                               DRI User Guide

          VA Linux Systems, Inc. Professional Services - Graphics.

                              20 November 2000

1.  Preamble

1.1  Copyright

Copyright © 2000 by VA Linux Systems, Inc.  All Rights Reserved.

Permission is granted to make and distribute verbatim copies of this document
provided the copyright notice and this permission notice are preserved on all
copies.

1.2  Trademarks

OpenGL is a registered trademark and SGI is a trademark of Silicon Graphics,
Inc.  Unix is a registered trademark of The Open Group.  The `X' device and X
Window System are trademarks of The Open Group.  XFree86 is a trademark of
The XFree86 Project.  Linux is a registered trademark of Linus Torvalds.
Intel is a registered trademark of Intel Corporation.  3Dlabs, GLINT, and
Oxygen are either registered trademarks or trademarks of 3Dlabs Inc. Ltd.
3dfx, Voodoo3, Voodoo4, and Voodoo5 are registered trademarks of 3dfx Inter-
active, Incorporated.  Matrox is a registered trademark of Matrox Electronic
Systems Ltd.  ATI Rage is a registered trademark of ATI Technologies, Inc.
All other trademarks mentioned are the property of their respective owners.

2.  Introduction

With XFree86 4.0 and the Direct Rendering Interface (DRI), hardware acceler-
ated 3D graphics can be considered a standard feature on Linux workstations.
Support for other operating systems, such as FreeBSD, is underway.

This document describes how to use the DRI system and troubleshoot problems
which may occur.  Readers should have a basic understanding of Linux, X and
OpenGL.  See the resources section at the end for more documentation and
software downloads.

This document does not cover compilation or installation of XFree86 4.0.  It
is assumed that you've already installed a Linux distribution which includes
XFree86 4.0 or that you're an experienced Linux developer who has compiled
the DRI for himself.  DRI download, compilation and installation instructions
can be found at http://dri.sourceforge.net/DRIcompile.html

Edits, corrections and updates to this document may be mailed to brianp@val-
inux.com.

3.  Supported Architectures & Hardware

     "

3.1  Architectures

     "

The Architectures currently supported by the DRI have grown from the initial
Intel i386 based machines to now include, the Alpha Processor and the Sun
SPARC machines.

The build environment for both of these new architectures have a pre-build
environment that will correctly build the DRI drivers and Mesa meaning no
extra configuration is necessary to build the DRI for these architectures.

3.1.1  Alpha Features

     "

On newer Alpha processors, it should be noted that a significant performance
increase can be seen with the addition of the -mcpu= command that should be
passed to GCC upon compilation. Dependent of the architecture of the proces-
sor, for example -mcpu=ev6 will build specifically for the EV6 based AXP's,
giving both byte and word alignment access to the DRI/Mesa drivers.

Use this as an example of compiling with this extra speed.  In your host.def
file that should reside in the xc/config directory, add the line.

#define DefaultGcc2AxpOpt -O2 -mcpu=ev6

Additional speed improvements to 3D rendering can be achieved by installing
Compaq's Math Libraries (CPML) which can be obtained from the following URL.

http://www.support.compaq.com/alpha-tools/software/index.html

Once installed, you can set this option in your host.def to build against the
CPML libraries.

#define UseCompaqMathLibrary YES

3.2  Graphics Hardware

     "

XFree86 4.0 (or later versions) includes 3D acceleration for the following
graphics hardware:

NOTE: This is a complete list of graphics hardware supported. It may not be
supported on your platform.

   o 3dfx:

        o Voodoo5 5500

        o Voodoo3 3500 TV

        o Voodoo3 3000 AGP

        o Voodoo3 3000 PCI

        o Voodoo3 2000 AGP

        o Voodoo3 2000 PCI

        o Voodoo Banshee

        o Velocity 100/200

     There are many configurations of 3dfx cards on the market.  Not all have
     been tested.

   o Matrox:

        o Matrox G200

        o Matrox G400

   o Intel i810

        o i810

        o i810-dc100

        o i810e

   o ATI Rage 128

        o Rage Fury AGP

        o Rage Magnum AGP

        o XPERT 2000 AGP

        o XPERT 128 AGP

        o XPERT 99 AGP

        o All-in-Wonder 128 AGP

     The PCI versions of these cards also have minimal support.  Note that
     there are also Rage 128 Pro based boards on the market, and these are
     not yet supported.

   o 3Dlabs Oxygen GMX 2000 (MX/Gamma based)

Support for other hardware is underway.

