e02188c90f
Drivers often need to associate pipeline objects to entities, and to take stream state into account when configuring entities and links. The pipeline API helps drivers manage that information. When starting streaming, drivers call media_entity_pipeline_start(). The function marks all entities connected to the given entity through enabled links, either directly or indirectly, as streaming. Similarly, when stopping the stream, drivers call media_entity_pipeline_stop(). The media_entity_pipeline_start() function takes a pointer to a media pipeline and stores it in every entity in the graph. Drivers should embed the media_pipeline structure in higher-level pipeline structures and can then access the pipeline through the media_entity structure. Link configuration will fail with -EBUSY by default if either end of the link is a streaming entity, unless the link is marked with the MEDIA_LNK_FL_DYNAMIC flag. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Acked-by: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
93 lines
3 KiB
XML
93 lines
3 KiB
XML
<refentry id="media-ioc-setup-link">
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<refmeta>
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<refentrytitle>ioctl MEDIA_IOC_SETUP_LINK</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>MEDIA_IOC_SETUP_LINK</refname>
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<refpurpose>Modify the properties of a link</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>struct media_link_desc *<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Arguments</title>
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<variablelist>
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<varlistentry>
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<term><parameter>fd</parameter></term>
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<listitem>
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<para>File descriptor returned by
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<link linkend='media-func-open'><function>open()</function></link>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>request</parameter></term>
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<listitem>
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<para>MEDIA_IOC_ENUM_LINKS</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>argp</parameter></term>
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<listitem>
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<para></para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Description</title>
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<para>To change link properties applications fill a &media-link-desc; with
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link identification information (source and sink pad) and the new requested
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link flags. They then call the MEDIA_IOC_SETUP_LINK ioctl with a pointer to
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that structure.</para>
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<para>The only configurable property is the <constant>ENABLED</constant>
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link flag to enable/disable a link. Links marked with the
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<constant>IMMUTABLE</constant> link flag can not be enabled or disabled.
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</para>
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<para>Link configuration has no side effect on other links. If an enabled
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link at the sink pad prevents the link from being enabled, the driver
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returns with an &EBUSY;.</para>
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<para>Only links marked with the <constant>DYNAMIC</constant> link flag can
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be enabled/disabled while streaming media data. Attempting to enable or
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disable a streaming non-dynamic link will return an &EBUSY;.</para>
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<para>If the specified link can't be found the driver returns with an
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&EINVAL;.</para>
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</refsect1>
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<refsect1>
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&return-value;
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<variablelist>
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<varlistentry>
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<term><errorcode>EBUSY</errorcode></term>
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<listitem>
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<para>The link properties can't be changed because the link is
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currently busy. This can be caused, for instance, by an active media
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stream (audio or video) on the link. The ioctl shouldn't be retried if
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no other action is performed before to fix the problem.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>EINVAL</errorcode></term>
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<listitem>
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<para>The &media-link-desc; references a non-existing link, or the
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link is immutable and an attempt to modify its configuration was made.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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</refentry>
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