Documentation/userspace-api/media/cec/cec-ioc-dqevent.rst

Source file repositories/reference/linux-study-clean/Documentation/userspace-api/media/cec/cec-ioc-dqevent.rst

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Linux kernel
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Documentation/userspace-api/media/cec/cec-ioc-dqevent.rst
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.rst
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Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
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Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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Annotated Snippet

.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. c:namespace:: CEC

.. _CEC_DQEVENT:

*****************
ioctl CEC_DQEVENT
*****************

Name
====

CEC_DQEVENT - Dequeue a CEC event

Synopsis
========

.. c:macro:: CEC_DQEVENT

``int ioctl(int fd, CEC_DQEVENT, struct cec_event *argp)``

Arguments
=========

``fd``
    File descriptor returned by :c:func:`open()`.

``argp``

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

CEC devices can send asynchronous events. These can be retrieved by
calling :c:func:`CEC_DQEVENT`. If the file descriptor is in
non-blocking mode and no event is pending, then it will return -1 and
set errno to the ``EAGAIN`` error code.

The internal event queues are per-filehandle and per-event type. If
there is no more room in a queue then the last event is overwritten with
the new one. This means that intermediate results can be thrown away but
that the latest event is always available. This also means that is it
possible to read two successive events that have the same value (e.g.
two :ref:`CEC_EVENT_STATE_CHANGE <CEC-EVENT-STATE-CHANGE>` events with
the same state). In that case the intermediate state changes were lost but
it is guaranteed that the state did change in between the two events.

.. tabularcolumns:: |p{1.2cm}|p{2.9cm}|p{13.2cm}|

.. c:type:: cec_event_state_change

.. flat-table:: struct cec_event_state_change
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 8

    * - __u16
      - ``phys_addr``
      - The current physical address. This is ``CEC_PHYS_ADDR_INVALID`` if no
        valid physical address is set.
    * - __u16
      - ``log_addr_mask``
      - The current set of claimed logical addresses. This is 0 if no logical
        addresses are claimed or if ``phys_addr`` is ``CEC_PHYS_ADDR_INVALID``.
	If bit 15 is set (``1 << CEC_LOG_ADDR_UNREGISTERED``) then this device
	has the unregistered logical address. In that case all other bits are 0.
    * - __u16
      - ``have_conn_info``
      - If non-zero, then HDMI connector information is available.
        This field is only valid if ``CEC_CAP_CONNECTOR_INFO`` is set. If that
        capability is set and ``have_conn_info`` is zero, then that indicates

Annotation

Implementation Notes