avoid calling the "_DIS" method during acpi interrupt link setup,
which hangs various nforce4 based motherboards.
when the problem is properly fixed, remove this hack. for now,
it allows someone (me) to have a valid kernel config that doesn't
require a source hack every new tree.
ok chs@
it to all kernel configs that contain "options MODULAR". This
option turns on module autoloading by default (which is the current
default). This allows people who don't want module autoloading on
by default to disable it by simply removing/commentting this line.
This is basically cribbed from regular serial ports, and just adds
hooks to call the pps support routines.
Also, note in the ucom(4) man page that there is about 1 ms of
latency. Discussed on tech-kern in October of 2013, with the only
concern being that someone who didn't know what they were doing might
set up a stratum 1 server, and that somehow might have worse
timekeeping than whatever else that person might have done; the man
page comment is a mitigation for this.
This patch has been live-tested in netbsd-5/i386 and netbsd-6/i386,
and has been running on machines without a USB-serial GPS device for
most of a year with no adverse consequences (very little happens if
the PPS ioctls are not invoked).
Somehow, options(4) ended up with a bizarre claim that DIAGNOSTIC can
reduce performance by 15%. While that might have been true at some
isolated point due to a bug, it's an outlier. Since at least 2BSD,
DIAGNOSTIC has added asserts, resulting in at most
difficult-to-perceived performance degredation, and many people have
been running production systems (meaning systems they intend to use,
rather than debugging targets) with this option. (The decision a
while ago to enable DIAGNOSTIC in -current's GENERIC reflects this; if
it really were a 15% hit such enabling by default would be unreasonable.)
