Hi Henrik,

On Fri, Mar 19, 2010 at 11:58:35AM +0100, Henrik Rydberg 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 am not sure if input core itself is the proper place to do such
thing, I'd envisioned something more like a library providing common
code that drivers could opt in to use, like we hane ff-memless for
memory-less force-feedback devices.

Does it make any sense? I guess post the skeleton of the code and we can
discuss further.

-- 
Dmitry