LXR linux/samples/kfifo/inttype-example.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Sample kfifo int type implementation
   4 *
   5 * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
   6 */
   7
   8#include <linux/init.h>
   9#include <linux/module.h>
  10#include <linux/proc_fs.h>
  11#include <linux/mutex.h>
  12#include <linux/kfifo.h>
  13
  14/*
  15 * This module shows how to create a int type fifo.
  16 */
  17
  18/* fifo size in elements (ints) */
  19#define FIFO_SIZE       32
  20
  21/* name of the proc entry */
  22#define PROC_FIFO       "int-fifo"
  23
  24/* lock for procfs read access */
  25static DEFINE_MUTEX(read_lock);
  26
  27/* lock for procfs write access */
  28static DEFINE_MUTEX(write_lock);
  29
  30/*
  31 * define DYNAMIC in this example for a dynamically allocated fifo.
  32 *
  33 * Otherwise the fifo storage will be a part of the fifo structure.
  34 */
  35#if 0
  36#define DYNAMIC
  37#endif
  38
  39#ifdef DYNAMIC
  40static DECLARE_KFIFO_PTR(test, int);
  41#else
  42static DEFINE_KFIFO(test, int, FIFO_SIZE);
  43#endif
  44
  45static const int expected_result[FIFO_SIZE] = {
  46         3,  4,  5,  6,  7,  8,  9,  0,
  47         1, 20, 21, 22, 23, 24, 25, 26,
  48        27, 28, 29, 30, 31, 32, 33, 34,
  49        35, 36, 37, 38, 39, 40, 41, 42,
  50};
  51
  52static int __init testfunc(void)
  53{
  54        int             buf[6];
  55        int             i, j;
  56        unsigned int    ret;
  57
  58        printk(KERN_INFO "int fifo test start\n");
  59
  60        /* put values into the fifo */
  61        for (i = 0; i != 10; i++)
  62                kfifo_put(&test, i);
  63
  64        /* show the number of used elements */
  65        printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
  66
  67        /* get max of 2 elements from the fifo */
  68        ret = kfifo_out(&test, buf, 2);
  69        printk(KERN_INFO "ret: %d\n", ret);
  70        /* and put it back to the end of the fifo */
  71        ret = kfifo_in(&test, buf, ret);
  72        printk(KERN_INFO "ret: %d\n", ret);
  73
  74        /* skip first element of the fifo */
  75        printk(KERN_INFO "skip 1st element\n");
  76        kfifo_skip(&test);
  77
  78        /* put values into the fifo until is full */
  79        for (i = 20; kfifo_put(&test, i); i++)
  80                ;
  81
  82        printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));
  83
  84        /* show the first value without removing from the fifo */
  85        if (kfifo_peek(&test, &i))
  86                printk(KERN_INFO "%d\n", i);
  87
  88        /* check the correctness of all values in the fifo */
  89        j = 0;
  90        while (kfifo_get(&test, &i)) {
  91                printk(KERN_INFO "item = %d\n", i);
  92                if (i != expected_result[j++]) {
  93                        printk(KERN_WARNING "value mismatch: test failed\n");
  94                        return -EIO;
  95                }
  96        }
  97        if (j != ARRAY_SIZE(expected_result)) {
  98                printk(KERN_WARNING "size mismatch: test failed\n");
  99                return -EIO;
 100        }
 101        printk(KERN_INFO "test passed\n");
 102
 103        return 0;
 104}
 105
 106static ssize_t fifo_write(struct file *file, const char __user *buf,
 107                                                size_t count, loff_t *ppos)
 108{
 109        int ret;
 110        unsigned int copied;
 111
 112        if (mutex_lock_interruptible(&write_lock))
 113                return -ERESTARTSYS;
 114
 115        ret = kfifo_from_user(&test, buf, count, &copied);
 116
 117        mutex_unlock(&write_lock);
 118
 119        return ret ? ret : copied;
 120}
 121
 122static ssize_t fifo_read(struct file *file, char __user *buf,
 123                                                size_t count, loff_t *ppos)
 124{
 125        int ret;
 126        unsigned int copied;
 127
 128        if (mutex_lock_interruptible(&read_lock))
 129                return -ERESTARTSYS;
 130
 131        ret = kfifo_to_user(&test, buf, count, &copied);
 132
 133        mutex_unlock(&read_lock);
 134
 135        return ret ? ret : copied;
 136}
 137
 138static const struct proc_ops fifo_proc_ops = {
 139        .proc_read      = fifo_read,
 140        .proc_write     = fifo_write,
 141        .proc_lseek     = noop_llseek,
 142};
 143
 144static int __init example_init(void)
 145{
 146#ifdef DYNAMIC
 147        int ret;
 148
 149        ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
 150        if (ret) {
 151                printk(KERN_ERR "error kfifo_alloc\n");
 152                return ret;
 153        }
 154#endif
 155        if (testfunc() < 0) {
 156#ifdef DYNAMIC
 157                kfifo_free(&test);
 158#endif
 159                return -EIO;
 160        }
 161
 162        if (proc_create(PROC_FIFO, 0, NULL, &fifo_proc_ops) == NULL) {
 163#ifdef DYNAMIC
 164                kfifo_free(&test);
 165#endif
 166                return -ENOMEM;
 167        }
 168        return 0;
 169}
 170
 171static void __exit example_exit(void)
 172{
 173        remove_proc_entry(PROC_FIFO, NULL);
 174#ifdef DYNAMIC
 175        kfifo_free(&test);
 176#endif
 177}
 178
 179module_init(example_init);
 180module_exit(example_exit);
 181MODULE_LICENSE("GPL");
 182MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");
 183