Today I had a chance to test OV5640 on mainline kernel 4.17.2 and see the status of OV5640 and CSI drivers, thanks to FE work and the author of the driver (help name here...). I tested on NanoPi K1 Plus (H5) to verify the images in very low light conditions, so don't expect good quality. I could take some images using fswebcam and you should expect basic v4l2 functionality already works if not all. I think motion (did not test  / had time to test it) can work with current OV5640 on mainline