/* * Retrieve current video scanout position of crtc on a given gpu, and * an optional accurate timestamp of when query happened. * * \param dev Device to query. * \param crtc Crtc to query. * \param flags Flags from caller (DRM_CALLED_FROM_VBLIRQ or 0). * \param *vpos Location where vertical scanout position should be stored. * \param *hpos Location where horizontal scanout position should go. * \param *stime Target location for timestamp taken immediately before * scanout position query. Can be NULL to skip timestamp. * \param *etime Target location for timestamp taken immediately after * scanout position query. Can be NULL to skip timestamp. * * Returns vpos as a positive number while in active scanout area. * Returns vpos as a negative number inside vblank, counting the number * of scanlines to go until end of vblank, e.g., -1 means "one scanline * until start of active scanout / end of vblank." * * \return Flags, or'ed together as follows: * * DRM_SCANOUTPOS_VALID = Query successful. * DRM_SCANOUTPOS_INVBL = Inside vblank. * DRM_SCANOUTPOS_ACCURATE = Returned position is accurate. A lack of * this flag means that returned position may be offset by a constant but * unknown small number of scanlines wrt. real scanout position. * */