300 lines
8.2 KiB
ReStructuredText
300 lines
8.2 KiB
ReStructuredText
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.. -*- coding: utf-8; mode: rst -*-
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.. _media_ioc_g_topology:
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**************************
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ioctl MEDIA_IOC_G_TOPOLOGY
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**************************
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Name
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====
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MEDIA_IOC_G_TOPOLOGY - Enumerate the graph topology and graph element properties
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Synopsis
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========
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.. c:function:: int ioctl( int fd, MEDIA_IOC_G_TOPOLOGY, struct media_v2_topology *argp )
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:name: MEDIA_IOC_G_TOPOLOGY
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Arguments
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=========
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``fd``
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File descriptor returned by :ref:`open() <media-func-open>`.
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``argp``
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Description
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===========
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The typical usage of this ioctl is to call it twice. On the first call,
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the structure defined at struct
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:c:type:`media_v2_topology` should be zeroed. At
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return, if no errors happen, this ioctl will return the
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``topology_version`` and the total number of entities, interfaces, pads
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and links.
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Before the second call, the userspace should allocate arrays to store
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the graph elements that are desired, putting the pointers to them at the
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ptr_entities, ptr_interfaces, ptr_links and/or ptr_pads, keeping the
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other values untouched.
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If the ``topology_version`` remains the same, the ioctl should fill the
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desired arrays with the media graph elements.
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.. tabularcolumns:: |p{1.6cm}|p{3.4cm}|p{12.5cm}|
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.. c:type:: media_v2_topology
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.. flat-table:: struct media_v2_topology
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 2 8
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* - __u64
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- ``topology_version``
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- Version of the media graph topology. When the graph is created,
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this field starts with zero. Every time a graph element is added
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or removed, this field is incremented.
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* - __u32
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- ``num_entities``
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- Number of entities in the graph
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* - __u32
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- ``reserved1``
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- Applications and drivers shall set this to 0.
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* - __u64
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- ``ptr_entities``
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- A pointer to a memory area where the entities array will be
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stored, converted to a 64-bits integer. It can be zero. if zero,
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the ioctl won't store the entities. It will just update
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``num_entities``
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* - __u32
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- ``num_interfaces``
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- Number of interfaces in the graph
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* - __u32
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- ``reserved2``
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- Applications and drivers shall set this to 0.
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* - __u64
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- ``ptr_interfaces``
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- A pointer to a memory area where the interfaces array will be
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stored, converted to a 64-bits integer. It can be zero. if zero,
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the ioctl won't store the interfaces. It will just update
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``num_interfaces``
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* - __u32
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- ``num_pads``
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- Total number of pads in the graph
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* - __u32
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- ``reserved3``
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- Applications and drivers shall set this to 0.
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* - __u64
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- ``ptr_pads``
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- A pointer to a memory area where the pads array will be stored,
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converted to a 64-bits integer. It can be zero. if zero, the ioctl
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won't store the pads. It will just update ``num_pads``
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* - __u32
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- ``num_links``
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- Total number of data and interface links in the graph
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* - __u32
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- ``reserved4``
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- Applications and drivers shall set this to 0.
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* - __u64
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- ``ptr_links``
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- A pointer to a memory area where the links array will be stored,
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converted to a 64-bits integer. It can be zero. if zero, the ioctl
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won't store the links. It will just update ``num_links``
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.. tabularcolumns:: |p{1.6cm}|p{3.2cm}|p{12.7cm}|
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.. c:type:: media_v2_entity
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.. flat-table:: struct media_v2_entity
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 2 8
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* - __u32
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- ``id``
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- Unique ID for the entity. Do not expect that the ID will
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always be the same for each instance of the device. In other words,
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do not hardcode entity IDs in an application.
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* - char
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- ``name``\ [64]
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- Entity name as an UTF-8 NULL-terminated string. This name must be unique
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within the media topology.
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* - __u32
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- ``function``
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- Entity main function, see :ref:`media-entity-functions` for details.
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* - __u32
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- ``flags``
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- Entity flags, see :ref:`media-entity-flag` for details.
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Only valid if ``MEDIA_V2_ENTITY_HAS_FLAGS(media_version)``
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returns true. The ``media_version`` is defined in struct
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:c:type:`media_device_info` and can be retrieved using
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:ref:`MEDIA_IOC_DEVICE_INFO`.
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* - __u32
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- ``reserved``\ [5]
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- Reserved for future extensions. Drivers and applications must set
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this array to zero.
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.. tabularcolumns:: |p{1.6cm}|p{3.2cm}|p{12.7cm}|
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.. c:type:: media_v2_interface
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.. flat-table:: struct media_v2_interface
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 2 8
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* - __u32
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- ``id``
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- Unique ID for the interface. Do not expect that the ID will
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always be the same for each instance of the device. In other words,
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do not hardcode interface IDs in an application.
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* - __u32
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- ``intf_type``
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- Interface type, see :ref:`media-intf-type` for details.
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* - __u32
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- ``flags``
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- Interface flags. Currently unused.
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* - __u32
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- ``reserved``\ [9]
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- Reserved for future extensions. Drivers and applications must set
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this array to zero.
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* - struct media_v2_intf_devnode
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- ``devnode``
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- Used only for device node interfaces. See
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:c:type:`media_v2_intf_devnode` for details.
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.. tabularcolumns:: |p{1.6cm}|p{3.2cm}|p{12.7cm}|
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.. c:type:: media_v2_intf_devnode
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.. flat-table:: struct media_v2_intf_devnode
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 2 8
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* - __u32
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- ``major``
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- Device node major number.
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* - __u32
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- ``minor``
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- Device node minor number.
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.. tabularcolumns:: |p{1.6cm}|p{3.2cm}|p{12.7cm}|
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.. c:type:: media_v2_pad
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.. flat-table:: struct media_v2_pad
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 2 8
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* - __u32
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- ``id``
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- Unique ID for the pad. Do not expect that the ID will
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always be the same for each instance of the device. In other words,
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do not hardcode pad IDs in an application.
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* - __u32
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- ``entity_id``
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- Unique ID for the entity where this pad belongs.
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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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- ``index``
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- Pad index, starts at 0. Only valid if ``MEDIA_V2_PAD_HAS_INDEX(media_version)``
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returns true. The ``media_version`` is defined in struct
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:c:type:`media_device_info` and can be retrieved using
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:ref:`MEDIA_IOC_DEVICE_INFO`.
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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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this array to zero.
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.. tabularcolumns:: |p{1.6cm}|p{3.2cm}|p{12.7cm}|
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.. c:type:: media_v2_link
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.. flat-table:: struct media_v2_link
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 2 8
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* - __u32
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- ``id``
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- Unique ID for the link. Do not expect that the ID will
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always be the same for each instance of the device. In other words,
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do not hardcode link IDs in an application.
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* - __u32
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- ``source_id``
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- On pad to pad links: unique ID for the source pad.
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On interface to entity links: unique ID for the interface.
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* - __u32
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- ``sink_id``
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- On pad to pad links: unique ID for the sink pad.
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On interface to entity links: unique ID for the entity.
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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``\ [6]
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- Reserved for future extensions. Drivers and applications must set
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this 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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ENOSPC
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This is returned when either one or more of the num_entities,
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num_interfaces, num_links or num_pads are non-zero and are
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smaller than the actual number of elements inside the graph. This
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may happen if the ``topology_version`` changed when compared to the
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last time this ioctl was called. Userspace should usually free the
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area for the pointers, zero the struct elements and call this ioctl
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again.
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