The lines exposed on the GPIO header of a Rubik Pi 3 seem to be part of the chip enumerated as gpiochip4 instead of gpiochip0 for the Linux character device GPIO API. The Raspberry Pi 5 was the same before raspberrypi/linux#6144 changed the numbering so that gpiochip0 supplies the lines for the external header and chips 10-13 supply the internal lines. While application programs can detect the Rubik Pi environment and select the right chip, renumbering the chips to match the convention set by Raspberry Pi would be more compatible with existing libraries and match the user expectation that device 0 is the default.
I’m requesting this for the PhotonVision project, which currently uses diozero to control GPIO pins for status and illumination LEDs. Unless a custom board definition overrides the pin detection procedure, diozero enumerates all available gpio chips and assumes that pin numbering starts at chip 0 and continues through each of the chips sequentially. This results in the incorrect numbering compared to the RubikPi’s documentation, potentially resulting in users accidentally setting internal pins while attempting to set external ones. We could add a custom board definition to diozero to resolve this, but changing the chip numbering while the RubikPi is in its early lifespan may lead to greater library compatibility.