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

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Message-ID: <AANLkTinAQ4ygkcX_4D_Lbi-eLbbghdSXlLzH3HZBhDou@mail.gmail.com>
Date:	Wed, 19 May 2010 21:18:36 -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 6:03 PM, Rafi Rubin <rafi@...s.upenn.edu> wrote:
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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?

The last sentence above should be "Maybe we should NOT use SYN_MT_SLOT
for my case?" or "Maybe I should use MT_BLOB_ID for that case?". A
typical typo for those whose hands are slower than their brains :).

>>> 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.

I hope this is the common goal for everyone who has been involved in
the _MT_ support.

Ping
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