I recently bought Steinberg WaveLab 7 for an upcoming project I'm planning, and since I know I'm going to be spending many hours inside that program, I wanted some kind of hardware controller to minimize the mouse work required to edit my audio files.
Steinberg makes a number of great hardware controllers, but the devices were all primarily designed for Cubase. They are not general-purpose MIDI controllers, and in fact only recently (with WaveLab 7.2) were any of them supported by WaveLab.
I have not found ANY official location that describes the WaveLab compatibility with Steinberg's controllers, but here's the info I've gathered both through personal experience and by prodding Steinberg staff at their official forums.
The king of Steinberg's hardware controllers is the Steinberg CC121 Advanced Integration Controller. This device is fully supported in WaveLab for both Mac and PC, but on both OSes you need to have both WaveLab 7.2.1 and the 1.7.4 version of "TOOLS for CC121." When you have the 7.2.1 WaveLab update, you'll find a page called "CC121 Advanced Integration Controller" in the program's built-in help documentation, which describes all the device's mappings. One thing worth noting is that in WaveLab, the CC121's EQ controls only handle EQ duties when the "EQ TYPE" button is lit on the device and you have mouse focus on an instance of the StudioEQ plugin. If EQ TYPE is unlit, then the knobs are all mapped to different WaveLab functions.
I have found literally zero official documentation about the smaller CMC series controllers, but according to a Steinberg rep at the forums, the following CMC devices are supported by WaveLab 7.2.1: CMC-AI, CMC-CH, CMC-QC, and CMC-TP. I imagine the mappings match what Steinberg did for the CC121, so the built-in help documentation for the CC121 is probably worth a read if you have the CMC controllers.