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Input: convert multi-touch protocol spec into ReST format

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This file require minimum adjustments to be a valid ReST file.
Do it, in order to be able to parse it with Sphinx

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
This commit is contained in:
Mauro Carvalho Chehab 2017-04-04 17:46:28 -07:00 committed by Dmitry Torokhov
parent c8ae270e0e
commit eba31a3af9
1 changed files with 94 additions and 102 deletions
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196
Documentation/input/multi-touch-protocol.txt
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@ -1,6 +1,10 @@
.. include:: <isonum.txt>
=========================
Multi-touch (MT) Protocol Multi-touch (MT) Protocol
------------------------- =========================
Copyright (C) 2009-2010 Henrik Rydberg <rydberg@euromail.se>
:Copyright: |copy| 2009-2010 Henrik Rydberg <rydberg@euromail.se>
Introduction Introduction
@ -47,12 +51,12 @@ The main difference between the stateless type A protocol and the stateful
type B slot protocol lies in the usage of identifiable contacts to reduce type B slot protocol lies in the usage of identifiable contacts to reduce
the amount of data sent to userspace. The slot protocol requires the use of the amount of data sent to userspace. The slot protocol requires the use of
the ABS_MT_TRACKING_ID, either provided by the hardware or computed from the ABS_MT_TRACKING_ID, either provided by the hardware or computed from
the raw data [5]. the raw data [#f5]_.
For type A devices, the kernel driver should generate an arbitrary For type A devices, the kernel driver should generate an arbitrary
enumeration of the full set of anonymous contacts currently on the enumeration of the full set of anonymous contacts currently on the
surface. The order in which the packets appear in the event stream is not surface. The order in which the packets appear in the event stream is not
important. Event filtering and finger tracking is left to user space [3]. important. Event filtering and finger tracking is left to user space [#f3]_.
For type B devices, the kernel driver should associate a slot with each For type B devices, the kernel driver should associate a slot with each
identified contact, and use that slot to propagate changes for the contact. identified contact, and use that slot to propagate changes for the contact.
@ -86,7 +90,7 @@ Protocol Example A
------------------ ------------------
Here is what a minimal event sequence for a two-contact touch would look Here is what a minimal event sequence for a two-contact touch would look
like for a type A device: like for a type A device::
ABS_MT_POSITION_X x[0] ABS_MT_POSITION_X x[0]
ABS_MT_POSITION_Y y[0] ABS_MT_POSITION_Y y[0]
@ -100,14 +104,14 @@ The sequence after moving one of the contacts looks exactly the same; the
raw data for all present contacts are sent between every synchronization raw data for all present contacts are sent between every synchronization
with SYN_REPORT. with SYN_REPORT.
Here is the sequence after lifting the first contact: Here is the sequence after lifting the first contact::
ABS_MT_POSITION_X x[1] ABS_MT_POSITION_X x[1]
ABS_MT_POSITION_Y y[1] ABS_MT_POSITION_Y y[1]
SYN_MT_REPORT SYN_MT_REPORT
SYN_REPORT SYN_REPORT
And here is the sequence after lifting the second contact: And here is the sequence after lifting the second contact::
SYN_MT_REPORT SYN_MT_REPORT
SYN_REPORT SYN_REPORT
@ -122,7 +126,7 @@ Protocol Example B
------------------ ------------------
Here is what a minimal event sequence for a two-contact touch would look Here is what a minimal event sequence for a two-contact touch would look
like for a type B device: like for a type B device::
ABS_MT_SLOT 0 ABS_MT_SLOT 0
ABS_MT_TRACKING_ID 45 ABS_MT_TRACKING_ID 45
@ -134,13 +138,13 @@ like for a type B device:
ABS_MT_POSITION_Y y[1] ABS_MT_POSITION_Y y[1]
SYN_REPORT SYN_REPORT
Here is the sequence after moving contact 45 in the x direction: Here is the sequence after moving contact 45 in the x direction::
ABS_MT_SLOT 0 ABS_MT_SLOT 0
ABS_MT_POSITION_X x[0] ABS_MT_POSITION_X x[0]
SYN_REPORT SYN_REPORT
Here is the sequence after lifting the contact in slot 0: Here is the sequence after lifting the contact in slot 0::
ABS_MT_TRACKING_ID -1 ABS_MT_TRACKING_ID -1
SYN_REPORT SYN_REPORT
@ -149,7 +153,7 @@ The slot being modified is already 0, so the ABS_MT_SLOT is omitted. The
message removes the association of slot 0 with contact 45, thereby message removes the association of slot 0 with contact 45, thereby
destroying contact 45 and freeing slot 0 to be reused for another contact. destroying contact 45 and freeing slot 0 to be reused for another contact.
