platform/x86: lenovo-wmi-other: Add HWMON for fan reporting/tuning

Register an HWMON device for fan reporting/tuning according to
Capability Data 00 (capdata00) and Fan Test Data (capdata_fan) provided
by lenovo-wmi-capdata. The corresponding HWMON nodes are:

 - fanX_div: internal RPM divisor
 - fanX_input: current RPM
 - fanX_max: maximum RPM
 - fanX_min: minimum RPM
 - fanX_target: target RPM (tunable, 0=auto)

Information from capdata00 and capdata_fan are used to control the
visibility and constraints of HWMON attributes. Fan info from capdata00
is collected on bind, while fan info from capdata_fan is collected in a
callback. Once all fan info is collected, register the HWMON device.

Signed-off-by: Rong Zhang <i@rong.moe>
Reviewed-by: Derek J. Clark <derekjohn.clark@gmail.com>
Tested-by: Kurt Borja <kuurtb@gmail.com>
Link: https://patch.msgid.link/20260120182104.163424-8-i@rong.moe
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: Rongronggg9

Documentation/wmi/devices/lenovo-wmi-other.rst

@@ -31,6 +31,8 @@ under the following path:
 
   /sys/class/firmware-attributes/lenovo-wmi-other/attributes/<attribute>/
 
+Additionally, this driver also exports attributes to HWMON.
+
 LENOVO_CAPABILITY_DATA_00
 -------------------------
 
@@ -39,6 +41,14 @@ WMI GUID ``362A3AFE-3D96-4665-8530-96DAD5BB300E``
 The LENOVO_CAPABILITY_DATA_00 interface provides various information that
 does not rely on the gamezone thermal mode.
 
+The following HWMON attributes are implemented:
+ - fanX_div: internal RPM divisor
+ - fanX_input: current RPM
+ - fanX_target: target RPM (tunable, 0=auto)
+
+Due to the internal RPM divisor, the current/target RPMs are rounded down to
+its nearest multiple. The divisor itself is not necessary to be a power of two.
+
 LENOVO_CAPABILITY_DATA_01
 -------------------------
 
@@ -70,6 +80,10 @@ WMI GUID ``B642801B-3D21-45DE-90AE-6E86F164FB21``
 The LENOVO_FAN_TEST_DATA interface provides reference data for self-test of
 cooling fans.
 
+The following HWMON attributes are implemented:
+ - fanX_max: maximum RPM
+ - fanX_min: minimum RPM
+
 WMI interface description
 =========================
 

drivers/platform/x86/lenovo/Kconfig

@@ -263,6 +263,7 @@ config LENOVO_WMI_GAMEZONE
 config LENOVO_WMI_TUNING
 	tristate "Lenovo Other Mode WMI Driver"
 	depends on ACPI_WMI
+	select HWMON
 	select FW_ATTR_CLASS
 	select LENOVO_WMI_CAPDATA
 	select LENOVO_WMI_EVENTS