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Date: Fri, 10 Dec 2010 10:13:06 -0800
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Ping Cheng <pinglinux@gmail.com>
Cc: Henrik Rydberg <rydberg@euromail.se>, Jiri Kosina <jkosina@suse.cz>,
        linux-input@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] input: mt: Interface and MT_TOOL documentation updates
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On Fri, Dec 10, 2010 at 09:55:12AM -0800, Ping Cheng wrote:
> On Thu, Dec 9, 2010 at 1:22 PM, Henrik Rydberg <rydberg@euromail.se> 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@euromail.se>
> > ---
> > ?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.

Are you saying that there is upcoming hardware models that do not report
individual contacts?

-- 
Dmitry
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