hwmon: add Corsair PSU HID controller driver

The Corsair digital power supplies of the series RMi, HXi and AXi include
a small micro-controller with a lot of sensors attached. The sensors can
be accessed by an USB connector from the outside.

This micro-controller provides the data by a simple proprietary USB HID
protocol. The data consist of temperatures, current and voltage levels,
power usage, uptimes, fan speed and some more. It is also possible to
configure the PSU (fan mode, mono/multi-rail, over current protection).

This driver provides access to the sensors/statistics of the RMi and HXi
series power supplies. It does not support configuring these devices,
because there would be many ways to misconfigure or even damage the PSU.

This patch adds:
- hwmon driver corsair-psu
- hwmon documentation
- updates MAINTAINERS
Signed-off-by: Wilken Gottwalt <wilken.gottwalt@posteo.net>
Link: https://lore.kernel.org/r/20201027131710.GA253280@monster.powergraphx.localSigned-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/corsair-psu.rst

+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver corsair-psu
+=========================
+
+Supported devices:
+
+* Corsair Power Supplies
+
+  Corsair HX550i
+
+  Corsair HX650i
+
+  Corsair HX750i
+
+  Corsair HX850i
+
+  Corsair HX1000i
+
+  Corsair HX1200i
+
+  Corsair RM550i
+
+  Corsair RM650i
+
+  Corsair RM750i
+
+  Corsair RM850i
+
+  Corsair RM1000i
+
+Author: Wilken Gottwalt
+
+Description
+-----------
+
+This driver implements the sysfs interface for the Corsair PSUs with a HID protocol
+interface of the HXi and RMi series.
+These power supplies provide access to a micro-controller with 2 attached
+temperature sensors, 1 fan rpm sensor, 4 sensors for volt levels, 4 sensors for
+power usage and 4 sensors for current levels and addtional non-sensor information
+like uptimes.
+
+Sysfs entries
+-------------
+
+=======================	========================================================
+curr1_input		Total current usage
+curr2_input		Current on the 12v psu rail
+curr3_input		Current on the 5v psu rail
+curr4_input		Current on the 3.3v psu rail
+fan1_input		RPM of psu fan
+in0_input		Voltage of the psu ac input
+in1_input		Voltage of the 12v psu rail
+in2_input		Voltage of the 5v psu rail
+in3_input		Voltage of the 3.3 psu rail
+power1_input		Total power usage
+power2_input		Power usage of the 12v psu rail
+power3_input		Power usage of the 5v psu rail
+power4_input		Power usage of the 3.3v psu rail
+temp1_input		Temperature of the psu vrm component
+temp2_input		Temperature of the psu case
+=======================	========================================================
+
+Usage Notes
+-----------
+
+It is an USB HID device, so it is auto-detected and supports hot-swapping.
+
+Flickering values in the rail voltage levels can be an indicator for a failing
+PSU. The driver also provides some additional useful values via debugfs, which
+do not fit into the hwmon class.
+
+Debugfs entries
+---------------
+
+=======================	========================================================
+uptime			Current uptime of the psu
+uptime_total		Total uptime of the psu
+vendor			Vendor name of the psu
+product			Product name of the psu
+=======================	========================================================

Documentation/hwmon/index.rst

@@ -49,6 +49,7 @@ Hardware Monitoring Kernel Drivers
    bt1-pvt
    coretemp
    corsair-cpro
+   corsair-psu
    da9052
    da9055
    dell-smm-hwmon

MAINTAINERS

@@ -4485,6 +4485,13 @@ L:	linux-hwmon@vger.kernel.org
 S:	Maintained
 F:	drivers/hwmon/corsair-cpro.c
 
+CORSAIR-PSU HARDWARE MONITOR DRIVER
+M:	Wilken Gottwalt <wilken.gottwalt@posteo.net>
+L:	linux-hwmon@vger.kernel.org
+S:	Maintained
+F:	Documentation/hwmon/corsair-psu.rst
+F:	drivers/hwmon/corsair-psu.c
+
 COSA/SRP SYNC SERIAL DRIVER
 M:	Jan "Yenya" Kasprzak <kas@fi.muni.cz>
 S:	Maintained

drivers/hwmon/Kconfig

@@ -449,6 +449,19 @@ config SENSORS_CORSAIR_CPRO
 	  This driver can also be built as a module. If so, the module
 	  will be called corsair-cpro.
 
+config SENSORS_CORSAIR_PSU
+	tristate "Corsair PSU HID controller"
+	depends on HID
+	help
+	  If you say yes here you get support for Corsair PSUs with a HID
+	  interface.
+	  Currently this driver supports the (RM/HX)550i, (RM/HX)650i,
+	  (RM/HX)750i, (RM/HX)850i, (RM/HX)1000i and HX1200i power supplies
+	  by Corsair.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called corsair-psu.
+
 config SENSORS_DRIVETEMP
 	tristate "Hard disk drives with temperature sensors"
 	depends on SCSI && ATA

drivers/hwmon/Makefile

@@ -57,6 +57,7 @@ obj-$(CONFIG_SENSORS_AXI_FAN_CONTROL) += axi-fan-control.o
 obj-$(CONFIG_SENSORS_BT1_PVT)	+= bt1-pvt.o
 obj-$(CONFIG_SENSORS_CORETEMP)	+= coretemp.o
 obj-$(CONFIG_SENSORS_CORSAIR_CPRO) += corsair-cpro.o
+obj-$(CONFIG_SENSORS_CORSAIR_PSU) += corsair-psu.o
 obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o
 obj-$(CONFIG_SENSORS_DA9055)+= da9055-hwmon.o
 obj-$(CONFIG_SENSORS_DELL_SMM)	+= dell-smm-hwmon.o