[PATCH] evdev: Support the "Calibration" string option.

[Daniel Stone]

Hi,

On Mon, Aug 03, 2009 at 09:44:13AM +1000, Peter Hutterer wrote:
> On Mon, Aug 03, 2009 at 02:31:02AM +0300, oliver.mcfadden at nokia.com wrote:
> > From: Oliver McFadden <oliver.mcfadden at nokia.com>
> > 
> > Originally based on a patch from Daniel Stone, this commit allows for
> > the calibration factors to be set either from Xorg.conf or via HAL.
> > 
> > Previously the only way was via the properties interface.
> 
> NACK, this was intentional.
> 
> Evdev sets itself up from the data the kernel provides. If you can
> statically configure the calibration (i.e. how far off the kernel
> data is from the real data) then fix the kernel driver.
> 
> Evdev calibration is just for those devices that require different
> calibration each time and this needs to be done at runtime anyway then.

Hmm.  The problem is that the kernel doesn't know this information, and
they have previously stated their distaste for adding tables for this
kind of thing.

So we store the calibration in userspace -- and allow the user to
calibrate it if the calibration creeps -- with a heuristic for choosing
_which_ calibration data to load, as it changes between hardware builds.
Having it only accessible via properties at runtime would mean that the
X server would always come up with an incorrectly-calibrated
touchscreen, which would then (hopefully) be fixed up by a client.

If you've got any better suggestions for handling this, I'm all ears.

Cheers,
Daniel
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