.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. c:namespace:: MC
.. _media_ioc_enum_links:
**************************
ioctl MEDIA_IOC_ENUM_LINKS
**************************
Name
====
MEDIA_IOC_ENUM_LINKS - Enumerate all pads and links for a given entity
Synopsis
========
.. c:macro:: MEDIA_IOC_ENUM_LINKS
``int ioctl(int fd, MEDIA_IOC_ENUM_LINKS, struct media_links_enum *argp)``
Arguments
=========
``fd``
File descriptor returned by :c:func:`open()`.
``argp``
Pointer to struct :c:type:`media_links_enum`.
Description
===========
To enumerate pads and/or links for a given entity, applications set the
entity field of a struct :c:type:`media_links_enum`
structure and initialize the struct
:c:type:`media_pad_desc` and struct
:c:type:`media_link_desc` structure arrays pointed by
the ``pads`` and ``links`` fields. They then call the
MEDIA_IOC_ENUM_LINKS ioctl with a pointer to this structure.
If the ``pads`` field is not NULL, the driver fills the ``pads`` array
with information about the entity's pads. The array must have enough
room to store all the entity's pads. The number of pads can be retrieved
with :ref:`MEDIA_IOC_ENUM_ENTITIES`.
If the ``links`` field is not NULL, the driver fills the ``links`` array
with information about the entity's outbound links. The array must have
enough room to store all the entity's outbound links. The number of
outbound links can be retrieved with :ref:`MEDIA_IOC_ENUM_ENTITIES`.
Only forward links that originate at one of the entity's source pads are
returned during the enumeration process.
.. c:type:: media_links_enum
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
.. flat-table:: struct media_links_enum
:header-rows: 0
:stub-columns: 0
:widths: 1 1 2
* - __u32
- ``entity``
- Entity id, set by the application.
* - struct :c:type:`media_pad_desc`
- \*\ ``pads``
- Pointer to a pads array allocated by the application. Ignored if
NULL.
* - struct :c:type:`media_link_desc`
- \*\ ``links``
- Pointer to a links array allocated by the application. Ignored if
NULL.
* - __u32
- ``reserved[4]``
- Reserved for future extensions. Drivers and applications must set
the array to zero.
.. c:type:: media_pad_desc
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
.. flat-table:: struct media_pad_desc
:header-rows: 0
:stub-columns: 0
:widths: 1 1 2
* - __u32
- ``entity``
- ID of the entity this pad belongs to.
* - __u16
- ``index``
- Pad index, starts at 0.
* - __u32
- ``flags``
- Pad flags, see :ref:`media-pad-flag` for more details.
* - __u32
- ``reserved[2]``
- Reserved for future extensions. Drivers and applications must set
the array to zero.
.. c:type:: media_link_desc
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
.. flat-table:: struct media_link_desc
:header-rows: 0
:stub-columns: 0
:widths: 1 1 2
* - struct :c:type:`media_pad_desc`
- ``source``
- Pad at the origin of this link.
* - struct :c:type:`media_pad_desc`
- ``sink``
- Pad at the target of this link.
* - __u32
- ``flags``
- Link flags, see :ref:`media-link-flag` for more details.
* - __u32
- ``reserved[2]``
- Reserved for future extensions. Drivers and applications must set
the array to zero.
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:`media_links_enum` ``id``
references a non-existing entity.
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