1088 /** * Called by \c drm_get_last_vbltimestamp. Should return a precise * timestamp when the most recent VBLANK interval ended or will end. * * Specifically, the timestamp in @vblank_time should correspond as * closely as possible to the time when the first video scanline of * the video frame after the end of VBLANK will start scanning out, * the time immediately after end of the VBLANK interval. If the * @crtc is currently inside VBLANK, this will be a time in the future. * If the @crtc is currently scanning out a frame, this will be the * past start time of the current scanout. This is meant to adhere * to the OpenML OML_sync_control extension specification. * * \param dev dev DRM device handle. * \param crtc crtc for which timestamp should be returned. * \param *max_error Maximum allowable timestamp error in nanoseconds. * Implementation should strive to provide timestamp * with an error of at most *max_error nanoseconds. * Returns true upper bound on error for timestamp. * \param *vblank_time Target location for returned vblank timestamp. * \param flags 0 = Defaults, no special treatment needed. * \param DRM_CALLED_FROM_VBLIRQ = Function is called from vblank * irq handler. Some drivers need to apply some workarounds * for gpu-specific vblank irq quirks if flag is set. * * \returns * Zero if timestamping isn't supported in current display mode or a * negative number on failure. A positive status code on success, * which describes how the vblank_time timestamp was computed. */