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-rw-r--r--Documentation/input/event-codes.txt24
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diff --git a/Documentation/input/event-codes.txt b/Documentation/input/event-codes.txt
index 53305bd0818..c587a966413 100644
--- a/Documentation/input/event-codes.txt
+++ b/Documentation/input/event-codes.txt
@@ -196,6 +196,17 @@ EV_MSC:
EV_MSC events are used for input and output events that do not fall under other
categories.
+A few EV_MSC codes have special meaning:
+
+* MSC_TIMESTAMP:
+ - Used to report the number of microseconds since the last reset. This event
+ should be coded as an uint32 value, which is allowed to wrap around with
+ no special consequence. It is assumed that the time difference between two
+ consecutive events is reliable on a reasonable time scale (hours).
+ A reset to zero can happen, in which case the time since the last event is
+ unknown. If the device does not provide this information, the driver must
+ not provide it to user space.
+
EV_LED:
----------
EV_LED events are used for input and output to set and query the state of
@@ -270,6 +281,19 @@ gestures can normally be extracted from it.
If INPUT_PROP_SEMI_MT is not set, the device is assumed to be a true MT
device.
+INPUT_PROP_TOPBUTTONPAD:
+-----------------------
+Some laptops, most notably the Lenovo *40 series provide a trackstick
+device but do not have physical buttons associated with the trackstick
+device. Instead, the top area of the touchpad is marked to show
+visual/haptic areas for left, middle, right buttons intended to be used
+with the trackstick.
+
+If INPUT_PROP_TOPBUTTONPAD is set, userspace should emulate buttons
+accordingly. This property does not affect kernel behavior.
+The kernel does not provide button emulation for such devices but treats
+them as any other INPUT_PROP_BUTTONPAD device.
+
Guidelines:
==========
The guidelines below ensure proper single-touch and multi-finger functionality.