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When _FPS indicates variable speed fan support, the thermal cooling
device for fan shows max performance state count as "max_state"
(greater than or equal to 1).
But the thermal cooling device doesn't expose the properties of each
performance state. This is not enough for smart fan control user
space software, which also considers speed, power and noise level.
This change exposes the properties of the fan performance states
in the sysfs directory of the ACPI device representing the fan,
that is
/sys/bus/acpi/devices/devices/INT3404:00
or
/sys/bus/platform/devices/PNP0C0B:00.
For example:
$ ls /sys/bus/acpi/devices/INT3404\:00
description path state0 state11 state4 state7 status
hid physical_node state1 state2 state5 state8 subsystem
modalias power state10 state3 state6 state9 uevent
uid wakeup
where each state* attribute lists the properties of a fan performance
state in the following format:
control_percent:trip_point:speed_rpm:noise_level_mdb:power_mw
$ cat /sys/bus/acpi/devices/INT3404\:00/state10
95:0:11600:47500:4500
as documented in
Documentation/admin-guide/acpi/fan_performance_states.rst
While at it, return the correct error code from acpi_fan_probe()
when acpi_fan_get_fps() or acpi_fan_get_fif() fails.
Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
[ rjw: Subject, changelog, documentation ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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