Bootloader binary locations using ubuntu-image

[David Harker]

Hello,

With ubuntu-device-flash I used to be able to specify exactly where
the bootloader binaries were located in the final disk image. I needed
this because my device has
eMMC operating in RAW mode, rather than an SD card, and the binaries
have to be in specific locations for the processor to find them on
boot-up. For example my MLO needs to be at an offset of 131072 bytes
from the start of the disk image.

With ubuntu-image, in the gadget snap, I can only specify the 'offset'
as a multiple of 1MB. Anything less and the binaries all appear at the
start of the disk image.
The 'offset-write' would seem to be the solution, but this doesn't
seem to actually locate the binary at the specified offset in bytes,
it just writes a 32 bit value which is
the location specified by 'offset'.

I may have misunderstood something, but does anyone know how I can get
ubuntu-image to put my binaries where I need them?

Thanks.