Device Tree Overlays with EEPROM

[thomas_marangoni]

Hi there,
I’m currently looking into cboot, EEPROMs and device tree overlays. Unfortunately I can’t find enough documentation on this. I have seen that there is a system called plugin-manager which dynamically loads the correct device tree overlay according to the data in the EEPROM at boot time. There is such an EEPROM on the Jetson TX2 NX module and on our carrier board.

We have three PCBs, one of which is the carrier board with the Jetson module. The other two also have an EEPROM on them. Is there already a system where I can load a specific overlay for each PCB depending on the content of each EEPROM?

I have already added each EEPROM to the device tree and it is being detected by cboot. What would the overlays look like to be loaded correctly? Is this even possible with cboot and plugin-manager?

Kind regards

[DaveYYY]

Hi,

It’s possible for different modules to share the same kernel dtb, but even with plugin manager(maybe with id and ODMDATA), the dtb overlay has be processed before they are actually flashed into the board, instead of at boot time, and the flashing script would only have access to the EEPROM on the module itself, but not carrier boards.

Please check the plugin-manager driver code(/kernel-4.9/drivers/of/plugin-manager.c) to look for something that may be possible for you.