I can't quite understand what constitutes a 'complete' openwrt build configation so I can back it up.  For BR-6104KP I know I need the top level .config, and also /target/linux/adm5120/router_le/config-*, and it seems also /target/linux/generic-2.6/config-*, but whenever I replace  kernel options, even if I replace them in all these files and rebuild from scratch I frequently get kernel config prompts on the next build (and of course, you don't see them if you are running 'make' without V=99, so it just waits forever).

Any ideas why this happens and what I can do to avoid it?

thanks.