No CC Pro support
For that you need the Classic Linker Plus.

Nice gadget for retro gamers that don't like the GC pad
This is a product long overdue. The Gamecube controller lacks a d-pad in a position usable for primary control so I've wanted to use either my PS dual analogue pad or Classic Controller for games like Mr. Driller Drill Land or Namco Museum 50th Anniversary.

Now you can. The cord is on the short side so a GC extension cable is a must. The only minor issue is the buttons don't map 1-1 with the GC ones so the GC A button is the CC B button and the GC B button is the CC X button.

Otherwise it works a treat!