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 i ...

. 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. Kerne ...

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. Moder ...

(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 In Unix-like operating systems, a device file or special file is an interface to a device driver that appears in a file system as if it were an ordinary file. There are also special files in DOS, OS/2, and Windows. These special files allow ...

system interface, avoiding the need for libraries like SVGAlib which effectively implemented video drivers in

. 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 Text mode is a computer display mode in which content is internally represented on a computer screen in terms of characters rather than individual pixels. Typically, the screen consists of a uniform rectangular grid of ''character cells'', each o ...

(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 for a ...

, independent of

video adapter A graphics card (also called a video card, display card, graphics adapter, VGA card/VGA, video adapter, display adapter, or mistakenly GPU) is an expansion card which generates a feed of output images to a display device, such as a computer moni ...

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 ...

. Examples of the third application include Linux programs such as

MPlayer MPlayer is a free and open-source media player software application. It is available for Linux, OS X and Microsoft Windows. Versions for OS/2, Syllable, AmigaOS, MorphOS and AROS Research Operating System are also available. A port for ...

links2 Links is a free software text and graphical web browser with a pull-down menu system. It renders complex pages, has partial HTML 4.0 support (including tables and frames and support for multiple character sets such as UTF-8), supports color and ...

, 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 DirectFB (Direct Frame Buffer) is a software library with a small memory footprint that provides graphics acceleration, input device handling and abstraction layer, and integrated windowing system with support for translucent windows and multi ...

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.

References

External links

*
XFree86 doc
{{Linux kernel Free software programmed in C Free system software Interfaces of the Linux kernel Linux APIs

Applications

History

See also

References

External links