Documentation/media/uapi/cec/cec-ioc-g-mode.rst

.. -*- coding: utf-8; mode: rst -*-

.. _CEC_MODE:
.. _CEC_G_MODE:
.. _CEC_S_MODE:

********************************
ioctls CEC_G_MODE and CEC_S_MODE
********************************

CEC_G_MODE, CEC_S_MODE - Get or set exclusive use of the CEC adapter

Synopsis
========

.. cpp:function:: int ioctl( int fd, int request, __u32 *argp )

Arguments
=========

``fd``
    File descriptor returned by :ref:`open() <cec-func-open>`.

``request``
    CEC_G_MODE, CEC_S_MODE

``argp``


Description
===========

.. note:: This documents the proposed CEC API. This API is not yet finalized
   and is currently only available as a staging kernel module.

By default any filehandle can use :ref:`CEC_TRANSMIT`, but in order to prevent
applications from stepping on each others toes it must be possible to
obtain exclusive access to the CEC adapter. This ioctl sets the
filehandle to initiator and/or follower mode which can be exclusive
depending on the chosen mode. The initiator is the filehandle that is
used to initiate messages, i.e. it commands other CEC devices. The
follower is the filehandle that receives messages sent to the CEC
adapter and processes them. The same filehandle can be both initiator
and follower, or this role can be taken by two different filehandles.

When a CEC message is received, then the CEC framework will decide how
it will be processed. If the message is a reply to an earlier
transmitted message, then the reply is sent back to the filehandle that
is waiting for it. In addition the CEC framework will process it.

If the message is not a reply, then the CEC framework will process it
first. If there is no follower, then the message is just discarded and a
feature abort is sent back to the initiator if the framework couldn't
process it. If there is a follower, then the message is passed on to the
follower who will use :ref:`ioctl CEC_RECEIVE <CEC_RECEIVE>` to dequeue
the new message. The framework expects the follower to make the right
decisions.

The CEC framework will process core messages unless requested otherwise
by the follower. The follower can enable the passthrough mode. In that
case, the CEC framework will pass on most core messages without
processing them and the follower will have to implement those messages.
There are some messages that the core will always process, regardless of
the passthrough mode. See :ref:`cec-core-processing` for details.

If there is no initiator, then any CEC filehandle can use
:ref:`ioctl CEC_TRANSMIT <CEC_TRANSMIT>`. If there is an exclusive
initiator then only that initiator can call
:ref:`CEC_TRANSMIT`. The follower can of course
always call :ref:`ioctl CEC_TRANSMIT <CEC_TRANSMIT>`.

Available initiator modes are:


.. _cec-mode-initiator_e:

.. flat-table:: Initiator Modes
    :header-rows:  0
    :stub-columns: 0
    :widths:       3 1 16


    -  .. _`CEC-MODE-NO-INITIATOR`:

       -  ``CEC_MODE_NO_INITIATOR``

       -  0x0

       -  This is not an initiator, i.e. it cannot transmit CEC messages or
	  make any other changes to the CEC adapter.

    -  .. _`CEC-MODE-INITIATOR`:

       -  ``CEC_MODE_INITIATOR``

       -  0x1

       -  This is an initiator (the default when the device is opened) and
	  it can transmit CEC messages and make changes to the CEC adapter,
	  unless there is an exclusive initiator.

    -  .. _`CEC-MODE-EXCL-INITIATOR`:

       -  ``CEC_MODE_EXCL_INITIATOR``

       -  0x2

       -  This is an exclusive initiator and this file descriptor is the
	  only one that can transmit CEC messages and make changes to the
	  CEC adapter. If someone else is already the exclusive initiator
	  then an attempt to become one will return the ``EBUSY`` error code
	  error.


Available follower modes are:


.. _cec-mode-follower_e:

.. flat-table:: Follower Modes
    :header-rows:  0
    :stub-columns: 0
    :widths:       3 1 16


    -  .. _`CEC-MODE-NO-FOLLOWER`:

       -  ``CEC_MODE_NO_FOLLOWER``

       -  0x00

       -  This is not a follower (the default when the device is opened).

    -  .. _`CEC-MODE-FOLLOWER`:

       -  ``CEC_MODE_FOLLOWER``

       -  0x10

       -  This is a follower and it will receive CEC messages unless there
	  is an exclusive follower. You cannot become a follower if
	  :ref:`CEC_CAP_TRANSMIT <CEC-CAP-TRANSMIT>` is not set or if :ref:`CEC_MODE_NO_INITIATOR <CEC-MODE-NO-INITIATOR>`
	  was specified, the ``EINVAL`` error code is returned in that case.

    -  .. _`CEC-MODE-EXCL-FOLLOWER`:

       -  ``CEC_MODE_EXCL_FOLLOWER``

       -  0x20

       -  This is an exclusive follower and only this file descriptor will
	  receive CEC messages for processing. If someone else is already
	  the exclusive follower then an attempt to become one will return
	  the ``EBUSY`` error code. You cannot become a follower if
	  :ref:`CEC_CAP_TRANSMIT <CEC-CAP-TRANSMIT>` is not set or if :ref:`CEC_MODE_NO_INITIATOR <CEC-MODE-NO-INITIATOR>`
	  was specified, the ``EINVAL`` error code is returned in that case.

