Re: How to use framebuffer(s) with ruby?

[Helge H. <hel...@hi...>]

dave giffin wrote:

>I've used backstreet ruby before with 2 regular
>XFree86 servers.
>  
>
This is possible with linux-2.6+ruby too.

>Now, I would like to be able to use an XDirectFB (an X
>server using the DirectFB framebuffer library)
>instance on one card while simultaneously using a
>regular XFree86.
>  
>
Why do you want to use the framebuffers?  X is usually faster using the
regular accelerated servers.  Or is that impossible for some reason?

>I want to be able to use a regular (non-framebuffer)
>XFree86 server on one graphics card and a framebuffer
>app on another graphics card.
>
>  
>
This is possible.

>If that is not possible, I would settle for using two
>independent framebuffer apps, one on each card (I'd
>just use two XDirectFBs)
>
>  
>
Also possible.

>How do I use ruby (linux-2.6) to setup multi-user
>framebuffers?
>  
>
First, install the hardware, i.e. your graphichs cards, monitors
mice, and keyboards.  Then compile a linux 2.5+ruby kernel, with
framebuffer support for the card you want to use.  You may want to
use framebuffer console support if you want to run regular logins on
the framebuffer when not using X.  If you use fbcon, you probably need
framebuffer support for your regular card too, so ruby will understand
that there is two consoles. IF you don't use fbcon, use the "dumbcon=1"
parameter on the kernel command line.  "dumbcon" create a input-only
console for the second keyboard.  A keyboard must hook up with
_some_ console, or it goes unused.

Install your regular xserver in the regular way, i.e. the way
it is usually installed with your distribution.  You may have to use
the prefbusid/isolatedevice/singlecard option in XF86config so the other 
card
doesn't get disabled.  (Read mailing list archives or search google
for details on that.)  If your xserver doesn't support this, compile 
your own
which is a lot of work.  The xserver in debian testing should be fine 
though.
If you get trouble, also look for the "hackvideo" solution which achieve the
same in a different way.

You may also want to verify that the framebuffer for the other display 
works.
Do that by catting a file into the framebuffer device, and verify that 
garbage
indeed appear on the other screen.
cat file > /dev/fb0
or
cat file > /dev/fb1
depending on which framebuffer device that card is.  (If you don't know,
look at dmesg output or just try the commands.) Any non-empty file will do.

Now set up the second xserver, by creating an alternate XF86Config-4 file.
Call it something different from XF86Config-4, because that filename is
used for your regular xserver. 

The "device" section should contain
Driver   "fbdev"
in order to use the X framebuffer driver, and
Option   "fbdev"   "/dev/fb0"
or
Option   "fbdev" "/dev/fb1"
depending on what framebuffer the second screen is on.

Framebuffer X does not need to know what card or what kind
of card it uses - it does everything through the kernel
framebuffer interface.  This is unaccelerated but usually fast enough
for 2D apps.  You can even use software 3D if you like - but it'll be way
too slow for anything but very simple effects.  (It is fine for playing
the frozen-bubble game :-)

When starting the second xserver, use the -xf86config parameter
to specify your alternate X config file.  Also specify what VT the
server should use.  With ruby, the second keyboard is usually on VT17.
(It might be higher up if you're using fbcon and runs a getty on vt17.  But
console switching on secondary framebuffers doesn't work too well yet, so
you probably don't do that.)

I use xdm to manage two xservers, one regular accelearated and one 
framebuffer.
My /etc/X11/xdm/Xservers look like this:

#regular, using /etc/X11/XF86Config-4, running on vt7

:0 local /usr/X11R6/bin/X :0 vt7  -deferglyphs 16 -nolisten tcp

#framebuffer, using /etc/X11/xf86config-4 running on vt17
:1 local /usr/X11R6/bin/X :1 vt17 -deferglyphs 16 -nolisten tcp 
-xf86config xf86config-4


If you want to start stuff from a script instead of xdm, use something 
like this (untested):
/usr/X11R6/bin/X :0 vt7  -deferglyphs 16 -nolisten tcp &
/usr/X11R6/bin/X :1 vt17 -deferglyphs 16 -nolisten tcp -xf86config 
xf86config-4  &



You might want to run a font server when using two xservers, for 
efficieny reasons.
If you don't then both xservers will run their own internal font server, 
but running two
font servers probably waste memory.  Using one xfs, and specifying
 FontPath        "unix/:7100"
in the X config files is probably better.

Helge Hafting