4.  Prerequisite Software

   o The DRI is available in XFree86 4.0 and later.

   o Some hardware drivers require specific versions of the Linux kernel for
     AGP support, etc.  See section 10 for specifics.

   o You DO NOT need to install Mesa separately.  The parts of Mesa needed
     for hardware acceleration are already in the XFree86/DRI project.

5.  Kernel Modules

    "

3D hardware acceleration requires a DRI kernel module that's specific to your
graphics hardware.

The DRI kernel module version must exactly match your running kernel version.
Since there are so many versions of the kernel, it's difficult to provide
precompiled kernel modules.

While the Linux source tree includes the DRI kernel module sources, the lat-
est DRI kernel sources will be found in the DRI source tree.

See the DRI Compilation Guide for information on compiling the DRI kernel
modules.

XFree86 4.0.1 added automatic kernel module loading to the X server.  On
Linux, the X server uses modprobe to load kernel modules.  In Linux 2.4.x the
DRM kernel modules should be kept in /lib/modules/2.4.x/ker-
nel/driver/char/drm/ for automatic loading to work.

Optionally, DRM kernel modules can be loaded manually with insmod prior to
starting the X server.

You can verify that the kernel module was installed with lsmod, checking the
X server startup log, and checking that /proc/dri/0 exists.

6.  XF86Config file

      "

The XFree86 configuration file is usually found in /etc/X11/XF86Config.  This
section describes the parts which must be specially set for the DRI.

First, the XF86Config file must load the GLX and DRI modules:

          Section "Module"
          ...
          # This loads the GLX module
              Load       "glx"
          # This loads the DRI module
              Load       "dri"
          EndSection

Next, the DRI section can be used to restrict access to direct rendering.

If you want all of the users on your system to be able to use direct-render-
ing, then use a simple DRI section:

          Section "DRI"
               Mode 0666
          EndSection

This section will allow any user with a current connection to the X server to
use direct rendering.

If you want to restrict the use of direct-rendering to a certain group of
users, then create a group for those users by editing the /etc/group file on
your system.  For example, you may want to create a group called xf86dri and
place two users (e.g., fred and jane) in that group.  To do that, you might
add the following line to /etc/group:

             xf86dri:x:8000:fred,jane

You have to be careful that the group id (8000 in this example) is unique.

Then you would use the following DRI section:

             Section "DRI"
                  Group "xf86dri"
                  Mode 0660
             EndSection

This would limit access to direct-rendering to those users in the xf86dri
group (fred and jane in this example).  When other users tried to use direct
rendering, they would fall back to unaccelerated indirect rendering.

[Note that there is a known bug in XFree86 4.0 that prevents some changes to
the DRI section from taking effect.  Until this bug is fixed, if you change
the DRI section, please also remove the /dev/dri directory with the rm -rf
/dev/dri command.]

Finally, the XF86Config file needs Device and Screen sections specific to
your hardware.  Look in section 10: Hardware-Specific Information and Trou-
bleshooting for details.

7.  Memory usage

Using the 3D features of a graphics card requires more memory than when it's
just used as a 2D device.  Double buffering, depth buffering, stencil
buffers, textures, etc. all require extra graphics memory.  These features
may require four times the memory used for a simple 2D display.

If your graphics card doesn't have a lot of memory (less than 16MB, for exam-
ple), you may have to reduce your screen size and/or color depth in order to
use 3D features.  Reducing the screen resolution will also leave more space
for texture images, possibly improving 3D performance.  If, for example, you
play Quake3 at 1024x768 but start your display at 1600x1200 you might con-
sider restarting X at 1024x768 in order to maximize your texture memory
space.

The documentation included with your card should have information about maxi-
mum screen size when using 3D.

8.  Using 3D Acceleration

This section describes how to link your application with libGL.so and verify
that you are in fact using 3D acceleration.

8.1  libGL.so

Your OpenGL program must link with the libGL.so.1.2 library provided by
XFree86 4.0.  The libGL.so.1.2 library contains a GLX protocol encoder for
indirect/remote rendering and DRI code for accessing hardware drivers.  In
particular, be sure you're not using libGL.so from another source such as
Mesa or the Utah GLX project.

Unless it was built in a special way, the libGL.so library does not contain
any 3D hardware driver code.  Instead, libGL.so dynamically loads the appro-
priate 3D driver during initialization.

Most simple OpenGL programs also use the GLUT and GLU libraries.  A source
for these libraries is listed in the Resources section below.

8.2  Compiling and linking an OpenGL program

A simple GLUT/OpenGL program may be compiled and linked as follows:

             gcc program.c -I/usr/local/include -L/usr/local/lib -L/usr/X11R6/lib -lglut -lGLU -lGL -o program

The -I option is used to specify where the GL/glut.h (and possibly the
GL/gl.h and GL/glu.h) header file may be found.

