Graphics

SprezzOS contains powerful graphics support.

Screen-based displays (primarily LEDs and CRTs) underpin most users' interactions with their desktops and mobile devices. Modern desktops regularly drive one or more large, colorful, high-resolution LEDs via one or sometimes multiple video cards. Graphics processing units commonly contain more transistors than the CPUs with which they are mated. Despite this, the basic process interface exposed by ANSI C and the UNIX kernel consists of two character streams.

To explain: Gallum, DRM, DRI, KMS, OpenGLES, OpenVG, X, Wayland, widgetsets, VESA. VBE, DDC, EDID, TMDS, DMI, HDMI, DisplayPort...

Displays

Standard Resolutions

Note that these terms are largely meaningless, and have been since SuperVGA.

Physical Connectors

Name	Picture	Standards body	Signal	Data
DE15 (High-density DE-shell, 15 pins)		N/A	Analog	DDC (serial link) / DDC2B (I²C link)
FPD-Link over LVDS (Low Voltage Differential Signaling)	N/A	NatSemi / Silicon Valley Analog (FPD-Link) ANSI/TIA/EIA-644-A (LVDS)	Digital	DDC/CI
DVI (Digital Video Interface)		Digital Display Working Group	Digital (DVI-D) / Analog (DVI-A) / Digital + Analog (DVI-I)	DDC2B
HDMI (High-Definiton Multimedia Interface)		HDMI Forum	Digital	E-DDC + HDCP DDC
DisplayPort		VESA	Digital	DDC

Graphical Output

Graphical output will require some kernel module(s) driving the video device(s). Framebuffer drivers are independent of userspace programs; they create a /dev entry, and can support the system console and the X framebuffer server. Direct Rendering Manager (DRM) drivers are used as part of X11's Direct Rendering Infrastructure (DRI), and require their own X servers. Framebuffer drivers generally accelerate only 2D operations (blitting, rectangular tiling, etc), or none at all. DRM drivers expose a much richer API, and can be used with fully hardware-accelerated X servers. In addition, closed source drivers -- usually paired with their own X servers, and not typically supporting a framebuffer device -- can be used. Use of both the DRI and framebuffer drivers with a device can lead to errors, although sometimes it works fine.

Framebuffer

An abstraction of hardware, mapping memory to displayed pixels. If a framebuffer driver is active, /dev/fbX devices will exist, and the fbset tool can be used to display their statuses. It is generally not advised to use a framebuffer driver at the same time as X-based hardware control, though this sometimes works in practice. When a framebuffer is present and supported at kernel boot time, Linux will display a Tux logo (see right) for each processor in the machine.

Framebuffer devices are typically named /dev/fbX. The fbset command can be used to access and control framebuffer devices. The framebuffer mode is generally configured via the kernel command line or arguments to modprobe(1)/init_module(2).

Xorg

X.org Server 1.13 was released 2012-09-05.

DRI is a combination of DRM, X.org, and Mesa.

Wayland

Wayland is not yet ready for general use.

Wayland is an experimental new compositing X server.

APIs

OpenGL

OpenGL 4.3 was released on 2012-08-06.

Mesa 9.0.1 was released on 2012-11-15.

OpenGL (the Open Graphics Library) is an API specification geared towards hardware-accelerated 3D primitives. On desktop Linux, there are three major implementations of OpenGL:

• NVIDIA's proprietary implementation, which supports most NVIDIA cards
• AMD's proprietary implementation, which supports most AMD cards
• Mesa, an open implementation mixing hardware acceleration with software fallback. It includes:
  • Nouveau, an open implementation for NVIDIA cards
  • Radeon, an open implementation for AMD cards
  • An open implementation for Intel cards

Generally, the proprietary drivers tend to support newer OpenGL features and provide better performance, while the Mesa drivers are more smoothly integrated with the rest of the graphics stack (Kernel Mode Switching, Direct Rendering Infrastructure, XRandr, etc). Standard Linux tools might fail to work with the proprietary drivers, forcing use of proprietary tools to control the device.

EGL

EGL provides window manager-specific functionality for an OpenGL stack.

OpenGL ES

OpenGL ES 3.0 was released on 2012-08-06.

OpenGL for Embedded Systems. Mesa targets this with drivers for:

• OMAP (Texas Instruments)
• SGX (PowerVR)

OpenVG

OpenVG 1.1 was released on 2008-12-09.

Vector graphics acceleration targeting embedded systems (ie, often used in conjunction with OpenGL ES).

See Also

• VGA compatible text mode on Wikipedia
• "The Linux Graphics Stack"