Ubuntu Manpage: acpi_thermal — ACPI thermal management subsystem

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NAME

     acpi_thermal — ACPI thermal management subsystem

SYNOPSIS

     device acpi

DESCRIPTION

     The acpi_thermal driver provides the thermal management features of the ACPI module.  This
     driver has a sysctl(8) interface and a devd(8) notification interface.  The sysctls export
     properties of each ACPI thermal zone object.

     There can be multiple thermal zones in a system.  For example, each CPU and the enclosure
     could all be separate thermal zones, each with its own setpoints and cooling devices.
     Thermal zones are numbered sequentially in the order they appear in the AML.

     The acpi_thermal driver also activates the active cooling system according to each thermal
     zone's setpoints.

SYSCTL VARIABLES

hw.acpi.thermal.min_runtime
Number of seconds to continue active cooling once started. A new active cooling
level will not be selected until this interval expires.

hw.acpi.thermal.polling_rate
Number of seconds between polling the current temperature.

hw.acpi.thermal.user_override
If set to 1, allow user override of various setpoints (below). The original values
for these settings are obtained from the BIOS and system overheating and possible
damage could occur if changed. Default is 0 (no override).

hw.acpi.thermal.tz%d.active
Current active cooling system state. If this is non-negative, the appropriate _AC%d
object is running. Set this value to the desired active cooling level to force the
corresponding fan object to the appropriate level.

hw.acpi.thermal.tz%d.passive_cooling
If set to 1, passive cooling is enabled. It does cooling without fans using
cpufreq(4) as the mechanism for controlling CPU speed. Default is enabled for tz0
where it is available.

hw.acpi.thermal.tz%d.thermal_flags
Current thermal zone status. These are bit-masked values.

hw.acpi.thermal.tz%d.temperature
Current temperature for this zone.

hw.acpi.thermal.tz%d._PSV
Temperature to start passive cooling by throttling down CPU, etc. This value can be
overridden by the user.

hw.acpi.thermal.tz%d._HOT
Temperature to start critical suspend to disk (S4). This value can be overridden by
the user.

hw.acpi.thermal.tz%d._CRT
Temperature to start critical shutdown (S5). This value can be overridden by the
user.

hw.acpi.thermal.tz%d._ACx
Temperatures at which to switch to the corresponding active cooling level. The
lower the _ACx value, the higher the cooling power.

All temperatures are printed in Celsius. Values can be set in Celsius (by providing a
trailing "C") or Kelvin (by leaving off any trailing letter). When setting a value by
sysctl(8), do not specify a trailing decimal (i.e., 90C instead of 90.0C).

NOTIFIES

     Notifies are passed to userland via devd(8).  See /etc/devd.conf and devd.conf(5) for
     examples.  The acpi_thermal driver sends events with the following attributes:

     system     ACPI
     subsystem  Thermal
     type       The fully qualified thermal zone object path as in the ASL.
     notify     An integer designating the event:

                0x80    Current temperature has changed.
                0x81    One or more trip points (_ACx, _PSV) have changed.
                0x82    One or more device lists (_ALx, _PSL, _TZD) have changed.
                0xcc    Non-standard notify that the system will shutdown if the temperature
                        stays above _CRT or _HOT for one more poll cycle.

AUTHORS