Vita DSI vertical active lines calculation

/*
<----------------------------------------------- vtotal ------------------------------------------------------>

VSYNC | VBP |----------------------------------------------- Pixel Rows ----------------------------------| VFP
             \                                         /\                                           /\   /
              HSYNC | HBP | --- Pixel Columns --- | HFP  | HSYNC | HBP | --- Pixel Columns --- | HFP  ...

              <----------------- htotal -------------->
*/

if (timing_info->mode == 1)   // Interlaced?
        height = timing_info->vtotal + 1 - 2 * (timing_info->VSYNC + timing_info->VBP + timing_info->VFP);
else                         // Progressive?
        height = timing_info->vtotal - (timing_info->VSYNC + timing_info->VBP + timing_info->VFP);