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diff --git a/Documentation/userspace-api/media/mediactl/media-ioc-enum-links.rst b/Documentation/userspace-api/media/mediactl/media-ioc-enum-links.rst new file mode 100644 index 000000000000..9929b639db97 --- /dev/null +++ b/Documentation/userspace-api/media/mediactl/media-ioc-enum-links.rst @@ -0,0 +1,157 @@ +.. Permission is granted to copy, distribute and/or modify this +.. document under the terms of the GNU Free Documentation License, +.. Version 1.1 or any later version published by the Free Software +.. Foundation, with no Invariant Sections, no Front-Cover Texts +.. and no Back-Cover Texts. A copy of the license is included at +.. Documentation/userspace-api/media/fdl-appendix.rst. +.. +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections + +.. _media_ioc_enum_links: + +************************** +ioctl MEDIA_IOC_ENUM_LINKS +************************** + +Name +==== + +MEDIA_IOC_ENUM_LINKS - Enumerate all pads and links for a given entity + + +Synopsis +======== + +.. c:function:: int ioctl( int fd, MEDIA_IOC_ENUM_LINKS, struct media_links_enum *argp ) + :name: MEDIA_IOC_ENUM_LINKS + + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() <media-func-open>`. + +``argp`` + Pointer to struct :c:type:`media_links_enum`. + + +Description +=========== + +To enumerate pads and/or links for a given entity, applications set the +entity field of a struct :c:type:`media_links_enum` +structure and initialize the struct +:c:type:`media_pad_desc` and struct +:c:type:`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. + + +.. c:type:: media_links_enum + +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| + +.. flat-table:: struct media_links_enum + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - __u32 + - ``entity`` + - Entity id, set by the application. + + * - struct :c:type:`media_pad_desc` + - \*\ ``pads`` + - Pointer to a pads array allocated by the application. Ignored if + NULL. + + * - struct :c:type:`media_link_desc` + - \*\ ``links`` + - Pointer to a links array allocated by the application. Ignored if + NULL. + + * - __u32 + - ``reserved[4]`` + - Reserved for future extensions. Drivers and applications must set + the array to zero. + + +.. c:type:: media_pad_desc + +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| + +.. flat-table:: struct media_pad_desc + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - __u32 + - ``entity`` + - ID of the entity this pad belongs to. + + * - __u16 + - ``index`` + - Pad index, starts at 0. + + * - __u32 + - ``flags`` + - Pad flags, see :ref:`media-pad-flag` for more details. + + * - __u32 + - ``reserved[2]`` + - Reserved for future extensions. Drivers and applications must set + the array to zero. + + + +.. c:type:: media_link_desc + +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| + +.. flat-table:: struct media_link_desc + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - struct :c:type:`media_pad_desc` + - ``source`` + - Pad at the origin of this link. + + * - struct :c:type:`media_pad_desc` + - ``sink`` + - Pad at the target of this link. + + * - __u32 + - ``flags`` + - Link flags, see :ref:`media-link-flag` for more details. + + * - __u32 + - ``reserved[2]`` + - Reserved for future extensions. Drivers and applications must set + the 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. + +EINVAL + The struct :c:type:`media_links_enum` ``id`` + references a non-existing entity. |