From d9920c08abb43a90d2d28c424ed1bafddd00cefe Mon Sep 17 00:00:00 2001
From: Hans Verkuil <hverkuil@xs4all.nl>
Date: Fri, 20 Feb 2009 09:55:39 +0100
Subject: v4l2: add V4L2_CTRL_FLAG_WRITE_ONLY flag.

From: Hans Verkuil <hverkuil@xs4all.nl>

Priority: normal

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
---
 linux/include/linux/videodev2.h |  1 +
 v4l2-spec/compat.sgml           |  3 +++
 v4l2-spec/vidioc-queryctrl.sgml | 15 +++++++++++++++
 3 files changed, 19 insertions(+)

diff --git a/linux/include/linux/videodev2.h b/linux/include/linux/videodev2.h
index 6969c3086..4167a0b44 100644
--- a/linux/include/linux/videodev2.h
+++ b/linux/include/linux/videodev2.h
@@ -830,6 +830,7 @@ struct v4l2_querymenu {
 #define V4L2_CTRL_FLAG_UPDATE 		0x0008
 #define V4L2_CTRL_FLAG_INACTIVE 	0x0010
 #define V4L2_CTRL_FLAG_SLIDER 		0x0020
+#define V4L2_CTRL_FLAG_WRITE_ONLY 	0x0040
 
 /*  Query flag, to be ORed with the control ID */
 #define V4L2_CTRL_FLAG_NEXT_CTRL	0x80000000
diff --git a/v4l2-spec/compat.sgml b/v4l2-spec/compat.sgml
index 1ee7c4a82..94713023d 100644
--- a/v4l2-spec/compat.sgml
+++ b/v4l2-spec/compat.sgml
@@ -2286,6 +2286,9 @@ was renamed to <structname id=v4l2-chip-ident-old>v4l2_chip_ident_old</structnam
     <section>
       <title>V4L2 in Linux 2.6.30</title>
       <orderedlist>
+	<listitem>
+	  <para>New control flag <constant>V4L2_CTRL_FLAG_WRITE_ONLY</constant> was added.</para>
+	</listitem>
 	<listitem>
 	  <para>New control <constant>V4L2_CID_COLORFX</constant> was added.</para>
 	</listitem>
diff --git a/v4l2-spec/vidioc-queryctrl.sgml b/v4l2-spec/vidioc-queryctrl.sgml
index 20c4147eb..9908a964d 100644
--- a/v4l2-spec/vidioc-queryctrl.sgml
+++ b/v4l2-spec/vidioc-queryctrl.sgml
@@ -361,6 +361,15 @@ control.</entry>
 	    <entry>A hint that this control is best represented as a
 slider-like element in a user interface.</entry>
 	  </row>
+	  <row>
+	    <entry><constant>V4L2_CTRL_FLAG_WRITE_ONLY</constant></entry>
+	    <entry>0x0040</entry>
+	    <entry>This control is permanently writable only. Any
+attempt to read the control will result in an &EACCES; error code. This
+flag is typically present for relative controls or action controls where
+writing a value will cause the device to carry out a given action
+(&eg; motor control) but no meaningful value can be returned.</entry>
+	  </row>
 	</tbody>
       </tgroup>
     </table>
@@ -378,6 +387,12 @@ is invalid. The &v4l2-querymenu; <structfield>id</structfield> or
 <structfield>index</structfield> is invalid.</para>
 	</listitem>
       </varlistentry>
+      <varlistentry>
+	<term><errorcode>EACCES</errorcode></term>
+	<listitem>
+	  <para>An attempt was made to read a write-only control.</para>
+	</listitem>
+      </varlistentry>
     </variablelist>
   </refsect1>
 </refentry>
-- 
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