[PATCH 2/7] Documentation: ABI: document the ASUS custom fan curve attributes

[Bartu Alev]

asus-wmi has exposed custom fan curve attributes since 5.17 for CPU
and GPU fans, and since 6.6 for the mid fan, but the sysfs ABI was
never documented.  Document the existing attributes before adding the
firmware fan floor tables.

This includes several embedded controller quirks: point Z is limited
to the temperature decade [30 + 10 * (Z - 1), 39 + 10 * (Z - 1)]
degrees Celsius, the EC clamps uploaded thresholds to that decade
while reads return the raw byte written, fan speeds step without
interpolation, and downward transitions use 5 degrees Celsius of
hysteresis.

Signed-off-by: Bartu Alev <bartualev@xxxxxxxxx>
---
 Documentation/ABI/testing/sysfs-platform-asus-wmi | 59 +++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-platform-asus-wmi b/Documentation/ABI/testing/sysfs-platform-asus-wmi
index f9825c6150b5c..775ea88625c0d 100644
--- a/Documentation/ABI/testing/sysfs-platform-asus-wmi
+++ b/Documentation/ABI/testing/sysfs-platform-asus-wmi
@@ -238,3 +238,62 @@ Description:
 		Set if the MCU can go in to low-power mode on system sleep
 			* 0 - False,
 			* 1 - True
+
+What:		/sys/class/hwmon/hwmonX/pwm[12]_enable
+Date:		Oct 2026
+KernelVersion:	5.17
+Contact:	Luke D. Jones <luke@xxxxxxxxxx>, Denis Benato <denis.benato@xxxxxxxxx>, Bartu Alev <bartualev@xxxxxxxxx>
+Description:
+		Enable or disable the custom fan curve of the CPU fan (pwm1)
+		or the GPU fan (pwm2).  Reads return 1 while the custom curve
+		is enabled and 2 while the firmware controls the fan.  Writes:
+
+		    * 1 - enable the stored curve,
+		    * 2 - disable the curve and let the firmware control the
+		      fan again,
+		    * 3 - reset the stored curve to the firmware defaults and
+		      disable it.
+
+		Enabling validates the curve: temperatures and duties must
+		not decrease from point to point, otherwise the write fails
+		with -EINVAL and the curve stays disabled.  Writing any
+		writable pwmY_auto_pointZ_temp or pwmY_auto_pointZ_pwm
+		attribute disables the curve, so a changed curve has to be
+		enabled again.
+
+What:		/sys/class/hwmon/hwmonX/pwm3_enable
+Date:		Oct 2026
+KernelVersion:	6.6
+Contact:	Luke D. Jones <luke@xxxxxxxxxx>, Denis Benato <denis.benato@xxxxxxxxx>, Bartu Alev <bartualev@xxxxxxxxx>
+Description:
+		Same as pwm1_enable and pwm2_enable, for the mid fan (pwm3)
+		of laptops whose firmware exposes a third fan curve.
+
+What:		/sys/class/hwmon/hwmonX/pwm[12]_auto_point[1-8]_temp
+What:		/sys/class/hwmon/hwmonX/pwm[12]_auto_point[1-8]_pwm
+Date:		Oct 2026
+KernelVersion:	5.17
+Contact:	Luke D. Jones <luke@xxxxxxxxxx>, Denis Benato <denis.benato@xxxxxxxxx>, Bartu Alev <bartualev@xxxxxxxxx>
+Description:
+		One point of the custom fan curve of the CPU fan (pwm1) or
+		the GPU fan (pwm2).  _temp is the temperature threshold of the
+		point in degrees Celsius, _pwm is its duty in pwm units
+		(0-255); the driver scales the duty to the percentage the
+		firmware expects when the curve is enabled.
+
+		The embedded controller binds point Z (Z = 1..8) to the
+		temperature decade [30 + 10 * (Z - 1), 39 + 10 * (Z - 1)]
+		degrees Celsius and silently clamps the threshold into that
+		decade when the curve is applied, while reads return the
+		value that was written.  On TUF series, the controller steps
+		from one point to the next without interpolating, and a point
+		is left downwards with 5 degrees Celsius of hysteresis.
+
+What:		/sys/class/hwmon/hwmonX/pwm3_auto_point[1-8]_temp
+What:		/sys/class/hwmon/hwmonX/pwm3_auto_point[1-8]_pwm
+Date:		Oct 2026
+KernelVersion:	6.6
+Contact:	Luke D. Jones <luke@xxxxxxxxxx>, Denis Benato <denis.benato@xxxxxxxxx>, Bartu Alev <bartualev@xxxxxxxxx>
+Description:
+		Same as the pwm1 and pwm2 curve points, for the mid fan
+		(pwm3) of laptops whose firmware exposes a third fan curve.

-- 
2.56.0