[U-Boot] single build of uboot supporting env stored in dynamically detected boot device

[Tim Harvey]

Greetings,

It seems the U-Boot's env storage is implemented by various types of
storage from common/env_*.c, one (and only one) which is included by
common/Makefile based off of the CONFIG_ENV_IS_IN_* config.

I want to build a single uboot image which can be installed on one of
several supported boot devices (NAND, SATA, SD for example) and have
the env storage hooked to the device that was detected as the boot
device. Am I correct in assuming this is not currently possible and
that instead I would have to build 3 versions of uboot each with one
type of storage defined?

If it turns out that this is not currently possible, I'm open to
suggestions on how to rectify it (or if you think I'm crazy for
wanting to have a single uboot image for the above please explain your
reasoning). I'm thinking I would start by making the env_init/saveenv
functions (I believe those are the only ones that need to be
implemented by an env storage subsystem) unique function names, then
creating a wrapper for those functions that call the right one.

Regards,

Tim