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

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Date:	Wed, 19 May 2010 21:03:10 -0400
From:	Rafi Rubin <rafi@...s.upenn.edu>
To:	Ping Cheng <pinglinux@...il.com>
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)

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On 05/19/10 20:51, Ping Cheng wrote:
> On Wed, May 19, 2010 at 5:26 PM, Rafi Rubin <rafi@...s.upenn.edu> wrote:
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>> 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
> 

Hey, sometimes Mark Twain's old advice is good, and sometimes its not.

It's better to keep your mouth shut and be thought a fool than to open it and
leave no doubt. --Mark Twain


I think this is definitely a case where he's wrong.  We need to sync up so that
we're all implementing the same protocol, and can move on to the next
interesting problem.

Rafi
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