I have an HP G7-1150us laptop with Intel Sandy Bridge integrated graphics. The built-in screen works fine, but the HDMI port is not detected. Even when my TV is connected at boot-time, in /var/log/syslog I see:
Nov 18 21:37:32 steve-HP-Pavilion-g7-Notebook-PC kernel: [ 12.902676] HDMI status: Codec=3 Pin=5 Presence_Detect=0 ELD_Valid=0
The Systems Settings -> Displays tools doesn't detect any additional monitors, even when I have my TV connected at boot time.
I have the TV set for input on the connected HDMI port, which works fine with other devices.
I have seen lots of discussion about sound problems and resolution problems, but I haven't seen anyone offering solutions to a failure to detect the port in the first place.