                 ______             ____  ______     _____  ______
                |  ____|           |  _ \|  ____|   / / _ \|  ____|
                | |__ _ __ ___  ___| |_) | |__     / / |_| | |__
                |  __| '__/ _ \/ _ \  _ <|  __|   / /|  _  |  __|
                | |  | | |  __/  __/ |_) | |____ / / | | | | |
                |_|  |_|  \___|\___|____/|______/_/  |_| |_|_|

                   The free VBE/AF driver project, version 1.1

                      http://www.talula.demon.co.uk/freebe/

                    "The nice thing about standards is that
                   there are so many of them to choose from."

# Introduction

VBE/AF is a low level driver interface for accessing graphics hardware. It provides all the same features as VESA 3.0 (access to linear framebuffer video memory, high speed protected mode bank switching, page flipping, hardware scrolling, etc), and adds the ability to use 2D hardware acceleration in an efficient and portable manner. An /AF driver is provided as a disk file (vbeaf.drv), and contains clean 32 bit machine code which can be called directly by a C program. If implemented correctly, these drivers have the potential to be binary portable across multiple operating systems, so the same driver file can be used from DOS, Windows, Linux, etc.

FreeBE/AF is an attempt to implement free VBE/AF drivers on as many cards as possible. This idea came about on the Allegro mailing list, due to the need for a dynamically loadable driver structure that could support hardware acceleration. VBE/AF seemed to fit the bill, and Allegro already had support for the SciTech drivers, so it seemed like a good idea to adopt this format for ourselves. The primary goal is to make these drivers work with Allegro, so the emphasis will be on implementing the functions that Allegro actually uses, but we encourage other developers to join us in taking advantage of this excellent driver architecture.

This project currently provides fully accelerated drivers for a handful of chipsets, plus a number of dumb framebuffer implementations based on the video drivers from older versions of the Allegro library. It has also defined a few extensions to the stock VBE/AF API, which allow Allegro programs to use these drivers in a true protected mode environment without having to resort to the nearptr hack, and provide a number of hook functions that will be needed to remain compatible with future generations of the SciTech drivers.

The current status of the VBE/AF standard is somewhat confused. It was designed by SciTech Software (http://www.scitechsoft.com/), who provide commercial VBE/AF drivers for a wide range of cards as part of their Display Doctor package. It was originally going to be released as a VESA standard, but the VESA people seriously messed this up by charging exorbitant sums of $$$ for copies of the spec. As a result, very few people bothered to support these drivers, and the FreeBE/AF project was only made possible by the information available in the SciTech MGL library source code, and the helpfulness of Kendall Bennett (the designer of the spec) himself. Unfortunately SciTech have now abandoned VBE/AF themselves, replacing it with an equivalent but non-public API called Nucleus, which is only available under NDA. SciTech will continue to provide VBE/AF drivers for the cards which they already support, but will not adding any new ones in the future, so this project is now the only active source of VBE/AF driver implementations.

At present, the Allegro (http://www.talula.demon.co.uk/allegro/) and MGL (http://www.scitechsoft.com) libraries are the only major packages which can take advantage of accelerated VBE/AF drivers. As such, this project is starting to look more like a implementation of video drivers specifically for the Allegro library, rather than a potential industry-wide standard :-) But it doesn't have to be this way! VBE/AF is technically an excellent design: efficient, easy to write and use, and highly portable. If you are writing graphics code, and getting frustrated by the many limitiations imposed by VESA, why not think about using VBE/AF instead? Even better, if you have a card that our project doesn't yet support, why not add a new driver for it? This can be a lot of fun, and we would be delighted to offer any help or advice that you might need.

# Usage

Each driver is located in a different subdirectory. Run "make" to compile them, choose the one you want, copy the vbeaf.drv file from this directory to c:\, and you are ready to go!

The stub directory contains a generic non-accelerated VBE/AF driver. This is not useful in any way, because it simply sits on top of your existing VESA driver and emulates a few "hardware" drawing operations with very slow software implementations. The stub is intended as a starting point for people who want to make drivers for a specific card, and should not be used directly.

To recompile FreeBE/AF, you need a working copy of djgpp. Run "make" to build all the available drivers, or "make dir/vbeaf.drv" to compile a specific driver (replacing {dir} with the directory name, eg. "make stub/vbeaf.drv"). To build the install.exe program for a binary distribution, run "make all" (this requires you to have the Allegro library installed, and the allegro/tools/ directory in your path). This documentation is converted from the custom ._tx format into ASCII and HTML by the Allegro makedoc program: run "make docs" to do this, after putting the makedoc utility somewhere in your path.

FreeBE/AF only supports the VBE/AF 2.0 API. It is not backward compatible with the assembler VBE/AF 1.0 interface, and programs that try to use those obsolete functions will not work correctly.

