USB debugging (was: ktrace-ing a command that locks up the machine)

[Edgar Fuß]

On Wed, Nov 18, 2020 at 09:05:47AM -0500, Greg Troxel wrote:
> another suggestion is to enable USB debugging in the kernel and use a serial 
> console (or even just framebuffer) to see the last message before crash.
I set options {USB,OHCI,EHCI}_DEBUG and sysctl -w hw.{usb,ohci,ehci}.debug=20 
and get zero output. What the hell am I missing?