include/linux/kfifo.h

   1 /*
   2  * A generic kernel FIFO implementation.
   3  *
   4  * Copyright (C) 2009 Stefani Seibold <stefani@seibold.net>
   5  * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  *
  21  */
  22 #ifndef _LINUX_KFIFO_H
  23 #define _LINUX_KFIFO_H
  24
  25 #include <linux/kernel.h>
  26 #include <linux/spinlock.h>
  27
  28 struct kfifo {
  29         unsigned char *buffer;  /* the buffer holding the data */
  30         unsigned int size;      /* the size of the allocated buffer */
  31         unsigned int in;        /* data is added at offset (in % size) */
  32         unsigned int out;       /* data is extracted from off. (out % size) */
  33         spinlock_t *lock;       /* protects concurrent modifications */
  34 };
  35
  36 extern void kfifo_init(struct kfifo *fifo, unsigned char *buffer,
  37                         unsigned int size, spinlock_t *lock);
  38 extern __must_check int kfifo_alloc(struct kfifo *fifo, unsigned int size,
  39                         gfp_t gfp_mask, spinlock_t *lock);
  40 extern void kfifo_free(struct kfifo *fifo);
  41 extern unsigned int __kfifo_put(struct kfifo *fifo,
  42                                 const unsigned char *buffer, unsigned int len);
  43 extern unsigned int __kfifo_get(struct kfifo *fifo,
  44                                 unsigned char *buffer, unsigned int len);
  45
  46 /**
  47  * __kfifo_reset - removes the entire FIFO contents, no locking version
  48  * @fifo: the fifo to be emptied.
  49  */
  50 static inline void __kfifo_reset(struct kfifo *fifo)
  51 {
  52         fifo->in = fifo->out = 0;
  53 }
  54
  55 /**
  56  * kfifo_reset - removes the entire FIFO contents
  57  * @fifo: the fifo to be emptied.
  58  */
  59 static inline void kfifo_reset(struct kfifo *fifo)
  60 {
  61         unsigned long flags;
  62
  63         spin_lock_irqsave(fifo->lock, flags);
  64
  65         __kfifo_reset(fifo);
  66
  67         spin_unlock_irqrestore(fifo->lock, flags);
  68 }
  69
  70 /**
  71  * kfifo_put - puts some data into the FIFO
  72  * @fifo: the fifo to be used.
  73  * @buffer: the data to be added.
  74  * @len: the length of the data to be added.
  75  *
  76  * This function copies at most @len bytes from the @buffer into
  77  * the FIFO depending on the free space, and returns the number of
  78  * bytes copied.
  79  */
  80 static inline unsigned int kfifo_put(struct kfifo *fifo,
  81                                 const unsigned char *buffer, unsigned int len)
  82 {
  83         unsigned long flags;
  84         unsigned int ret;
  85
  86         spin_lock_irqsave(fifo->lock, flags);
  87
  88         ret = __kfifo_put(fifo, buffer, len);
  89
  90         spin_unlock_irqrestore(fifo->lock, flags);
  91
  92         return ret;
  93 }
  94
  95 /**
  96  * kfifo_get - gets some data from the FIFO
  97  * @fifo: the fifo to be used.
  98  * @buffer: where the data must be copied.
  99  * @len: the size of the destination buffer.
 100  *
 101  * This function copies at most @len bytes from the FIFO into the
 102  * @buffer and returns the number of copied bytes.
 103  */
 104 static inline unsigned int kfifo_get(struct kfifo *fifo,
 105                                      unsigned char *buffer, unsigned int len)
 106 {
 107         unsigned long flags;
 108         unsigned int ret;
 109
 110         spin_lock_irqsave(fifo->lock, flags);
 111
 112         ret = __kfifo_get(fifo, buffer, len);
 113
 114         /*
 115          * optimization: if the FIFO is empty, set the indices to 0
 116          * so we don't wrap the next time
 117          */
 118         if (fifo->in == fifo->out)
 119                 fifo->in = fifo->out = 0;
 120
 121         spin_unlock_irqrestore(fifo->lock, flags);
 122
 123         return ret;
 124 }
 125
 126 /**
 127  * __kfifo_len - returns the number of bytes available in the FIFO, no locking version
 128  * @fifo: the fifo to be used.
 129  */
 130 static inline unsigned int __kfifo_len(struct kfifo *fifo)
 131 {
 132         return fifo->in - fifo->out;
 133 }
 134
 135 /**
 136  * kfifo_len - returns the number of bytes available in the FIFO
 137  * @fifo: the fifo to be used.
 138  */
 139 static inline unsigned int kfifo_len(struct kfifo *fifo)
 140 {
 141         unsigned long flags;
 142         unsigned int ret;
 143
 144         spin_lock_irqsave(fifo->lock, flags);
 145
 146         ret = __kfifo_len(fifo);
 147
 148         spin_unlock_irqrestore(fifo->lock, flags);
 149
 150         return ret;
 151 }
 152
 153 #endif