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Diffstat (limited to 'Documentation/DocBook/media/v4l/media-ioc-enum-links.xml')
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diff --git a/Documentation/DocBook/media/v4l/media-ioc-enum-links.xml b/Documentation/DocBook/media/v4l/media-ioc-enum-links.xml new file mode 100644 index 000000000..74fb394ec --- /dev/null +++ b/Documentation/DocBook/media/v4l/media-ioc-enum-links.xml @@ -0,0 +1,216 @@ +<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>&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>&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> + <row> + <entry><constant>MEDIA_PAD_FL_MUST_CONNECT</constant></entry> + <entry>If this flag is set and the pad is linked to any other + pad, then at least one of those links must be enabled for the + entity to be able to stream. There could be temporary reasons + (e.g. device configuration dependent) for the pad to need + enabled links even when this flag isn't set; the absence of the + flag doesn't imply there is none.</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>&media-pad-desc;</entry> + <entry><structfield>source</structfield></entry> + <entry>Pad at the origin of this link.</entry> + </row> + <row> + <entry>&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> |