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62 lines
2.2 KiB
62 lines
2.2 KiB
.. 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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