projects / linux-block.git / blame
| Commit | Line | Data |
|---|---|---|
| d19e470b SP |
1 | .. SPDX-License-Identifier: GPL-2.0 |
| 2 | ||
| 3 | =========================== | |
| 4 | ACPI Fan Performance States | |
| 5 | =========================== | |
| 6 | ||
| 7 | When the optional _FPS object is present under an ACPI device representing a | |
| 8 | fan (for example, PNP0C0B or INT3404), the ACPI fan driver creates additional | |
| 9 | "state*" attributes in the sysfs directory of the ACPI device in question. | |
| 10 | These attributes list properties of fan performance states. | |
| 11 | ||
| 12 | For more information on _FPS refer to the ACPI specification at: | |
| 13 | ||
| 14 | http://uefi.org/specifications | |
| 15 | ||
| 16 | For instance, the contents of the INT3404 ACPI device sysfs directory | |
| 17 | may look as follows:: | |
| 18 | ||
| 19 | $ ls -l /sys/bus/acpi/devices/INT3404:00/ | |
| 20 | total 0 | |
| ae99fb8b | 21 | ... |
| d19e470b SP |
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 | ||
| 37 | where each of the "state*" files represents one performance state of the fan | |
| 38 | and contains a colon-separated list of 5 integer numbers (fields) with the | |
| 39 | following interpretation:: | |
| 40 | ||
| ae99fb8b | 41 | control_percent:trip_point_index:speed_rpm:noise_level_mdb:power_mw |
| d19e470b SP |
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 | ||
| 56 | For example:: | |
| 57 | ||
| 58 | $cat /sys/bus/acpi/devices/INT3404:00/state1 | |
| 59 | 25:0:3200:12500:1250 | |
| 60 | ||
| 61 | When a given field is not populated or its value provided by the platform | |
| 62 | firmware is invalid, the "not-defined" string is shown instead of the value. |