XChangeDeviceControl/XGetDeviceControl ?

Andrew Zabolotny anpaza at mail.ru
Sun Apr 16 11:57:01 PDT 2006


What would be the correct way to change/query some settings of a
extended input device? By looking into the Wacom tablet driver that
comes with Xorg, it looks like it uses a horrible hack in order to be
able to dynamically change settings like active area boundaries,
orientation and so on: the XChangeDeviceControl in reality supports
just a single parameter DEVICE_RESOLUTION, so it 'pretends' to
be changing the resolution (while in reality it changes his own
private settings).

This hack, however, has a number of problems: first, the device must
have at least two axes, then the values for every axis 'resolution' is
sanity checked inside the X11 core, and this call doesn't provide any
feedback so you can't query private device settings.

Wouldn't it be good to have a generic call like Unix ioctl(), which
doesn't have any knowledge of the input/output data structure: the only
thing it needs is the length of input/output data? Or I missed


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