linux-kernel - Re: [PATCH 3/3] hid: 3m: Correct touchscreen emulation

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Date:	Sat, 28 Aug 2010 18:08:15 +0200
From:	Henrik Rydberg <rydberg@...omail.se>
To:	Stéphane Chatty <chatty@...c.fr>
CC:	Jiri Kosina <jkosina@...e.cz>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] hid: 3m: Correct touchscreen emulation

On 08/28/2010 05:56 PM, Stéphane Chatty wrote:

> 
> Le 28 août 10 à 16:29, Henrik Rydberg a écrit :
> 
>> The current code sometimes misses to report the last BTN_TOUCH event
>> when multiple fingers are lifted simultaneously.  With the
>> introduction of MT slots, the tracking id is available to determine
>> the oldest active contact.
> 
> Hi Henrik,
> 
> good job on exploiting the sync quirk!
> 
> About the oldest active contact, I'm not so sure though. I don't have the device
> with me but I remember that 3M recycle IDs, giving the lowest available ID to
> any new finger; this means that the lowest ID is not always the oldest finger.


Hi Stéphane,

I think we use the term tracking id differently here. The HID_DG_CONTACTID is
actually the slot id, and the tracking id is a sequential number, increased
whenever the touch is new. I believe the patchset works correctly as long as
there is less than 32768 new touches before releasing the oldest one. :-)

Cheers,
Henrik
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