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Linux/samples/kfifo/inttype-example.c

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  1 /*
  2  * Sample kfifo int type 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 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 
114         if (mutex_lock_interruptible(&write_lock))
115                 return -ERESTARTSYS;
116 
117         ret = kfifo_from_user(&test, buf, count, &copied);
118 
119         mutex_unlock(&write_lock);
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 
130         if (mutex_lock_interruptible(&read_lock))
131                 return -ERESTARTSYS;
132 
133         ret = kfifo_to_user(&test, buf, count, &copied);
134 
135         mutex_unlock(&read_lock);
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 
152         ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
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 {
176         remove_proc_entry(PROC_FIFO, NULL);
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 <stefani@seibold.net>");
186 

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