Merge tag 'platform-drivers-x86-v4.15-1' of git://git.infradead.org/linux-platform...

[linux-2.6-microblaze.git] / Documentation / admin-guide / thunderbolt.rst

diff --git a/Documentation/admin-guide/thunderbolt.rst b/Documentation/admin-guide/thunderbolt.rst
index 5c62d11..de50a85 100644 (file)
--- a/Documentation/admin-guide/thunderbolt.rst
+++ b/Documentation/admin-guide/thunderbolt.rst
@@ -221,3 +221,18 @@ The driver will create one virtual ethernet interface per Thunderbolt
 port which are named like ``thunderbolt0`` and so on. From this point
 you can either use standard userspace tools like ``ifconfig`` to
 configure the interface or let your GUI to handle it automatically.
+
+Forcing power
+-------------
+Many OEMs include a method that can be used to force the power of a
+thunderbolt controller to an "On" state even if nothing is connected.
+If supported by your machine this will be exposed by the WMI bus with
+a sysfs attribute called "force_power".
+
+For example the intel-wmi-thunderbolt driver exposes this attribute in:
+  /sys/devices/platform/PNP0C14:00/wmi_bus/wmi_bus-PNP0C14:00/86CCFD48-205E-4A77-9C48-2021CBEDE341/force_power
+
+  To force the power to on, write 1 to this attribute file.
+  To disable force power, write 0 to this attribute file.
+
+Note: it's currently not possible to query the force power state of a platform.