samples/kfifo/inttype-example.c

   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 */
  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 #if 0
  38 #define DYNAMIC
  39 #endif
  40
  41 #ifdef DYNAMIC
  42 static DECLARE_KFIFO_PTR(test, int);
  43 #else
  44 static DEFINE_KFIFO(test, int, FIFO_SIZE);
  45 #endif
  46
  47 static 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
  54 static 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
 108 static 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
 124 static 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
 140 static const struct file_operations fifo_fops = {
 141         .owner          = THIS_MODULE,
 142         .read           = fifo_read,
 143         .write          = fifo_write,
 144         .llseek         = noop_llseek,
 145 };
 146
 147 static 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
 174 static void __exit example_exit(void)
 175 {
 176         remove_proc_entry(PROC_FIFO, NULL);
 177 #ifdef DYNAMIC
 178         kfifo_free(&test);
 179 #endif
 180 }
 181
 182 module_init(example_init);
 183 module_exit(example_exit);
 184 MODULE_LICENSE("GPL");
 185 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");