Right now I'm working on adding dynamic reconfigure to a camera driver
and I am having a few issues.

I'm trying to figure out if there is a way to dynamically generate a
list of usable resolutions for dynamic reconfigure to use based on which
device is currently selected. I would like the list of cameras and the
list of resolutions to both be enums.

It looks like there is no easy way to do this, and the only possible way
might be to rebuild the node's .cfg file each time the device is
changed.

If this is the case is it possible to have some sort of callback
interface in the .cfg file in the future?