This is a Secondary Program Loader initrd for InkBox. It permits you to switch between Nickel and InkBox at boot by kexec'ing a new kernel from userspace. Only Libra is supported currently, because kexec is actually reliable there.

We're doing it! eMMCs won't stop us!
I've already got a basic initrd booting with kexec and U-Boot supports fastboot, loady as well as command prompt (bootdelay's set to 1 :D)
kexec is very reliable in this kernel, so I think I'm going to make a tiny kernel that will go in the eMMC's unpartitioned space, then make it boot InkBox's kernel (which is too big for the standard allowed space), a bit like U-Boot SPL.
I must admit, 4.1.15 is a breeze after months with 2.6.35.3! Don't worry though, support will continue for all of these older devices.

I need to do some changes

The binary was too big and caused run-time problems such as EPDC behavior issues (waveform was not present). It will be in some unpartitioned space instead.

The kernel size grew up to ~6MB, and was eating the waveform when written to the MMC. I moved it to sector 18435 so that we won't have this problem again.