Date: Fri, 24 Feb 2012 01:14:52 -0800
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Henrik Rydberg <rydberg@euromail.se>
Cc: Daniel Kurtz <djkurtz@chromium.org>, Chung-yih Wang <cywang@chromium.org>,
        Alessandro Rubini <rubini@cvml.unipv.it>, linux-input@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] CHROMIUM: Input: synaptics - filter out the events with
 low z values
Message-ID: <20120224091452.GD10763@core.coreip.homeip.net>
References: <1329896503-28394-1-git-send-email-cywang@chromium.org>
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 <20120222110459.GA28126@polaris.bitmath.org>
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 <20120222152425.GA29436@polaris.bitmath.org>
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On Fri, Feb 24, 2012 at 10:08:35AM +0100, Henrik Rydberg wrote:
> > > The most striking effect is the ability to better retain a
> > > drag. Although the statement was made in light of possible
> > > (1-strong,1-weak) packets, it should help in the 2-weak case too.
> > 
> > The bigger question is why is this needed in kernel. The original
> > hysteresis with BTN_TOUCH was done for sole benefit of mousedev so that
> > we could allow somewhat better transition from standard PS/2 mode into
> > native Synaptics mode with absolute coordinates at time when barely
> > anyone had Synaptics X driver installed. This was, what, 10 years ago?
> 
> The semi-mt behavior is obviously a special case, where userspace
> relies on the reported number of fingers to transition between one
> touch and two touches. There is no pressure information sent to
> userspace in this case, so the situation is in fact quite similar to
> the ancient mousedev situation.

We still report ABS_PRESSURE but maybe we should report ABS_MT_PRESSURE
as well?

-- 
Dmitry
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