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
  27 struct 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
  35 extern struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
  36                                 gfp_t gfp_mask, spinlock_t *lock);
  37 extern struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask,
  38                                  spinlock_t *lock);
  39 extern void kfifo_free(struct kfifo *fifo);
  40 extern unsigned int __kfifo_put(struct kfifo *fifo,
  41                                 unsigned char *buffer, unsigned int len);
  42 extern unsigned int __kfifo_get(struct kfifo *fifo,
  43                                 unsigned char *buffer, unsigned int len);
  44 extern unsigned int __kfifo_get_to_user(struct kfifo *fifo,
  45                                         unsigned char __user *buffer,
  46                                         unsigned int len);
  47
  48 /**
  49  * __kfifo_reset - removes the entire FIFO contents, no locking version
  50  * @fifo: the fifo to be emptied.
  51  */
  52 static inline void __kfifo_reset(struct kfifo *fifo)
  53 {
  54         fifo->in = fifo->out = 0;
  55 }
  56
  57 /**
  58  * kfifo_reset - removes the entire FIFO contents
  59  * @fifo: the fifo to be emptied.
  60  */
  61 static inline void kfifo_reset(struct kfifo *fifo)
  62 {
  63         unsigned long flags;
  64
  65         spin_lock_irqsave(fifo->lock, flags);
  66
  67         __kfifo_reset(fifo);
  68
  69         spin_unlock_irqrestore(fifo->lock, flags);
  70 }
  71
  72 /**
  73  * kfifo_put - puts some data into the FIFO
  74  * @fifo: the fifo to be used.
  75  * @buffer: the data to be added.
  76  * @len: the length of the data to be added.
  77  *
  78  * This function copies at most @len bytes from the @buffer into
  79  * the FIFO depending on the free space, and returns the number of
  80  * bytes copied.
  81  */
  82 static inline unsigned int kfifo_put(struct kfifo *fifo,
  83                                      unsigned char *buffer, unsigned int len)
  84 {
  85         unsigned long flags;
  86         unsigned int ret;
  87
  88         spin_lock_irqsave(fifo->lock, flags);
  89
  90         ret = __kfifo_put(fifo, buffer, len);
  91
  92         spin_unlock_irqrestore(fifo->lock, flags);
  93
  94         return ret;
  95 }
  96
  97 /**
  98  * kfifo_get - gets some data from the FIFO
  99  * @fifo: the fifo to be used.
 100  * @buffer: where the data must be copied.
 101  * @len: the size of the destination buffer.
 102  *
 103  * This function copies at most @len bytes from the FIFO into the
 104  * @buffer and returns the number of copied bytes.
 105  */
 106 static inline unsigned int kfifo_get(struct kfifo *fifo,
 107                                      unsigned char *buffer, unsigned int len)
 108 {
 109         unsigned long flags;
 110         unsigned int ret;
 111
 112         spin_lock_irqsave(fifo->lock, flags);
 113
 114         ret = __kfifo_get(fifo, buffer, len);
 115
 116         /*
 117          * optimization: if the FIFO is empty, set the indices to 0
 118          * so we don't wrap the next time
 119          */
 120         if (fifo->in == fifo->out)
 121                 fifo->in = fifo->out = 0;
 122
 123         spin_unlock_irqrestore(fifo->lock, flags);
 124
 125         return ret;
 126 }
 127
 128 /**
 129  * __kfifo_len - returns the number of bytes available in the FIFO, no locking version
 130  * @fifo: the fifo to be used.
 131  */
 132 static inline unsigned int __kfifo_len(struct kfifo *fifo)
 133 {
 134         return fifo->in - fifo->out;
 135 }
 136
 137 /**
 138  * kfifo_len - returns the number of bytes available in the FIFO
 139  * @fifo: the fifo to be used.
 140  */
 141 static inline unsigned int kfifo_len(struct kfifo *fifo)
 142 {
 143         unsigned long flags;
 144         unsigned int ret;
 145
 146         spin_lock_irqsave(fifo->lock, flags);
 147
 148         ret = __kfifo_len(fifo);
 149
 150         spin_unlock_irqrestore(fifo->lock, flags);
 151
 152         return ret;
 153 }
 154
 155 /**
 156  * kfifo_get_to_user - gets some data from the FIFO
 157  * @fifo: the fifo to be used.
 158  * @buffer: where the data must be copied. user buffer
 159  * @len: the size of the destination buffer.
 160  *
 161  * This function copies at most @len bytes from the FIFO into the
 162  * user @buffer and returns the number of copied bytes.
 163  */
 164 static inline unsigned int kfifo_get_to_user(struct kfifo *fifo,
 165                                              unsigned char __user *buffer,
 166                                              unsigned int len)
 167 {
 168         unsigned long flags;
 169         unsigned int ret;
 170
 171         spin_lock_irqsave(fifo->lock, flags);
 172
 173         ret = __kfifo_get_to_user(fifo, buffer, len);
 174
 175         /*
 176          * optimization: if the FIFO is empty, set the indices to 0
 177          * so we don't wrap the next time
 178          */
 179         if (fifo->in == fifo->out)
 180                 fifo->in = fifo->out = 0;
 181
 182         spin_unlock_irqrestore(fifo->lock, flags);
 183
 184         return ret;
 185 }
 186
 187 #endif