HID: sensor: Custom and Generic sensor support

HID Sensor Spec defines two usage ids for custom sensors

	HID_USAGE_SENSOR_TYPE_OTHER_CUSTOM (0x09, 0xE1)
	HID_USAGE_SENSOR_TYPE_OTHER_GENERIC(0x09, 0xE2)

	In addition the standard also defines usage ids for custom fields.
The purpose of these sensors is to extend the functionality or provide a way to
obfuscate the data being communicated by a sensor. Without knowing the mapping
between the data and its encapsulated form, it is difficult for an driver to
determine what data is being communicated by the sensor.  This allows some
differentiating use cases, where vendor can provide applications.  Since these
can't be represented by standard sensor interfaces like IIO, we present these
as fields with

- type (input/output)
- units
- min/max
- get/set value

In addition an dev interface to transfer report events. Details about this
interface is described in /Documentation/hid/hid-sensor.txt.  Manufacturers
should not use these ids for any standard sensors, otherwise the the
product/vendor id can be added to black list.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Reviewed-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/Kconfig

@@ -885,6 +885,21 @@ config HID_SENSOR_HUB
 	  for events and handle data streams. Each sensor driver can format
 	  data and present to user mode using input or IIO interface.
 
+config HID_SENSOR_CUSTOM_SENSOR
+	tristate "HID Sensors hub custom sensor support"
+	depends on HID_SENSOR_HUB
+	default n
+	---help---
+	  HID Sensor hub specification allows definition of some custom and
+	  generic sensors. Unlike other HID sensors, they can't be exported
+	  via Linux IIO because of custom fields. This is up to the manufacturer
+	  to decide how to interpret these special sensor ids and process in
+	  the user space. Currently some manufacturers are using these ids for
+	  sensor calibration and debugging other sensors. Manufacturers
+	  should't use these special custom sensor ids to export any of the
+	  standard sensors.
+	  Select this config option for custom/generic sensor support.
+
 endmenu
 
 endif # HID

drivers/hid/Makefile

@@ -101,6 +101,7 @@ obj-$(CONFIG_HID_WACOM)		+= wacom.o
 obj-$(CONFIG_HID_WALTOP)	+= hid-waltop.o
 obj-$(CONFIG_HID_WIIMOTE)	+= hid-wiimote.o
 obj-$(CONFIG_HID_SENSOR_HUB)	+= hid-sensor-hub.o
+obj-$(CONFIG_HID_SENSOR_CUSTOM_SENSOR)	+= hid-sensor-custom.o
 
 obj-$(CONFIG_USB_HID)		+= usbhid/
 obj-$(CONFIG_USB_MOUSE)		+= usbhid/