# Supported Hardware

Not all VBE/AF drivers provide the complete set of possible features. Some may be written in a 100% clean and portable manner, allowing them to be used on any platform, but others make use of the video BIOS in order to set the initial video mode: this makes them a lot easier to write, but means that it can only be used under DOS. Some of the drivers, in particular the ones based on the old Allegro library chipset support, don't support any hardware accelerated drawing at all: these are still usefull because they provide high speed protected mode bank switching and can work around the bugs in some manufacturer's VESA implementations, but are obviously not nearly as cool as a fully accelerated driver.

This table lists the currently available FreeBE/AF drivers, and what features they each provide:

ATI 18800/28800 | Uses BIOS | Banked modes only | Supports farptr extension | Dumb framebuffer

ATI mach64 | Uses BIOS | Banked and linear modes | No FreeBE/AF extensions | Hardware accelerated

Avance Logic ALG-2101, ALG-2201, ALG-2228, ALG-2301, ALG-2302 | Uses BIOS | Banked modes only | No FreeBE/AF extensions | Dumb framebuffer

Cirrus 54xx (not 546x). Should be ok with 5426, 5428, 7541, 7543 | Uses BIOS | Banked and linear modes | No FreeBE/AF extensions | Hardware accelerated

Matrox Millenium, Mystique, Millenium II | Uses BIOS | Banked and linear modes | Supports farptr and config extensions | Hardware accelerated

Paradise | Uses BIOS | Banked modes only | Supports farptr extension | Dumb framebuffer

S3 | Uses BIOS | Banked modes only | Supports farptr extension | Hardware accelerated

Trident TGUI 9440. Doesn't work under Windows! | 100% portable | Banked and linear modes | No FreeBE/AF extensions | Hardware accelerated

Trident | Uses BIOS | Banked modes only | Supports farptr extension | Dumb framebuffer

Tseng ET3000/ET4000/ET6000 | Uses BIOS | Banked modes only | Supports farptr extension | Dumb framebuffer

Video-7 | Uses BIOS | Banked modes only | Supports farptr extension | Dumb framebuffer

stub driver (for testing and development purposes only) | Uses BIOS | Banked and linear modes | Supports farptr and config extensions | Slow software emulation of hardware drawing functions

# Contributing

If you want to add a new driver, follow these steps:

          md cardname
          copy stub\*.* cardname
          edit makefile
          { add a new entry to the DRIVERS variable at the top of the file }
          cd cardname
          edit drvhdr.c
          { replace "stub driver implementation" with your driver name }
          edit driver.c
          { fill in the blanks, replacing the VESA calls with chipset-specific }
          { code, and fleshing out the accelerated drawing functions }
          edit notes.txt
          { describe anything interesting about your driver, most importantly }
          { listing what drawing functions it supports in hardware }
          cd..
          done!

The makefile requires each driver to provide a drvhdr.c file, which will be linked into the drvgen.exe utility and used to generate the VBE/AF header. You must also provide a notes.txt, which will be displayed by the installation program, but everything else is entirely up to you. Any C source files placed into your driver directory will automatically be compiled and linked into the driver binary, so you can organise your code in whatever style you prefer.

Because the VBE/AF drivers are output as relocatable binary modules, they cannot use any C library functions. There are a few utility functions in helper.c, but these will not work on any platforms other than DOS+DPMI, so it would be better to avoid using them if you can manage without.

A great deal of hardware information can be found in the VGADOC package (ftp://x2ftp.oulu.fi/pub/msdos/programming/docs/vgadoc4b.zip) and the XFree86 sources (http://www.xfree86.org/). If this isn't enough, try asking the manufacturer for more details.

# Files

       freebe.txt        - ASCII format documentation
       freebe.html       - HTML format documentation
       freebe._tx        - custom format documentation source file
       makefile          - script for building the drivers
       vbeaf.h           - VBE/AF structures and constants
       start.s           - driver relocation code
       helper.c          - debugging trace printf() and VESA helper routines
       drvgen.c          - modified version of DXEGEN, for building vbeaf.drv
       drv.ld            - linker script
       install.c         - installation program for binary distributions

       stub/vbeaf.drv    - example driver, using VESA to access the hardware
       stub/driver.c     - main implementation file for the example driver
       stub/drvhdr.c     - VBE/AF header structure for the example driver
       stub/notes.txt    - more information about the example driver

       ati/              - ATI 18800/28800 driver, based on old Allegro code
       avance/           - Avance Logic driver, by George Foot
       cirrus54/         - Cirrus 54x driver, by Michal Mertl
       mach64/           - ATI mach64 driver, by Ove Kaaven
       matrox/           - Matrox driver, by Shawn Hargreaves
       paradise/         - Paradise driver, based on old Allegro code
       s3/               - S3 driver, by Michal Stencl
       tgui/             - Trident TGUI 9440 driver, by Salvador Eduardo Tropea
       trident/          - Trident driver, based on old Allegro code
       tseng/            - Tseng driver, based on old Allegro code
       video7/           - Video-7 driver, based on old Allegro code

# Copyright

As the name implies, FreeBE/AF is free. Both the driver binaries and sources may be distributed and modified without restriction. If you find any of this stuff useful, the best way to repay us is by writing a new driver for a card that isn't currently supported.

