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