LXR linux/include/linux/kfifo.h

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