The -L options specify where the libglut.so and the X libraries are located.
libGL.so and libGLU.so should be in /usr/lib, as specified by the
Linux/OpenGL ABI standard.

The -lglut -lGLU -lGL arguments specify that the application should link with
the GLUT, GLU and GL libraries, in that order.

8.3  Running your OpenGL program

Simply typing ./program in your shell should execute the program.

If you get an error message such as

             gears: error in loading shared libraries: libGL.so.1: cannot
             open shared object file: No such file or directory

if means that the libGL.so.1 file is not the right location.  Proceed to the
trouble shooting section.

8.4  libOSMesa.so

OSMesa (Off-Screen Mesa) is an interface and driver for rendering 3D images
into a user-allocated block of memory rather than an on-screen window.  It
was originally developed for Mesa before Mesa became part of the XFree86/DRI
project.  It can now be used with the XFree86/DRI libGL.so as well.

libOSMesa.so implements the OSMesa interface and it must be linked with your
application if you want to use the OSMesa functions.  You must also link with
libGL.so.  For example:

             gcc osdemo.c -lOSMesa -lGLU -lGL -o osdemo

In stand-alone Mesa this interface was compiled into the monolithic libGL.so
(formerly libMesaGL.so) library.  In XFree86 4.0.1 and later this interface
is implemented in a separate library.

8.5  glxinfo

glxinfo is a useful program for checking which version of libGL you're using
as well as which DRI-based driver.  Simply type glxinfo and examine the
OpenGL vendor, renderer, and version lines.  Among the output you should see
something like this:

               OpenGL vendor string: Precision Insight, Inc.
               OpenGL renderer string: Mesa DRI Voodoo3 20000224
               OpenGL version string: 1.2 Mesa 3.3 beta

or this:

               OpenGL vendor string: Precision Insight, Inc.
               OpenGL renderer string: Mesa GLX Indirect
               OpenGL version string: 1.2 Mesa 3.3 beta

The first example indicates that the 3dfx driver is using Voodoo3 hardware.
The second example indicates that no hardware driver was found and indirect,
unaccelerated rendering is being used.

If you see that indirect rendering is being used when direct rendering was
expected, proceed to the troubleshooting section.

glxinfo also lists all of the GLX-enhanced visuals available so you can
determine which visuals are double-bufferd, have depth (Z) buffers, stencil
buffers, accumulation buffers, etc.

8.6  Environment Variables

The libGL.so library recognizes three environment variables.  Normally, none
of them need to be defined.  If you're using the csh or tcsh shells, type
setenv VARNAME value to set the variable.  Otherwise, if you're using sh or
bash, type export VARNAME=value.

  1.  LIBGL_DEBUG, if defined will cause libGL.so to print error and diagnos-
      tic messages.  This can help to solve problems.  Setting LIBGL_DEBUG to
      verbose may provide additional information.

  2.  LIBGL_ALWAYS_INDIRECT, if defined this will force libGL.so to always
      use indirect rendering instead of hardware acceleration.  This can be
      useful to isolate rendering errors.

  3.  LIBGL_DRIVERS_PATH can be used to override the default directories
      which are searched for 3D drivers.  The value is one or more paths sep-
      arated by colons.  In a typical XFree86 installation, the 3D drivers
      should be in /usr/X11R6/lib/modules/dri/ and LIBGL_DRIVERS_PATH need
      not be defined.  Note that this feature is disabled for set-uid pro-
      grams.  This variable replaces the LIBGL_DRIVERS_DIR env var used in
      XFree86 4.0.

  4.  MESA_DEBUG, if defined, will cause Mesa-based 3D drivers to print user
      error messages to stderr.  These are errors that you'd otherwise detect
      by calling glGetError.

Mesa-based drivers (this includes most of the drivers listed above) also
observe many of the existing Mesa environment variables.  These include the
MESA_DEBUG and MESA_INFO variables.

9.  General Trouble Shooting

This section contains information to help you diagnose general problems.  See
below for additional information for specific hardware.

9.1  The X Server

  1.  Before you start the X server, verify the appropriate 3D kernel module
      is installed.  Type lsmod and look for the appropriate kernel module.
      For 3dfx hardware you should see tdfx, for example.

  2.  Verify you're running XFree86 4.0 (or newer) and not an older version.
      If you run xdpyinfo and look for the following line near the top:

                       vendor release number:    4000

  3.  Verify that your XF86Config file (usually found at /etc/X11/XF86Config)
      loads the glx and dri modules and has a DRI section.

      See the Software Resources section below for sample XF86Config files.

