GPIO inputs on Pis?

Is there support somewhere in the 13.x for other than "read current 
state" / "set current state"?

Specifically, there is evidence in the sys/gpio.h header file that I can 
open up a file descriptor and then use select()/read() to grab the 
contents of a ring buffer of some size (presumably interrupt-posted) of 
events since last look, and determine if there's anything in there.  
Provided you're reasonably fast this might be enough to, for example, 
read an optical encoder that has a modest pulse rate.

I see apparent review code at https://reviews.freebsd.org/D27398 from 
late 2020, but nothing else I can find digging around; an example 
(assuming it is actually implemented and works) would be helpful.

Thanks in advance!

-- 
Karl Denninger
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