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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>