VESA FrameBuffer Kernel documentation

X11
===

XF68_FBDev should work just fine, but it is non-accelerated. Running
another (accelerated) X-Server like XF86_SVGA might or might not work.
It depends on X-Server and graphics board.

The X-Server must restore the video mode correctly, else you end up
with a broken console (and vesafb cannot do anything about this).

Refresh rates
=============

There is no way to change the vesafb video mode and/or timings after
booting linux. If you are not happy with the 60 Hz refresh rate, you
have these options:

* configure and load the DOS-Tools for your the graphics board (if
available) and boot linux with loadlin.
* use a native driver (matroxfb/atyfb) instead if vesafb. If none
is available, write a new one!
* VBE 3.0 might work too. I have neither a gfx board with VBE 3.0
support nor the specs, so I have not checked this yet.

Configuration
=============

The VESA BIOS provides protected mode interface for changing
some parameters. vesafb can use it for palette changes and
to pan the display. It is turned off by default because it
seems not to work with some BIOS versions, but there are options
to turn it on.

You can pass options to vesafb using “video=vesafb:option” on
the kernel command line. Multiple options should be separated
by comma, like this: “video=vesafb:ypan,invers”

Accepted options:

invers no comment…

ypan enable display panning using the VESA protected mode
interface. The visible screen is just a window of the
video memory, console scrolling is done by changing the
start of the window.
pro: * scrolling (fullscreen) is fast, because there is
no need to copy around data.
* You’ll get scrollback (the Shift-PgUp thing),
the video memory can be used as scrollback buffer
kontra: * scrolling only parts of the screen causes some
ugly flicker effects (boot logo flickers for
example).

ywrap Same as ypan, but assumes your gfx board can wrap-around
the video memory (i.e. starts reading from top if it
reaches the end of video memory). Faster than ypan.

redraw scroll by redrawing the affected part of the screen, this
is the safe (and slow) default.

vgapal Use the standard vga registers for palette changes.
This is the default.
pmipal Use the protected mode interface for palette changes.

mtrr:n setup memory type range registers for the vesafb framebuffer
where n:
0 – disabled (equivalent to nomtrr) (default)
1 – uncachable
2 – write-back
3 – write-combining
4 – write-through

If you see the following in dmesg, choose the type that matches the
old one. In this example, use “mtrr:2”.

mtrr: type mismatch for e0000000,8000000 old: write-back new: write-combining

nomtrr disable mtrr

vremap:n
remap ‘n’ MiB of video RAM. If 0 or not specified, remap memory
according to video mode. (2.5.66 patch/idea by Antonino Daplas
reversed to give override possibility (allocate more fb memory
than the kernel would) to 2.4 by tmb@iki.fi)

vtotal:n
if the video BIOS of your card incorrectly determines the total
amount of video RAM, use this option to override the BIOS (in MiB).

Have fun!

Gerd


Gerd Knorr <kraxel@goldbach.in-berlin.de>

Minor (mostly typo) changes
by Nico Schmoigl <schmoigl@rumms.uni-mannheim.de>

Author: stratus

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