[media] DocBook: mention that EINVAL can be returned for invalid menu indices

The documentation suggested that if the control value is wrong only
ERANGE can be returned. But in some cases (an invalid menu index)
EINVAL can also be returned. Clarify this.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/DocBook/media/v4l/vidioc-g-ctrl.xml

@@ -64,7 +64,9 @@ return an &EINVAL;. When the <structfield>value</structfield> is out
 of bounds drivers can choose to take the closest valid value or return
 an &ERANGE;, whatever seems more appropriate. However,
 <constant>VIDIOC_S_CTRL</constant> is a write-only ioctl, it does not
-return the actual new value.</para>
+return the actual new value. If the <structfield>value</structfield>
+is inappropriate for the control (e.g. if it refers to an unsupported
+menu index of a menu control), then &EINVAL; is returned as well.</para>
 
     <para>These ioctls work only with user controls. For other
 control classes the &VIDIOC-G-EXT-CTRLS;, &VIDIOC-S-EXT-CTRLS; or
@@ -99,7 +101,9 @@ application.</entry>
 	<term><errorcode>EINVAL</errorcode></term>
 	<listitem>
 	  <para>The &v4l2-control; <structfield>id</structfield> is
-invalid.</para>
+invalid or the <structfield>value</structfield> is inappropriate for
+the given control (i.e. if a menu item is selected that is not supported
+by the driver according to &VIDIOC-QUERYMENU;).</para>
 	</listitem>
       </varlistentry>
       <varlistentry>

Documentation/DocBook/media/v4l/vidioc-g-ext-ctrls.xml

@@ -106,7 +106,9 @@ value or if an error is returned.</para>
 &EINVAL;. When the value is out of bounds drivers can choose to take
 the closest valid value or return an &ERANGE;, whatever seems more
 appropriate. In the first case the new value is set in
-&v4l2-ext-control;.</para>
+&v4l2-ext-control;. If the new control value is inappropriate (e.g. the
+given menu index is not supported by the menu control), then this will
+also result in an &EINVAL; error.</para>
 
     <para>The driver will only set/get these controls if all control
 values are correct. This prevents the situation where only some of the
@@ -331,8 +333,10 @@ These controls are described in <xref
 	<term><errorcode>EINVAL</errorcode></term>
 	<listitem>
 	  <para>The &v4l2-ext-control; <structfield>id</structfield>
-is invalid or the &v4l2-ext-controls;
-<structfield>ctrl_class</structfield> is invalid. This error code is
+is invalid, the &v4l2-ext-controls;
+<structfield>ctrl_class</structfield> is invalid, or the &v4l2-ext-control;
+<structfield>value</structfield> was inappropriate (e.g. the given menu
+index is not supported by the driver). This error code is
 also returned by the <constant>VIDIOC_S_EXT_CTRLS</constant> and
 <constant>VIDIOC_TRY_EXT_CTRLS</constant> ioctls if two or more
 control values are in conflict.</para>