Disclaimer: no warranty is provided with this software. We are not to be held liable if it fries your monitor, eats your graphics card, or roasts your motherboard.

# Credits

The DRVGEN utility is based on the djgpp DXEGEN system, by Charles Sandmann (sandmann@clio.rice.edu) and DJ Delorie (dj@delorie.com).

Linking/relocation system and ATI mach64 driver by Ove Kaaven (ovek@arcticnet.no).

VBE/AF framework, stub driver, Matrox driver, most of the old Allegro chipset drivers, conversion from Allegro to VBE/AF format, and installation program by Shawn Hargreaves (shawn@talula.demon.co.uk).

Cirrus 54x driver by Michal Mertl (mime@eunet.cz).

Trident TGUI 9440 driver by Salvador Eduardo Tropea (set-soft@usa.net).

Avance Logic driver by George Foot (george.foot@merton.oxford.ac.uk).

Fixes to the Cirrus 5446 MMIO routines by Keir Fraser (kaf24@cam.ac.uk).

Tseng ET6000 support by Ben Chauveau (bendomc@worldnet.fr).

Paradise driver by Francois Charton (deef@pobox.oleane.com).

Tseng ET4000 15/24 bit support by Marco Campinoti (marco@etruscan.li.it).

Trident driver improved by Mark Habersack (grendel@ananke.amu.edu.pl).

Video-7 fixes by Markus Oberhumer (markus.oberhumer@jk.uni-linz.ac.at).

S3 driver improved by Michael Bukin (M.A.Bukin@inp.nsk.su).

Video-7 driver by Peter Monks (Peter_Monks@australia.notes.pw.com).

S3 hardware acceleration by Michal Stencl (stenclpmd@ba.telecom.sk).

Website logo by Colin Walsh (cwalsh@nf.sympatico.ca).

More graphics hardware support by [insert your name here] :-)

VBE/AF itself is the brainchild of SciTech software, and in particular Kendall Bennett (KendallB@scitechsoft.com).

The Video Electronics Standards Association does _not_ deserve any mention here. The absurd prices they charge for copies of the /AF specification have prevented it from being widely supported, and I think this is a great pity. Long live freedom!

# History

30 March, 1998 - v0.1. First public release, containing an example driver implementation that runs on top of VESA.

31 March, 1998 - v0.11. Added support for multi-buffered modes.

5 April, 1998 - v0.2. Added an accelerated Matrox driver.

8 April, 1998 - v0.3. Added accelerated drivers for ATI mach64 and Cirrus 54x cards, plus minor updates to the Matrox driver.

12 April, 1998 - v0.4. Proper installation program, more drawing functions implemented by the stub and Matrox drivers, improved ATI driver, compiled with PGCC for a 5% speed boost.

26 April, 1998 - v0.5. More accelerated features in the Cirrus and ATI drivers. Fixed bugs in the Matrox driver. Added an option to disable hardware emulation in the stub driver, which produces a non-accelerated, dumb framebuffer implementation. The init code will now politely fail any programs that try to use VBE/AF 1.0 functions, rather than just crashing.

10 June, 1998 - v0.6. Fixed scrolling problem on Millenium cards.

1 November, 1998 - v0.7. Added drivers for Trident TGUI 9440 and Avance Logic cards, and improved the build process.

14 December, 1998 - v0.8. Bugfixes to the Matrox Millenium II and Cirrus drivers. Converted all the old Allegro library chipset drivers into non-accelerated VBE/AF format, adding support for ATI 18800/28800, Paradise, S3, Trident, Tseng ET3000/ET4000/ET6000, and Video-7 boards. Designed and implemented an API extension mechanism, providing the ability to use these drivers in a true protected mode environment, a more rational relocation scheme, and various hooks that will later be needed for supporting the SciTech Nucleus drivers.

20 December, 1998 - v0.9. Bugfixes. Added a config mechanism, allowing the install program to optionally disable some features of a driver.

3 January, 1999 - v1.0 Bugfixes.

27 March, 1999 - v1.1 Added acceleration support to the S3 driver, plus some bugfixes.