LXR linux-bk/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#ifdef __KERNEL__
  25
  26#include <linux/kernel.h>
  27#include <linux/spinlock.h>
  28
  29struct kfifo {
  30        unsigned char *buffer;  /* the buffer holding the data */
  31        unsigned int size;      /* the size of the allocated buffer */
  32        unsigned int in;        /* data is added at offset (in % size) */
  33        unsigned int out;       /* data is extracted from off. (out % size) */
  34        spinlock_t *lock;       /* protects concurrent modifications */
  35};
  36
  37extern struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
  38                                int gfp_mask, spinlock_t *lock);
  39extern struct kfifo *kfifo_alloc(unsigned int size, int gfp_mask,
  40                                 spinlock_t *lock);
  41extern void kfifo_free(struct kfifo *fifo);
  42extern unsigned int __kfifo_put(struct kfifo *fifo,
  43                                unsigned char *buffer, unsigned int len);
  44extern unsigned int __kfifo_get(struct kfifo *fifo,
  45                                unsigned char *buffer, unsigned int len);
  46
  47/*
  48 * __kfifo_reset - removes the entire FIFO contents, no locking version
  49 * @fifo: the fifo to be emptied.
  50 */
  51static inline void __kfifo_reset(struct kfifo *fifo)
  52{
  53        fifo->in = fifo->out = 0;
  54}
  55
  56/*
  57 * kfifo_reset - removes the entire FIFO contents
  58 * @fifo: the fifo to be emptied.
  59 */
  60static inline void kfifo_reset(struct kfifo *fifo)
  61{
  62        unsigned long flags;
  63
  64        spin_lock_irqsave(fifo->lock, flags);
  65
  66        __kfifo_reset(fifo);
  67
  68        spin_unlock_irqrestore(fifo->lock, flags);
  69}
  70
  71/*
  72 * kfifo_put - puts some data into the FIFO
  73 * @fifo: the fifo to be used.
  74 * @buffer: the data to be added.
  75 * @len: the length of the data to be added.
  76 *
  77 * This function copies at most 'len' bytes from the 'buffer' into
  78 * the FIFO depending on the free space, and returns the number of
  79 * bytes copied.
  80 */
  81static inline unsigned int kfifo_put(struct kfifo *fifo,
  82                                     unsigned char *buffer, unsigned int len)
  83{
  84        unsigned long flags;
  85        unsigned int ret;
  86
  87        spin_lock_irqsave(fifo->lock, flags);
  88
  89        ret = __kfifo_put(fifo, buffer, len);
  90
  91        spin_unlock_irqrestore(fifo->lock, flags);
  92
  93        return ret;
  94}
  95
  96/*
  97 * kfifo_get - gets some data from the FIFO
  98 * @fifo: the fifo to be used.
  99 * @buffer: where the data must be copied.
 100 * @len: the size of the destination buffer.
 101 *
 102 * This function copies at most 'len' bytes from the FIFO into the
 103 * 'buffer' and returns the number of copied bytes.
 104 */
 105static inline unsigned int kfifo_get(struct kfifo *fifo,
 106                                     unsigned char *buffer, unsigned int len)
 107{
 108        unsigned long flags;
 109        unsigned int ret;
 110
 111        spin_lock_irqsave(fifo->lock, flags);
 112
 113        ret = __kfifo_get(fifo, buffer, len);
 114
 115        /*
 116         * optimization: if the FIFO is empty, set the indices to 0
 117         * so we don't wrap the next time
 118         */
 119        if (fifo->in == fifo->out)
 120                fifo->in = fifo->out = 0;
 121
 122        spin_unlock_irqrestore(fifo->lock, flags);
 123
 124        return ret;
 125}
 126
 127/*
 128 * __kfifo_len - returns the number of bytes available in the FIFO, no locking version
 129 * @fifo: the fifo to be used.
 130 */
 131static inline unsigned int __kfifo_len(struct kfifo *fifo)
 132{
 133        return fifo->in - fifo->out;
 134}
 135
 136/*
 137 * kfifo_len - returns the number of bytes available in the FIFO
 138 * @fifo: the fifo to be used.
 139 */
 140static inline unsigned int kfifo_len(struct kfifo *fifo)
 141{
 142        unsigned long flags;
 143        unsigned int ret;
 144
 145        spin_lock_irqsave(fifo->lock, flags);
 146
 147        ret = __kfifo_len(fifo);
 148
 149        spin_unlock_irqrestore(fifo->lock, flags);
 150
 151        return ret;
 152}
 153
 154#else
 155#warning "don't include kernel headers in userspace"
 156#endif /* __KERNEL__ */
 157#endif
 158