mjhjmtu

What Load "fb" in Section "Module" of xorg.conf actually does?

Tried to RTFM and searching first.

Load "fb" is telling X to load the framebuffer module.

(II) Loading sub module "fb"
(II) LoadModule: "fb"
(II) Loading /usr/lib/xorg/modules//libfb.so
(II) Module fb: vendor="X.Org Foundation"
 compiled for 1.4.2, module version = 1.0.0
 ABI class: X.Org ANSI C Emulation, version 0.3

 The fb library is what is responsible for almost all of the software
 rendering that your X Server might do.

 You're probably mostly spending your time in fbComposite() and its
 children, which is the Render extension software implementation. Some
 drivers have hardware implementations of this, and we're working on
 making this be the case for more hardware.

 -- 
 Eric Anholt anholt at FreeBSD.org
 eric at anholt.net eric.anholt at intel.com

On most distros you can locate files like this:

$ locate libfb.so
/usr/lib64/xorg/modules/libfb.so
$ rpm -qf /usr/lib64/xorg/modules/libfb.so
xorg-x11-server-Xorg-1.19.5-5.el7.x86_64

And inquire into the package itself about the contents/purpose.

What's a framebuffer

So the next question might be, what's a framebuffer. For that look to wikipedia: Framebuffer:

A framebuffer (frame buffer, or sometimes framestore) is a portion of RAM1 containing a bitmap that drives a video display. It is a memory buffer containing a complete frame of data.2 Modern video cards contain framebuffer circuitry in their cores. This circuitry converts an in-memory bitmap into a video signal that can be displayed on a computer monitor.

In computers, buffers such as this, are used to directly map a region of memory to a display/screen, which has a driver that's monitoring the region. Anything placed into this location is picked up and rendered on the display/screen itself.

For more on frame buffers, please refer to this U&L Q&A titled: What is a framebuffer device and is it required to obtain a higher resolution?.

Reference

• What is libfb.so responsible for?