drivers/char/nozomi/kfifo.c

   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
  22 #include <linux/kernel.h>
  23 #include <linux/module.h>
  24 #include <linux/slab.h>
  25 #include <asm/uaccess.h>
  26 #include <linux/err.h>
  27 #include "kfifo.h"
  28
  29
  30 /**
  31  * kfifo_init - allocates a new FIFO using a preallocated buffer
  32  * @buffer: the preallocated buffer to be used.
  33  * @size: the size of the internal buffer, this have to be a power of 2.
  34  * @gfp_mask: get_free_pages mask, passed to kmalloc()
  35  * @lock: the lock to be used to protect the fifo buffer
  36  *
  37  * Do NOT pass the kfifo to kfifo_free() after use ! Simply free the
  38  * struct kfifo with kfree().
  39  */
  40 struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
  41                          unsigned int  gfp_mask, void *lock)
  42 {
  43         struct kfifo *fifo;
  44
  45         /* size must be a power of 2 */
  46         BUG_ON(size & (size - 1));
  47
  48         fifo = kmalloc(sizeof(struct kfifo), gfp_mask);
  49         if (!fifo)
  50                 return ERR_PTR(-ENOMEM);
  51
  52         fifo->buffer = buffer;
  53         fifo->size = size;
  54         fifo->in = fifo->out = 0;
  55
  56         return fifo;
  57 }
  58
  59 /**
  60  * kfifo_alloc - allocates a new FIFO and its internal buffer
  61  * @size: the size of the internal buffer to be allocated.
  62  * @gfp_mask: get_free_pages mask, passed to kmalloc()
  63  * @lock: the lock to be used to protect the fifo buffer
  64  *
  65  * The size will be rounded-up to a power of 2.
  66  */
  67 struct kfifo *kfifo_alloc(unsigned int size, unsigned int  gfp_mask, void *lock)
  68 {
  69         unsigned char *buffer;
  70         struct kfifo *ret;
  71
  72         /*
  73          * round up to the next power of 2, since our 'let the indices
  74          * wrap' tachnique works only in this case.
  75          */
  76         if (size & (size - 1)) {
  77                 BUG_ON(size > 0x80000000);
  78                 printk("Do not support no power of two!\n");
  79                 //size = roundup_pow_of_two(size);
  80         }
  81
  82         buffer = kmalloc(size, gfp_mask);
  83         if (!buffer)
  84                 return ERR_PTR(-ENOMEM);
  85
  86         ret = kfifo_init(buffer, size, gfp_mask, lock);
  87
  88         if (IS_ERR(ret))
  89                 kfree(buffer);
  90
  91         return ret;
  92 }
  93
  94 /**
  95  * kfifo_free - frees the FIFO
  96  * @fifo: the fifo to be freed.
  97  */
  98 void kfifo_free(struct kfifo *fifo)
  99 {
 100         kfree(fifo->buffer);
 101         kfree(fifo);
 102 }
 103
 104 /**
 105  * __kfifo_put - puts some data into the FIFO, no locking version
 106  * @fifo: the fifo to be used.
 107  * @buffer: the data to be added.
 108  * @len: the length of the data to be added.
 109  *
 110  * This function copies at most 'len' bytes from the 'buffer' into
 111  * the FIFO depending on the free space, and returns the number of
 112  * bytes copied.
 113  *
 114  * Note that with only one concurrent reader and one concurrent
 115  * writer, you don't need extra locking to use these functions.
 116  */
 117 unsigned int __kfifo_put(struct kfifo *fifo,
 118                          unsigned char *buffer, unsigned int len)
 119 {
 120         unsigned int l;
 121
 122         len = min(len, fifo->size - fifo->in + fifo->out);
 123
 124         /* first put the data starting from fifo->in to buffer end */
 125         l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
 126         memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
 127
 128         /* then put the rest (if any) at the beginning of the buffer */
 129         memcpy(fifo->buffer, buffer + l, len - l);
 130
 131         fifo->in += len;
 132
 133         return len;
 134 }
 135
 136 /** __kfifio_put_user works like __kfifo_put, but copies data from
 137  *  user space.
 138  */
 139
 140 unsigned int __kfifo_put_user(struct kfifo *fifo,
 141                          unsigned char *buffer, unsigned int len)
 142 {
 143         unsigned int l;
 144
 145         len = min(len, fifo->size - fifo->in + fifo->out);
 146
 147         /* first put the data starting from fifo->in to buffer end */
 148         l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
 149         copy_from_user(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
 150
 151         /* then put the rest (if any) at the beginning of the buffer */
 152         copy_from_user(fifo->buffer, buffer + l, len - l);
 153
 154         fifo->in += len;
 155
 156         return len;
 157 }
 158
 159
 160
 161 /**
 162  * __kfifo_get - gets some data from the FIFO, no locking version
 163  * @fifo: the fifo to be used.
 164  * @buffer: where the data must be copied.
 165  * @len: the size of the destination buffer.
 166  *
 167  * This function copies at most 'len' bytes from the FIFO into the
 168  * 'buffer' and returns the number of copied bytes.
 169  *
 170  * Note that with only one concurrent reader and one concurrent
 171  * writer, you don't need extra locking to use these functions.
 172  */
 173 unsigned int __kfifo_get(struct kfifo *fifo,
 174                          unsigned char *buffer, unsigned int len)
 175 {
 176         unsigned int l;
 177
 178         len = min(len, fifo->in - fifo->out);
 179
 180         /* first get the data from fifo->out until the end of the buffer */
 181         l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
 182         memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
 183
 184         /* then get the rest (if any) from the beginning of the buffer */
 185         memcpy(buffer + l, fifo->buffer, len - l);
 186
 187         fifo->out += len;
 188
 189         return len;
 190 }