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SubjectRe: [PATCH] forced recalibration for the OLPC hgpk touchpad
FromPaul Fox <>
DateWed, 17 Jun 2009 16:16:11 -0400
hi dmitry --

have you had a chance to think any more about this? i'm open to
suggestions on implementation detail, but i think that a full
reset of the device won't really work, because of the time it
adds to the recalibration.

paul

andres wrote:
> On Wed, 03 Jun 2009 23:58:33 -0400
> Paul Fox <pgf@laptop.org> wrote:
>
> > 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.)
> >
>
> I do like the idea of having a sysfs trigger for recalibrations. We've
> never been successful in having the kernel driver handle recalibrations
> seamlessly. Perhaps touchpad hardware screwups would be easier to
> detect in userspace, given a daemon that can keep a history of the last
> N touchpad coordinates?

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

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