diff --git a/Documentation/DocBook/media/v4l/vidioc-g-dv-timings.xml b/Documentation/DocBook/media/v4l/vidioc-g-dv-timings.xml
index 7236970..c433657 100644
--- a/Documentation/DocBook/media/v4l/vidioc-g-dv-timings.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-g-dv-timings.xml
@@ -156,19 +156,19 @@
 	    <entry>__u32</entry>
 	    <entry><structfield>il_vfrontporch</structfield></entry>
 	    <entry>Vertical front porch in lines for the even field (aka field 2) of
-	    interlaced field formats.</entry>
+	    interlaced field formats. Must be 0 for progressive formats.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>il_vsync</structfield></entry>
 	    <entry>Vertical sync length in lines for the even field (aka field 2) of
-	    interlaced field formats.</entry>
+	    interlaced field formats. Must be 0 for progressive formats.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>il_vbackporch</structfield></entry>
 	    <entry>Vertical back porch in lines for the even field (aka field 2) of
-	    interlaced field formats.</entry>
+	    interlaced field formats. Must be 0 for progressive formats.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>