acpi doc misconfusion...

[Kevin Oberman]

> Date: Fri, 02 Oct 2009 19:30:58 +0400
> From: "Marat N.Afanasyev" <amarat at ksu.ru>
> Sender: owner-freebsd-stable at freebsd.org
> 
> kama wrote:
> > Hi,
> > 
> > there are a lot of different errors in various document regarding acpi
> > that are wrong.
> > 
> > In 'man acpi' it says that 'hint.acpi.0.disabled' should be placed in
> > loader.conf.
> > 
> > -------------
> > LOADER TUNABLES
> >      Tunables can be set at the loader(8) prompt before booting the kernel
> > or
> >      stored in /boot/loader.conf.  Many of these tunables also have a
> > matching
> >      sysctl(8) entry for access after boot.
> > ...
> >      hint.acpi.0.disabled
> >              Set this to 1 to disable all of ACPI.  If ACPI has been
> > disabled
> >              on your system due to a blacklist entry for your BIOS, you
> > can
> >              set this to 0 to re-enable ACPI for testing.
> > ...
> > -------------
> > 
> > 
> > 
> > In 'man loader' it says:
> > -------------
> >      acpi_load
> >                Unset this to disable automatic loading of the ACPI module.
> >                See also hint.acpi.0.disabled in device.hints(5).
> > -------------
> > 
> > In 'man device.hints'
> > -------------
> >      The following example disables the ACPI driver:
> > 
> >            hint.acpi.0.disabled="1"
> > -------------
> > 
> > http://www.freebsd.org/doc/en/articles/laptop/article.html page also
> > states that it should be in device.hints.
> > 
> > 
> > Well, these are the ones I have found. There are a lot of misconfusion in
> > various forums what to put where and how its done. Maybe its accurate on
> > both places, but then that should be noted somewhere.
> > 
> > /Bjorn
> > 
> I was told that there's no difference between loader.conf and 
> device.hints, so you can place this option in either file

This is sort of correct. Hints may be placed in either place with the
same results. But there is a difference on how the files, themselves are
handled.

/boot/loader.conf is never touched by a FreeBSD update, even for major
versions. /boot/device.hints is subject to modification between
versions. It is not automatically updated, but a new version is included
in the /sys/ARCH/conf directory and an update may be required as drivers
change. This will delete any custom hints. (E.g. The sio to uart
transition on 8.0.)

This is why I generally but any hints that really need to survive in
/boot/loader.conf. (In my case, I have to disable APIC on my laptop.)
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751