Input: trackpoint: document sysfs interface

Descriptions have been collected from git commit logs, code commits and
the TrackPoint System Version 4.0 Engineering Specification.

Signed-off-by: Aishwarya Pant <aishpant@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/Documentation/ABI/testing/sysfs-devices-platform-trackpoint b/Documentation/ABI/testing/sysfs-devices-platform-trackpoint
new file mode 100644 (file)
index 0000000..df11901
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-platform-trackpoint
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+What:          /sys/devices/platform/i8042/.../sensitivity
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) Trackpoint sensitivity.
+
+What:          /sys/devices/platform/i8042/.../intertia
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) Negative inertia factor. High values cause the cursor to
+               snap backward when the trackpoint is released.
+
+What:          /sys/devices/platform/i8042/.../reach
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) Backup range for z-axis press.
+
+What:          /sys/devices/platform/i8042/.../draghys
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) The drag hysteresis controls how hard it is to drag with
+               z-axis pressed.
+
+What:          /sys/devices/platform/i8042/.../mindrag
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) Minimum amount of force needed to trigger dragging.
+
+What:          /sys/devices/platform/i8042/.../speed
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) Speed of the trackpoint cursor.
+
+What:          /sys/devices/platform/i8042/.../thresh
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) Minimum value for z-axis force required to trigger a press
+               or release, relative to the running average.
+
+What:          /sys/devices/platform/i8042/.../upthresh
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) The offset from the running average required to generate a
+               select (click) on z-axis on release.
+
+What:          /sys/devices/platform/i8042/.../ztime
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) This attribute determines how sharp a press has to be in
+               order to be recognized.
+
+What:          /sys/devices/platform/i8042/.../jenks
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) Minimum curvature in degrees required to generate a double
+               click without a release.
+
+What:          /sys/devices/platform/i8042/.../skipback
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) When the skipback bit is set, backup cursor movement during
+               releases from drags will be suppressed. The default value for
+               this bit is 0.
+
+What:          /sys/devices/platform/i8042/.../ext_dev
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) Disable (0) or enable (1) external pointing device.
+
+What:          /sys/devices/platform/i8042/.../press_to_select
+Date:          Aug, 2005
+KernelVersion: 2.6.14
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) Writing a value of 1 to this file will enable the Press to
+               Select functions like tapping the control stick to simulate a
+               left click, and writing 0 will disable it.
+
+What:          /sys/devices/platform/i8042/.../drift_time
+Date:          Dec, 2014
+KernelVersion: 3.19
+Contact:       linux-input@vger.kernel.org
+Description:
+               (RW) This parameter controls the period of time to test for a
+               ‘hands off’ condition (i.e. when no force is applied) before a
+               drift (noise) calibration occurs.
+
+               IBM Trackpoints have a feature to compensate for drift by
+               recalibrating themselves periodically. By default, if for 0.5
+               seconds there is no change in position, it's used as the new
+               zero. This duration is too low. Often, the calibration happens
+               when the trackpoint is in fact being used.