Finally, here is the sequence after lifting the second contact: Finally, here is the sequence after lifting the second contact::
ABS_MT_SLOT 1 ABS_MT_SLOT 1
ABS_MT_TRACKING_ID -1 ABS_MT_TRACKING_ID -1
@ -181,6 +185,8 @@ ABS_MT_PRESSURE may be used to provide the pressure on the contact area
instead. Devices capable of contact hovering can use ABS_MT_DISTANCE to instead. Devices capable of contact hovering can use ABS_MT_DISTANCE to
indicate the distance between the contact and the surface. indicate the distance between the contact and the surface.
::
Linux MT Win8 Linux MT Win8
__________ _______________________ __________ _______________________
@ -212,7 +218,7 @@ via ABS_MT_BLOB_ID.
The ABS_MT_TOOL_TYPE may be used to specify whether the touching tool is a The ABS_MT_TOOL_TYPE may be used to specify whether the touching tool is a
finger or a pen or something else. Finally, the ABS_MT_TRACKING_ID event finger or a pen or something else. Finally, the ABS_MT_TRACKING_ID event
may be used to track identified contacts over time [5]. may be used to track identified contacts over time [#f5]_.
In the type B protocol, ABS_MT_TOOL_TYPE and ABS_MT_TRACKING_ID are In the type B protocol, ABS_MT_TOOL_TYPE and ABS_MT_TRACKING_ID are
implicitly handled by input core; drivers should instead call implicitly handled by input core; drivers should instead call
@ -223,117 +229,103 @@ Event Semantics
--------------- ---------------
ABS_MT_TOUCH_MAJOR ABS_MT_TOUCH_MAJOR
The length of the major axis of the contact. The length should be given in
The length of the major axis of the contact. The length should be given in surface units. If the surface has an X times Y resolution, the largest
surface units. If the surface has an X times Y resolution, the largest possible value of ABS_MT_TOUCH_MAJOR is sqrt(X^2 + Y^2), the diagonal [#f4]_.
possible value of ABS_MT_TOUCH_MAJOR is sqrt(X^2 + Y^2), the diagonal [4].
ABS_MT_TOUCH_MINOR ABS_MT_TOUCH_MINOR
The length, in surface units, of the minor axis of the contact. If the
The length, in surface units, of the minor axis of the contact. If the contact is circular, this event can be omitted [#f4]_.
contact is circular, this event can be omitted [4].
ABS_MT_WIDTH_MAJOR ABS_MT_WIDTH_MAJOR
The length, in surface units, of the major axis of the approaching
The length, in surface units, of the major axis of the approaching tool. This should be understood as the size of the tool itself. The
tool. This should be understood as the size of the tool itself. The orientation of the contact and the approaching tool are assumed to be the
orientation of the contact and the approaching tool are assumed to be the same [#f4]_.
same [4].
ABS_MT_WIDTH_MINOR ABS_MT_WIDTH_MINOR
The length, in surface units, of the minor axis of the approaching
tool. Omit if circular [#f4]_.
The length, in surface units, of the minor axis of the approaching The above four values can be used to derive additional information about
tool. Omit if circular [4]. the contact. The ratio ABS_MT_TOUCH_MAJOR / ABS_MT_WIDTH_MAJOR approximates
the notion of pressure. The fingers of the hand and the palm all have
The above four values can be used to derive additional information about different characteristic widths.
the contact. The ratio ABS_MT_TOUCH_MAJOR / ABS_MT_WIDTH_MAJOR approximates
the notion of pressure. The fingers of the hand and the palm all have
different characteristic widths.
ABS_MT_PRESSURE ABS_MT_PRESSURE
The pressure, in arbitrary units, on the contact area. May be used instead
The pressure, in arbitrary units, on the contact area. May be used instead of TOUCH and WIDTH for pressure-based devices or any device with a spatial
of TOUCH and WIDTH for pressure-based devices or any device with a spatial signal intensity distribution.
signal intensity distribution.
ABS_MT_DISTANCE ABS_MT_DISTANCE
The distance, in surface units, between the contact and the surface. Zero
The distance, in surface units, between the contact and the surface. Zero distance means the contact is touching the surface. A positive number means
distance means the contact is touching the surface. A positive number means the contact is hovering above the surface.
the contact is hovering above the surface.
