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- .. -*- coding: utf-8; mode: rst -*-
- .. _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:function:: int ioctl( int fd, MEDIA_IOC_ENUM_LINKS, struct media_links_enum *argp )
- :name: MEDIA_IOC_ENUM_LINKS
- Arguments
- =========
- ``fd``
- File descriptor returned by :ref:`open() <media-func-open>`.
- ``argp``
- 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{8.7cm}|
- .. flat-table:: struct media_links_enum
- :header-rows: 0
- :stub-columns: 0
- :widths: 1 1 2
- - .. row 1
- - __u32
- - ``entity``
- - Entity id, set by the application.
- - .. row 2
- - struct :c:type:`media_pad_desc`
- - \*\ ``pads``
- - Pointer to a pads array allocated by the application. Ignored if
- NULL.
- - .. row 3
- - struct :c:type:`media_link_desc`
- - \*\ ``links``
- - Pointer to a links array allocated by the application. Ignored if
- NULL.
- .. c:type:: media_pad_desc
- .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
- .. flat-table:: struct media_pad_desc
- :header-rows: 0
- :stub-columns: 0
- :widths: 1 1 2
- - .. row 1
- - __u32
- - ``entity``
- - ID of the entity this pad belongs to.
- - .. row 2
- - __u16
- - ``index``
- - 0-based pad index.
- - .. row 3
- - __u32
- - ``flags``
- - Pad flags, see :ref:`media-pad-flag` for more details.
- .. c:type:: media_link_desc
- .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
- .. flat-table:: struct media_link_desc
- :header-rows: 0
- :stub-columns: 0
- :widths: 1 1 2
- - .. row 1
- - struct :c:type:`media_pad_desc`
- - ``source``
- - Pad at the origin of this link.
- - .. row 2
- - struct :c:type:`media_pad_desc`
- - ``sink``
- - Pad at the target of this link.
- - .. row 3
- - __u32
- - ``flags``
- - Link flags, see :ref:`media-link-flag` for more details.
- 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.
|
