media-ioc-enum-entities.rst

.. -*- coding: utf-8; mode: rst -*-

.. _media-ioc-enum-entities:

*****************************
ioctl MEDIA_IOC_ENUM_ENTITIES
*****************************

NAME
====

MEDIA_IOC_ENUM_ENTITIES - Enumerate entities and their properties

SYNOPSIS
========

.. cpp:function:: int ioctl( int fd, int request, struct media_entity_desc *argp )


ARGUMENTS
=========

``fd``
    File descriptor returned by :ref:`open() <media-func-open>`.

``request``
    MEDIA_IOC_ENUM_ENTITIES

``argp``


DESCRIPTION
===========

To query the attributes of an entity, applications set the id field of a
struct :ref:`media_entity_desc <media-entity-desc>` structure and
call the MEDIA_IOC_ENUM_ENTITIES ioctl with a pointer to this
structure. The driver fills the rest of the structure or returns an
EINVAL error code when the id is invalid.

Entities can be enumerated by or'ing the id with the
``MEDIA_ENT_ID_FLAG_NEXT`` flag. The driver will return information
about the entity with the smallest id strictly larger than the requested
one ('next entity'), or the ``EINVAL`` error code if there is none.

Entity IDs can be non-contiguous. Applications must *not* try to
enumerate entities by calling MEDIA_IOC_ENUM_ENTITIES with increasing
id's until they get an error.


.. _media-entity-desc:

.. flat-table:: struct media_entity_desc
    :header-rows:  0
    :stub-columns: 0


    -  .. row 1

       -  __u32

       -  ``id``

       -
       -
       -  Entity id, set by the application. When the id is or'ed with
	  ``MEDIA_ENT_ID_FLAG_NEXT``, the driver clears the flag and returns
	  the first entity with a larger id.

    -  .. row 2

       -  char

       -  ``name``\ [32]

       -
       -
       -  Entity name as an UTF-8 NULL-terminated string.

    -  .. row 3

       -  __u32

       -  ``type``

       -
       -
       -  Entity type, see :ref:`media-entity-type` for details.

    -  .. row 4

       -  __u32

       -  ``revision``

       -
       -
       -  Entity revision. Always zero (obsolete)

    -  .. row 5

       -  __u32

       -  ``flags``

       -
       -
       -  Entity flags, see :ref:`media-entity-flag` for details.

    -  .. row 6

       -  __u32

       -  ``group_id``

       -
       -
       -  Entity group ID. Always zero (obsolete)

    -  .. row 7

       -  __u16

       -  ``pads``

       -
       -
       -  Number of pads

    -  .. row 8

       -  __u16

       -  ``links``

       -
       -
       -  Total number of outbound links. Inbound links are not counted in
	  this field.

    -  .. row 9

       -  union

    -  .. row 10

       -
       -  struct

       -  ``dev``

       -
       -  Valid for (sub-)devices that create a single device node.

    -  .. row 11

       -
       -
       -  __u32

       -  ``major``

       -  Device node major number.

    -  .. row 12

       -
       -
       -  __u32

       -  ``minor``

       -  Device node minor number.

    -  .. row 13

       -
       -  __u8

       -  ``raw``\ [184]

       -
       -


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 :ref:`media_entity_desc <media-entity-desc>` ``id``
    references a non-existing entity.