linux-kernel - Re: input: mt: Software finger tracking in the kernel?

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Message-ID: <5d5443651003201227w27314533w6be3cdd8fb9bf5aa@mail.gmail.com>
Date:	Sun, 21 Mar 2010 00:57:20 +0530
From:	Trilok Soni <soni.trilok@...il.com>
To:	Ping Cheng <pinglinux@...il.com>
Cc:	Henrik Rydberg <rydberg@...esh.se>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: input: mt: Software finger tracking in the kernel?

Hi Ping,

On Sat, Mar 20, 2010 at 10:21 AM, Ping Cheng <pinglinux@...il.com> wrote:
> On Fri, Mar 19, 2010 at 3:58 AM, Henrik Rydberg <rydberg@...esh.se> wrote:
>> Hi Dmitry,
>>
>> there is an ongoing discussion about adding multitouch to X
>> (http://lists.x.org/archives/xorg-devel/2010-March/006206.html), which is
>> beginning to take on more solid form.
>>
>> One of the suggestions emerging from that discussion is to add the software
>> finger tracking to the kernel. Back in summer 2009 when I thought about this, I
>> disregarded it as being too experimental. I have since then reconsidered,
>> starting to think it really is the right place.
>>
>> The MT protocol allows applications to take advantage of multi-contact hardware,
>> but leaves the problems of finger tracking and filtering to the user. Arguably,
>> no application can make good use of MT without these, so the problem is pushed
>> forward, in this case to evdev or equivalent.
>>
>> The knowledge of signal-to-noise ratios and prior input states resides in the
>> kernel. Because of this, the finger matching and filtering would naturally
>> reside within the kernel.
>>
>> So, if there were to appear patches to include matching in the input core, would
>> you consider them? :-)
>
> I support the idea to add a tracking ID and a filter to _MT_.  I'd
> also like to make the filtering method more "device driver developer"
> friendly, i.e., give the developer the option to turn the filter on or
> off.  If you plan to use a constant for the filtering method, please
> allow the developer to choose that constant too.
>
> Another attribute associated with _MT_ is the pressure/capacity.
> Report this value would offer more room for MT-aware application to
> add new features.

We have ABS_MT_PRESSURE added recently. I hope you are asking the same.


-- 
---Trilok Soni
http://triloksoni.wordpress.com
http://www.linkedin.com/in/triloksoni
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