Extending desktop over laptop HDMI port to LCD monitor

[Michael B Allen]

Hi,

What is currently the best method for extending a laptop desktop to an
external LCD monitor using the HDMI port on the laptop to the DVI port
of the monitor?

The laptop is a Toshiba R705-P25 with Intel graphics running CentOS 5.6:

  $ /sbin/lspci
  00:00.0 Host bridge: Intel Corporation Core Processor DRAM Controller (rev 02)
  00:02.0 VGA compatible controller: Intel Corporation Core Processor
Integrated Graphics Controller (rev 02)
  00:16.0 Communication controller: Intel Corporation 5 Series/3400
Series Chipset HECI Controller (rev 06)
  ...

How does one even address the HDMI port in the Xorg config?

With the current default config, if I boot with the HDMI to DVI cable
connected, the display goes to the external LCD and the builtin LCD
backlight is off. If it is connected after booting, there is no
visible change in either display.

Where do I go from here?

Thanks,
Mike