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 */
  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 DECLARE_KFIFO_PTR(test, int);
  43#else
  44static DEFINE_KFIFO(test, int, FIFO_SIZE);
  45#endif
  46
  47static 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
  54static 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
 108static 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
 124static 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
 140static const struct file_operations fifo_fops = {
 141        .owner          = THIS_MODULE,
 142        .read           = fifo_read,
 143        .write          = fifo_write,
 144        .llseek         = noop_llseek,
 145};
 146
 147static 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
 174static void __exit example_exit(void)
 175{
 176        remove_proc_entry(PROC_FIFO, NULL);
 177#ifdef DYNAMIC
 178        kfifo_free(&test);
 179#endif
 180}
 181
 182module_init(example_init);
 183module_exit(example_exit);
 184MODULE_LICENSE("GPL");
 185MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");
 186
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