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AN2641

Linux frame buffer

Doc ID 14027 Rev 1

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Linux frame buffer

This section describes how to use the CLCD in a Linux environment from user space, what

modifications are needed in the kernel when adding a new CLCD in Linux, and explains the

concept of the frame buffer.

6.1

Frame buffer

The frame buffer is a part of the Linux Kernel and should not be confused with the Panel

Data Frame buffer register of the CLCD controller (as discussed inSection 3.1).

The frame buffer device provides a general abstraction for the graphics hardware and hence

allows application software to access the graphics hardware through a well-defined

programming interface, so the application software doesn't need to know anything about the

low-level (hardware register) stuff. Figure 6 show the advantage of frame buffer which allows

applications to be independent of the vagaries of the underlying graphics hardware.

Applications run unchanged over diverse types of video hardware if they and the display

drivers conform to the frame buffer interface.

Figure 6.

Advantage of using the frame buffer architecture

If GUIs (Graphic User Interface) such as MiniGUI, MicroWindows are used, LCD device

drivers must be implemented as Linux frame buffer device drivers in addition to those low

level operations which only deal with commands provided by LCD controllers.

●

The device is accessed through special device nodes, usually located in the /dev

directory, and have names such as /dev/fb0 (or /dev/fb/0), /dev/fb1 etc. The frame

buffer devices are also `normal' memory devices, this means one can read and write

their contents. You can, for example, even make a screen snapshot using:

cat /dev/fb0 > myfile

●

Application software that uses the frame buffer device (for example the X server) can

use /dev/fb0 by default. One can specify an alternative frame buffer device by setting

GUI, Console, Movie

Players etc

Common framebuffer API

Framebuffer driver 1

Framebuffer driver N

Video card 1

Video card N

… Video cards having

different graphics

controllers

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