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

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Date:	Wed, 19 May 2010 17:51:31 -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 Wed, May 19, 2010 at 5:26 PM, Rafi Rubin <rafi@...s.upenn.edu> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 05/19/10 20:13, Ping Cheng wrote:
>> On Wed, May 19, 2010 at 4:34 PM, Rafi Rubin <rafi@...s.upenn.edu> wrote:
>>> My understanding is that it would be more like
>>> +   SYN_MT_SLOT 0
>>> +   ABS_MT_POSITION_X x
>>> +   ABS_MT_POSITION_Y y
>>> +   SYN_REPORT
>>> +   SYN_MT_SLOT 0
>>> +   ABS_MT_POSITION_X x
>>> +   ABS_MT_POSITION_Y y
>>> +   SYN_REPORT
>>> +   SYN_MT_SLOT 0
>>> +   ABS_MT_POSITION_X x
>>> +   ABS_MT_POSITION_Y y
>>> +   SYN_MT_SLOT 1
>>> +   ABS_MT_POSITION_X x
>>> +   ABS_MT_POSITION_Y y
>>> +   SYN_REPORT
>>
>> You are right if one slot only has or is only allowed to have one
>> point. My scenario is that one slot can have more than one point.
>> Basically, my intention is to utilize the MT_SLOT and MT_TRACKING_ID
>> in such a way that it avoids as much overlap as possible.
>>
>> And hopefully it makes sesne in the reality too.
>
> Please clarify by what you mean by more than one point.

I might have been confused myself by ABS_MT_BLOB_ID and SYN_MT_SLOT
here.  What I meant by "more than one point" is a contact (or touch, I
am not sure which one is the right term :) is represented by a few
(x,y) coordinates. Maybe we should use SYN_MT_SLOT for my case?

> I may be misunderstanding, but I thought that these slots are basically a
> superior replacement to tracking id.
>
> one finger -> one slot

This is what I needed to understand. Is slot for one (x,y) only or can
it also be used for more than one set of (x,y)?

> But with slots we can use the filtering that input provides, which we've been
> by-passing with the existing MT protocol (at least that's what I think Henrik's
> goal is).

Good to know that filtering has already been considered. I know I must
be out of sync with Henrik's goal.  That's why I wanted to show my
ignorance :).

Ping
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