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Stefani Seibold5bf2b192010-08-10 18:03:39 -07001/*
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 */
27static DEFINE_MUTEX(read_lock);
28
29/* lock for procfs write access */
30static 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
42static struct kfifo test;
43#else
44static DECLARE_KFIFO(test, unsigned char, FIFO_SIZE);
45#endif
46
47static 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
90static 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
106static 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
122static const struct file_operations fifo_fops = {
123 .owner = THIS_MODULE,
124 .read = fifo_read,
125 .write = fifo_write,
126};
127
128static 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
152static void __exit example_exit(void)
153{
154 remove_proc_entry(PROC_FIFO, NULL);
155#ifdef DYNAMIC
156 kfifo_free(&test);
157#endif
158}
159
160module_init(example_init);
161module_exit(example_exit);
162MODULE_LICENSE("GPL");
163MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");