I was working with a RaspiCam on my 3B+ when something in the hardware broke. The Pi does not recognize my cam anymore. But when I connected it to the display CSI the LED on the cam started glowing. So now I wonder: Is there any way to control the RaspiCam using the Pi's builtin CSI port for the display?
Two major problems: the first is, of course, that neither the CSI nor the DSI interfaces are documented openly, so even if it is possible to switch the signal assignments in software (it may not be), you still have to figure out how to do it. The second problem is that the SDA/SCL signals on the connectors are in different places (look at the (partial) schematics: https://www.raspberrypi.org/documentation/hardware/raspberrypi/schematics/rpi_SCH_3bplus_1p0_reduced.pdf), so even if you could overcome the first problem, you would still have to make a custom cable. As fun as all this may be, it's cheaper to just buy a new Pi :)