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.