Meaning of frame_length and coarse_time

Analyzing different MIPI sensor drivers (ov5693, imx185, …) I’ve come up with some terminology I can’t fully understand. I’ve seen that frame_length is related to the frame_rate, and coarse_time to the exposure time, but how? I’ve searched in the sensor datasheet and no clue about these terms. Moreover, why some sensors need 3 addresses for, let’s say, frame_length, while others need only 2? Any documentation where this is detailed?
I’ve read the Sensor Driver Programming Guide, but yet the explanations are too generic.

@euskadi
All of your questions is about the sensors behavior. You should consult to sensor vendor to get the detail information.