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

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Sample dynamic sized record fifo 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 variable sized record fifo.
  16 */
  17
  18/* fifo size in elements (bytes) */
  19#define FIFO_SIZE       128
  20
  21/* name of the proc entry */
  22#define PROC_FIFO       "record-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/*
  40 * struct kfifo_rec_ptr_1 and  STRUCT_KFIFO_REC_1 can handle records of a
  41 * length between 0 and 255 bytes.
  42 *
  43 * struct kfifo_rec_ptr_2 and  STRUCT_KFIFO_REC_2 can handle records of a
  44 * length between 0 and 65535 bytes.
  45 */
  46
  47#ifdef DYNAMIC
  48struct kfifo_rec_ptr_1 test;
  49
  50#else
  51typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest;
  52
  53static mytest test;
  54#endif
  55
  56static const char *expected_result[] = {
  57        "a",
  58        "bb",
  59        "ccc",
  60        "dddd",
  61        "eeeee",
  62        "ffffff",
  63        "ggggggg",
  64        "hhhhhhhh",
  65        "iiiiiiiii",
  66        "jjjjjjjjjj",
  67};
  68
  69static int __init testfunc(void)
  70{
  71        char            buf[100];
  72        unsigned int    i;
  73        unsigned int    ret;
  74        struct { unsigned char buf[6]; } hello = { "hello" };
  75
  76        printk(KERN_INFO "record fifo test start\n");
  77
  78        kfifo_in(&test, &hello, sizeof(hello));
  79
  80        /* show the size of the next record in the fifo */
  81        printk(KERN_INFO "fifo peek len: %u\n", kfifo_peek_len(&test));
  82
  83        /* put in variable length data */
  84        for (i = 0; i < 10; i++) {
  85                memset(buf, 'a' + i, i + 1);
  86                kfifo_in(&test, buf, i + 1);
  87        }
  88
  89        /* skip first element of the fifo */
  90        printk(KERN_INFO "skip 1st element\n");
  91        kfifo_skip(&test);
  92
  93        printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
  94
  95        /* show the first record without removing from the fifo */
  96        ret = kfifo_out_peek(&test, buf, sizeof(buf));
  97        if (ret)
  98                printk(KERN_INFO "%.*s\n", ret, buf);
  99
 100        /* check the correctness of all values in the fifo */
 101        i = 0;
 102        while (!kfifo_is_empty(&test)) {
 103                ret = kfifo_out(&test, buf, sizeof(buf));
 104                buf[ret] = '\0';
 105                printk(KERN_INFO "item = %.*s\n", ret, buf);
 106                if (strcmp(buf, expected_result[i++])) {
 107                        printk(KERN_WARNING "value mismatch: test failed\n");
 108                        return -EIO;
 109                }
 110        }
 111        if (i != ARRAY_SIZE(expected_result)) {
 112                printk(KERN_WARNING "size mismatch: test failed\n");
 113                return -EIO;
 114        }
 115        printk(KERN_INFO "test passed\n");
 116
 117        return 0;
 118}
 119
 120static ssize_t fifo_write(struct file *file, const char __user *buf,
 121                                                size_t count, loff_t *ppos)
 122{
 123        int ret;
 124        unsigned int copied;
 125
 126        if (mutex_lock_interruptible(&write_lock))
 127                return -ERESTARTSYS;
 128
 129        ret = kfifo_from_user(&test, buf, count, &copied);
 130
 131        mutex_unlock(&write_lock);
 132        if (ret)
 133                return ret;
 134
 135        return copied;
 136}
 137
 138static ssize_t fifo_read(struct file *file, char __user *buf,
 139                                                size_t count, loff_t *ppos)
 140{
 141        int ret;
 142        unsigned int copied;
 143
 144        if (mutex_lock_interruptible(&read_lock))
 145                return -ERESTARTSYS;
 146
 147        ret = kfifo_to_user(&test, buf, count, &copied);
 148
 149        mutex_unlock(&read_lock);
 150        if (ret)
 151                return ret;
 152
 153        return copied;
 154}
 155
 156static const struct proc_ops fifo_proc_ops = {
 157        .proc_read      = fifo_read,
 158        .proc_write     = fifo_write,
 159        .proc_lseek     = noop_llseek,
 160};
 161
 162static int __init example_init(void)
 163{
 164#ifdef DYNAMIC
 165        int ret;
 166
 167        ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
 168        if (ret) {
 169                printk(KERN_ERR "error kfifo_alloc\n");
 170                return ret;
 171        }
 172#else
 173        INIT_KFIFO(test);
 174#endif
 175        if (testfunc() < 0) {
 176#ifdef DYNAMIC
 177                kfifo_free(&test);
 178#endif
 179                return -EIO;
 180        }
 181
 182        if (proc_create(PROC_FIFO, 0, NULL, &fifo_proc_ops) == NULL) {
 183#ifdef DYNAMIC
 184                kfifo_free(&test);
 185#endif
 186                return -ENOMEM;
 187        }
 188        return 0;
 189}
 190
 191static void __exit example_exit(void)
 192{
 193        remove_proc_entry(PROC_FIFO, NULL);
 194#ifdef DYNAMIC
 195        kfifo_free(&test);
 196#endif
 197}
 198
 199module_init(example_init);
 200module_exit(example_exit);
 201MODULE_LICENSE("GPL");
 202MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");
 203