xref: /openbmc/linux/Documentation/userspace-api/media/cec/cec-func-open.rst (revision 54f38fca)

.. Permission is granted to copy, distribute and/or modify this
.. document under the terms of the GNU Free Documentation License,
.. Version 1.1 or any later version published by the Free Software
.. Foundation, with no Invariant Sections, no Front-Cover Texts
.. and no Back-Cover Texts. A copy of the license is included at
.. Documentation/userspace-api/media/fdl-appendix.rst.
..
.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections

.. _cec-func-open:

**********
cec open()
**********

Name
====

cec-open - Open a cec device

Synopsis
========

.. code-block:: c

    #include <fcntl.h>


.. c:function:: int open( const char *device_name, int flags )
   :name: cec-open


Arguments
=========

``device_name``
    Device to be opened.

``flags``
    Open flags. Access mode must be ``O_RDWR``.

    When the ``O_NONBLOCK`` flag is given, the
    :ref:`CEC_RECEIVE <CEC_RECEIVE>` and :ref:`CEC_DQEVENT <CEC_DQEVENT>` ioctls
    will return the ``EAGAIN`` error code when no message or event is available, and
    ioctls :ref:`CEC_TRANSMIT <CEC_TRANSMIT>`,
    :ref:`CEC_ADAP_S_PHYS_ADDR <CEC_ADAP_S_PHYS_ADDR>` and
    :ref:`CEC_ADAP_S_LOG_ADDRS <CEC_ADAP_S_LOG_ADDRS>`
    all return 0.

    Other flags have no effect.


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

To open a cec device applications call :c:func:`open() <cec-open>` with the
desired device name. The function has no side effects; the device
configuration remain unchanged.

When the device is opened in read-only mode, attempts to modify its
configuration will result in an error, and ``errno`` will be set to
EBADF.


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

:c:func:`open() <cec-open>` returns the new file descriptor on success. On error,
-1 is returned, and ``errno`` is set appropriately. Possible error codes
include:

``EACCES``
    The requested access to the file is not allowed.

``EMFILE``
    The process already has the maximum number of files open.

``ENFILE``
    The system limit on the total number of open files has been reached.

``ENOMEM``
    Insufficient kernel memory was available.

``ENXIO``
    No device corresponding to this device special file exists.