Linux Kernel  3.7.1
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inttype-example.c
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1 /*
2  * Sample kfifo int type implementation
3  *
4  * Copyright (C) 2010 Stefani Seibold <[email protected]>
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 int type fifo.
18  */
19 
20 /* fifo size in elements (ints) */
21 #define FIFO_SIZE 32
22 
23 /* name of the proc entry */
24 #define PROC_FIFO "int-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 DECLARE_KFIFO_PTR(test, int);
43 #else
44 static DEFINE_KFIFO(test, int, FIFO_SIZE);
45 #endif
46 
47 static const int expected_result[FIFO_SIZE] = {
48  3, 4, 5, 6, 7, 8, 9, 0,
49  1, 20, 21, 22, 23, 24, 25, 26,
50  27, 28, 29, 30, 31, 32, 33, 34,
51  35, 36, 37, 38, 39, 40, 41, 42,
52 };
53 
54 static int __init testfunc(void)
55 {
56  int buf[6];
57  int i, j;
58  unsigned int ret;
59 
60  printk(KERN_INFO "int fifo test start\n");
61 
62  /* put values into the fifo */
63  for (i = 0; i != 10; i++)
64  kfifo_put(&test, &i);
65 
66  /* show the number of used elements */
67  printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
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  /* skip first element of the fifo */
77  printk(KERN_INFO "skip 1st element\n");
78  kfifo_skip(&test);
79 
80  /* put values into the fifo until is full */
81  for (i = 20; kfifo_put(&test, &i); i++)
82  ;
83 
84  printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));
85 
86  /* show the first value without removing from the fifo */
87  if (kfifo_peek(&test, &i))
88  printk(KERN_INFO "%d\n", i);
89 
90  /* check the correctness of all values in the fifo */
91  j = 0;
92  while (kfifo_get(&test, &i)) {
93  printk(KERN_INFO "item = %d\n", i);
94  if (i != expected_result[j++]) {
95  printk(KERN_WARNING "value mismatch: test failed\n");
96  return -EIO;
97  }
98  }
99  if (j != ARRAY_SIZE(expected_result)) {
100  printk(KERN_WARNING "size mismatch: test failed\n");
101  return -EIO;
102  }
103  printk(KERN_INFO "test passed\n");
104 
105  return 0;
106 }
107 
108 static ssize_t fifo_write(struct file *file, const char __user *buf,
109  size_t count, loff_t *ppos)
110 {
111  int ret;
112  unsigned int copied;
113 
115  return -ERESTARTSYS;
116 
117  ret = kfifo_from_user(&test, buf, count, &copied);
118 
120 
121  return ret ? ret : copied;
122 }
123 
124 static ssize_t fifo_read(struct file *file, char __user *buf,
125  size_t count, loff_t *ppos)
126 {
127  int ret;
128  unsigned int copied;
129 
131  return -ERESTARTSYS;
132 
133  ret = kfifo_to_user(&test, buf, count, &copied);
134 
136 
137  return ret ? ret : copied;
138 }
139 
140 static const struct file_operations fifo_fops = {
141  .owner = THIS_MODULE,
142  .read = fifo_read,
143  .write = fifo_write,
144  .llseek = noop_llseek,
145 };
146 
147 static int __init example_init(void)
148 {
149 #ifdef DYNAMIC
150  int ret;
151 
153  if (ret) {
154  printk(KERN_ERR "error kfifo_alloc\n");
155  return ret;
156  }
157 #endif
158  if (testfunc() < 0) {
159 #ifdef DYNAMIC
160  kfifo_free(&test);
161 #endif
162  return -EIO;
163  }
164 
165  if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) {
166 #ifdef DYNAMIC
167  kfifo_free(&test);
168 #endif
169  return -ENOMEM;
170  }
171  return 0;
172 }
173 
174 static void __exit example_exit(void)
175 {
177 #ifdef DYNAMIC
178  kfifo_free(&test);
179 #endif
180 }
181 
182 module_init(example_init);
183 module_exit(example_exit);
184 MODULE_LICENSE("GPL");
185 MODULE_AUTHOR("Stefani Seibold <[email protected]>");