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Date: Sun, 12 Oct 2014 22:14:53 +1100 (EST)
From: Ian Smith <smithi@nimnet.asn.au>
To: Eric McCorkle <eric@metricspace.net>
Subject: Re: ACPI debug messages
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On Sat, 11 Oct 2014 14:10:07 -0400, Eric McCorkle wrote:
 > Hello,
 > 
 > I decided to try tracing through the evaluation of the DSM method in order to
 > track down where the graphics driver failure I mentioned earlier is coming
 > from.
 > 
 > However, it looks like there's already an extensive debug logging system in
 > place in the acpica system.
 > 
 > Can this be controlled from user space (presumably through sysctls), or does
 > it need to be compiled in?

It's all in acpi(4), and in the Handbook in the nowadays rather 
poorly-named "Power and Resource Management" at section 12.13.4: 
http://www.freebsd.org/doc/handbook/acpi-overview.html

You can add it to your kernel, but I think acpi is now always loaded as 
a module, therefore you just need to rebuild the module, as described.

cheers, Ian