gone_in(majar, msg); If we're running in FreeBSD major, tell
the user this code may be deleted soon.
If we're running in FreeBSD major - 1,
the the user is deprecated and will
be gone in major.
Otherwise say nothing.
gone_in_dev(dev, major, msg) Just like gone_in, except use device_printf.
New tunable / sysctl debug.oboslete_panic: 0 - don't panic,
1 - panic in major or newer , 2 - panic in major - 1 or newer
default: 0
if NO_OBSOLETE_CODE is defined, then both of these turn into compile
time errors when building for major. Add options NO_OBSOLETE_CODE to
kernel build system.
This lets us tag code that's going away so users know it will be gone,
as well as automatically manage things.
Differential Review: https://reviews.freebsd.org/D13818
7faed6e3e9