I have worked configuration for this, if it is actually question.
I connected aux encoder 1u resoluution to aux to drive. Connected it to hal by xml config, named linear-pos.
And change actual position to linear-pos. And its works.
About points to 1 rotation - i connected to drive, and calculate gear ratio, on my case it was 1.4 - you put electronic gear 1:1 and move 1 rotation of motor, and look at measurement "clocks" what is movement on mm. And calculate. Also coefficient in my case for linear aux was 7000 . There are manual from delta for calculation.
Also important point that i put in xml file in linuxcnc (lcec some.xml) electronic gear values, and every load of linuxcnc it download by ethercat .
the link seems dead 