Re: [PATCH] input: mt: Interface and MT_TOOL documentation updates

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On Thu, Dec 9, 2010 at 1:22 PM, Henrik Rydberg <rydberg@xxxxxxxxxxx> wrote:
> The recent input-mt interface changes together with
> recent discussions about pen and touch and support
> for legacy multitouch pads suggest that the documentation
> on MT tool types be expanded. This patch adds references
> to the new interface, and adds a section for MT_TOOL types,
> in particular documenting the use of MT_TOOL_ENVELOPE.
>
> Signed-off-by: Henrik Rydberg <rydberg@xxxxxxxxxxx>
> ---
>  Documentation/input/multi-touch-protocol.txt |   37 ++++++++++++++++++-------
>  1 files changed, 26 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/input/multi-touch-protocol.txt b/Documentation/input/multi-touch-protocol.txt
> index 351fab8..e190943 100644
> --- a/Documentation/input/multi-touch-protocol.txt
> +++ b/Documentation/input/multi-touch-protocol.txt
> @@ -169,12 +169,14 @@ described by adding the MINOR parameters, such that MAJOR and MINOR are the
>  major and minor axis of an ellipse. Finally, the orientation of the oval
>  shape can be describe with the ORIENTATION parameter.
>
> +For type A devices, further specification of the touch shape is possible
> +via ABS_MT_BLOB_ID.
> +
>  The ABS_MT_TOOL_TYPE may be used to specify whether the touching tool is a
> -contact or a pen or something else.  Devices with more granular information
> -may specify general shapes as blobs, i.e., as a sequence of rectangular
> -shapes grouped together by an ABS_MT_BLOB_ID. Finally, for the few devices
> -that currently support it, the ABS_MT_TRACKING_ID event may be used to
> -report contact tracking from hardware [5].
> +contact or a pen or something else. Finally, the ABS_MT_TRACKING_ID event
> +may be used to track identified contacts over time [5]. In the type B
> +protocol, the use of ABS_MT_TOOL_TYPE and ABS_MT_TRACKING_ID is implicit
> +via the input_mt_report_slot_state() function.
>
>
>  Event Semantics
> @@ -247,21 +249,34 @@ ABS_MT_TOOL_TYPE
>  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
>  event should be omitted. The protocol currently supports MT_TOOL_FINGER and
> -MT_TOOL_PEN and MT_TOOL_ENVELOPE [2].
> +MT_TOOL_PEN and MT_TOOL_ENVELOPE [2]. For type B devices, this event is
> +handled by input core, via the input_mt interface.
> +
> +- The MT_TOOL_FINGER type is the default, and represents a finger touch.
> +
> +- The MT_TOOL_PEN type represents a pen, and the list of related tools is
> +expected to grow with time.
> +
> +- The MT_TOOL_ENVELOPE type is used to indicate that the contact position
> +is not well-defined, and is only used for legacy hardware. The real contact
> +positions are to be found within the bounding rectangle formed by the
> +envelope contact positions.

Can we make MT_TOOL_ENVELOPE cover a bit more cases by:

1. Removing ", and is only used for legacy hardware";
2. Adding "Or the number of contacts inside the bounding rectangle is
reported if hardware provides the number but not the real contact
positions" to the end of the paragraph.

Ping

>  ABS_MT_BLOB_ID
>
>  The BLOB_ID groups several packets together into one arbitrarily shaped
> -contact. This is a low-level anonymous grouping for type A devices, and
> +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
>  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.
>
>  ABS_MT_TRACKING_ID
>
>  The TRACKING_ID identifies an initiated contact throughout its life cycle
> -[5]. This event is mandatory for type B devices. The value range of the
> -TRACKING_ID should be large enough to ensure unique identification of a
> -contact maintained over an extended period of time.
> +[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
> +time. For type B devices, this event is handled by input core, via the
> +input_mt interface.
>
>
>  Event Computation
> @@ -321,6 +336,6 @@ difference between the contact position and the approaching tool position
>  could be used to derive tilt.
>  [2] ABS_MT_ENVELOPE contacts represent an envelope of the contacts rather
>  than the actual contacts. Used with older, not fully MT capable, devices.
> -[3] Multitouch X driver project: http://bitmath.org/code/multitouch/.
> +[3] The mtdev project: http://bitmath.org/code/mtdev/.
>  [4] See the section on event computation.
>  [5] See the section on finger tracking.
> --
> 1.7.1
>
> --
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