how do cape overlays work

Hi, I’m trying to get the cape overlay functionality working on a beaglebone black running the latest Yocto bits and u-boot/kernel from meta-ti. From what I can tell, the process is:

  1. u-boot detects a cape
  2. kernel loads overlay from rootfs

I don’t see any evidence of cape detection in the u-boot. Where are the best u-boot sources for the BBB? Are there kernel bits as well, and how do I tell if I have them?

On point 2. U-Boot loads overlay from rootfs:…


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Is the DT merged by u-boot, or does that happen in the kernel?

Have these mechanisms every been accepted upstream, or what is the current status?

Trying to determine if we should port the DT parts to the board DTS file, or try to get the overlay mechanism working in the latest TI kernels. For this project, we do not need dynamic cape detection as its a fixed config.

Everything should be done in u-boot:

Nothing should be done “while” the kernel is loading…


Thanks Robert – that looks very useful!