So, I just, finally, came across something that suggests remoteproc is the new way to talk to the PRUs, implying uio is the old way. Thing is, I have all this code that only knows how to talk to uio sysfs nodes, and those nodes are not showing up in my system.
I can see remoteproc stuff trying to happen during boot, but nothing about uio. Are the two mutually exclusive? I have the uio_pruss module loaded.
I've tried several uEnv.txt dtbs, including am335x-boneblack-emmc-overlay.dtb with an overlay to enable the PRU, and am335x-boneblack-replicape.dtb.
This is getting pretty frustrating. I have about 40 browser tabs open on the subject, and nowhere is there any insight into what's going wrong.