linux-kernel - Re: [PATCH 2/2] input: mt: Document the MT event slot protocol (rev2)

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Date:	Fri, 21 May 2010 08:40:51 -0700
From:	Ping Cheng <pinglinux@...il.com>
To:	Rafi Rubin <rafi@...s.upenn.edu>
Cc:	Henrik Rydberg <rydberg@...omail.se>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Mika Kuoppala <mika.kuoppala@...ia.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	Benjamin Tissoires <tissoire@...a.fr>,
	Stephane Chatty <chatty@...c.fr>,
	Michael Poole <mdpoole@...ilus.org>
Subject: Re: [PATCH 2/2] input: mt: Document the MT event slot protocol (rev2)

On Fri, May 21, 2010 at 8:19 AM, Rafi Rubin <rafi@...s.upenn.edu> wrote:
>> ABS_MT_BLOB_ID 11
>> ABS_MT_TRACKING_ID 45
>> ABS_MT_SLOT_ID 0
>> ABS_MT_POSITION_X x[0]
>> ABS_MT_POSITION_Y y[0]
>> ABS_MT_SLOT_ID 1
>> ABS_MT_POSITION_X x[1]
>> ABS_MT_POSITION_Y y[1]
>> ABS_MT_SLOT_ID 2
>> ABS_MT_POSITION_X x[2]
>> ABS_MT_POSITION_Y y[2]
>> SYN_MT_BLOB
>> ABS_MT_BLOB_ID 89
>> ABS_MT_SLOT_ID 3
>> ABS_MT_TRACKING_ID 30
>> ABS_MT_POSITION_X x[3]
>> ABS_MT_POSITION_Y y[3]
>> SYN_MT_BLOB
>> SYN_REPORT
>>
>> where we have two blob of data. They represent finger 1 and finger 2.
>> Finger 1 has a tracking number 11 while finger 2 has 30.  We do not
>> track the three contacts inside the blob since they all belong to the
>> same finger.  We could even combine type A and B as:
>
> ???
>
> Ping: please confirm, are you actually talking about each finger simultaneously sending multiple positions?

You are definitely on the right track.  The fingers/touch objects can
be represented two-dimensionally (x,y) instead of one-dimensionally
(ABS_MT_TRACKING_ID).  I think we can survive with the current MT_BLOB
definition although some optimization would be helpful, especially for
filtering. For the sake of Henrik great effort, I'd like to see his
current patchset gets in the tree before we start another round of
"suggestions".

Thank you for asking.

Ping
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