  4.  Examine the messages printed during X server startup and check that the
      DRM module loaded.  Using the Voodoo3 as an example:

                   (==) TDFX(0): Write-combining range (0xf0000000,0x2000000)
                   (II) TDFX(0): Textures Memory 7.93 MB
                   (0): [drm] created "tdfx" driver at busid "PCI:1:0:0"
                   (0): [drm] added 4096 byte SAREA at 0xc65dd000
                   (0): [drm] mapped SAREA 0xc65dd000 to 0x40013000
                   (0): [drm] framebuffer handle = 0xf0000000
                   (0): [drm] added 1 reserved context for kernel
                   (II) TDFX(0): [drm] Registers = 0xfc000000
                   (II) TDFX(0): visual configs initialized
                   (II) TDFX(0): Using XFree86 Acceleration Architecture (XAA)
                           Screen to screen bit blits
                           Solid filled rectangles
                           8x8 mono pattern filled rectangles
                           Indirect CPU to Screen color expansion
                           Solid Lines
                           Dashed Lines
                           Offscreen Pixmaps
                           Driver provided NonTEGlyphRenderer replacement
                           Setting up tile and stipple cache:
                                   10 128x128 slots
                   (==) TDFX(0): Backing store disabled
                   (==) TDFX(0): Silken mouse enabled
                   (0): X context handle = 0x00000001
                   (0): [drm] installed DRM signal handler
                   (0): [DRI] installation complete
                   (II) TDFX(0): direct rendering enabled

  5.  After the X server has started, verify that the required X server
      extensions are loaded.  Run xdpyinfo and look for the following entries
      in the extensions list:

                  GLX
                  SGI-GLX
                  XFree86-DRI

9.2  Linking, running and verifying 3D acceleration

After you've verified that the X server and DRI have started correctly it's
time to verify that the GL library and hardware drivers are working cor-
rectly.

  1.  Verify that you're using the correct libGL.so library with ldd.  The
      /usr/lib and /usr/X11R6/lib directories are expected locations for
      libGL.so.

      Example:

                   % ldd /usr/local/bin/glxinfo
                           libglut.so.3 => /usr/local/lib/libglut.so.3 (0x40019000)
                           libGLU.so.1 => /usr/local/lib/libGLU.so.1 (0x40051000)
                           libGL.so.1 => /usr/lib/libGL.so.1 (0x40076000)
                           libXmu.so.6 => /usr/X11R6/lib/libXmu.so.6 (0x402ee000)
                           libXi.so.6 => /usr/X11R6/lib/libXi.so.6 (0x40301000)
                           libm.so.6 => /lib/libm.so.6 (0x40309000)
                           libc.so.6 => /lib/libc.so.6 (0x40325000)
                           libX11.so.6 => /usr/X11R6/lib/libX11.so.6 (0x40419000)
                           libXt.so.6 => /usr/X11R6/lib/libXt.so.6 (0x404bd000)
                           libSM.so.6 => /usr/X11R6/lib/libSM.so.6 (0x40509000)
                           libICE.so.6 => /usr/X11R6/lib/libICE.so.6 (0x40512000)
                           libXext.so.6 => /usr/X11R6/lib/libXext.so.6 (0x40529000)
                           libvga.so.1 => /usr/lib/libvga.so.1 (0x40537000)
                           libpthread.so.0 => /lib/libpthread.so.0 (0x4057d000)
                           /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

  2.  You may also double check that libGL.so is in fact DRI-capable.  Run
      strings libGL.so.1.2 | grep DRI and look for symbols prefixed with
      "XF86DRI", such as "XF86DRIQueryExtension".

  3.  To be safe one should run ldconfig after installing libGL.so to be sure
      the runtime loader will find the proper library.

  4.  Verify that the appropriate 3D driver is in /usr/X11R6/lib/modules/dri/
      For example, the 3dfx driver will be named tdfx_dri.so.

  5.  Set the LIBGL_DEBUG environment variable.  This will cause libGL.so to
      print an error message if it fails to load a DRI driver.  Any error
      message printed should be self-explanatory.

  6.  Run glxinfo.  Note the line labeled "OpenGL renderer string".  It
      should have a value which starts with "Mesa DRI" followed by the name
      of your hardware.

  7.  Older Linux OpenGL applications may have been linked against Mesa's GL
      library and will not automatically use libGL.so.  In some cases, making
      symbolic links from the Mesa GL library to libGL.so.1 will solve the
      problem:

                   ln -s libGL.so.1 libMesaGL.so.3

      In other cases, the application will have to be relinked against the
      new XFree86 libGL.so.

      It is reported that part of the problem is that running ldconfig will
      silently rewrite symbolic links based on the SONAME field in libraries.

