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