It's a setup for the 5d3 made by timbytheriver and myself that facilitates optimising the gains on the camera to improve dynamic range and reduce noise in the shadows, especially chroma noise.
A1ex discovered the registers many years ago but development stopped quickly afterward. It has since become taboo in this community, but if you search the forum you can find information if you are interested.
The long and the short of it:
If you carefully calibrate your camera, you can gain close to 1 stop of usable dynamic range, which is important to some of us. It is not supported and there is no cooperation from anyone here. Quite the opposite.
Everything you need to know is searchable. I made a couple of tutorial videos some time ago.
It is only useful to anyone who is wanting to push their camera right to the limit. For "typical" users it is probably not useful. A possible barometer of applicability would be if you use a hardware tool to calibrate your monitor, and if you can see the details of my shirt in the video above.