Because of style conformance and the fact that a // comment can cause some C-compilers to be upset, please change these comments to:

    #define DSM_FRAME_SIZE<tab>16<tab><tab>/**< The DSM dsm frame size in bytes */

A full set of examples is given in the PX4 code style:
https://pixhawk.ethz.ch/px4/dev/code_style

Sorry for the pedantic review, it will make it easier to read though if its consistent.