1/* $XFree86: mit/server/ddx/x386/vga256/drivers/et4000/bank.s,v 1.11 1993/02/24 10:42:32 dawes Exp $ */ 2/* 3 * Copyright 1990,91 by Thomas Roell, Dinkelscherben, Germany. 4 * 5 * Permission to use, copy, modify, distribute, and sell this software and its 6 * documentation for any purpose is hereby granted without fee, provided that 7 * the above copyright notice appear in all copies and that both that 8 * copyright notice and this permission notice appear in supporting 9 * documentation, and that the name of Thomas Roell not be used in 10 * advertising or publicity pertaining to distribution of the software without 11 * specific, written prior permission. Thomas Roell makes no representations 12 * about the suitability of this software for any purpose. It is provided 13 * "as is" without express or implied warranty. 14 * 15 * THOMAS ROELL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, 16 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO 17 * EVENT SHALL THOMAS ROELL BE LIABLE FOR ANY SPECIAL, INDIRECT OR 18 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, 19 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER 20 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 21 * PERFORMANCE OF THIS SOFTWARE. 22 * 23 * Author: Thomas Roell, roell@informatik.tu-muenchen.de 24 * 25 * $Header: /proj/X11/mit/server/ddx/x386/drivers/et4000/RCS/bank.s,v 1.1 1991/06/02 22:37:04 root Exp $ 26 */ 27 28 29/* 30 * These are here the very lowlevel VGA bankswitching routines. 31 * The segment to switch to is passed via %eax. Only %eax and %edx my be used 32 * without saving the original contents. 33 * 34 * WHY ASSEMBLY LANGUAGE ??? 35 * 36 * These routines must be callable by other assembly routines. But I don't 37 * want to have the overhead of pushing and poping the normal stack-frame. 38 */ 39 40/* 41 * first we have here a mirror for the segment register. That's because a 42 * I/O read costs so much more time, that is better to keep the value of it 43 * in memory. 44 */ 45 46#include "assyntax.h" 47 48 FILE("et4000bank.s") 49 50 AS_BEGIN 51 52 SEG_DATA 53Segment: 54 D_BYTE 0 55 56 57 SEG_TEXT 58 59 ALIGNTEXT4 60 GLOBL GLNAME(ET4000SetRead) 61GLNAME(ET4000SetRead): 62 MOV_B (CONTENT(Segment),AH) 63 AND_B (CONST(0x0f),AH) 64 SHL_B (CONST(4),AL) 65 OR_B (AH,AL) 66 MOV_B (AL,CONTENT(Segment)) 67 MOV_L (CONST(0x3CD),EDX) 68 OUT_B 69 RET 70 71 ALIGNTEXT4 72 GLOBL GLNAME(ET4000SetWrite) 73GLNAME(ET4000SetWrite): 74 MOV_B (CONTENT(Segment),AH) 75 AND_B (CONST(0xf0),AH) 76 OR_B (AH,AL) 77 MOV_B (AL,CONTENT(Segment)) 78 MOV_L (CONST(0x3CD),EDX) 79 OUT_B 80 RET 81 82 ALIGNTEXT4 83 GLOBL GLNAME(ET4000SetReadWrite) 84GLNAME(ET4000SetReadWrite): 85 MOV_B (AL,AH) 86 SHL_B (CONST(4),AH) 87 OR_B (AH,AL) 88 MOV_B (AL,CONTENT(Segment)) 89 MOV_L (CONST(0x3CD),EDX) 90 OUT_B 91 RET 92