Elias Vanderstuyft
Remove the dependency of the calculation of Linux "phase" on "period",
currently the "phase" parameter is interpreted as a time shift, instead of a phase shift.
The Linux input documentation is not clear about the exact units of the "phase" parameter (see http://lxr.free-electrons.com/source/include/uapi/linux/input.h?v=3.17#L1075 ),
but we're about to standardize the 'phase shift' interpretation into the Linux input documentation,
since this will ease the job of a driver to recalculate the effect's state when the user dynamically updates the "period" parameter.
Elias Vanderstuyft
It's not obvious from the general "haptic direction" description what the SDL direction actually means in terms of force magnitude sign,
currently its meaning is only reflected by the example.
Sam Lantinga
Philipp Wiesemann