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 int __init testfunc(void)
  48 {
  49         int             buf[6];
  50         int             i;
  51         unsigned int    ret;
  52
  53         printk(KERN_INFO "int fifo test start\n");
  54
  55         /* put values into the fifo */
  56         for (i = 0; i != 10; i++)
  57                 kfifo_put(&test, &i);
  58
  59         /* show the number of used elements */
  60         printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
  61
  62         /* get max of 2 elements from the fifo */
  63         ret = kfifo_out(&test, buf, 2);
  64         printk(KERN_INFO "ret: %d\n", ret);
  65         /* and put it back to the end of the fifo */
  66         ret = kfifo_in(&test, buf, ret);
  67         printk(KERN_INFO "ret: %d\n", ret);
  68
  69         for (i = 20; i != 30; i++)
  70                 kfifo_put(&test, &i);
  71
  72         printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));
  73
  74         /* show the first value without removing from the fifo */
  75         if (kfifo_peek(&test, &i))
  76                 printk(KERN_INFO "%d\n", i);
  77
  78         /* print out all values in the fifo */
  79         while (kfifo_get(&test, &i))
  80                 printk("%d ", i);
  81         printk("\n");
  82
  83         return 0;
  84 }
  85
  86 static ssize_t fifo_write(struct file *file, const char __user *buf,
  87                                                 size_t count, loff_t *ppos)
  88 {
  89         int ret;
  90         unsigned int copied;
  91
  92         if (mutex_lock_interruptible(&write_lock))
  93                 return -ERESTARTSYS;
  94
  95         ret = kfifo_from_user(&test, buf, count, &copied);
  96
  97         mutex_unlock(&write_lock);
  98
  99         return ret ? ret : copied;
 100 }
 101
 102 static ssize_t fifo_read(struct file *file, char __user *buf,
 103                                                 size_t count, loff_t *ppos)
 104 {
 105         int ret;
 106         unsigned int copied;
 107
 108         if (mutex_lock_interruptible(&read_lock))
 109                 return -ERESTARTSYS;
 110
 111         ret = kfifo_to_user(&test, buf, count, &copied);
 112
 113         mutex_unlock(&read_lock);
 114
 115         return ret ? ret : copied;
 116 }
 117
 118 static const struct file_operations fifo_fops = {
 119         .owner          = THIS_MODULE,
 120         .read           = fifo_read,
 121         .write          = fifo_write,
 122 };
 123
 124 static int __init example_init(void)
 125 {
 126 #ifdef DYNAMIC
 127         int ret;
 128
 129         ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
 130         if (ret) {
 131                 printk(KERN_ERR "error kfifo_alloc\n");
 132                 return ret;
 133         }
 134 #endif
 135         testfunc();
 136
 137         if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) {
 138 #ifdef DYNAMIC
 139                 kfifo_free(&test);
 140 #endif
 141                 return -ENOMEM;
 142         }
 143         return 0;
 144 }
 145
 146 static void __exit example_exit(void)
 147 {
 148         remove_proc_entry(PROC_FIFO, NULL);
 149 #ifdef DYNAMIC
 150         kfifo_free(&test);
 151 #endif
 152 }
 153
 154 module_init(example_init);
 155 module_exit(example_exit);
 156 MODULE_LICENSE("GPL");
 157 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");