- Build kernel without ums support (either statically or as a module).
- Plug in USB mouse.
- The kernel module load should be attempted, but should fail.
- The error message doesn't seem sensible to expose to the end user; I recommend it be quieted for improved user experience and to reduce log spam.
Real life scenario:
- Virtual USB keyboards and mice are generally emulated by BMC firmware. If the developer decides to build the kernel without ukbd/ums, it will always warn (via devd) that it failed to load the modules, because they do not exist.