ABS_MT_ORIENTATION ABS_MT_ORIENTATION
The orientation of the touching ellipse. The value should describe a signed
quarter of a revolution clockwise around the touch center. The signed value
range is arbitrary, but zero should be returned for an ellipse aligned with
the Y axis of the surface, a negative value when the ellipse is turned to
the left, and a positive value when the ellipse is turned to the
right. When completely aligned with the X axis, the range max should be
returned.
The orientation of the touching ellipse. The value should describe a signed Touch ellipsis are symmetrical by default. For devices capable of true 360
quarter of a revolution clockwise around the touch center. The signed value degree orientation, the reported orientation must exceed the range max to
range is arbitrary, but zero should be returned for an ellipse aligned with indicate more than a quarter of a revolution. For an upside-down finger,
the Y axis of the surface, a negative value when the ellipse is turned to range max * 2 should be returned.
the left, and a positive value when the ellipse is turned to the
right. When completely aligned with the X axis, the range max should be
returned.
Touch ellipsis are symmetrical by default. For devices capable of true 360 Orientation can be omitted if the touch area is circular, or if the
degree orientation, the reported orientation must exceed the range max to information is not available in the kernel driver. Partial orientation
indicate more than a quarter of a revolution. For an upside-down finger, support is possible if the device can distinguish between the two axis, but
range max * 2 should be returned. not (uniquely) any values in between. In such cases, the range of
ABS_MT_ORIENTATION should be [0, 1] [#f4]_.
Orientation can be omitted if the touch area is circular, or if the
information is not available in the kernel driver. Partial orientation
support is possible if the device can distinguish between the two axis, but
not (uniquely) any values in between. In such cases, the range of
ABS_MT_ORIENTATION should be [0, 1] [4].
ABS_MT_POSITION_X ABS_MT_POSITION_X
The surface X coordinate of the center of the touching ellipse.
The surface X coordinate of the center of the touching ellipse.
ABS_MT_POSITION_Y ABS_MT_POSITION_Y
The surface Y coordinate of the center of the touching ellipse.
The surface Y coordinate of the center of the touching ellipse.
ABS_MT_TOOL_X ABS_MT_TOOL_X
The surface X coordinate of the center of the approaching tool. Omit if
The surface X coordinate of the center of the approaching tool. Omit if the device cannot distinguish between the intended touch point and the
the device cannot distinguish between the intended touch point and the tool itself.
tool itself.
ABS_MT_TOOL_Y ABS_MT_TOOL_Y
The surface Y coordinate of the center of the approaching tool. Omit if the
device cannot distinguish between the intended touch point and the tool
itself.
The surface Y coordinate of the center of the approaching tool. Omit if the The four position values can be used to separate the position of the touch
device cannot distinguish between the intended touch point and the tool from the position of the tool. If both positions are present, the major
itself. tool axis points towards the touch point [#f1]_. Otherwise, the tool axes are
aligned with the touch axes.
The four position values can be used to separate the position of the touch
from the position of the tool. If both positions are present, the major
tool axis points towards the touch point [1]. Otherwise, the tool axes are
aligned with the touch axes.
ABS_MT_TOOL_TYPE ABS_MT_TOOL_TYPE
The type of approaching tool. A lot of kernel drivers cannot distinguish
The type of approaching tool. A lot of kernel drivers cannot distinguish between different tool types, such as a finger or a pen. In such cases, the
between different tool types, such as a finger or a pen. In such cases, the event should be omitted. The protocol currently supports MT_TOOL_FINGER,
event should be omitted. The protocol currently supports MT_TOOL_FINGER, MT_TOOL_PEN, and MT_TOOL_PALM [#f2]_. For type B devices, this event is
MT_TOOL_PEN, and MT_TOOL_PALM [2]. For type B devices, this event is handled handled by input core; drivers should instead use
by input core; drivers should instead use input_mt_report_slot_state(). input_mt_report_slot_state(). A contact's ABS_MT_TOOL_TYPE may change over
A contact's ABS_MT_TOOL_TYPE may change over time while still touching the time while still touching the device, because the firmware may not be able
device, because the firmware may not be able to determine which tool is being to determine which tool is being used when it first appears.
used when it first appears.
