To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Subject: Re: [PATCH] forced recalibration for the OLPC hgpk touchpad 
From: Paul Fox <pgf@laptop.org>
cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
       dilinger@laptop.org, dsaxena@laptop.org
In-reply-to: <200906030804.57340.dmitry.torokhov@gmail.com> 
References: <3026.1243972079@foxharp.boston.ma.us> <200906030804.57340.dmitry.torokhov@gmail.com>
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Date: Wed, 03 Jun 2009 23:58:33 -0400
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dmitry wrote:
 > Hi Paul,
 > 
 > On Tuesday 02 June 2009 12:47:59 pgf@laptop.org wrote:
 > > The OLPC XO laptop incorporates a combination touchpad/tablet
 > > device which unfortunately requires frequent recalibration.  The
 > > driver will force this automatically when various suspicious
 > > behaviors are observed, and the user can recalibrate manually
 > > (with a special keyboard sequence).  There's currently no way,
 > > however, for an external program to cause recalibration.
 > >
 > > This patch creates a new node in /sys which, when written with '1',
 > > will force a touchpad recalibration.  No other writes (or reads)
 > > of this node are supported.
 > >
 > 
 > 
 > Instead of creating a new sysfs attribute maybe we should make
 > the touchpad recalibrate upon resume (reconnect)? Userspace can
 > already request reconnect via sysfs.

dmitry -- thanks for the suggestion.

i took a look, and tried it.  the problem is that doing a full
reset of the touchpad takes quite a long time -- 1.1 or 1.2
seconds.  recalibration deprives the user of their touchpad for
long enough as it is -- i don't think we can afford that time.
(remember that this is a workaround for bad hardware -- the XO
no longer uses this touchpad at least partly due to this very
issue, but there are enough in use that we're still trying to
improve things.)

paul
=---------------------
 paul fox, pgf@laptop.org
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