Re: Touchpad problems with 2.6.11-rc2

[Vojtech Pavlik <vojtech@suse.cz>]

On Thu, Feb 03, 2005 at 10:54:51PM +0100, Peter Osterlund wrote:
> Vojtech Pavlik <vojtech@suse.cz> writes:
> 
> > On Wed, Feb 02, 2005 at 11:58:05PM +0100, Peter Osterlund wrote:
> > 
> > > In practice I don't think it will make any significant difference. What
> > > the code should do depends on what you want to happen if you move the
> > > mouse pointer 1/2 pixel with one finger stroke, then move it another 1/2
> > > pixel with a second stroke. The patch I posted will move the pointer one
> > > pixel in this case and your code will move it 0 pixels. (The X driver does
> > > not reset the fractions, but that doesn't of course mean that it's the
> > > only right thing to do.)
> > > 
> > > > Also, I think the extra unary minus is uncoth.
> > > 
> > > The code was written like that to emphasize the fact that X and Y use the
> > > same formula, with the only difference that the kernel Y axis is mirrored
> > > compared to the touchpad Y axis.
> > > 
> > > It didn't make any difference for the generated assembly code though,
> > > using gcc 3.4.2 from Fedora Core 3.
> > > 
> > > > +	enum {  FRACTION_DENOM = 100 };
> > > 
> > > The enum is much nicer than my #define.
> > 
> > OK. I like this patch, too. Can you guys send me a final version
> > incorporating the changes of you both for inclusion in the input tree?
> 
> Here it is, with the suggestions from Pete and Dmitry included. The
> patch does the following:
> 
> * Compensates for the lack of floating point arithmetic by keeping
>   track of remainders from the integer divisions.

This was likely the main cause of the slow motion problems.

> * Removes the xres/yres scaling so that you get the same speed in the
>   X and Y directions even if your screen is not square.

The old code assumed that both the pad and the screen are 4:3, not
square. It was wrong still.

> * Sets scale factors to make the speed for synaptics and alps equal to
>   each other and equal to the synaptics speed from 2.6.10.
> 
> Signed-off-by: Peter Osterlund <petero2@telia.com>

OK. I'll add it to my tree today.

-- 
Vojtech Pavlik
SuSE Labs, SuSE CR