/sys/kernel/debug/dynamic_debug/control not writable, follow xhci_hcd debug guide

I want to follow this tutorial . But I can't write to /sys/kernel/debug/dynamic_debug/control- or [debugfs]/dynamic_debug/control-file as suggested by the guide, even tough I am root, the special filesystem is mounted rw and the control-file has rw-mode for root. How can I make the control-file writable? I also have another side question. I will ask it, if I may: All lines in the control-file look like this: # filename:lineno [module]function flags format init/main.c:782 [main]initcall_blacklisted =p "initcall %s blacklisted\012" The guide asks me to add the following line: echo 'module xhci_hcd +p' > /dynamic_debug/control So is this the way to go? Or is there something _terribly wrong_ with writing the above line to the control-file, that may break my system or anything?