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.