release/src-rt-6.x.4708/linux/linux-2.6.36/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
  38 #ifdef DYNAMIC
  39 static struct kfifo test;
  40 #else
  41 static DECLARE_KFIFO(test, unsigned char, FIFO_SIZE);
  42 #endif
  43
  44 static const unsigned char expected_result[FIFO_SIZE] = {
  45          3,  4,  5,  6,  7,  8,  9,  0,
  46          1, 20, 21, 22, 23, 24, 25, 26,
  47         27, 28, 29, 30, 31, 32, 33, 34,
  48         35, 36, 37, 38, 39, 40, 41, 42,
  49 };
  50
  51 static int __init testfunc(void)
  52 {
  53         unsigned char   buf[6];
  54         unsigned char   i, j;
  55         unsigned int    ret;
  56
  57         printk(KERN_INFO "byte stream fifo test start\n");
  58
  59         /* put string into the fifo */
  60         kfifo_in(&test, "hello", 5);
  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 5 bytes from the fifo */
  70         i = kfifo_out(&test, buf, 5);
  71         printk(KERN_INFO "buf: %.*s\n", i, buf);
  72
  73         /* get max of 2 elements from the fifo */
  74         ret = kfifo_out(&test, buf, 2);
  75         printk(KERN_INFO "ret: %d\n", ret);
  76         /* and put it back to the end of the fifo */
  77         ret = kfifo_in(&test, buf, ret);
  78         printk(KERN_INFO "ret: %d\n", ret);
  79
  80         /* skip first element of the fifo */
  81         printk(KERN_INFO "skip 1st element\n");
  82         kfifo_skip(&test);
  83
  84         /* put values into the fifo until is full */
  85         for (i = 20; kfifo_put(&test, &i); i++)
  86                 ;
  87
  88         printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));
  89
  90         /* show the first value without removing from the fifo */
  91         if (kfifo_peek(&test, &i))
  92                 printk(KERN_INFO "%d\n", i);
  93
  94         /* check the correctness of all values in the fifo */
  95         j = 0;
  96         while (kfifo_get(&test, &i)) {
  97                 printk(KERN_INFO "item = %d\n", i);
  98                 if (i != expected_result[j++]) {
  99                         printk(KERN_WARNING "value mismatch: test failed\n");
 100                         return -EIO;
 101                 }
 102         }
 103         if (j != ARRAY_SIZE(expected_result)) {
 104                 printk(KERN_WARNING "size mismatch: test failed\n");
 105                 return -EIO;
 106         }
 107         printk(KERN_INFO "test passed\n");
 108
 109         return 0;
 110 }
 111
 112 static ssize_t fifo_write(struct file *file, const char __user *buf,
 113                                                 size_t count, loff_t *ppos)
 114 {
 115         int ret;
 116         unsigned int copied;
 117
 118         if (mutex_lock_interruptible(&write_lock))
 119                 return -ERESTARTSYS;
 120
 121         ret = kfifo_from_user(&test, buf, count, &copied);
 122
 123         mutex_unlock(&write_lock);
 124
 125         return ret ? ret : copied;
 126 }
 127
 128 static ssize_t fifo_read(struct file *file, char __user *buf,
 129                                                 size_t count, loff_t *ppos)
 130 {
 131         int ret;
 132         unsigned int copied;
 133
 134         if (mutex_lock_interruptible(&read_lock))
 135                 return -ERESTARTSYS;
 136
 137         ret = kfifo_to_user(&test, buf, count, &copied);
 138
 139         mutex_unlock(&read_lock);
 140
 141         return ret ? ret : copied;
 142 }
 143
 144 static const struct file_operations fifo_fops = {
 145         .owner          = THIS_MODULE,
 146         .read           = fifo_read,
 147         .write          = fifo_write,
 148 };
 149
 150 static int __init example_init(void)
 151 {
 152 #ifdef DYNAMIC
 153         int ret;
 154
 155         ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
 156         if (ret) {
 157                 printk(KERN_ERR "error kfifo_alloc\n");
 158                 return ret;
 159         }
 160 #else
 161         INIT_KFIFO(test);
 162 #endif
 163         if (testfunc() < 0) {
 164 #ifdef DYNAMIC
 165                 kfifo_free(&test);
 166 #endif
 167                 return -EIO;
 168         }
 169
 170         if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) {
 171 #ifdef DYNAMIC
 172                 kfifo_free(&test);
 173 #endif
 174                 return -ENOMEM;
 175         }
 176         return 0;
 177 }
 178
 179 static void __exit example_exit(void)
 180 {
 181         remove_proc_entry(PROC_FIFO, NULL);
 182 #ifdef DYNAMIC
 183         kfifo_free(&test);
 184 #endif
 185 }
 186
 187 module_init(example_init);
 188 module_exit(example_exit);
 189 MODULE_LICENSE("GPL");
 190 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");