sys/arch/i386/stand/lib/diskbuf.c

   1 /*      $NetBSD: diskbuf.c,v 1.6 2005/12/11 12:17:48 christos Exp $     */
   2
   3 /*
   4  * Copyright (c) 1996
   5  *      Matthias Drochner.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  *
  27  */
  28
  29 /* data buffer for BIOS disk / DOS I/O  */
  30
  31 #include <lib/libsa/stand.h>
  32 #include "diskbuf.h"
  33
  34 char *diskbufp;         /* allocated from heap */
  35
  36 const void *diskbuf_user;
  37
  38 /*
  39  * Global shared "diskbuf" is used as read ahead buffer.
  40  * This MAY have to not cross a 64k boundary.
  41  * In practise it is allocated out of the heap early on...
  42  * NB a statically allocated diskbuf is not guaranteed to not
  43  * cross a 64k boundary.
  44  */
  45 char *
  46 alloc_diskbuf(const void *user)
  47 {
  48         diskbuf_user = user;
  49         if (!diskbufp) {
  50                 diskbufp = alloc(DISKBUFSIZE);
  51                 if (((int)diskbufp & 0xffff) + DISKBUFSIZE > 0x10000) {
  52                         printf("diskbufp %x\n", (unsigned)diskbufp);
  53                         panic("diskbuf crosses 64k boundary");
  54                 }
  55         }
  56         return diskbufp;
  57 }