re-probing DDC/EDID

[perryh at pluto.rain.com]

Is there any way to re-probe the monitor's DDC/EDID while the
X server is running?

I don't expect the server to change the settings it is _using_
without restarting, but would like to get the list of supported
Modelines for a newly-connected monitor -- as would be generated
in the course of "Xorg -configure" -- while the server continues
to run using its old settings.  Of course there would be no need
to re-probe anything but the monitor, since all other hardware
remains the same.

The motivation is to simplify a monitor upgrade from:

* Log out of X session (restarts X).
* Disable xdm in /etc/ttys (shuts down X).
* Xorg -configure.
* Merge the Modelines from the "Xorg -configure" output into
  the existing xorg.conf -- using the text-mode console (or
  restart X with the old settings just to do this merge).
* Re-enable xdm in /etc/ttys (restarts X).
* Log in/start new X session.

to

* Re-probe monitor.
* Merge the new Modelines into xorg.conf.
* Log out / log in (restarts X session using new settings).