If you're still having trouble, look in the next section for information spe-
cific to your graphics card.

10.  Hardware-Specific Information and Troubleshooting

This section presents hardware-specific information for normal use and trou-
bleshooting.

10.1  3dfx Voodoo3 Series

10.1.1  Dependencies

The Voodoo3 DRI driver requires a special versions of the 3dfx Glide library.
It can be downloaded from the DRI website.

10.1.2  Configuration

Your XF86Config file's device section must specify the tdfx device:

             Section "Device"
                 Identifier  "Voodoo3"
                 VendorName  "3dfx"
                 Driver      "tdfx"
             EndSection

The Screen section should then reference the Voodoo3 device:

          Section "Screen"
              Identifier  "Screen 1"
              Device      "Voodoo3"
              Monitor     "High Res Monitor"
              DefaultDepth 16
              Subsection "Display"
               Depth       16
               Modes       "1280x1024" "1024x768" "800x600" "640x480"
               ViewPort    0 0
              EndSubsection
             EndSection

The kernel module for the Voodoo3 is named tdfx.o and should be installed in
/lib/modules/2.4.x/kernel/driver/char/drm/.  It will be automatically loaded
by the Xserver if needed.

The DRI 3D driver for the Voodoo3 should be in /usr/X11R6/lib/mod-
ules/dri/tdfx_dri.so.  This will be automatically loaded by libGL.so.

10.1.3  Troubleshooting

   o If you try to run an OpenGL application and see an error message similar
     to

                gd error (glide): gd error (glide): grSstSelect:  non-existent SSTgd error (glide): grSstSelect:  non-existent SSTS

     it means that you have the wrong version of the Glide library for your
     hardware.

   o 3D acceleration for Voodoo3 is only supported in the 16 bit/pixel screen
     mode.  Use xdpyinfo to verify that all your visuals are depth 16.  Edit
     your XF86Config file if needed.

   o The /dev/3dfx device is not used for DRI; it's only for Glide on older
     3dfx hardware.

10.1.4  Performance

   o Normally, buffer swapping in double-buffered applications is synchro-
     nized to your monitor's refresh rate.  This may be overridden by setting
     the FX_GLIDE_SWAPINTERNVAL environment variable.  The value of this
     variable indicates the maximum number of swap buffer commands can be
     buffered.  Zero allows maximum frame rate.

   o The glTexEnv mode GL_BLEND is not directly supported by the Voodoo3
     hardware.  It can be accomplished with a multipass algorithm but it's
     not implemented at this time.  Applications which use that mode, such as
     the Performer Town demo, may become sluggish when falling back to soft-
     ware rendering to render in that mode.

   o The Voodoo3/Banshee driver reverts to software rendering under the fol-
     lowing conditions:

        o Setting GL_LIGHT_MODEL_COLOR_CONTROL to GL_SEPARATE_SPECULAR_COLOR.

        o Enabling line stippling or polygon stippling.

        o Enabling point smoothing or polygon smoothing.

        o Enabling line smoothing when line width is not 1.0.  That is,
          antialiased lines are done in hardware only when the line width is
          1.0.

        o Using 1-D or 3-D texture maps.

        o Using the GL_BLEND texture environment.

        o Using stencil operations.

        o Using the accumulation buffer.

        o Using glBlendEquation(GL_LOGIC_OP).

        o Using glDrawBuffer(GL_FRONT_AND_BACK).

        o Using glPolygonMode(face, GL_POINT) or glPolygonMode(face,
          GL_LINE).

        o Using point size attenuation (i.e. GL_DISTANCE_ATTENUATION_EXT).

        o Using glColorMask(r, g, b, a) when r!=g or g!=b.

10.1.5  Known Problems

   o The Glide library cannot be used directly; it's only meant to be used
     via the tdfx DRI driver.

   o SSystem has problems because of poorly set near and far clipping planes.
     The office.unc Performer model also suffers from this problem.

   o The lowest mipmap level is sometimes miscolored in trilinear- sampled
     polygons.

10.2  3dfx Voodoo5 Series

10.2.1  Dependencies

The Voodoo5 DRI driver requires a special versions of the 3dfx Glide library,
different than that used for Voodoo3 hardware.  It can be downloaded from the
DRI website.

