A way to enable the HoneyComb's ACPI thermally controlled two speed fan control via /etc/sysctl.conf and /etc/rc.conf

Updating /etc/sysctl.conf and /etc/rc.conf as indicated below
enables the thermally controlled 2-speed fan control.

/etc/sysctl.conf : add . . .

#
# Part of enabling the HoneyComb 2-speed fan control that is based
# on temerature. See both /etc/sysctl.conf (executed first) and 
# /etc/rc.conf (execute muliple times later). /etc/rc.conf happens 
# to execute multiple times with time/activity between and this 
# seems to be important.
hw.acpi.thermal.tz0.passive_cooling=0
hw.acpi.thermal.tz0.active=1

(I'll note that the passive_cooling fails and turns itself off
when it is attempted.)

/etc/rc.conf : add . . .

#
# Part of enabling the HoneyComb 2-speed fan control that is based
# on temerature. See both /etc/sysctl.conf (executed first) and
# /etc/rc.conf (execute muliple times later). /etc/rc.conf happens
# to execute multiple times with time/activity between and this
# seems to be important.
sysctl hw.acpi.thermal.tz0.active=0 > /dev/null



My guess is that there is something more that the
hw.acpi.thermal.tz0 driver could do that would
automatically lead to the result.

The EDK2 sets up the full-speed fan until it detects
that the OS has started the thermal zone AML activity.
Absent the proof-of-capablity to initiate changes,
full-speed stays enabled for safety reasons.

Effectively what I've done is force some activity for
EDK2 to detect that the OS has hw.acpi.thermal.tz0
usefully operational.

===
Mark Millard
marklmi at yahoo.com