The dynamic debugging interface

RE: How and when is the control file created? If I load a kernel module which wasn't available at boot time, how to I update the control file to include the new module and the location of its source code?

A year late, and youve probably found it, but:

The control file is automatically created if youre mounting dbgfs, appears in <dbgmountpt>/dynamic_debug/control. It contains a line for every pr_debug(etc) call in the kernel and its modules, when you modprobe another, its pr_debug() calls appear too.