Re: [PATCH] Apple USB Touchpad driver (new)

[Stelian Pop]

Le lundi 11 juillet 2005 Ã 13:00 +0200, Vojtech Pavlik a Ãcrit :
> On Mon, Jul 11, 2005 at 12:39:31PM +0200, Stelian Pop wrote:
>  
> > > > Using a function like
> > > > 
> > > > 	return (x_old * 3 + x) / 4;
> > > > 
> > > > eliminates the need for a FIFO, and has similar (if not better)
> > > > properties to floating average, because its coefficients are
> > > > [ .25 .18 .14 .10 ... ].
> > > 
> > > Agreed.
> > 
> > Except that this does not work well enough.
> 
> I guess the quick motion compensation in input bites you. The above
> equation should do even more smoothing than regular 4-point floating
> average.

Possible. The 'fuzz' parameter in input core serves too many usages
ihmo. Let me try removing the quick motion compensation and see...

> > I already thought about this, one problem is that the sensors do not
> > report the pressure but only the amount of surface touched. A person
> > with thick fingers will always generate higher pressures then one with
> > thin ones, no matter how hard they push on the touchpad.
> 
> That's what all other touchpads do.

I thought the hardware is capable of calculating real pressure...

> > I don't think this value is reliable enough to be reported to the
> > userspace as ABS_PRESSURE...
> 
> I believe it'd still be more useful than a two-value (0 and 100) output.

Ok, I'll do it.

> > +			/*
> > +			 * in the future, we could add here code to search for
> > +			 * a second finger...
> > +			 * for now, scrolling using the synaptics X driver is
> > +			 * much more simpler to achieve.
> > +			 */
> 
> This could be quite useful, too, for right and middle button taps (2 and
> 3 fingers) - since the Macs lack these buttons.

Indeed. But this can be a later improvement, let's make one finger work
for now :)

Stelian.
-- 
Stelian Pop <stelian@xxxxxxxxxx>

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