/dev/fb*/dev/fb*
/dev/fb*From the user's point of view, the frame buffer device looks just like any
other device in /dev. It's a character device using major 29, the
minor specifies the frame buffer number.
By convention, the following device nodes are used (numbers indicate the device minor numbers):
/dev/fb0First frame buffer
/dev/fb1Second frame buffer
/dev/fb78th frame buffer
For backwards compatibility, you may want to create a symbolic link from
/dev/fb0current to fb0.
The frame buffer devices are also `normal' memory devices, this means, you can read and write their contents. You can, for example, make a screen snapshot by
cp /dev/fb0 myfile
There also can be more than one frame buffer at a time, e.g. if you have a
graphics card in addition to the built-in hardware. The corresponding frame
buffer devices (/dev/fb0 and /dev/fb1 etc.) work
independently.
Application software that uses the frame buffer device (e.g. the X server) will
use /dev/fb0 by default (older software uses
/dev/fb0current). You can specify an alternative frame buffer device
by setting the environment variable $FRAMEBUFFER to the path
name of a frame buffer device, e.g. (for sh/bash users):
export FRAMEBUFFER=/dev/fb1
or (for csh users):
setenv FRAMEBUFFER /dev/fb1
After this the X server will use the second frame buffer.
/dev/fb*/dev/fb*