129 lines
3.9 KiB
Groff
129 lines
3.9 KiB
Groff
.\" $NetBSD: acpitz.4,v 1.12 2011/01/09 15:12:34 jruoho Exp $
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.\"
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.\" Copyright (c) 2003, 2004, 2011 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd January 9, 2011
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.Dt ACPITZ 4
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.Os
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.Sh NAME
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.Nm acpitz
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.Nd ACPI Thermal Zone
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.Sh SYNOPSIS
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.Cd "acpitz* at acpi?"
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.Sh DESCRIPTION
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The
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.Nm
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driver supports so-called
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.Tn ACPI
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.Dq Thermal Zones .
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The temperature can be monitored by the
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.Xr envsys 4
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API or the
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.Xr envstat 8
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command.
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.Pp
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The distinction between
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.Dq active
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and
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.Dq passive
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cooling is central to the abstractions behind
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.Nm .
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These are inversely related to each other:
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.Bl -enum -offset 2n
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.It
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Active cooling means that the system increases the power consumption of the
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machine by performing active thermal management (for example, by turning on
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a fan) in order to reduce the temperatures.
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.It
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Passive cooling means that the system reduces the power consumption of
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devices at the cost of system performance (for example, by lowering the
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.Tn CPU
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frequencies) in order to reduce the temperatures.
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.El
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.Pp
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Only active cooling is currently supported on
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.Nx .
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.Pp
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It should be also noted that the internal
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functioning of these cooling policies vary across machines.
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On some machines the operating system may have little control over
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the thermal zones as the firmware manages the thermal control internally,
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whereas on other machines the policies may be exposed to the implementation
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at their full extent.
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.Sh EVENTS
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The
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.Nm
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driver knows about the active cooling levels, the current
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temperatures, and critical, hot, and passive temperature thresholds
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(as supported by the hardware).
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The driver is able to send events to
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.Xr powerd 8
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when the sensor's state has changed.
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When a Thermal Zone is either critical or
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.Dq hot ,
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the
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.Pa /etc/powerd/scripts/sensor_temperature
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script will be invoked with a
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.Em critical-over
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event.
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.Pp
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The critical temperature is the threshold for system shutdown.
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Depending on the hardware, the mainboard will take down the system
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instantly and no event will have a chance to be sent.
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.Sh SEE ALSO
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.Xr acpi 4 ,
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.Xr acpifan 4 ,
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.Xr envsys 4 ,
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.Xr envstat 8 ,
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.Xr powerd 8
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.Sh HISTORY
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The
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.Nm
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driver
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appeared in
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.Nx 2.0 .
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.Sh AUTHORS
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.An Jared D. McNeill Aq jmcneill@invisible.ca
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.Sh CAVEATS
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While no pronounced bugs are known to exist,
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several caveats can be mentioned:
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.Bl -bullet
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.It
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Passive cooling is not implemented.
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.It
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There is no user-controllable way to switch between active and passive
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cooling, although the specifications support such transforms on some machines.
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.It
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The
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.Dq hot
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temperature is a threshold in which the system ought to be put into
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.Tn S4
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sleep.
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This sleep state
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.Pq Dq suspend to disk
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is not supported on
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.Nx .
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.El
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