    -  .. _`CEC-MODE-EXCL-FOLLOWER-PASSTHRU`:

       -  ``CEC_MODE_EXCL_FOLLOWER_PASSTHRU``

       -  0x30

       -  This is an exclusive follower and only this file descriptor will
	  receive CEC messages for processing. In addition it will put the
	  CEC device into passthrough mode, allowing the exclusive follower
	  to handle most core messages instead of relying on the CEC
	  framework for that. If someone else is already the exclusive
	  follower then an attempt to become one will return the ``EBUSY`` error
	  code. You cannot become a follower if :ref:`CEC_CAP_TRANSMIT <CEC-CAP-TRANSMIT>`
	  is not set or if :ref:`CEC_MODE_NO_INITIATOR <CEC-MODE-NO-INITIATOR>` was specified,
	  the ``EINVAL`` error code is returned in that case.

    -  .. _`CEC-MODE-MONITOR`:

       -  ``CEC_MODE_MONITOR``

       -  0xe0

       -  Put the file descriptor into monitor mode. Can only be used in
	  combination with :ref:`CEC_MODE_NO_INITIATOR <CEC-MODE-NO-INITIATOR>`, otherwise EINVAL error
	  code will be returned. In monitor mode all messages this CEC
	  device transmits and all messages it receives (both broadcast
	  messages and directed messages for one its logical addresses) will
	  be reported. This is very useful for debugging. This is only
	  allowed if the process has the ``CAP_NET_ADMIN`` capability. If
	  that is not set, then the ``EPERM`` error code is returned.

    -  .. _`CEC-MODE-MONITOR-ALL`:

       -  ``CEC_MODE_MONITOR_ALL``

       -  0xf0

       -  Put the file descriptor into 'monitor all' mode. Can only be used
	  in combination with :ref:`CEC_MODE_NO_INITIATOR <CEC-MODE-NO-INITIATOR>`, otherwise
	  the ``EINVAL`` error code will be returned. In 'monitor all' mode all messages
	  this CEC device transmits and all messages it receives, including
	  directed messages for other CEC devices will be reported. This is
	  very useful for debugging, but not all devices support this. This
	  mode requires that the :ref:`CEC_CAP_MONITOR_ALL <CEC-CAP-MONITOR-ALL>` capability is set,
	  otherwise the ``EINVAL`` error code is returned. This is only allowed if
	  the process has the ``CAP_NET_ADMIN`` capability. If that is not
	  set, then the ``EPERM`` error code is returned.


Core message processing details:


.. _cec-core-processing:

.. flat-table:: Core Message Processing
    :header-rows:  0
    :stub-columns: 0
    :widths: 1 8


    -  .. _`CEC-MSG-GET-CEC-VERSION`:

       -  ``CEC_MSG_GET_CEC_VERSION``

       -  When in passthrough mode this message has to be handled by
	  userspace, otherwise the core will return the CEC version that was
	  set with :ref:`ioctl CEC_ADAP_S_LOG_ADDRS <CEC_ADAP_S_LOG_ADDRS>`.

    -  .. _`CEC-MSG-GIVE-DEVICE-VENDOR-ID`:

       -  ``CEC_MSG_GIVE_DEVICE_VENDOR_ID``

       -  When in passthrough mode this message has to be handled by
	  userspace, otherwise the core will return the vendor ID that was
	  set with :ref:`ioctl CEC_ADAP_S_LOG_ADDRS <CEC_ADAP_S_LOG_ADDRS>`.

    -  .. _`CEC-MSG-ABORT`:

       -  ``CEC_MSG_ABORT``

       -  When in passthrough mode this message has to be handled by
	  userspace, otherwise the core will return a feature refused
	  message as per the specification.

    -  .. _`CEC-MSG-GIVE-PHYSICAL-ADDR`:

       -  ``CEC_MSG_GIVE_PHYSICAL_ADDR``

       -  When in passthrough mode this message has to be handled by
	  userspace, otherwise the core will report the current physical
	  address.

    -  .. _`CEC-MSG-GIVE-OSD-NAME`:

       -  ``CEC_MSG_GIVE_OSD_NAME``

       -  When in passthrough mode this message has to be handled by
	  userspace, otherwise the core will report the current OSD name as
	  was set with :ref:`ioctl CEC_ADAP_S_LOG_ADDRS <CEC_ADAP_S_LOG_ADDRS>`.

    -  .. _`CEC-MSG-GIVE-FEATURES`:

       -  ``CEC_MSG_GIVE_FEATURES``

       -  When in passthrough mode this message has to be handled by
	  userspace, otherwise the core will report the current features as
	  was set with :ref:`ioctl CEC_ADAP_S_LOG_ADDRS <CEC_ADAP_S_LOG_ADDRS>`
	  or the message is ignored if the CEC version was older than 2.0.

    -  .. _`CEC-MSG-USER-CONTROL-PRESSED`:

       -  ``CEC_MSG_USER_CONTROL_PRESSED``

       -  If :ref:`CEC_CAP_RC <CEC-CAP-RC>` is set, then generate a remote control key
	  press. This message is always passed on to userspace.

    -  .. _`CEC-MSG-USER-CONTROL-RELEASED`:

       -  ``CEC_MSG_USER_CONTROL_RELEASED``

       -  If :ref:`CEC_CAP_RC <CEC-CAP-RC>` is set, then generate a remote control key
	  release. This message is always passed on to userspace.

    -  .. _`CEC-MSG-REPORT-PHYSICAL-ADDR`:

       -  ``CEC_MSG_REPORT_PHYSICAL_ADDR``

       -  The CEC framework will make note of the reported physical address
	  and then just pass the message on to userspace.



Return Value
============

On success 0 is returned, on error -1 and the ``errno`` variable is set
appropriately. The generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.