If you're adding parameters to existing unixcalls you should at least zero-init them in the caller.
I planned to do that when achieving a single `mmdevdrv.c`, but to avoid confusion I'll do it in this MR instead.
Also, this MR is getting rather long. I'd suggest just pushing the first five or so commits, saving the rest for later MRs.
We would end up with a single "topic" split between different MRs, though.
I think it would make more sense to divide the commits like this:
- 1-3 in this MR. - 4-12 in a 2nd MR. - 13 in a 3rd MR.