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

[Peter Hutterer]

On Thu, Oct 08, 2009 at 01:35:54PM +1100, Daniel Stone wrote:
> 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.

Oh, good thing you sent this. Ping convinced me of this a while ago and I
completely forgot about this patch (I even started reimplementing...). 
Will review in a second, this is one of the reasons I'm holding evdev 2.3
back.

Cheers,
  Peter