Pin Assignment on Raspberry Pi 3 with PX4

Which configuration file is responsible for I/O pin assignment on Raspberry Pi 3 when make posix_rpi_native is used?
At least how will I know which Raspberry Pi 3 GPIO pin is assigned to which sensor driver with default native build (followed the steps provided in the PX4 documentation)?

I am trying to run PX4 on Raspberry Pi 3 with Ubuntu 18.04 using a custom sensor board. Perhaps I need to write the driver for the sensor which has SPI interface as it is not available in df_ in px4.config. Any documentation or resource I should look into to write the driver? One of the drivers in is quite similar to what I need but it is for NuttX. Is there any procedure to migrate NuttX driver to Linux?

We are trying to move away from DriverFramework, see

Therefore, I’d suggest to think about how you could add it to the existing driver infrastructure in Firmware.

Thanks JulianOes for the update.
One more thing I want to ask for the Navio 2 board. There is an EEPROM connected to pin 27 and 28 of Raspberry Pi 3 board. I read somewhere that this EEPROM is used for auto configuration or Navio 2 board specific ID. I need to know if PX4 code will work without the EEPROM?

BTW I found the following link which answers my earlier query.

Usually on “Posix” which is what we call non-NuttX boards the params are just saved in a params file.