Comment 1 for bug 1002099

It kind of depends of how the rest of the boot looks like; one way you could cheat a bit is by having u-boot try SD and then fallback to eMMC, setting root= from this logic as well. You would need to have the same partition layout from linaro-image-tools perspective for the images to be mostly similar so that MMC layout doesn't matter.

Alternatively, you could set root device in an initrd.

Finally, we could have some options on top of hwpacks. Hwpacks were meant to split out board specific things from userspace specific things, but they also made it harder to support multiple similar boards, or multiple use cases for the same board; I guess it might make sense to have multiple profiles in the same hwpack? For instance we could have multiple manifests in the same hwpack and have a linaro-media-create flag to select the manifest (profile) that you want to use. Profiles could differ per-board or per use case so that we could have a single omap3 hwpack with support for beagle and overo, or a single snowball hwpack with support for SD and eMMC.