1.. SPDX-License-Identifier: GPL-2.0
2
3===========================
4ACPI Fan Performance States
5===========================
6
7When the optional _FPS object is present under an ACPI device representing a
8fan (for example, PNP0C0B or INT3404), the ACPI fan driver creates additional
9"state*" attributes in the sysfs directory of the ACPI device in question.
10These attributes list properties of fan performance states.
11
12For more information on _FPS refer to the ACPI specification at:
13
14http://uefi.org/specifications
15
16For instance, the contents of the INT3404 ACPI device sysfs directory
17may look as follows::
18
19 $ ls -l /sys/bus/acpi/devices/INT3404:00/
20 total 0
21 ...
22 -r--r--r-- 1 root root 4096 Dec 13 20:38 state0
23 -r--r--r-- 1 root root 4096 Dec 13 20:38 state1
24 -r--r--r-- 1 root root 4096 Dec 13 20:38 state10
25 -r--r--r-- 1 root root 4096 Dec 13 20:38 state11
26 -r--r--r-- 1 root root 4096 Dec 13 20:38 state2
27 -r--r--r-- 1 root root 4096 Dec 13 20:38 state3
28 -r--r--r-- 1 root root 4096 Dec 13 20:38 state4
29 -r--r--r-- 1 root root 4096 Dec 13 20:38 state5
30 -r--r--r-- 1 root root 4096 Dec 13 20:38 state6
31 -r--r--r-- 1 root root 4096 Dec 13 20:38 state7
32 -r--r--r-- 1 root root 4096 Dec 13 20:38 state8
33 -r--r--r-- 1 root root 4096 Dec 13 20:38 state9
34 -r--r--r-- 1 root root 4096 Dec 13 01:00 status
35 ...
36
37where each of the "state*" files represents one performance state of the fan
38and contains a colon-separated list of 5 integer numbers (fields) with the
39following interpretation::
40
41  control_percent:trip_point_index:speed_rpm:noise_level_mdb:power_mw
42
43* ``control_percent``: The percent value to be used to set the fan speed to a
44  specific level using the _FSL object (0-100).
45
46* ``trip_point_index``: The active cooling trip point number that corresponds
47  to this performance state (0-9).
48
49* ``speed_rpm``: Speed of the fan in rotations per minute.
50
51* ``noise_level_mdb``: Audible noise emitted by the fan in this state in
52  millidecibels.
53
54* ``power_mw``: Power draw of the fan in this state in milliwatts.
55
56For example::
57
58 $cat /sys/bus/acpi/devices/INT3404:00/state1
59 25:0:3200:12500:1250
60
61When a given field is not populated or its value provided by the platform
62firmware is invalid, the "not-defined" string is shown instead of the value.
63