After unsuccessfully attempting to install NEC calibration software to calibrate monitors on a GeForce GTS450 card in a Linux system, it occurred to me that the nVidia driver does not support DDC/CI. (It is supported in Windows.)
Am I correct in concluding that the current driver does not support DDC/CI? Several recent posts appear to confirm that this protocol is not supported.
Moreover you don’t post any gddccontrol error messages which means you’re not really interested in solving your own problem. You haven’t provided any information about your setup either (nvidia-bug-report.log would suffice).
Also, it would be better if you joined the existing discussion instead of creating a new one.