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Diffstat (limited to 'Documentation/media/uapi/mediactl/media-ioc-enum-links.rst')
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diff --git a/Documentation/media/uapi/mediactl/media-ioc-enum-links.rst b/Documentation/media/uapi/mediactl/media-ioc-enum-links.rst new file mode 100644 index 000000000000..87443b1ce42d --- /dev/null +++ b/Documentation/media/uapi/mediactl/media-ioc-enum-links.rst @@ -0,0 +1,170 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _media_ioc_enum_links: + +************************** +ioctl MEDIA_IOC_ENUM_LINKS +************************** + +Name +==== + +MEDIA_IOC_ENUM_LINKS - Enumerate all pads and links for a given entity + + +Synopsis +======== + +.. cpp:function:: int ioctl( int fd, int request, struct media_links_enum *argp ) + + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() <media-func-open>`. + +``request`` + MEDIA_IOC_ENUM_LINKS + +``argp`` + + +Description +=========== + +To enumerate pads and/or links for a given entity, applications set the +entity field of a struct :ref:`media_links_enum <media-links-enum>` +structure and initialize the struct +:ref:`media_pad_desc <media-pad-desc>` and struct +:ref:`media_link_desc <media-link-desc>` structure arrays pointed by +the ``pads`` and ``links`` fields. They then call the +MEDIA_IOC_ENUM_LINKS ioctl with a pointer to this structure. + +If the ``pads`` field is not NULL, the driver fills the ``pads`` array +with information about the entity's pads. The array must have enough +room to store all the entity's pads. The number of pads can be retrieved +with :ref:`MEDIA_IOC_ENUM_ENTITIES`. + +If the ``links`` field is not NULL, the driver fills the ``links`` array +with information about the entity's outbound links. The array must have +enough room to store all the entity's outbound links. The number of +outbound links can be retrieved with :ref:`MEDIA_IOC_ENUM_ENTITIES`. + +Only forward links that originate at one of the entity's source pads are +returned during the enumeration process. + + +.. _media-links-enum: + +.. flat-table:: struct media_links_enum + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - __u32 + + - ``entity`` + + - Entity id, set by the application. + + - .. row 2 + + - struct :ref:`media_pad_desc <media-pad-desc>` + + - \*\ ``pads`` + + - Pointer to a pads array allocated by the application. Ignored if + NULL. + + - .. row 3 + + - struct :ref:`media_link_desc <media-link-desc>` + + - \*\ ``links`` + + - Pointer to a links array allocated by the application. Ignored if + NULL. + + + +.. _media-pad-desc: + +.. flat-table:: struct media_pad_desc + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - __u32 + + - ``entity`` + + - ID of the entity this pad belongs to. + + - .. row 2 + + - __u16 + + - ``index`` + + - 0-based pad index. + + - .. row 3 + + - __u32 + + - ``flags`` + + - Pad flags, see :ref:`media-pad-flag` for more details. + + + +.. _media-link-desc: + +.. flat-table:: struct media_link_desc + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - struct :ref:`media_pad_desc <media-pad-desc>` + + - ``source`` + + - Pad at the origin of this link. + + - .. row 2 + + - struct :ref:`media_pad_desc <media-pad-desc>` + + - ``sink`` + + - Pad at the target of this link. + + - .. row 3 + + - __u32 + + - ``flags`` + + - Link flags, see :ref:`media-link-flag` for more details. + + +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_links_enum <media-links-enum>` ``id`` + references a non-existing entity. |