platform/x86: wmi: Add bus ABI documentation

Add documentation for the WMI bus sysfs interface so userspace
applications can use it to access additional data about WMI devices.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20240624173116.31314-3-W_Armin@gmx.de


Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Documentation/ABI/testing/sysfs-bus-wmi

+What:		/sys/bus/wmi/devices/.../driver_override
+Date:		February 2024
+Contact:	Armin Wolf <W_Armin@gmx.de>
+Description:
+		This file allows the driver for a device to be specified which
+		will override standard ID table matching.
+		When specified, only a driver with a name matching the value
+		written to driver_override will have an opportunity to bind
+		to the device.
+		The override is specified by writing a string to the
+		driver_override file (echo wmi-event-dummy > driver_override).
+		The override may be cleared with an empty string (echo > \
+		driver_override) which returns the device to standard matching
+		rules binding.
+		Writing to driver_override does not automatically unbind the
+		device from its current driver or make any attempt to automatically
+		load the specified driver. If no driver with a matching name is
+		currently loaded in the kernel, the device will not bind to any
+		driver.
+		This also allows devices to opt-out of driver binding using a
+		driver_override name such as "none". Only a single driver may be
+		specified in the override, there is no support for parsing delimiters.
+
+What:		/sys/bus/wmi/devices/.../modalias
+Date:		November 20:15
+Contact:	Andy Lutomirski <luto@kernel.org>
+Description:
+		This file contains the MODALIAS value emitted by uevent for a
+		given WMI device.
+
+		Format: wmi:XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX.
+
+What:		/sys/bus/wmi/devices/.../guid
+Date:		November 2015
+Contact:	Andy Lutomirski <luto@kernel.org>
+Description:
+		This file contains the GUID used to match WMI devices to
+		compatible WMI drivers. This GUID is not necessarily unique
+		inside a given machine, it is solely used to identify the
+		interface exposed by a given WMI device.
+
+What:		/sys/bus/wmi/devices/.../object_id
+Date:		November 2015
+Contact:	Andy Lutomirski <luto@kernel.org>
+Description:
+		This file contains the WMI object ID used internally to construct
+		the ACPI method names used by non-event WMI devices. It contains
+		two ASCII letters.
+
+What:		/sys/bus/wmi/devices/.../notify_id
+Date:		November 2015
+Contact:	Andy Lutomirski <luto@kernel.org>
+Description:
+		This file contains the WMI notify ID used internally to map ACPI
+		events to WMI event devices. It contains two ASCII letters.
+
+What:		/sys/bus/wmi/devices/.../instance_count
+Date:		November 2015
+Contact:	Andy Lutomirski <luto@kernel.org>
+Description:
+		This file contains the number of WMI object instances being
+		present on a given WMI device. It contains a non-negative
+		number.
+
+What:		/sys/bus/wmi/devices/.../expensive
+Date:		November 2015
+Contact:	Andy Lutomirski <luto@kernel.org>
+Description:
+		This file contains a boolean flag signaling if interacting with
+		the given WMI device will consume significant CPU resources.
+		The WMI driver core will take care of enabling/disabling such
+		WMI devices.
+
+What:		/sys/bus/wmi/devices/.../setable
+Date:		May 2017
+Contact:	Darren Hart (VMware) <dvhart@infradead.org>
+Description:
+		This file contains a boolean flags signaling the data block
+		aassociated with the given WMI device is writable. If the
+		given WMI device is not associated with a data block, then
+		this file will not exist.

MAINTAINERS

@@ -392,6 +392,7 @@ ACPI WMI DRIVER
 M:	Armin Wolf <W_Armin@gmx.de>
 L:	platform-driver-x86@vger.kernel.org
 S:	Maintained
+F:	Documentation/ABI/testing/sysfs-bus-wmi
 F:	Documentation/driver-api/wmi.rst
 F:	Documentation/wmi/
 F:	drivers/platform/x86/wmi.c