I have no experience with the commercial IDA tool or generally ARM assembler but wanted to support the porting efforts for the 77D model.
So far I have little results but at least a stable build environment.

I used it to toy around with Ghidra. Here are my first steps so far:
https://github.com/calle2010/magic-lantern-77d-vagrant/blob/master/ghidra.mdAt least I could make sense of some of the bootloader code. Also Ghidra finds functions, strings, embedded JPEG images and other data. It can be scripted with Java or Python, but I haven't tried this yet.
If anybody has tipps and hints on how to use Ghidra effectively I would be happy about replies.