roadmap ?

[perryh_(_at_)_pluto_(_dot_)_rain_(_dot_)_com (Perry Hutchison)]

This feels like it might be an FAQ, but I couldn't find it there.

How do I find the source file which implements a given device?

Specifically, I'm looking for the code which implements the
/dev/srandom and /dev/urandom special files.  There's a file
named srandom.c in sys/lib/libkern, but all it appears to do
is set _randseed.  How do I find out where the real work is
being done (short of find ... -print | xargs grep ...)?