hwmon: add Corsair Commander Pro driver

This is v7 of a driver for the Corsair Commander Pro.
It provides sysfs attributes for:
- Reading fan speed
- Reading temp sensors
- Reading voltage values
- Writing pwm and reading last written pwm
- Reading fan and temp connection status

It is an usb driver, so it needs to be ignored by usbhid.
The Corsair Commander Pro is a fan controller and provides
no means for user interaction.
The two device numbers are there, because there is a slightly
different version of the same device. (Only difference
seem to be in some presets.)

Squashed:
 hwmon: (corsair-cpro) add fan_target

 This adds fan_target entries to the corsair-cpro driver.
 Reading the attribute from the device does not seem possible, so
 it returns the last set value (same as pwm).

 send_usb_cmd now has one more argument, which is needed for the
 fan_target command.

 hwmon: corsair-cpro: Change to HID driver

 This changes corsair-cpro to a hid driver using hid reports.
Signed-off-by: Marius Zachmann <mail@mariuszachmann.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20200626055936.4441-1-mail@mariuszachmann.de
Link: https://lore.kernel.org/r/20200709141413.30790-1-mail@mariuszachmann.de
[groeck: Squashed follow-up patches to avoid changes in HID code]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/corsair-cpro.rst

+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver corsair-cpro
+==========================
+
+Supported devices:
+
+  * Corsair Commander Pro
+  * Corsair Commander Pro (1000D)
+
+Author: Marius Zachmann
+
+Description
+-----------
+
+This driver implements the sysfs interface for the Corsair Commander Pro.
+The Corsair Commander Pro is a USB device with 6 fan connectors,
+4 temperature sensor connectors and 2 Corsair LED connectors.
+It can read the voltage levels on the SATA power connector.
+
+Usage Notes
+-----------
+
+Since it is a USB device, hotswapping is possible. The device is autodetected.
+
+Sysfs entries
+-------------
+
+======================= =====================================================================
+in0_input		Voltage on SATA 12v
+in1_input		Voltage on SATA 5v
+in2_input		Voltage on SATA 3.3v
+temp[1-4]_input		Temperature on connected temperature sensors
+fan[1-6]_input		Connected fan rpm.
+fan[1-6]_label		Shows fan type as detected by the device.
+fan[1-6]_target		Sets fan speed target rpm.
+			When reading, it reports the last value if it was set by the driver.
+			Otherwise returns 0.
+pwm[1-6]		Sets the fan speed. Values from 0-255.
+			When reading, it reports the last value if it was set by the driver.
+			Otherwise returns 0.
+======================= =====================================================================

Documentation/hwmon/index.rst

@@ -47,6 +47,7 @@ Hardware Monitoring Kernel Drivers
    bel-pfe
    bt1-pvt
    coretemp
+   corsair-cpro
    da9052
    da9055
    dell-smm-hwmon

MAINTAINERS

@@ -4401,6 +4401,12 @@ S:	Maintained
 F:	Documentation/hwmon/coretemp.rst
 F:	drivers/hwmon/coretemp.c
 
+CORSAIR-CPRO HARDWARE MONITOR DRIVER
+M:	Marius  <mail@mariuszachmann.de>
+L:	linux-hwmon@vger.kernel.org
+S:	Maintained
+F:	drivers/hwmon/corsair-cpro.c
+
 COSA/SRP SYNC SERIAL DRIVER
 M:	Jan "Yenya" Kasprzak <kas@fi.muni.cz>
 S:	Maintained

drivers/hwmon/Kconfig

@@ -439,6 +439,16 @@ config SENSORS_BT1_PVT_ALARMS
 	  the data conversion will be periodically performed and the data will be
 	  saved in the internal driver cache.
 
+config SENSORS_CORSAIR_CPRO
+	tristate "Corsair Commander Pro controller"
+	depends on HID
+	help
+	  If you say yes here you get support for the Corsair Commander Pro
+	  controller.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called corsair-cpro.
+
 config SENSORS_DRIVETEMP
 	tristate "Hard disk drives with temperature sensors"
 	depends on SCSI && ATA

drivers/hwmon/Makefile

@@ -56,6 +56,7 @@ obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
 obj-$(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_DA9052_ADC)+= da9052-hwmon.o
 obj-$(CONFIG_SENSORS_DA9055)+= da9055-hwmon.o
 obj-$(CONFIG_SENSORS_DELL_SMM)	+= dell-smm-hwmon.o