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CyBlaFB is a framebuffer driver for the Cyberblade/i1 graphics core integrated
into the VIA Apollo PLE133 (aka vt8601) south bridge. It is developed and
tested using a VIA EPIA 5000 board.
Cyblafb - compiled into the kernel or as a module?
==================================================
You might compile cyblafb either as a module or compile it permanently into the
kernel.
Unless you have a real reason to do so you should not compile both vesafb and
cyblafb permanently into the kernel. It's possible and it helps during the
developement cycle, but it's useless and will at least block some otherwise
usefull memory for ordinary users.
Selecting Modes
===============
Startup Mode
============
First of all, you might use the "vga=???" boot parameter as it is
documented in vesafb.txt and svga.txt. Cyblafb will detect the video
mode selected and will use the geometry and timings found by
inspecting the hardware registers.
video=cyblafb vga=0x317
Alternatively you might use a combination of the mode, ref and bpp
parameters. If you compiled the driver into the kernel, add something
like this to the kernel command line:
video=cyblafb:1280x1024,bpp=16,ref=50 ...
If you compiled the driver as a module, the same mode would be
selected by the following command:
modprobe cyblafb mode=1280x1024 bpp=16 ref=50 ...
None of the modes possible to select as startup modes are affected by
the problems described at the end of the next subsection.
For all startup modes cyblafb chooses a virtual x resolution of 2048,
the only exception is mode 1280x1024 in combination with 32 bpp. This
allows ywrap scrolling for all those modes if rotation is 0 or 2, and
also fast scrolling if rotation is 1 or 3. The default virtual y reso-
lution is 4096 for bpp == 8, 2048 for bpp==16 and 1024 for bpp == 32,
again with the only exception of 1280x1024 at 32 bpp.
Please do set your video memory size to 8 Mb in the Bios setup. Other
values will work, but performace is decreased for a lot of modes.
Mode changes using fbset
========================
You might use fbset to change the video mode, see "man fbset". Cyblafb
generally does assume that you know what you are doing. But it does
some checks, especially those that are needed to prevent you from
damaging your hardware.
- only 8, 16, 24 and 32 bpp video modes are accepted
- interlaced video modes are not accepted
- double scan video modes are not accepted
- if a flat panel is found, cyblafb does not allow you
to program a resolution higher than the physical
resolution of the flat panel monitor
- cyblafb does not allow vclk to exceed 230 MHz. As 32 bpp
and (currently) 24 bit modes use a doubled vclk internally,
the dotclock limit as seen by fbset is 115 MHz for those
modes and 230 MHz for 8 and 16 bpp modes.
- cyblafb will allow you to select very high resolutions as
long as the hardware can be programmed to these modes. The
documented limit 1600x1200 is not enforced, but don't expect
perfect signal quality.
Any request that violates the rules given above will be either changed
to something the hardware supports or an error value will be returned.
If you program a virtual y resolution higher than the hardware limit,
cyblafb will silently decrease that value to the highest possible
value. The same is true for a virtual x resolution that is not
supported by the hardware. Cyblafb tries to adapt vyres first because
vxres decides if ywrap scrolling is possible or not.
Attempts to disable acceleration are ignored, I believe that this is
safe.
Some video modes that should work do not work as expected. If you use
the standard fb.modes, fbset 640x480-60 will program that mode, but
you will see a vertical area, about two characters wide, with only
much darker characters than the other characters on the screen.
Cyblafb does allow that mode to be set, as it does not violate the
official specifications. It would need a lot of code to reliably sort
out all invalid modes, playing around with the margin values will
give a valid mode quickly. And if cyblafb would detect such an invalid
mode, should it silently alter the requested values or should it
report an error? Both options have some pros and cons. As stated
above, none of the startup modes are affected, and if you set
verbosity to 1 or higher, cyblafb will print the fbset command that
would be needed to program that mode using fbset.
Other Parameters
================
crt don't autodetect, assume monitor connected to
standard VGA connector
fp don't autodetect, assume flat panel display
connected to flat panel monitor interface
nativex inform driver about native x resolution of
flat panel monitor connected to special
interface (should be autodetected)
stretch stretch image to adapt low resolution modes to
higer resolutions of flat panel monitors
connected to special interface
center center image to adapt low resolution modes to
higer resolutions of flat panel monitors
connected to special interface
memsize use if autodetected memsize is wrong ...
should never be necessary
nopcirr disable PCI read retry
nopciwr disable PCI write retry
nopcirb disable PCI read bursts
nopciwb disable PCI write bursts
bpp bpp for specified modes
valid values: 8 || 16 || 24 || 32
ref refresh rate for specified mode
valid values: 50 <= ref <= 85
mode 640x480 or 800x600 or 1024x768 or 1280x1024
if not specified, the startup mode will be detected
and used, so you might also use the vga=??? parameter
described in vesafb.txt. If you do not specify a mode,
bpp and ref parameters are ignored.
verbosity 0 is the default, increase to at least 2 for every
bug report!
Development hints
=================
It's much faster do compile a module and to load the new version after
unloading the old module than to compile a new kernel and to reboot. So if you
try to work on cyblafb, it might be a good idea to use cyblafb as a module.
In real life, fast often means dangerous, and that's also the case here. If
you introduce a serious bug when cyblafb is compiled into the kernel, the
kernel will lock or oops with a high probability before the file system is
mounted, and the danger for your data is low. If you load a broken own version
of cyblafb on a running system, the danger for the integrity of the file
system is much higher as you might need a hard reset afterwards. Decide
yourself.
Module unloading, the vfb method
================================
If you want to unload/reload cyblafb using the virtual framebuffer, you need
to enable vfb support in the kernel first. After that, load the modules as
shown below:
modprobe vfb vfb_enable=1
modprobe fbcon
modprobe cyblafb
fbset -fb /dev/fb1 1280x1024-60 -vyres 2662
con2fb /dev/fb1 /dev/tty1
...
If you now made some changes to cyblafb and want to reload it, you might do it
as show below:
con2fb /dev/fb0 /dev/tty1
...
rmmod cyblafb
modprobe cyblafb
con2fb /dev/fb1 /dev/tty1
...
Of course, you might choose another mode, and most certainly you also want to
map some other /dev/tty* to the real framebuffer device. You might also choose
to compile fbcon as a kernel module or place it permanently in the kernel.
I do not know of any way to unload fbcon, and fbcon will prevent the
framebuffer device loaded first from unloading. [If there is a way, then
please add a description here!]
Module unloading, the vesafb method
===================================
Configure the kernel:
<*> Support for frame buffer devices
[*] VESA VGA graphics support
<M> Cyberblade/i1 support
Add e.g. "video=vesafb:ypan vga=0x307" to the kernel parameters. The ypan
parameter is important, choose any vga parameter you like as long as it is
a graphics mode.
After booting, load cyblafb without any mode and bpp parameter and assign
cyblafb to individual ttys using con2fb, e.g.:
modprobe cyblafb
con2fb /dev/fb1 /dev/tty1
Unloading cyblafb works without problems after you assign vesafb to all
ttys again, e.g.:
con2fb /dev/fb0 /dev/tty1
rmmod cyblafb