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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: MC
+
+.. _media_ioc_g_topology:
+
+**************************
+ioctl MEDIA_IOC_G_TOPOLOGY
+**************************
+
+Name
+====
+
+MEDIA_IOC_G_TOPOLOGY - Enumerate the graph topology and graph element properties
+
+Synopsis
+========
+
+.. c:macro:: MEDIA_IOC_G_TOPOLOGY
+
+``int ioctl(int fd, MEDIA_IOC_G_TOPOLOGY, struct media_v2_topology *argp)``
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :c:func:`open()`.
+
+``argp``
+ Pointer to struct :c:type:`media_v2_topology`.
+
+Description
+===========
+
+The typical usage of this ioctl is to call it twice. On the first call,
+the structure defined at struct
+:c:type:`media_v2_topology` should be zeroed. At
+return, if no errors happen, this ioctl will return the
+``topology_version`` and the total number of entities, interfaces, pads
+and links.
+
+Before the second call, the userspace should allocate arrays to store
+the graph elements that are desired, putting the pointers to them at the
+ptr_entities, ptr_interfaces, ptr_links and/or ptr_pads, keeping the
+other values untouched.
+
+If the ``topology_version`` remains the same, the ioctl should fill the
+desired arrays with the media graph elements.
+
+.. tabularcolumns:: |p{1.6cm}|p{3.4cm}|p{12.3cm}|
+
+.. c:type:: media_v2_topology
+
+.. flat-table:: struct media_v2_topology
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 2 8
+
+ * - __u64
+ - ``topology_version``
+ - Version of the media graph topology. When the graph is created,
+ this field starts with zero. Every time a graph element is added
+ or removed, this field is incremented.
+
+ * - __u32
+ - ``num_entities``
+ - Number of entities in the graph
+
+ * - __u32
+ - ``reserved1``
+ - Applications and drivers shall set this to 0.
+
+ * - __u64
+ - ``ptr_entities``
+ - A pointer to a memory area where the entities array will be
+ stored, converted to a 64-bits integer. It can be zero. if zero,
+ the ioctl won't store the entities. It will just update
+ ``num_entities``
+
+ * - __u32
+ - ``num_interfaces``
+ - Number of interfaces in the graph
+
+ * - __u32
+ - ``reserved2``
+ - Applications and drivers shall set this to 0.
+
+ * - __u64
+ - ``ptr_interfaces``
+ - A pointer to a memory area where the interfaces array will be
+ stored, converted to a 64-bits integer. It can be zero. if zero,
+ the ioctl won't store the interfaces. It will just update
+ ``num_interfaces``
+
+ * - __u32
+ - ``num_pads``
+ - Total number of pads in the graph
+
+ * - __u32
+ - ``reserved3``
+ - Applications and drivers shall set this to 0.
+
+ * - __u64
+ - ``ptr_pads``
+ - A pointer to a memory area where the pads array will be stored,
+ converted to a 64-bits integer. It can be zero. if zero, the ioctl
+ won't store the pads. It will just update ``num_pads``
+
+ * - __u32
+ - ``num_links``
+ - Total number of data and interface links in the graph
+
+ * - __u32
+ - ``reserved4``
+ - Applications and drivers shall set this to 0.
+
+ * - __u64
+ - ``ptr_links``
+ - A pointer to a memory area where the links array will be stored,
+ converted to a 64-bits integer. It can be zero. if zero, the ioctl
+ won't store the links. It will just update ``num_links``
+
+.. tabularcolumns:: |p{1.6cm}|p{3.2cm}|p{12.5cm}|
+
+.. c:type:: media_v2_entity
+
+.. flat-table:: struct media_v2_entity
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 2 8
+
+ * - __u32
+ - ``id``
+ - Unique ID for the entity. Do not expect that the ID will
+ always be the same for each instance of the device. In other words,
+ do not hardcode entity IDs in an application.
+
+ * - char
+ - ``name``\ [64]
+ - Entity name as an UTF-8 NULL-terminated string. This name must be unique
+ within the media topology.
+
+ * - __u32
+ - ``function``
+ - Entity main function, see :ref:`media-entity-functions` for details.
+
+ * - __u32
+ - ``flags``
+ - Entity flags, see :ref:`media-entity-flag` for details.
