63 lines
2.2 KiB
ReStructuredText
63 lines
2.2 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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===========================
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ACPI Fan Performance States
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===========================
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When the optional _FPS object is present under an ACPI device representing a
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fan (for example, PNP0C0B or INT3404), the ACPI fan driver creates additional
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"state*" attributes in the sysfs directory of the ACPI device in question.
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These attributes list properties of fan performance states.
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For more information on _FPS refer to the ACPI specification at:
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http://uefi.org/specifications
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For instance, the contents of the INT3404 ACPI device sysfs directory
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may look as follows::
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$ ls -l /sys/bus/acpi/devices/INT3404:00/
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total 0
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...
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state0
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state1
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state10
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state11
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state2
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state3
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state4
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state5
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state6
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state7
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state8
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-r--r--r-- 1 root root 4096 Dec 13 20:38 state9
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-r--r--r-- 1 root root 4096 Dec 13 01:00 status
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...
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where each of the "state*" files represents one performance state of the fan
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and contains a colon-separated list of 5 integer numbers (fields) with the
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following interpretation::
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control_percent:trip_point_index:speed_rpm:noise_level_mdb:power_mw
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* ``control_percent``: The percent value to be used to set the fan speed to a
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specific level using the _FSL object (0-100).
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* ``trip_point_index``: The active cooling trip point number that corresponds
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to this performance state (0-9).
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* ``speed_rpm``: Speed of the fan in rotations per minute.
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* ``noise_level_mdb``: Audible noise emitted by the fan in this state in
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millidecibels.
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* ``power_mw``: Power draw of the fan in this state in milliwatts.
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For example::
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$cat /sys/bus/acpi/devices/INT3404:00/state1
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25:0:3200:12500:1250
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When a given field is not populated or its value provided by the platform
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firmware is invalid, the "not-defined" string is shown instead of the value.
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