How can I obtain a copy of the “capemgr.c” source?
I think support for cape manager ended around 3.8.x. If you need it anyway, checkout as follows:
git checkout origin/am33x-v3.8 -b tmp
the the capemgr.c source should be in:
./KERNEL/drivers/misc/cape/beaglebone/capemgr.c
HTH,
Dave.