ABS_MT_BLOB_ID ABS_MT_BLOB_ID
The BLOB_ID groups several packets together into one arbitrarily shaped
The BLOB_ID groups several packets together into one arbitrarily shaped contact. The sequence of points forms a polygon which defines the shape of
contact. The sequence of points forms a polygon which defines the shape of the contact. This is a low-level anonymous grouping for type A devices, and
the contact. This is a low-level anonymous grouping for type A devices, and should not be confused with the high-level trackingID [#f5]_. Most type A
should not be confused with the high-level trackingID [5]. Most type A devices do not have blob capability, so drivers can safely omit this event.
devices do not have blob capability, so drivers can safely omit this event.
ABS_MT_TRACKING_ID ABS_MT_TRACKING_ID
The TRACKING_ID identifies an initiated contact throughout its life cycle
The TRACKING_ID identifies an initiated contact throughout its life cycle [#f5]_. The value range of the TRACKING_ID should be large enough to ensure
[5]. The value range of the TRACKING_ID should be large enough to ensure unique identification of a contact maintained over an extended period of
unique identification of a contact maintained over an extended period of time. For type B devices, this event is handled by input core; drivers
time. For type B devices, this event is handled by input core; drivers should instead use input_mt_report_slot_state().
should instead use input_mt_report_slot_state().
Event Computation Event Computation
@ -346,7 +338,7 @@ this section gives recipes for how to compute certain events.
For devices reporting contacts as rectangular shapes, signed orientation For devices reporting contacts as rectangular shapes, signed orientation
cannot be obtained. Assuming X and Y are the lengths of the sides of the cannot be obtained. Assuming X and Y are the lengths of the sides of the
touching rectangle, here is a simple formula that retains the most touching rectangle, here is a simple formula that retains the most
information possible: information possible::
ABS_MT_TOUCH_MAJOR := max(X, Y) ABS_MT_TOUCH_MAJOR := max(X, Y)
ABS_MT_TOUCH_MINOR := min(X, Y) ABS_MT_TOUCH_MINOR := min(X, Y)
@ -356,7 +348,7 @@ The range of ABS_MT_ORIENTATION should be set to [0, 1], to indicate that
the device can distinguish between a finger along the Y axis (0) and a the device can distinguish between a finger along the Y axis (0) and a
finger along the X axis (1). finger along the X axis (1).
For win8 devices with both T and C coordinates, the position mapping is For win8 devices with both T and C coordinates, the position mapping is::
ABS_MT_POSITION_X := T_X ABS_MT_POSITION_X := T_X
ABS_MT_POSITION_Y := T_Y ABS_MT_POSITION_Y := T_Y
@ -365,7 +357,7 @@ For win8 devices with both T and C coordinates, the position mapping is
Unfortunately, there is not enough information to specify both the touching Unfortunately, there is not enough information to specify both the touching
ellipse and the tool ellipse, so one has to resort to approximations. One ellipse and the tool ellipse, so one has to resort to approximations. One
simple scheme, which is compatible with earlier usage, is: simple scheme, which is compatible with earlier usage, is::
ABS_MT_TOUCH_MAJOR := min(X, Y) ABS_MT_TOUCH_MAJOR := min(X, Y)
ABS_MT_TOUCH_MINOR := <not used> ABS_MT_TOUCH_MINOR := <not used>
@ -386,7 +378,7 @@ The process of finger tracking, i.e., to assign a unique trackingID to each
initiated contact on the surface, is a Euclidian Bipartite Matching initiated contact on the surface, is a Euclidian Bipartite Matching
problem. At each event synchronization, the set of actual contacts is problem. At each event synchronization, the set of actual contacts is
matched to the set of contacts from the previous synchronization. A full matched to the set of contacts from the previous synchronization. A full
implementation can be found in [3]. implementation can be found in [#f3]_.
Gestures Gestures
@ -411,8 +403,8 @@ subsequent events of the same type refer to different fingers.
For example usage of the type A protocol, see the bcm5974 driver. For For example usage of the type A protocol, see the bcm5974 driver. For
example usage of the type B protocol, see the hid-egalax driver. example usage of the type B protocol, see the hid-egalax driver.
[1] Also, the difference (TOOL_X - POSITION_X) can be used to model tilt. .. [#f1] Also, the difference (TOOL_X - POSITION_X) can be used to model tilt.
[2] The list can of course be extended. .. [#f2] The list can of course be extended.
[3] The mtdev project: http://bitmath.org/code/mtdev/. .. [#f3] The mtdev project: http://bitmath.org/code/mtdev/.
[4] See the section on event computation. .. [#f4] See the section on event computation.
[5] See the section on finger tracking. .. [#f5] See the section on finger tracking.