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 */
  25 static DEFINE_MUTEX(read_lock);
  26
  27 /* lock for procfs write access */
  28 static 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
  40 static DECLARE_KFIFO_PTR(test, int);
  41 #else
  42 static DEFINE_KFIFO(test, int, FIFO_SIZE);
  43 #endif
  44
  45 static 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
  52 static 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
 106 static 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
 122 static 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
 138 static const struct proc_ops fifo_proc_ops = {
 139         .proc_read      = fifo_read,
 140         .proc_write     = fifo_write,
 141         .proc_lseek     = noop_llseek,
 142 };
 143
 144 static 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
 171 static void __exit example_exit(void)
 172 {
 173         remove_proc_entry(PROC_FIFO, NULL);
 174 #ifdef DYNAMIC
 175         kfifo_free(&test);
 176 #endif
 177 }
 178
 179 module_init(example_init);
 180 module_exit(example_exit);
 181 MODULE_LICENSE("GPL");
 182 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");