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- .. SPDX-License-Identifier: GPL-2.0
- ===========================
- ACPI Fan Performance States
- ===========================
- When the optional _FPS object is present under an ACPI device representing a
- fan (for example, PNP0C0B or INT3404), the ACPI fan driver creates additional
- "state*" attributes in the sysfs directory of the ACPI device in question.
- These attributes list properties of fan performance states.
- For more information on _FPS refer to the ACPI specification at:
- http://uefi.org/specifications
- For instance, the contents of the INT3404 ACPI device sysfs directory
- may look as follows::
- $ ls -l /sys/bus/acpi/devices/INT3404:00/
- total 0
- ...
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state0
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state1
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state10
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state11
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state2
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state3
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state4
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state5
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state6
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state7
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state8
- -r--r--r-- 1 root root 4096 Dec 13 20:38 state9
- -r--r--r-- 1 root root 4096 Dec 13 01:00 status
- ...
- where each of the "state*" files represents one performance state of the fan
- and contains a colon-separated list of 5 integer numbers (fields) with the
- following interpretation::
- control_percent:trip_point_index:speed_rpm:noise_level_mdb:power_mw
- * ``control_percent``: The percent value to be used to set the fan speed to a
- specific level using the _FSL object (0-100).
- * ``trip_point_index``: The active cooling trip point number that corresponds
- to this performance state (0-9).
- * ``speed_rpm``: Speed of the fan in rotations per minute.
- * ``noise_level_mdb``: Audible noise emitted by the fan in this state in
- millidecibels.
- * ``power_mw``: Power draw of the fan in this state in milliwatts.
- For example::
- $cat /sys/bus/acpi/devices/INT3404:00/state1
- 25:0:3200:12500:1250
- When a given field is not populated or its value provided by the platform
- firmware is invalid, the "not-defined" string is shown instead of the value.
- ACPI Fan Fine Grain Control
- =============================
- When _FIF object specifies support for fine grain control, then fan speed
- can be set from 0 to 100% with the recommended minimum "step size" via
- _FSL object. User can adjust fan speed using thermal sysfs cooling device.
- Here use can look at fan performance states for a reference speed (speed_rpm)
- and set it by changing cooling device cur_state. If the fine grain control
- is supported then user can also adjust to some other speeds which are
- not defined in the performance states.
- The support of fine grain control is presented via sysfs attribute
- "fine_grain_control". If fine grain control is present, this attribute
- will show "1" otherwise "0".
- This sysfs attribute is presented in the same directory as performance states.
- ACPI Fan Performance Feedback
- =============================
- The optional _FST object provides status information for the fan device.
- This includes field to provide current fan speed in revolutions per minute
- at which the fan is rotating.
- This speed is presented in the sysfs using the attribute "fan_speed_rpm",
- in the same directory as performance states.
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