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+<partinfo>
+  <authorgroup>
+    <author>
+      <firstname>Hans</firstname>
+      <surname>Verkuil</surname>
+      <affiliation><address><email>hans.verkuil@cisco.com</email></address></affiliation>
+      <contrib>Initial version.</contrib>
+    </author>
+  </authorgroup>
+  <copyright>
+    <year>2016</year>
+    <holder>Hans Verkuil</holder>
+  </copyright>
+
+  <revhistory>
+    <!-- Put document revisions here, newest first. -->
+    <revision>
+      <revnumber>1.0.0</revnumber>
+      <date>2016-03-17</date>
+      <authorinitials>hv</authorinitials>
+      <revremark>Initial revision</revremark>
+    </revision>
+  </revhistory>
+</partinfo>
+
+<title>CEC API</title>
+
+<chapter id="cec-api">
+  <title>CEC: Consumer Electronics Control</title>
+
+  <section id="cec-intro">
+    <title>Introduction</title>
+    <para>
+      Note: this documents the proposed CEC API. This API is not yet finalized and
+      is currently only available as a staging kernel module.
+    </para>
+    <para>HDMI connectors provide a single pin for use by the Consumer Electronics
+    Control protocol. This protocol allows different devices connected by an HDMI cable
+    to communicate. The protocol for CEC version 1.4 is defined in supplements 1 (CEC)
+    and 2 (HEAC or HDMI Ethernet and Audio Return Channel) of the HDMI 1.4a
+    (<xref linkend="hdmi" />) specification and the extensions added to CEC version 2.0
+    are defined in chapter 11 of the HDMI 2.0 (<xref linkend="hdmi2" />) specification.
+    </para>
+
+    <para>The bitrate is very slow (effectively no more than 36 bytes per second) and
+    is based on the ancient AV.link protocol used in old SCART connectors. The protocol
+    closely resembles a crazy Rube Goldberg contraption and is an unholy mix of low and
+    high level messages. Some messages, especially those part of the HEAC protocol layered
+    on top of CEC, need to be handled by the kernel, others can be handled either by the
+    kernel or by userspace.</para>
+
+    <para>In addition, CEC can be implemented in HDMI receivers, transmitters and in USB
+    devices that have an HDMI input and an HDMI output and that control just the CEC pin.</para>
+
+    <para>Drivers that support CEC will create a CEC device node (/dev/cecX)
+    to give userspace access to the CEC adapter. The &CEC-ADAP-G-CAPS; ioctl will tell userspace
+    what it is allowed to do.</para>
+  </section>
+</chapter>
+
+<appendix id="cec-user-func">
+  <title>Function Reference</title>
+  <!-- Keep this alphabetically sorted. -->
+  &sub-cec-func-open;
+  &sub-cec-func-close;
+  &sub-cec-func-ioctl;
+  &sub-cec-func-poll;
+  <!-- All ioctls go here. -->
+  &sub-cec-ioc-adap-g-caps;
+  &sub-cec-ioc-adap-g-log-addrs;
+  &sub-cec-ioc-adap-g-phys-addr;
+  &sub-cec-ioc-dqevent;
+  &sub-cec-ioc-g-mode;
+  &sub-cec-ioc-receive;
+</appendix>