54f38fcae5
Since 2017, there is an space reserved for userspace API,
created by changeset 1d596dee38 ("docs: Create a user-space API guide").
As the media subsystem was one of the first subsystems to use
Sphinx, until this patch, we were keeping things on a separate
place.
Let's just use the new location, as having all uAPI altogether
will likely make things easier for developers.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
75 lines
2.2 KiB
ReStructuredText
75 lines
2.2 KiB
ReStructuredText
.. Permission is granted to copy, distribute and/or modify this
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.. document under the terms of the GNU Free Documentation License,
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.. Version 1.1 or any later version published by the Free Software
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.. Foundation, with no Invariant Sections, no Front-Cover Texts
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.. and no Back-Cover Texts. A copy of the license is included at
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.. Documentation/userspace-api/media/fdl-appendix.rst.
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..
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.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
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.. _media_ioc_setup_link:
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**************************
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ioctl MEDIA_IOC_SETUP_LINK
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**************************
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Name
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====
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MEDIA_IOC_SETUP_LINK - Modify the properties of a link
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Synopsis
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========
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.. c:function:: int ioctl( int fd, MEDIA_IOC_SETUP_LINK, struct media_link_desc *argp )
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:name: MEDIA_IOC_SETUP_LINK
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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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Pointer to struct :c:type:`media_link_desc`.
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Description
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===========
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To change link properties applications fill a struct
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:c:type:`media_link_desc` with link identification
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information (source and sink pad) and the new requested link flags. They
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then call the MEDIA_IOC_SETUP_LINK ioctl with a pointer to that
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structure.
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The only configurable property is the ``ENABLED`` link flag to
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enable/disable a link. Links marked with the ``IMMUTABLE`` link flag can
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not be enabled or disabled.
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Link configuration has no side effect on other links. If an enabled link
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at the sink pad prevents the link from being enabled, the driver returns
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with an ``EBUSY`` error code.
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Only links marked with the ``DYNAMIC`` link flag can be enabled/disabled
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while streaming media data. Attempting to enable or disable a streaming
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non-dynamic link will return an ``EBUSY`` error code.
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If the specified link can't be found the driver returns with an ``EINVAL``
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error code.
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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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EINVAL
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The struct :c:type:`media_link_desc` references a
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non-existing link, or the link is immutable and an attempt to modify
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its configuration was made.
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