linux-kernel - Re: [PATCH 1/4] Input: synaptics - add multitouch packet support

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Message-ID: <AANLkTikNGKgyRrn9EMYA+oXipU2VThCWFe+1sJQn7p8L@mail.gmail.com>
Date:	Sat, 18 Dec 2010 14:44:47 -0600
From:	Chris Bagwell <chris@...bagwell.com>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Chase Douglas <chase.douglas@...onical.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Takashi Iwai <tiwai@...e.de>
Subject: Re: [PATCH 1/4] Input: synaptics - add multitouch packet support

On Sat, Dec 18, 2010 at 11:54 AM, Henrik Rydberg <rydberg@...omail.se> wrote:
> Hi Chris,
>
> Thanks for you comments.
>
>> > While in MT mode and two or three fingers are touching, two sets of
>> > data are sent.  The first is a new format buffer with lower resolution
>> > reporting of stationary finger and the second is standard data format
>> > reporting movement.
>>
>> We should probably update this comment and remove parts that mention
>> stationary and movement.  It appears to be doing finger tracking and
>> first packet is always first touch... except we are getting reports
>> that clickpads/integrated button pads may not be consistently like
>> this.
>
> Yes, good point. Will update.
>
>> This tracking is partly why type B protocol is being used in later patches.
>
> The original thought was that the two points corresponded well to the
> two fingers, only sometimes in the wrong order. The solution then was
> to use the tracking module to order them appropriately. As it turned
> out that the fingers are not followed that well after all, the whole
> idea fell flat, so we resorted to only sending the bounding rectangle,
> which requires no tracking.
>
> All in all, this patchset contains enough information to resolve
> jumping and clickpad issues in user space, at the same time as it
> keeps compatibility with mousedev and older hardware. We know there
> are still issues, but I see no real reason to postpone these changes
> any further.
>

Agree.  I've found no issues in daily usage for a couple of weeks now
and with an unmodified xf86-input-synaptics (newer then 1.3.0 btw).

I can't speak for clickpads since I do not have access to one but I'm
happy to help narrow down any problems.  I really suspect any
remaining issues are on user land side.

The fact that this patch allows BTN_TOOL_DOUBLETAP to finally be sent
will surely help user land filter out cursor jumps much easier as
well.

Chris
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