Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 EST.
1 <refentry id="media-ioc-enum-links"> 2 <refmeta> 3 <refentrytitle>ioctl MEDIA_IOC_ENUM_LINKS</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>MEDIA_IOC_ENUM_LINKS</refname> 9 <refpurpose>Enumerate all pads and links for a given entity</refpurpose> 10 </refnamediv> 11 12 <refsynopsisdiv> 13 <funcsynopsis> 14 <funcprototype> 15 <funcdef>int <function>ioctl</function></funcdef> 16 <paramdef>int <parameter>fd</parameter></paramdef> 17 <paramdef>int <parameter>request</parameter></paramdef> 18 <paramdef>struct media_links_enum *<parameter>argp</parameter></paramdef> 19 </funcprototype> 20 </funcsynopsis> 21 </refsynopsisdiv> 22 23 <refsect1> 24 <title>Arguments</title> 25 26 <variablelist> 27 <varlistentry> 28 <term><parameter>fd</parameter></term> 29 <listitem> 30 <para>File descriptor returned by 31 <link linkend='media-func-open'><function>open()</function></link>.</para> 32 </listitem> 33 </varlistentry> 34 <varlistentry> 35 <term><parameter>request</parameter></term> 36 <listitem> 37 <para>MEDIA_IOC_ENUM_LINKS</para> 38 </listitem> 39 </varlistentry> 40 <varlistentry> 41 <term><parameter>argp</parameter></term> 42 <listitem> 43 <para></para> 44 </listitem> 45 </varlistentry> 46 </variablelist> 47 </refsect1> 48 49 <refsect1> 50 <title>Description</title> 51 52 <para>To enumerate pads and/or links for a given entity, applications set 53 the entity field of a &media-links-enum; structure and initialize the 54 &media-pad-desc; and &media-link-desc; structure arrays pointed by the 55 <structfield>pads</structfield> and <structfield>links</structfield> fields. 56 They then call the MEDIA_IOC_ENUM_LINKS ioctl with a pointer to this 57 structure.</para> 58 <para>If the <structfield>pads</structfield> field is not NULL, the driver 59 fills the <structfield>pads</structfield> array with information about the 60 entity's pads. The array must have enough room to store all the entity's 61 pads. The number of pads can be retrieved with the &MEDIA-IOC-ENUM-ENTITIES; 62 ioctl.</para> 63 <para>If the <structfield>links</structfield> field is not NULL, the driver 64 fills the <structfield>links</structfield> array with information about the 65 entity's outbound links. The array must have enough room to store all the 66 entity's outbound links. The number of outbound links can be retrieved with 67 the &MEDIA-IOC-ENUM-ENTITIES; ioctl.</para> 68 <para>Only forward links that originate at one of the entity's source pads 69 are returned during the enumeration process.</para> 70 71 <table pgwide="1" frame="none" id="media-links-enum"> 72 <title>struct <structname>media_links_enum</structname></title> 73 <tgroup cols="3"> 74 &cs-str; 75 <tbody valign="top"> 76 <row> 77 <entry>__u32</entry> 78 <entry><structfield>entity</structfield></entry> 79 <entry>Entity id, set by the application.</entry> 80 </row> 81 <row> 82 <entry>&media-pad-desc;</entry> 83 <entry>*<structfield>pads</structfield></entry> 84 <entry>Pointer to a pads array allocated by the application. Ignored 85 if NULL.</entry> 86 </row> 87 <row> 88 <entry>&media-link-desc;</entry> 89 <entry>*<structfield>links</structfield></entry> 90 <entry>Pointer to a links array allocated by the application. Ignored 91 if NULL.</entry> 92 </row> 93 </tbody> 94 </tgroup> 95 </table> 96 97 <table pgwide="1" frame="none" id="media-pad-desc"> 98 <title>struct <structname>media_pad_desc</structname></title> 99 <tgroup cols="3"> 100 &cs-str; 101 <tbody valign="top"> 102 <row> 103 <entry>__u32</entry> 104 <entry><structfield>entity</structfield></entry> 105 <entry>ID of the entity this pad belongs to.</entry> 106 </row> 107 <row> 108 <entry>__u16</entry> 109 <entry><structfield>index</structfield></entry> 110 <entry>0-based pad index.</entry> 111 </row> 112 <row> 113 <entry>__u32</entry> 114 <entry><structfield>flags</structfield></entry> 115 <entry>Pad flags, see <xref linkend="media-pad-flag" /> for more details.</entry> 116 </row> 117 </tbody> 118 </tgroup> 119 </table> 120 121 <table pgwide="1" frame="none" id="media-link-desc"> 122 <title>struct <structname>media_link_desc</structname></title> 123 <tgroup cols="3"> 124 &cs-str; 125 <tbody valign="top"> 126 <row> 127 <entry>&media-pad-desc;</entry> 128 <entry><structfield>source</structfield></entry> 129 <entry>Pad at the origin of this link.</entry> 130 </row> 131 <row> 132 <entry>&media-pad-desc;</entry> 133 <entry><structfield>sink</structfield></entry> 134 <entry>Pad at the target of this link.</entry> 135 </row> 136 <row> 137 <entry>__u32</entry> 138 <entry><structfield>flags</structfield></entry> 139 <entry>Link flags, see <xref linkend="media-link-flag" /> for more details.</entry> 140 </row> 141 </tbody> 142 </tgroup> 143 </table> 144 145 </refsect1> 146 147 <refsect1> 148 &return-value; 149 150 <variablelist> 151 <varlistentry> 152 <term><errorcode>EINVAL</errorcode></term> 153 <listitem> 154 <para>The &media-links-enum; <structfield>id</structfield> references 155 a non-existing entity.</para> 156 </listitem> 157 </varlistentry> 158 </variablelist> 159 </refsect1> 160 </refentry>