10.2.2  Configuration

Your XF86Config file's device section must specify the tdfx device:

             Section "Device"
                 Identifier  "Voodoo5"
                 VendorName  "3dfx"
                 Driver      "tdfx"
             EndSection

The Screen section should then reference the Voodoo3 device:

          Section "Screen"
              Identifier  "Screen 1"
              Device      "Voodoo5"
              Monitor     "High Res Monitor"
              DefaultDepth 24
              Subsection "Display"
               Depth       16
               Modes       "1280x1024" "1024x768" "800x600" "640x480"
               ViewPort    0 0
              EndSubsection
              Subsection "Display"
               Depth       24
               Modes       "1280x1024" "1024x768" "800x600" "640x480"
               ViewPort    0 0
              EndSubsection
             EndSection

The kernel module for the Voodoo5 is named tdfx.o and should be installed in
/lib/modules/2.4.x/kernel/driver/char/drm/.  It will be automatically loaded
by the Xserver if needed.

The DRI 3D driver for the Voodoo5 should be in /usr/X11R6/lib/mod-
ules/dri/tdfx_dri.so.  This will be automatically loaded by libGL.so.

The Voodoo5 supports 3D rendering in 16 and 32 bpp modes.  When running in
32bpp mode an 8-bit stencil buffer and 24-bit Z (depth) buffer are offered.
When running in 16bpp mode only a 16-bit Z (depth) buffer is offered and
stencil is implemented in software.

A software-based accumulation buffer is available in both 16 and 32bpp modes.

10.2.3  Troubleshooting

   o The /dev/3dfx device is not used for DRI; it's only for Glide on older
     3dfx hardware.

   o Different versions of Glide are needed for Voodoo3 and Voodoo5.  See the
     DRI website's resources page to download the right version of Glide.

10.2.4  Performance

   o Normally, buffer swapping in double-buffered applications is synchro-
     nized to your monitor's refresh rate.  This may be overridden by setting
     the FX_GLIDE_SWAPINTERNVAL environment variable.  The value of this
     variable indicates the maximum number of swap buffer commands can be
     buffered.  Zero allows maximum frame rate.

   o Rendering with 16-bit per texel textures is faster than using 32-bit per
     texel textures.  The internalFormat parameter to glTexImage2D can be
     used to control texel size.

   o The Voodoo5 driver reverts to software rendering under the same condi-
     tions Voodoo3 with three exceptions.  First, stencil operations are
     implemented in hardware when the screen is configured for 32 bits/pixel.
     Second, the GL_BLEND texture env mode is fully supported in hardware.
     Third, glColorMask is fully supported in hardware when the screen is
     configured for 32 bits/pixel.

10.2.5  Known Problems

   o The Glide library cannot be used directly; it's only meant to be used
     via the tdfx DRI driver.

   o 24bpp screen modes are supported by the hardware but not by the current
     driver.  32bpp is fully supported.

   o As of October, 2000 the second VSA-100 chip on the Voodoo5 is not yet
     operational.  Therefore, the board isn't being used to its full capac-
     ity.  The second VSA-100 chip will allow Scan-Line Interleave (SLI) mode
     for full-screen applications and games, potentially doubling the sys-
     tem's fill rate.

10.3  Intel i810

        "

10.3.1  Dependencies

          "

A Linux kernel with AGP GART support is required.  The 2.2.x kernel series
does not have AGP GART support.  The 2.4.x test kernels have AGP GART and
have been tested with the i810.

10.3.2  Configuration

          "

Your XF86Config file's device section must specify the i810 device, and spec-
ify a usable amount of video ram to reserve.

             Section "Device"
                 Identifier  "i810"
                 VendorName  "Intel"
                 Driver      "i810"
              VideoRam    10000
             EndSection

The Screen section should then reference the i810 device:

          Section "Screen"
              Identifier  "Screen 1"
              Device      "i810"
              Monitor     "High Res Monitor"
              DefaultDepth 16
              Subsection "Display"
               Depth       16
               Modes       "1280x1024" "1024x768" "800x600" "640x480"
               ViewPort    0 0
              EndSubsection
             EndSection

The kernel module for the i810 is named i810.o and should be installed in
/lib/modules/2.4.x/kernel/driver/char/drm/.  It will be automatically loaded
by the Xserver if needed.

The DRI 3D driver for the i810 should be in /usr/X11R6/lib/mod-
ules/dri/i810_dri.so.  This will be automatically loaded by libGL.so.

10.3.3  Troubleshooting

   o 3D acceleration for the i810 is only available in the 16 bit/pixel
     screen mode at this time.  32bpp acceleration is not supported by this
     hardware.  Use xdpyinfo to verify that all your visuals are depth 16.
     Edit your XF86Config file if needed.

   o The i810 uses system ram for video and 3d graphics.  The X server will
     ordinarily reserve 4mb of ram for graphics, which is too little for an
     effective 3d setup.  To tell the driver to use a larger amount, specify
     a VideoRam option in the Device section of your XF86Config file.  A num-
     ber between 10000 and 16384 seems adequate for most requirements.  If
     too little memory is available for DMA buffers, back and depth buffers
     and textures, direct rendering will be disabled.

