samples/kfifo/bytestream-example.c

   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 unsigned char 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         unsigned char   buf[6];
  57         unsigned char   i, j;
  58         unsigned int    ret;
  59
  60         printk(KERN_INFO "byte stream fifo test start\n");
  61
  62         /* put string into the fifo */
  63         kfifo_in(&test, "hello", 5);
  64
  65         /* put values into the fifo */
  66         for (i = 0; i != 10; i++)
  67                 kfifo_put(&test, &i);
  68
  69         /* show the number of used elements */
  70         printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
  71
  72         /* get max of 5 bytes from the fifo */
  73         i = kfifo_out(&test, buf, 5);
  74         printk(KERN_INFO "buf: %.*s\n", i, buf);
  75
  76         /* get max of 2 elements from the fifo */
  77         ret = kfifo_out(&test, buf, 2);
  78         printk(KERN_INFO "ret: %d\n", ret);
  79         /* and put it back to the end of the fifo */
  80         ret = kfifo_in(&test, buf, ret);
  81         printk(KERN_INFO "ret: %d\n", ret);
  82
  83         /* skip first element of the fifo */
  84         printk(KERN_INFO "skip 1st element\n");
  85         kfifo_skip(&test);
  86
  87         /* put values into the fifo until is full */
  88         for (i = 20; kfifo_put(&test, &i); i++)
  89                 ;
  90
  91         printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));
  92
  93         /* check the correctness of all values in the fifo */
  94         j = 0;
  95         while (kfifo_get(&test, &i)) {
  96                 if (i != expected_result[j++]) {
  97                         printk(KERN_WARNING "value mismatch: test failed\n");
  98                         return -EIO;
  99                 }
 100         }
 101         if (j != ARRAY_SIZE(expected_result)) {
 102                 printk(KERN_WARNING "size mismatch: test failed\n");
 103                 return -EIO;
 104         }
 105         printk(KERN_INFO "test passed\n");
 106
 107         return 0;
 108 }
 109
 110 static ssize_t fifo_write(struct file *file, const char __user *buf,
 111                                                 size_t count, loff_t *ppos)
 112 {
 113         int ret;
 114         unsigned int copied;
 115
 116         if (mutex_lock_interruptible(&write_lock))
 117                 return -ERESTARTSYS;
 118
 119         ret = kfifo_from_user(&test, buf, count, &copied);
 120
 121         mutex_unlock(&write_lock);
 122
 123         return ret ? ret : copied;
 124 }
 125
 126 static ssize_t fifo_read(struct file *file, char __user *buf,
 127                                                 size_t count, loff_t *ppos)
 128 {
 129         int ret;
 130         unsigned int copied;
 131
 132         if (mutex_lock_interruptible(&read_lock))
 133                 return -ERESTARTSYS;
 134
 135         ret = kfifo_to_user(&test, buf, count, &copied);
 136
 137         mutex_unlock(&read_lock);
 138
 139         return ret ? ret : copied;
 140 }
 141
 142 static const struct file_operations fifo_fops = {
 143         .owner          = THIS_MODULE,
 144         .read           = fifo_read,
 145         .write          = fifo_write,
 146 };
 147
 148 static int __init example_init(void)
 149 {
 150 #ifdef DYNAMIC
 151         int ret;
 152
 153         ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
 154         if (ret) {
 155                 printk(KERN_ERR "error kfifo_alloc\n");
 156                 return ret;
 157         }
 158 #else
 159         INIT_KFIFO(test);
 160 #endif
 161         if (testfunc() < 0) {
 162 #ifdef DYNAMIC
 163                 kfifo_free(&test);
 164 #endif
 165                 return -EIO;
 166         }
 167
 168         if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) {
 169 #ifdef DYNAMIC
 170                 kfifo_free(&test);
 171 #endif
 172                 return -ENOMEM;
 173         }
 174         return 0;
 175 }
 176
 177 static void __exit example_exit(void)
 178 {
 179         remove_proc_entry(PROC_FIFO, NULL);
 180 #ifdef DYNAMIC
 181         kfifo_free(&test);
 182 #endif
 183 }
 184
 185 module_init(example_init);
 186 module_exit(example_exit);
 187 MODULE_LICENSE("GPL");
 188 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");