-returned in the preset field of &v4l2-dv-preset;. When detection is not
-possible or fails, the value V4L2_DV_INVALID is returned.</para>
+returned in the preset field of &v4l2-dv-preset;. If the preset could not be
+detected because there was no signal, or the signal was unreliable, or the
+signal did not map to a supported preset, then the value V4L2_DV_INVALID is
+returned.</para>