95 lines
2.6 KiB
ReStructuredText
95 lines
2.6 KiB
ReStructuredText
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.. -*- coding: utf-8; mode: rst -*-
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.. _cec:
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#######
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CEC API
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#######
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.. _cec-api:
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*********************************
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CEC: Consumer Electronics Control
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*********************************
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.. _cec-intro:
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Introduction
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============
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Note: this documents the proposed CEC API. This API is not yet finalized
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and is currently only available as a staging kernel module.
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HDMI connectors provide a single pin for use by the Consumer Electronics
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Control protocol. This protocol allows different devices connected by an
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HDMI cable to communicate. The protocol for CEC version 1.4 is defined
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in supplements 1 (CEC) and 2 (HEAC or HDMI Ethernet and Audio Return
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Channel) of the HDMI 1.4a (:ref:`hdmi`) specification and the
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extensions added to CEC version 2.0 are defined in chapter 11 of the
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HDMI 2.0 (:ref:`hdmi2`) specification.
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The bitrate is very slow (effectively no more than 36 bytes per second)
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and is based on the ancient AV.link protocol used in old SCART
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connectors. The protocol closely resembles a crazy Rube Goldberg
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contraption and is an unholy mix of low and high level messages. Some
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messages, especially those part of the HEAC protocol layered on top of
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CEC, need to be handled by the kernel, others can be handled either by
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the kernel or by userspace.
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In addition, CEC can be implemented in HDMI receivers, transmitters and
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in USB devices that have an HDMI input and an HDMI output and that
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control just the CEC pin.
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Drivers that support CEC will create a CEC device node (/dev/cecX) to
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give userspace access to the CEC adapter. The
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:ref:`CEC_ADAP_G_CAPS <cec-ioc-adap-g-caps>` ioctl will tell
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userspace what it is allowed to do.
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.. _cec-user-func:
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******************
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Function Reference
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******************
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.. toctree::
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:maxdepth: 1
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cec-func-open
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cec-func-close
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cec-func-ioctl
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cec-func-poll
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cec-ioc-adap-g-caps
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cec-ioc-adap-g-log-addrs
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cec-ioc-adap-g-phys-addr
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cec-ioc-dqevent
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cec-ioc-g-mode
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cec-ioc-receive
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**********************
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Revision and Copyright
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**********************
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:author: Verkuil Hans
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:address: hans.verkuil@cisco.com
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:contrib: Initial version.
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**Copyright** 2016 : Hans Verkuil
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:revision: 1.0.0 / 2016-03-17 (*hv*)
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Initial revision
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.. ------------------------------------------------------------------------------
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.. This file was automatically converted from DocBook-XML with the dbxml
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.. library (https://github.com/return42/sphkerneldoc). The origin XML comes
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.. from the linux kernel, refer to:
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..
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.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
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.. ------------------------------------------------------------------------------
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