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-<refentry id="media-ioc-enum-links">
- <refmeta>
- <refentrytitle>ioctl MEDIA_IOC_ENUM_LINKS</refentrytitle>
- &manvol;
- </refmeta>
-
- <refnamediv>
- <refname>MEDIA_IOC_ENUM_LINKS</refname>
- <refpurpose>Enumerate all pads and links for a given entity</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcprototype>
- <funcdef>int <function>ioctl</function></funcdef>
- <paramdef>int <parameter>fd</parameter></paramdef>
- <paramdef>int <parameter>request</parameter></paramdef>
- <paramdef>struct media_links_enum *<parameter>argp</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Arguments</title>
-
- <variablelist>
- <varlistentry>
- <term><parameter>fd</parameter></term>
- <listitem>
- <para>File descriptor returned by
- <link linkend='media-func-open'><function>open()</function></link>.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><parameter>request</parameter></term>
- <listitem>
- <para>MEDIA_IOC_ENUM_LINKS</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><parameter>argp</parameter></term>
- <listitem>
- <para></para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-
- <refsect1>
- <title>Description</title>
-
- <para>To enumerate pads and/or links for a given entity, applications set
- the entity field of a &media-links-enum; structure and initialize the
- &media-pad-desc; and &media-link-desc; structure arrays pointed by the
- <structfield>pads</structfield> and <structfield>links</structfield> fields.
- They then call the MEDIA_IOC_ENUM_LINKS ioctl with a pointer to this
- structure.</para>
- <para>If the <structfield>pads</structfield> field is not NULL, the driver
- fills the <structfield>pads</structfield> 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 the &MEDIA-IOC-ENUM-ENTITIES;
- ioctl.</para>
- <para>If the <structfield>links</structfield> field is not NULL, the driver
- fills the <structfield>links</structfield> 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
- the &MEDIA-IOC-ENUM-ENTITIES; ioctl.</para>
- <para>Only forward links that originate at one of the entity's source pads
- are returned during the enumeration process.</para>
-
- <table pgwide="1" frame="none" id="media-links-enum">
- <title>struct <structname>media_links_enum</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>__u32</entry>
- <entry><structfield>entity</structfield></entry>
- <entry>Entity id, set by the application.</entry>
- </row>
- <row>
- <entry>struct &media-pad-desc;</entry>
- <entry>*<structfield>pads</structfield></entry>
- <entry>Pointer to a pads array allocated by the application. Ignored
- if NULL.</entry>
- </row>
- <row>
- <entry>struct &media-link-desc;</entry>
- <entry>*<structfield>links</structfield></entry>
- <entry>Pointer to a links array allocated by the application. Ignored
- if NULL.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-
- <table pgwide="1" frame="none" id="media-pad-desc">
- <title>struct <structname>media_pad_desc</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>__u32</entry>
- <entry><structfield>entity</structfield></entry>
- <entry>ID of the entity this pad belongs to.</entry>
- </row>
- <row>
- <entry>__u16</entry>
- <entry><structfield>index</structfield></entry>
- <entry>0-based pad index.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>flags</structfield></entry>
- <entry>Pad flags, see <xref linkend="media-pad-flag" /> for more details.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-
- <table frame="none" pgwide="1" id="media-pad-flag">
- <title>Media pad flags</title>
- <tgroup cols="2">
- <colspec colname="c1"/>
- <colspec colname="c2"/>
- <tbody valign="top">
- <row>
- <entry><constant>MEDIA_PAD_FL_SINK</constant></entry>
- <entry>Input pad, relative to the entity. Input pads sink data and
- are targets of links.</entry>
- </row>
- <row>
- <entry><constant>MEDIA_PAD_FL_SOURCE</constant></entry>
- <entry>Output pad, relative to the entity. Output pads source data
- and are origins of links.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-
- <table pgwide="1" frame="none" id="media-link-desc">
- <title>struct <structname>media_link_desc</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>struct &media-pad-desc;</entry>
- <entry><structfield>source</structfield></entry>
- <entry>Pad at the origin of this link.</entry>
- </row>
- <row>
- <entry>struct &media-pad-desc;</entry>
- <entry><structfield>sink</structfield></entry>
- <entry>Pad at the target of this link.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>flags</structfield></entry>
- <entry>Link flags, see <xref linkend="media-link-flag" /> for more details.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-
- <table frame="none" pgwide="1" id="media-link-flag">
- <title>Media link flags</title>
- <tgroup cols="2">
- <colspec colname="c1"/>
- <colspec colname="c2"/>
- <tbody valign="top">
- <row>
- <entry><constant>MEDIA_LNK_FL_ENABLED</constant></entry>
- <entry>The link is enabled and can be used to transfer media data.
- When two or more links target a sink pad, only one of them can be
- enabled at a time.</entry>
- </row>
- <row>
- <entry><constant>MEDIA_LNK_FL_IMMUTABLE</constant></entry>
- <entry>The link enabled state can't be modified at runtime. An
- immutable link is always enabled.</entry>
- </row>
- <row>
- <entry><constant>MEDIA_LNK_FL_DYNAMIC</constant></entry>
- <entry>The link enabled state can be modified during streaming. This
- flag is set by drivers and is read-only for applications.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- <para>One and only one of <constant>MEDIA_PAD_FL_SINK</constant> and
- <constant>MEDIA_PAD_FL_SOURCE</constant> must be set for every pad.</para>
- </refsect1>
-
- <refsect1>
- &return-value;
-
- <variablelist>
- <varlistentry>
- <term><errorcode>EINVAL</errorcode></term>
- <listitem>
- <para>The &media-links-enum; <structfield>id</structfield> references
- a non-existing entity.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-</refentry>