d19e470b66
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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.