Running Linux, 5th Edition - Matthias Kalle Dalheimer [328]
A kernel module for multiplexing the graphics hardware so it can be used by multiple processes. This is called the Direct Rendering Manager (DRM), and the module is hardware specific. The modules are typically located in /lib/modules/2.x.y/kernel/drivers/char/drm. The kernel will normally autoload the correct module when X is started.
The 2D X.org driver. For each type of card there is a 2D driver in X.org that initializes the display, performs 2D drawing, and so forth. The drivers are typically located in /usr/X11R6/lib/modules/drivers/.
The 3D DRI driver. This component talks to the 3D part of the graphics card and effectively converts OpenGL commands to hardware commands. When using direct rendering, the DRI driver is loaded by libGL.so so the application can access the graphics card directly without going through X. The DRI drivers are normally located in /usr/X11R6/lib/modules/dri.
libGL, which is the OpenGL library that client applications must link to in order to use OpenGL. When using direct rendering, libGL loads the DRI driver and uses it directly, and when using indirect rendering (for example, if the X display is remote), it creates GLX commands that are sent to the X server over the regular X socket.
Proprietary drivers
Unfortunately, not all graphics hardware manufacturers want to publish information about how their hardware works. This is especially true for modern 3D accelerated hardware. But fortunately, the X.org XAA driver architecture is binary-compatible even across versions of operating systems (as long as the hardware architecture is the same), so installing a proprieratary binary-only driver is quite easy these days.
NVIDIA and ATI graphics cards are commonly found in PCs today. Newer versions of those cards are not supported by X.org/DRI for 3D hardware accelerated graphics, so we need to use the proprietary drivers published by the manufacturer.
The NVIDIA (http://www.nvidia.com/) driver doesn't seem to use DRI, but the overall design is quite similar. The driver comes as a ready-to-run installer-binary file that builds and installs a kernel module (which corresponds to the DRM driver in DRI) and then installs an X.org 2D XAA driver and replaces the libGL library on the system with an NVIDIA specific one. Notice that the kernel module comes with source code, but the other two components are binary only. For more details about how to install the NVIDIA driver , please read the information available on the company's web site.
ATI (http://www.ati.com/) also provides an accelerated 3D driver for its modern cards for Linux. Unlike NVIDIA's, this one actually uses the DRI framework. Except for that, they work in similar ways: kernel module with source available, binary-only X.org driver, binary-only DRI driver, and a replacement libGL.
Configuring X.org for OpenGL
With all the components of OpenGL and the related drivers in place, you can configure your system to use it.
Diagnosis. glxinfo is a valuable tool for setting up X.org for OpenGL. it gives information about the OpenGL capabilities of the current X11 display. Example output from glxinfo is as follows:
$ glxinfo|less
name of display: :0.0
display: :0 screen: 0
direct rendering: Yes
server glx vendor string: SGI
server glx version string: 1.2
server glx extensions:
GLX_ARB_multisample, ...
client glx vendor string: SGI
client glx version string: 1.4
client glx extensions:
GLX_ARB_get_proc_address, ...
GLX extensions:
GLX_ARB_get_proc_address, ...
OpenGL vendor string: Tungsten Graphics, Inc.
OpenGL renderer string: Mesa
DRI Radeon 20030328 AGP 1x x86/MMX/SSE2 TCL
OpenGL version string: 1.2 Mesa 6.1
OpenGL extensions:
...
This listing shows that we are currently using direct rendering with a Mesa-based DRI driver for an ATI Radeon graphics card. If hardware acceleration was not set up properly or something