file *file, char __user *buf, | |
107 | size_t count, loff_t *ppos) | |
108 | { | |
109 | int ret; | |
110 | unsigned int copied; | |
111 | ||
112 | if (mutex_lock_interruptible(&read_lock)) | |
113 | return -ERESTARTSYS; | |
114 | ||
115 | ret = kfifo_to_user(&test, buf, count, &copied); | |
116 | ||
117 | mutex_unlock(&read_lock); | |
118 | ||
119 | return ret ? ret : copied; | |
120 | } | |
121 | ||
122 | static const struct file_operations fifo_fops = { | |
123 | .owner = THIS_MODULE, | |
124 | .read = fifo_read, | |
125 | .write = fifo_write, | |
126 | }; | |
127 | ||
128 | static int __init example_init(void) | |
129 | { | |
130 | #ifdef DYNAMIC | |
131 | int ret; | |
132 | ||
133 | ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); | |
134 | if (ret) { | |
135 | printk(KERN_ERR "error kfifo_alloc\n"); | |
136 | return ret; | |
137 | } | |
138 | #else | |
139 | INIT_KFIFO(test); | |
140 | #endif | |
141 | testfunc(); | |
142 | ||
143 | if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { | |
144 | #ifdef DYNAMIC | |
145 | kfifo_free(&test); | |
146 | #endif | |
147 | return -ENOMEM; | |
148 | } | |
149 | return 0; | |
150 | } | |
151 | ||
152 | static void __exit example_exit(void) | |
153 | { | |
154 | remove_proc_entry(PROC_FIFO, NULL); | |
155 | #ifdef DYNAMIC | |
156 | kfifo_free(&test); | |
157 | #endif | |
158 | } | |
159 | ||
160 | module_init(example_init); | |
161 | module_exit(example_exit); | |
162 | MODULE_LICENSE("GPL"); | |
163 | MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); |