GM45 HDMI output

[tsuraan]

I have a Vaio Z-series with a GM45 video controller.  For outputs, it
has a VGA and an HDMI port; I can use the VGA port without any
trouble, but I can't find any evidence from software that the HDMI
port even exists.  xrandr give me this output:

Screen 0: minimum 320 x 200, current 1600 x 900, maximum 8192 x 8192
VGA1 disconnected (normal left inverted right x axis y axis)
LVDS1 connected 1600x900+0+0 (normal left inverted right x axis y
axis) 0mm x 0mm
   1600x900       59.9*+
   1152x864       75.0
   1024x768       85.0     75.0     70.1     60.0
   832x624        74.6
   800x600        85.1     72.2     75.0     60.3     56.2
   640x480        85.0     72.8     75.0     59.9
   720x400        85.0
   640x400        85.1
   640x350        85.1

So, there's no apparent HDMI output listed there.  This laptop is a
hybrid graphics machine with an nVidia card; is it possible that the
nVidia card "owns" the HDMI port and the Intel one just cannot see it,
or do I have something misconfigured?