In the case that an unknown drm device shows up, send it down the
default handler. This handler is just a passthrough and assumes that the
kernel doesn't have any compat handlers for that device.
This is nicer than crashing or returning EPERM, since then downstream
drm drivers like Xe, Asahi, and PVR and still try to run.
We of course still want to run their struct definitions through CI once
they go upstream.
These strings don't actually null-terminate and previous checks were
working just because it would usually be null terminated due to
initialization.
Since this isn't guaranteed, I noticed a failure to determine drm device
due to some trailing garbage in the string.
Ryan Houdek