+ Only valid if ``MEDIA_V2_ENTITY_HAS_FLAGS(media_version)``
+ returns true. The ``media_version`` is defined in struct
+ :c:type:`media_device_info` and can be retrieved using
+ :ref:`MEDIA_IOC_DEVICE_INFO`.
+
+ * - __u32
+ - ``reserved``\ [5]
+ - Reserved for future extensions. Drivers and applications must set
+ this array to zero.
+
+.. tabularcolumns:: |p{1.6cm}|p{3.2cm}|p{12.5cm}|
+
+.. c:type:: media_v2_interface
+
+.. flat-table:: struct media_v2_interface
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 2 8
+
+ * - __u32
+ - ``id``
+ - Unique ID for the interface. Do not expect that the ID will
+ always be the same for each instance of the device. In other words,
+ do not hardcode interface IDs in an application.
+
+ * - __u32
+ - ``intf_type``
+ - Interface type, see :ref:`media-intf-type` for details.
+
+ * - __u32
+ - ``flags``
+ - Interface flags. Currently unused.
+
+ * - __u32
+ - ``reserved``\ [9]
+ - Reserved for future extensions. Drivers and applications must set
+ this array to zero.
+
+ * - struct media_v2_intf_devnode
+ - ``devnode``
+ - Used only for device node interfaces. See
+ :c:type:`media_v2_intf_devnode` for details.
+
+.. tabularcolumns:: |p{1.6cm}|p{3.2cm}|p{12.5cm}|
+
+.. c:type:: media_v2_intf_devnode
+
+.. flat-table:: struct media_v2_intf_devnode
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 2 8
+
+ * - __u32
+ - ``major``
+ - Device node major number.
+
+ * - __u32
+ - ``minor``
+ - Device node minor number.
+
+.. tabularcolumns:: |p{1.6cm}|p{3.2cm}|p{12.5cm}|
+
+.. c:type:: media_v2_pad
+
+.. flat-table:: struct media_v2_pad
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 2 8
+
+ * - __u32
+ - ``id``
+ - Unique ID for the pad. Do not expect that the ID will
+ always be the same for each instance of the device. In other words,
+ do not hardcode pad IDs in an application.
+
+ * - __u32
+ - ``entity_id``
+ - Unique ID for the entity where this pad belongs.
+
+ * - __u32
+ - ``flags``
+ - Pad flags, see :ref:`media-pad-flag` for more details.
+
+ * - __u32
+ - ``index``
+ - Pad index, starts at 0. Only valid if ``MEDIA_V2_PAD_HAS_INDEX(media_version)``
+ returns true. The ``media_version`` is defined in struct
+ :c:type:`media_device_info` and can be retrieved using
+ :ref:`MEDIA_IOC_DEVICE_INFO`.
+
+ * - __u32
+ - ``reserved``\ [4]
+ - Reserved for future extensions. Drivers and applications must set
+ this array to zero.
+
+.. tabularcolumns:: |p{1.6cm}|p{3.2cm}|p{12.5cm}|
+
+.. c:type:: media_v2_link
+
+.. flat-table:: struct media_v2_link
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 2 8
+
+ * - __u32
+ - ``id``
+ - Unique ID for the link. Do not expect that the ID will
+ always be the same for each instance of the device. In other words,
+ do not hardcode link IDs in an application.
+
+ * - __u32
+ - ``source_id``
+ - On pad to pad links: unique ID for the source pad.
+
+ On interface to entity links: unique ID for the interface.
+
+ * - __u32
+ - ``sink_id``
+ - On pad to pad links: unique ID for the sink pad.
+
+ On interface to entity links: unique ID for the entity.
+
+ * - __u32
+ - ``flags``
+ - Link flags, see :ref:`media-link-flag` for more details.
+
+ * - __u32
+ - ``reserved``\ [6]
+ - Reserved for future extensions. Drivers and applications must set
+ this 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.
+
+ENOSPC
+ This is returned when either one or more of the num_entities,
+ num_interfaces, num_links or num_pads are non-zero and are
+ smaller than the actual number of elements inside the graph. This
+ may happen if the ``topology_version`` changed when compared to the
+ last time this ioctl was called. Userspace should usually free the
+ area for the pointers, zero the struct elements and call this ioctl
+ again.