linux-kernel - Re: [PATCH 8/9 v2] Input: add BTN_TOOL_QUINTTAP for reporting 5 fingers on touchpad

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Date:	Thu, 11 Aug 2011 22:07:08 +0200
From:	"Henrik Rydberg" <rydberg@...omail.se>
To:	Daniel Kurtz <djkurtz@...omium.org>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	chase.douglas@...onical.com, rubini@...l.unipv.it,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	derek.foreman@...labora.co.uk, daniel.stone@...labora.co.uk,
	olofj@...omium.org
Subject: Re: [PATCH 8/9 v2] Input: add BTN_TOOL_QUINTTAP for reporting 5
 fingers on touchpad

> > That, or nothing... The fact that the device can report 5 finger touch
> > does not mean that anybody cares about this.
> > --
> > Dmitry
> 
> The only current use of this is to detect "resting thumb + 4-finger-scroll".
> "4-finger scroll" is a gesture supported by some applications and
> operating systems.
> "resting thumb" is when a clickpad user rests a finger (typically a
> thumb), in the bottom left "click zone" in anticipation of
> click+move=select gestures.
> Thus, this 4-finger scroll is actually sometimes a 5-finger gesture.

Which is actually the same reason QUADTAP was added originally... are
we entering a recursion here? ;-)

I tend to agree with Dmitry - without a clear usage, it makes sense to
instead wait to see which comes first - a five-finger usecase or a
true MT device that everybody can afford.

> Similarly, I work with many touchpads from different vendors, some of
> which do actually provide 5 independent finger coordinates.  The
> drivers for these touchpads truly send 5 MT-B slots when 5 fingers are
> present.
> 
> Should these drivers perform input_mt_report_pointer_emulation()?
> If so, should we add BTN_TOOL_QUINTTAP to allow them to report 5
> fingers in emulation mode?

Pointer emulation is a separate issue from the number of finger
reports.

> Or is that ridiculous, since emulation is only for old userspace
> programs which wouldn't know what to do with QUINTTAP, anyway?

I would say yes. ;-)

Cheers,
Henrik
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