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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _media_ioc_g_topology:
+
+**************************
+ioctl MEDIA_IOC_G_TOPOLOGY
+**************************
+
+Name
+====
+
+MEDIA_IOC_G_TOPOLOGY - Enumerate the graph topology and graph element properties
+
+
+Synopsis
+========
+
+.. cpp:function:: int ioctl( int fd, int request, struct media_v2_topology *argp )
+
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`open() <media-func-open>`.
+
+``request``
+    MEDIA_IOC_G_TOPOLOGY
+
+``argp``
+
+
+Description
+===========
+
+The typical usage of this ioctl is to call it twice. On the first call,
+the structure defined at struct
+:ref:`media_v2_topology <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.
+
+
+.. _media-v2-topology:
+
+.. flat-table:: struct media_v2_topology
+    :header-rows:  0
+    :stub-columns: 0
+    :widths: 1 2 8
+
+
+    -  .. row 1
+
+       -  __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.
+
+    -  .. row 2
+
+       -  __u64
+
+       -  ``num_entities``
+
+       -  Number of entities in the graph
+
+    -  .. row 3
+
+       -  __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``
+
+    -  .. row 4
+
+       -  __u64
+
+       -  ``num_interfaces``
+
+       -  Number of interfaces in the graph
+
+    -  .. row 5
+
+       -  __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``
+
+    -  .. row 6
+
+       -  __u64
+
+       -  ``num_pads``
+
+       -  Total number of pads in the graph
+
+    -  .. row 7
+
+       -  __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``
+
+    -  .. row 8
+
+       -  __u64
+
+       -  ``num_links``
+
+       -  Total number of data and interface links in the graph
+
+    -  .. row 9
+
+       -  __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``
+
+
+
+.. _media-v2-entity:
+
+.. flat-table:: struct media_v2_entity
+    :header-rows:  0
+    :stub-columns: 0
+    :widths: 1 2 8
+
+
+    -  .. row 1
+
+       -  __u32
+
+       -  ``id``
+
+       -  Unique ID for the entity.
+
+    -  .. row 2
+
+       -  char
+
+       -  ``name``\ [64]
+
+       -  Entity name as an UTF-8 NULL-terminated string.
+
+    -  .. row 3
+
+       -  __u32
+
+       -  ``function``
+
+       -  Entity main function, see :ref:`media-entity-type` for details.
+
+    -  .. row 4
+
+       -  __u32
+
+       -  ``reserved``\ [12]
+
+       -  Reserved for future extensions. Drivers and applications must set
+	  this array to zero.
+
+
+
+.. _media-v2-interface:
+
+.. flat-table:: struct media_v2_interface
+    :header-rows:  0
+    :stub-columns: 0
+    :widths: 1 2 8
+
+    -  .. row 1
+
+       -  __u32
+
+       -  ``id``
+
+       -  Unique ID for the interface.
+
+    -  .. row 2
+
+       -  __u32
+
+       -  ``intf_type``
+
+       -  Interface type, see :ref:`media-intf-type` for details.
+
+    -  .. row 3
+
+       -  __u32
+
+       -  ``flags``
+
+       -  Interface flags. Currently unused.
+
+    -  .. row 4
+
+       -  __u32
+
+       -  ``reserved``\ [9]
+
+       -  Reserved for future extensions. Drivers and applications must set
+	  this array to zero.
+
+    -  .. row 5
+
+       -  struct media_v2_intf_devnode
+
+       -  ``devnode``
+
+       -  Used only for device node interfaces. See
+	  :ref:`media-v2-intf-devnode` for details..
+
+
+
+.. _media-v2-intf-devnode:
+
+.. flat-table:: struct media_v2_interface
+    :header-rows:  0
+    :stub-columns: 0
+    :widths: 1 2 8
+
+
+    -  .. row 1
+
+       -  __u32
+
+       -  ``major``
+
+       -  Device node major number.
+
+    -  .. row 2
+
+       -  __u32
+
+       -  ``minor``
+
+       -  Device node minor number.
+
+
+
+.. _media-v2-pad:
+
+.. flat-table:: struct media_v2_pad
+    :header-rows:  0
+    :stub-columns: 0
+    :widths: 1 2 8
+
+
+    -  .. row 1
+
+       -  __u32
+
+       -  ``id``
+
+       -  Unique ID for the pad.
+
+    -  .. row 2
+
+       -  __u32
+
+       -  ``entity_id``
+
+       -  Unique ID for the entity where this pad belongs.
+
+    -  .. row 3
+
+       -  __u32
+
+       -  ``flags``
+
+       -  Pad flags, see :ref:`media-pad-flag` for more details.
+
+    -  .. row 4
+
+       -  __u32
+
+       -  ``reserved``\ [9]
+
+       -  Reserved for future extensions. Drivers and applications must set
+	  this array to zero.
+
+
+
+.. _media-v2-link:
+
+.. flat-table:: struct media_v2_pad
+    :header-rows:  0
+    :stub-columns: 0
+    :widths: 1 2 8
+
+
+    -  .. row 1
+
+       -  __u32
+
+       -  ``id``
+
+       -  Unique ID for the pad.
+
+    -  .. row 2
+
+       -  __u32
+
+       -  ``source_id``
+
+       -  On pad to pad links: unique ID for the source pad.
+
+	  On interface to entity links: unique ID for the interface.
+
+    -  .. row 3
+
+       -  __u32
+
+       -  ``sink_id``
+
+       -  On pad to pad links: unique ID for the sink pad.
+
+	  On interface to entity links: unique ID for the entity.
+
+    -  .. row 4
+
+       -  __u32
+
+       -  ``flags``
+
+       -  Link flags, see :ref:`media-link-flag` for more details.
+
+    -  .. row 5
+
+       -  __u32
+
+       -  ``reserved``\ [5]
+
+       -  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.