10.4  Matrox G200 and G400

      "

10.4.1  Dependencies

        "

A Linux kernel with AGP GART support (such as the 2.4.x test kernels) is
needed.

10.4.2  Configuration

        "

Your XF86Config file's device section must specify the mga device:

             Section "Device"
                 Identifier  "MGA"
                 VendorName  "Matrox"
                 Driver      "mga"
              VideoRam    32768
             EndSection

The Screen section should then reference the MGA device:

          Section "Screen"
              Identifier  "Screen 1"
              Device      "MGA"
              Monitor     "High Res Monitor"
              DefaultDepth 16
              Subsection "Display"
               Depth       16
               Modes       "1280x1024" "1024x768" "800x600" "640x480"
               ViewPort    0 0
              EndSubsection
             EndSection

To use a 32bpp screen mode, use this Screen section instead:

          Section "Screen"
              Identifier  "Screen 1"
              Device      "MGA"
              Monitor     "High Res Monitor"
              DefaultDepth 24
                 DefaultFbBpp 32
              Subsection "Display"
               Depth       24
               Modes       "1280x1024" "1024x768" "800x600" "640x480"
               ViewPort    0 0
              EndSubsection
             EndSection

The kernel module for the G200/G400 is named mga.o and should be installed in
/lib/modules/2.4.x/kernel/driver/char/drm/.  It will be automatically loaded
by the Xserver if needed.

The DRI 3D driver for the G200/G400 should be in /usr/X11R6/lib/mod-
ules/dri/mga_dri.so.  This will be automatically loaded by libGL.so.

10.4.3  Performance

Software rendering will be used under any of the following conditions:

   o Using glDrawBuffer(GL_FRONT_AND_BACK).

   o Using point, line, or triangle smoothing.

   o Using glLogicOp.

   o Using glPolygonStipple or glLineStipple.

   o Using 1D or 3D textures.

   o Using the accumulation buffer.

10.4.4  IRQ Assignment

There have been problems in the past with the MGA driver being very sluggish
when the DRI is enabled (to the point of being unusable.)  This is caused by
the graphics card not having an interrupt assigned to it.  The current DRI
trunk will attempt to detect this condition and bail out gracefully.

The solution to the above problem is to assign an interrupt to your graphics
card.  This is something you must turn on in your system BIOS configuration.
Please consult your system BIOS manual for instructions on how to enable an
interrupt for your graphics card.

10.4.5  MGA HAL lib

MGAHALlib.a is a binary library Matrox has provided for use under Linux to
expose functionality for which they can not provide documentation.  (For
example TV-Out requires MacroVision be enabled on the output.)  This binary
library also sets the pixel/memory clocks to the optimal settings for your
Matrox card.

Currently the MGAHAL library is required for the G450 to work.  You can down-
load this from the driver section on Matrox's website: www.matrox.com/mga

Here modifications to the DRI build instructions which make the mga ddx
driver use the MGAHAL library:

            1.Put the following define in your host.def file
                 #define UseMatroxHal YES
            2. Place mgaHALlib.a in the following directory
                 xc/programs/Xserver/hw/xfree86/drivers/mga/HALlib/

You can use DualHead on the G400/G450 DH cards by creating two device sec-
tions which both point to the same BusID.  For most AGP devices the BusID
will be "PCI:1:0:0".  Configure your screen section as you would normally
configure XFree86 4.x Multihead.  It should be noted that currently the sec-
ond head does not support direct rendering.

10.4.6  Known Problems

None.

10.5  ATI Rage 128

      "

10.5.1  Dependencies

        "

A Linux kernel with AGP GART support (such as the 2.4.x test kernels) is
needed.

10.5.2  Configuration

        "

Your XF86Config file's device section must specify the r128 device:

             Section "Device"
                 Identifier  "Rage128"
                 VendorName  "ATI"
                 Driver      "r128"
             EndSection

The Screen section should then reference the Rage 128 device:

          Section "Screen"
              Identifier  "Screen 1"
              Device      "Rage128"
              Monitor     "High Res Monitor"
              DefaultDepth 16
              Subsection "Display"
               Depth       16
               Modes       "1280x1024" "1024x768" "800x600" "640x480"
               ViewPort    0 0
              EndSubsection
              Subsection "Display"
               Depth       32
               Modes       "1280x1024" "1024x768" "800x600" "640x480"
               ViewPort    0 0
              EndSubsection
             EndSection

The kernel module for the Rage 128 is named r128.o and should be installed in
/lib/modules/2.4.x/kernel/driver/char/drm/.  It will be automatically loaded
by the Xserver if needed.

