The Linux framebuffer (fbdev) is a linux subsystem used to show
graphics
Graphics () are visual images or designs on some surface, such as a wall, canvas, screen, paper, or stone, to inform, illustrate, or entertain. In contemporary usage, it includes a pictorial representation of data, as in design and manufacture, ...
on a
computer monitor
A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a visual display, support electronics, power supply, housing, electrical connectors, and external user controls.
The ...
, typically on the
system console
One meaning of system console, computer console, root console, operator's console, or simply console is the text entry and display device for system administration messages, particularly those from the BIOS or boot loader, the kernel, from the ...
.
It was designed as a hardware-independent
API to give
user space
A modern computer operating system usually segregates virtual memory into user space and kernel space. Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour.
Kernel ...
software access to the
framebuffer
A framebuffer (frame buffer, or sometimes framestore) is a portion of random-access memory (RAM) containing a bitmap that drives a video display. It is a memory buffer containing data representing all the pixels in a complete video frame. Mode ...
(the part of a computer's
video memory
Dynamic random-access memory (dynamic RAM or DRAM) is a type of random-access semiconductor memory that stores each bit of data in a memory cell, usually consisting of a tiny capacitor and a transistor, both typically based on metal-oxid ...
containing a current
video frame) using only the
Linux kernel
The Linux kernel is a free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally authored in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU ...
's own basic facilities and its
device file system interface, avoiding the need for libraries like
SVGAlib
SVGAlib was an open-source low-level graphics library which ran on Linux and FreeBSD and allowed programs to change video mode and display full-screen graphics, without the use of a windowing system. Some popular games like '' Quake'' and ''D ...
which effectively implemented video drivers in
user space
A modern computer operating system usually segregates virtual memory into user space and kernel space. Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour.
Kernel ...
.
In most applications, fbdev has been superseded by the linux
Direct Rendering Manager
The Direct Rendering Manager (DRM) is a subsystem of the Linux kernel responsible for interfacing with GPUs of modern video cards. DRM exposes an API that user-space programs can use to send commands and data to the GPU and perform operations ...
subsystem, but as of 2022, several
drivers provide both DRM and fbdev APIs for backwards compatibility with software that has not been updated to use the DRM system, and there are still fbdev drivers for older (mostly embedded) hardware that does not have a DRM driver.
Applications
There are three applications of the Linux framebuffer:
* An implementation of text
Linux console
The Linux console is a system console internal to the Linux kernel. A system console is the device which receives all kernel messages and warnings and which allows logins in single user mode. The Linux console provides a way for the kernel and ...
that doesn't use hardware
text mode (useful when that mode is unavailable, or to overcome its restrictions on glyph size, number of code points etc.). One popular aspect of this is the ability to have console show the
Tux logo at boot up.
* A possible graphic output method for a
display server
In computing, a windowing system (or window system) is software that manages separately different parts of display screens. It is a type of graphical user interface (GUI) which implements the WIMP ( windows, icons, menus, pointer) paradigm ...
, independent of
video adapter hardware and its drivers.
* Graphic programs avoiding the
overhead of the
X Window System
The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems.
X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wi ...
.
Examples of the third application include Linux programs such as
MPlayer,
links2,
Netsurf,
w3m, fbff, fbida, and fim and libraries such as
GLUT,
SDL (version 1.2),
GTK, and
Qt, which can all use the framebuffer directly. This use case is particularly popular in
embedded system
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded ...
s.
The now defunct
DirectFB is another project aimed at providing a framework for hardware acceleration of the Linux framebuffer.
There was also a windowing system called FramebufferUI (fbui) implemented in kernel-space that provided a basic 2D windowing experience with very little memory use.
History
Linux has generic framebuffer support since 2.1.109 kernel.
Framebuffer HOWTO
/ref>
It was originally implemented to allow the kernel to emulate a text console on systems such as the Apple Macintosh
The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and software ...
that do not have a text-mode display, and was later expanded to Linux's originally supported IBM PC compatible
IBM PC compatible computers are similar to the original IBM PC, XT, and AT, all from computer giant IBM, that are able to use the same software and expansion cards. Such computers were referred to as PC clones, IBM clones or IBM PC clones ...
platform.
See also
* Direct Rendering Infrastructure
The Direct Rendering Infrastructure (DRI) is the framework comprising the modern Linux graphics stack which allows unprivileged user-space programs to issue commands to graphics hardware without conflicting with other programs. The main use ...
* KMS driver
The Direct Rendering Manager (DRM) is a subsystem of the Linux kernel responsible for interfacing with GPUs of modern video cards. DRM exposes an API that user-space programs can use to send commands and data to the GPU and perform operations ...
* SVGAlib
SVGAlib was an open-source low-level graphics library which ran on Linux and FreeBSD and allowed programs to change video mode and display full-screen graphics, without the use of a windowing system. Some popular games like '' Quake'' and ''D ...
.
References
External links
*
XFree86 doc
{{Linux kernel
Free software programmed in C
Free system software
Interfaces of the Linux kernel
Linux APIs