[ltp] Smooth trackpoint acceleration

[Richard]

> On Monday 05 June 2006 6:41 am, Richard Neill rn214-at-hermes.cam.ac.uk |
> LinuxThinkpad| wrote:
>> Guarded Identity wrote:
>>> I was wondering if anyone has found a solution for smoother acceleration
>>> of the trackpoint device.  It seems to me that the best way to fix this
>>> problem is to develop a kernel patch for the psmouse/trackpoint driver.
>>> Then smooth acceleration can be controlled by SysFS.  If this could be
>>> done, then acceleration could just be turned off in xset.
>>
>> What you wanted was to configure the gain of the hardware itself! Much
>> nicer than low-gain + scrolling.
>> The old way was called tp4d; the new way is a kernel driver, as of
>> k.2.6.14: thinkwiki.org/wiki/How_to_configure_the_TrackPoint
>>
>
> Sorry, I was afraid it might be difficult for me to express myself clearly.
> What I really meant to say is that I think Steven Evanchik's kernel patch in
> 2.6.14 can be even smoother... more responsive.  The algorithm tp-scroll uses
> is an exponential acceleration.  (actually, I'm pretty sure Evanchik's driver
> doesn't even have acceleration, just speed; acceleration is handled by xset).
>
> I imagine that the Thinkpad community in general has gotten used to using the
> device with what's available.  I just realized now that it's possible to make
> this device even more accurate than it is now.  I think exponential or
> polynomial acceleration is a good start.
>


I see what you mean - but I think that perhaps you haven't got the most 
out of the existing setup.

Firstly, if you get the kernel >= 2.6.14, you can then set the mouse 
sensitivity to 255. I use:

    echo -n 255 > /sys/devices/platform/i8042/serio0/sensitivity
    echo -n 100 > /sys/devices/platform/i8042/serio0/speed
    echo -n 3 > /sys/devices/platform/i8042/serio0/inertia

This provides a very light touch. Secondly, you can then add acceleration 
of about 2x, taking effect after 5 pixels. If you tweak *both* these 
numbers, it will be very nice to use.

What you will absolutely hate is acceleration > about 5x. That does cause 
the "2 speed bicyle effect" I agree, polynomial acceleration would be 
nice, but I think you may find that, if well-adjusted, the 2-speed dogleg 
approach is good enough.



That said, if you actually do decide to write an exponential acceleration, 
it would be nice to have; especially with ordinary mice! If so, you need 
to patch the X mouse driver, rather than the trackpoint, and I'd suggest 
starting by raising an issue in the xorg bugzilla.

Best wishes,

Richard