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acpi_thermal - ACPI thermal management subsystem
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.
Number of seconds to continue active cooling once started. A new
active cooling level will not be selected until this interval
Number of seconds between polling the current temperature.
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).
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.
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.
Current thermal zone status. These are bit-masked values.
Current temperature for this zone.
Temperature to start passive cooling by throttling down CPU, etc.
This value can be overridden by the user.
Temperature to start critical suspend to disk (S4). This value
can be overridden by the user.
Temperature to start critical shutdown (S5). This value can be
overridden by the user.
Temperatures at which to switch to the corresponding active
cooling level. The lower the _ACx value, the higher the cooling
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 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
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
0xcc Non-standard notify that the system will shutdown if
the temperature stays above _CRT or _HOT for one more
acpi(4), cpufreq(4), acpidump(8)
This manual page was written by Takanori Watanabe.