Nit: AIUI, the kernel has no stable API. It has no ABI period.
API stability is not guaranteed, though it's stable enough that the likes of Nvidia can write installers for their proprietary drivers that recompile a bit of interface glue between kernel and blob.
Given a particular install, yes, but it will change independent of kernel version based on e.g. build flags and even conceivably compiler chosen, etc.
> it's stable enough that the likes of Nvidia can write installers for their proprietary drivers that recompile a bit of interface glue between kernel and blob
Well...they certainly can. It also can infuriate me beyond all reason...
Making a stable API that covers the entire kernel would be a monumental task on the other hand.