.. 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.