/sys/kernel was chosen ages ago and I completely forgot to move it to configfs.
IBTRS is not a block device, so for some read-only entries (statistics
or states)
something else should be probably used, not configfs.  Or it is fine
to read state
of the connection from configfs?  For me sounds a bit weird.

Configs go via configfs, states and alike go to sysfs (but you need your
own class device).