One year ago, I deprecated 'kern' in favor of 'kernel' for the system
name for some power events. I'm about to remove it from the kernel, but
realized there's been no warning generated for users. Preserve POLA by
converting on the fly here and issuing a warning for 14.x, and an fatal
error after we branch 15. Make compiling it an error on 16 to remove
the gross hack after we branch.
Sponsored by: Netflix
Reviewed by: bapt
Differential Revision: https://reviews.freebsd.org/D37584
Currently, subr_bus.c shares logic for (a) maintaining all HW devices
(e.g. discovery/attach/detach logic) and (b) generic devctl notification
layer for devices/PMU/GEOM/interfaces/etc).
These two subsystems share really tiny interaction interface, composed of 3
notification functions. With that in mind, move devctl layer to a
separate file, establishing a clear notification interface between the
sub.c bus layer and the provider (devctl).
The primary driver of this change is netlink implementation (D36002).
The idea is to propagate device-level events to netlink as well, so all
netlink customers can subscribe to these changes.
The long-term goal is to deprecate devctl and to use netlink as the
kernel<> userland transport provided netlink gets enough traction.
Reviewed by: imp, markj
Differential Revision: https://reviews.freebsd.org/D36091
MFC after: 1 month