The DRI 3D driver for the Rage 128 should be in /usr/X11R6/lib/mod-
ules/dri/r128_dri.so.  This will be automatically loaded by libGL.so.

You may also set your screen depth to 32 for 32bpp mode.

10.5.3  Performance

While PCI Rage 128 based cards are supported, they do not yet support PCI
GART, so they will not perform as well as their AGP counterparts.

10.5.4  Known Problems

DGA is not yet supported in the ATI Rage 128 X server.  This feature will be
added in a future release.

10.6  3DLabs Oxygen GMX 2000

The driver for this hardware was experimental and is no longer being devel-
oped or supported.

11.  General Limitations and Known Bugs

11.1  OpenGL

The following OpenGL features are not supported at this time: overlays,
stereo, hardware-accelerated indirect rendering.

OpenGL-like functionality is provided with the Mesa library.  XFree86 4.0.1
uses Mesa 3.3.  Subsequent releases of XFree86 will use newer versions of
Mesa.  When newer versions of Mesa are available, the 3D drivers can be
updated without reinstalling XFree86 or libGL.so.

11.2  GLX

The GLX 1.3 API is exported but none of the new 1.3 functions are opera-
tional.

The new glXGetProcAddressARB function is fully supported.

GLXPixmap rendering is only supported for indirect rendering contexts.  This
is a common OpenGL limitation.  Attempting to use a direct rendering context
with a GLXPixmap will result in an X protocol error.

11.3  Debugging

Debugging DRI drivers with gdb can be difficult because of the locking
involved.  When debugging OpenGL applications, you should avoid stepping
inside the GL functions.  If you're trying to debug a DRI driver it's recom-
mended that you do so remotely, from a second system.

11.4  Scheduling

When you run multiple GL applications at once you may notice poor time slic-
ing.  This is due to an interaction problem with the Linux scheduler which
will be addressed in the future.

11.5  libGL.so and dlopen()

A number of popular OpenGL applications on Linux (such as Quake3, HereticII,
Heavy Gear 2, etc) dynamically open the libGL.so library at runtime with
dlopen(), rather than linking with -lGL at compile/link time.

If dynamic loading of libGL.so is not implemented carefully, there can be a
number of serious problems.  Here are the things to be careful of in your
application:

   o Specify the RTLD_GLOBAL flag to dlopen().  If you don't do this then
     you'll likely see a runtime error message complaining that _glapi_Con-
     text is undefined when libGL.so tries to open a hardware-specific
     driver.  Without this flag, nested opening of dynamic libraries does not
     work.

   o Do not close the library with dlclose() until after XCloseDisplay() has
     been called.  When libGL.so initializes itself it registers several
     callbacks functions with Xlib.  When XCloseDisplay() is called those
     callback functions are called.  If libGL.so has already been unloaded
     with dlclose() this will cause a segmentation fault.

   o Your application should link with -lpthread.  On Linux, libGL.so uses
     the pthreads library in order to provide thread safety.  There is appar-
     ently a bug in the dlopen()/dlclose() code which causes crashes if the
     library uses pthreads but the parent application doesn't.  The only
     known work-around is to link the application with -lpthread.

Some applications don't yet incorporate these procedures and may fail.  For
example, changing the graphics settings in some video games will expose this
problem.  The DRI developers are working with game vendors to prevent this
problem in the future.

11.6  Bug Database

The DRI bug database which includes bugs related to specific drivers is at
the SourceForge DRI Bug Database

Please scan both the open and closed bug lists to determine if your problem
has already been reported and perhaps fixed.

12.  Resources

12.1  Software

A collection of useful configuration files, libraries, headers, utilities and
demo programs is available from http://dri.source-
forge.net/resources/resources.html

12.2  Documentation

   o General OpenGL information is available at the OpenGL Home Page

   o XFree86 information is available at the XFree86 Home Page

   o Information about the design of the DRI is available from Precision
     Insight, Inc.

   o Visit the DRI project on SourceForge.net for the latest development news
     about the DRI and 3D drivers.

   o The DRI Compilation Guide explains how to download, compile and install
     the DRI for yourself.

12.3  Support

   o The DRI-users mailing list at SourceForge is a forum for people to dis-
     cuss DRI problems.

   o In the future there may be IHV and Linux vendor support resources for
     the DRI.

     Generated from XFree86: xc/programs/Xserver/hw/xfree86/doc/sgml/DRI.sgml,v 1.15 2000/12/12 18:54:29 dawes Exp $


$XFree86: xc/programs/Xserver/hw/xfree86/doc/README.DRI,v 1.12.2.1 2001/03/13 17:19:27 dawes Exp $
