[Letux-kernel] Letux: tsc2007 driver

H. Nikolaus Schaller hns at goldelico.com
Sun Feb 21 19:03:28 CET 2016

I have reworked the tsc2007 driver [1] a little because tests on the
Pyra hardware did show a potential bug with x/y swapping.

Together with that change, I have removed the clamping function
which did restrict the reported coordinates to the window defined
by the min/max ADC coordinates.

Clamping is discouraged by some document in Android (I do not
remember the link), because it allows to better interpolate movements
with jitter close to the touch screen edges.

A side effect is that the precalibrated touch may now report
negative x and y coordinates (although small values). A real
calibration done in user space can compensate for that.

The good side is that you still have the full touch screen range
even if the precalibration is wrong. Before that change, it was
not always possible to move the cursor to the screen edges.

I have checked that it is not a problem for the X11 system, and
they can handle negative touch coordinates.


[1]: http://git.goldelico.com/?p=gta04-kernel.git;a=shortlog;h=refs/heads/work/hns/input/tsc2007-v3

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