You are probably looking for a way to enable raw image data in LiveView, correct?
In this case, I'm not sure lv_rec is the best place to start (as it's quite complex and I don't remember it ever working reliably) - but it did capture the first raw image.
I'd say the first steps are to understand how the current EDMAC transfers are used - besides the current status of EDMAC channels (I remember seeing some screenshots on PowerShots, just not sure where), you can try to log each pointer periodically (as it reads from or writes to the main memory). Something like this:
http://www.magiclantern.fm/forum/index.php?topic=18315.msg176347#msg176347The graphs were created from logs saved with this code (log_edmac_usage):
https://bitbucket.org/hudson/magic-lantern/src/edmac/modules/edmac/edmac.cOn EOS, the raw stream in LiveView is always available from connection 0. Whether this connection is hardwired to deliver raw image data, or it's just the EOS software configuring the DIGIC that way, I have no idea.
Rather than porting lv_rec, it's probably best to port just the EDMAC_RAW_SLURP backend (which is basically raw_lv_vsync in raw.c and edmac_raw_slurp in edmac-memcpy.c). These two functions simply bring the raw data in a buffer in the main memory, and the raw recording modules just take it from there.
Then, you could look at mlv_lite, since it's a bit simpler.