xref: /kernel/linux/linux-5.10/Documentation/userspace-api/media/v4l/vidioc-enum-dv-timings.rst

.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. c:namespace:: V4L

.. _VIDIOC_ENUM_DV_TIMINGS:

***********************************************************
ioctl VIDIOC_ENUM_DV_TIMINGS, VIDIOC_SUBDEV_ENUM_DV_TIMINGS
***********************************************************

Name
====

VIDIOC_ENUM_DV_TIMINGS - VIDIOC_SUBDEV_ENUM_DV_TIMINGS - Enumerate supported Digital Video timings

Synopsis
========

.. c:macro:: VIDIOC_ENUM_DV_TIMINGS

``int ioctl(int fd, VIDIOC_ENUM_DV_TIMINGS, struct v4l2_enum_dv_timings *argp)``

.. c:macro:: VIDIOC_SUBDEV_ENUM_DV_TIMINGS

``int ioctl(int fd, VIDIOC_SUBDEV_ENUM_DV_TIMINGS, struct v4l2_enum_dv_timings *argp)``

Arguments
=========

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

``argp``
    Pointer to struct :c:type:`v4l2_enum_dv_timings`.

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

While some DV receivers or transmitters support a wide range of timings,
others support only a limited number of timings. With this ioctl
applications can enumerate a list of known supported timings. Call
:ref:`VIDIOC_DV_TIMINGS_CAP` to check if it
also supports other standards or even custom timings that are not in
this list.

To query the available timings, applications initialize the ``index``
field, set the ``pad`` field to 0, zero the reserved array of struct
:c:type:`v4l2_enum_dv_timings` and call the
``VIDIOC_ENUM_DV_TIMINGS`` ioctl on a video node with a pointer to this
structure. Drivers fill the rest of the structure or return an ``EINVAL``
error code when the index is out of bounds. To enumerate all supported
DV timings, applications shall begin at index zero, incrementing by one
until the driver returns ``EINVAL``.

.. note::

   Drivers may enumerate a different set of DV timings after
   switching the video input or output.

When implemented by the driver DV timings of subdevices can be queried
by calling the ``VIDIOC_SUBDEV_ENUM_DV_TIMINGS`` ioctl directly on a
subdevice node. The DV timings are specific to inputs (for DV receivers)
or outputs (for DV transmitters), applications must specify the desired
pad number in the struct
:c:type:`v4l2_enum_dv_timings` ``pad`` field.
Attempts to enumerate timings on a pad that doesn't support them will
return an ``EINVAL`` error code.

.. c:type:: v4l2_enum_dv_timings

.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|

.. flat-table:: struct v4l2_enum_dv_timings
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 2

    * - __u32
      - ``index``
      - Number of the DV timings, set by the application.
    * - __u32
      - ``pad``
      - Pad number as reported by the media controller API. This field is
	only used when operating on a subdevice node. When operating on a
	video node applications must set this field to zero.
    * - __u32
      - ``reserved``\ [2]
      - Reserved for future extensions. Drivers and applications must set
	the array to zero.
    * - struct :c:type:`v4l2_dv_timings`
      - ``timings``
      - The timings.

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.

EINVAL
    The struct :c:type:`v4l2_enum_dv_timings`
    ``index`` is out of bounds or the ``pad`` number is invalid.

ENODATA
    Digital video presets are not supported for this input or output.