hwmon: Add driver for ASUS ROG RYUJIN II 360 AIO cooler

This driver exposes hardware sensors of the ASUS ROG RYUJIN II 360
all-in-one CPU liquid cooler, which communicates through a proprietary
USB HID protocol. Report offsets were initially discovered in [1] by
Florian Freudiger.

Available sensors are pump, internal and external
(controller) fan speed in RPM, their duties in PWM, as well as
coolant temperature.

Attaching external fans to the controller is optional and allows them
to be controlled from the device. If not connected, the fan-related
sensors will report zeroes. The controller is a separate hardware unit
that comes bundled with the AIO and connects to it to allow fan control.

The addressable LCD screen is not supported in this
driver and should be controlled through userspace tools.

[1]: https://github.com/liquidctl/liquidctl/pull/653

Tested-by: Florian Freudiger <florian.freudiger@proton.me>
Signed-off-by: Aleksa Savic <savicaleksa83@gmail.com>
Link: https://lore.kernel.org/r/20240108094453.22986-1-savicaleksa83@gmail.com
[groeck: Add HID dependency]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/asus_rog_ryujin.rst

@@ -0,0 +1,47 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver asus_rog_ryujin
+=============================
+
+Supported devices:
+
+* ASUS ROG RYUJIN II 360
+
+Author: Aleksa Savic
+
+Description
+-----------
+
+This driver enables hardware monitoring support for the listed ASUS ROG RYUJIN
+all-in-one CPU liquid coolers. Available sensors are pump, internal and external
+(controller) fan speed in RPM, their duties in PWM, as well as coolant temperature.
+
+Attaching external fans to the controller is optional and allows them to be
+controlled from the device. If not connected, the fan-related sensors will
+report zeroes. The controller is a separate hardware unit that comes bundled
+with the AIO and connects to it to allow fan control.
+
+The addressable LCD screen is not supported in this driver and should
+be controlled through userspace tools.
+
+Usage notes
+-----------
+
+As these are USB HIDs, the driver can be loaded automatically by the kernel and
+supports hot swapping.
+
+Sysfs entries
+-------------
+
+=========== =============================================
+fan1_input  Pump speed (in rpm)
+fan2_input  Internal fan speed (in rpm)
+fan3_input  External (controller) fan 1 speed (in rpm)
+fan4_input  External (controller) fan 2 speed (in rpm)
+fan5_input  External (controller) fan 3 speed (in rpm)
+fan6_input  External (controller) fan 4 speed (in rpm)
+temp1_input Coolant temperature (in millidegrees Celsius)
+pwm1        Pump duty
+pwm2        Internal fan duty
+pwm3        External (controller) fan duty
+=========== =============================================

Documentation/hwmon/index.rst

@@ -46,6 +46,7 @@ Hardware Monitoring Kernel Drivers
    asc7621
    aspeed-pwm-tacho
    asus_ec_sensors
+   asus_rog_ryujin
    asus_wmi_sensors
    bcm54140
    bel-pfe

MAINTAINERS

@@ -3181,6 +3181,12 @@ S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git
 F:	drivers/platform/x86/asus-tf103c-dock.c
 
+ASUS ROG RYUJIN AIO HARDWARE MONITOR DRIVER
+M:	Aleksa Savic <savicaleksa83@gmail.com>
+L:	linux-hwmon@vger.kernel.org
+S:	Maintained
+F:	drivers/hwmon/asus_rog_ryujin.c
+
 ASUS WIRELESS RADIO CONTROL DRIVER
 M:	João Paulo Rechi Vita <jprvita@gmail.com>
 L:	platform-driver-x86@vger.kernel.org

drivers/hwmon/Kconfig

@@ -301,6 +301,16 @@ config SENSORS_ASC7621
 	  This driver can also be built as a module. If so, the module
 	  will be called asc7621.
 
+config SENSORS_ASUS_ROG_RYUJIN
+	tristate "ASUS ROG RYUJIN II 360 hardware monitoring driver"
+	depends on HID
+	help
+	  If you say yes here you get support for the fans and sensors of
+	  the ASUS ROG RYUJIN II 360 AIO CPU liquid cooler.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called asus_rog_ryujin.
+
 config SENSORS_AXI_FAN_CONTROL
 	tristate "Analog Devices FAN Control HDL Core driver"
 	help

drivers/hwmon/Makefile

@@ -55,6 +55,7 @@ obj-$(CONFIG_SENSORS_ARM_SCPI)	+= scpi-hwmon.o
 obj-$(CONFIG_SENSORS_AS370)	+= as370-hwmon.o
 obj-$(CONFIG_SENSORS_ASC7621)	+= asc7621.o
 obj-$(CONFIG_SENSORS_ASPEED)	+= aspeed-pwm-tacho.o
+obj-$(CONFIG_SENSORS_ASUS_ROG_RYUJIN)	+= asus_rog_ryujin.o
 obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
 obj-$(CONFIG_SENSORS_AXI_FAN_CONTROL) += axi-fan-control.o
 obj-$(CONFIG_SENSORS_BT1_PVT)	+= bt1-pvt.o