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1651333b LP |
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>struct &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>struct &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 frame="none" pgwide="1" id="media-pad-flag"> | |
122 | <title>Media pad flags</title> | |
123 | <tgroup cols="2"> | |
124 | <colspec colname="c1"/> | |
125 | <colspec colname="c2"/> | |
126 | <tbody valign="top"> | |
127 | <row> | |
128 | <entry><constant>MEDIA_PAD_FL_SINK</constant></entry> | |
129 | <entry>Input pad, relative to the entity. Input pads sink data and | |
130 | are targets of links.</entry> | |
131 | </row> | |
132 | <row> | |
133 | <entry><constant>MEDIA_PAD_FL_SOURCE</constant></entry> | |
134 | <entry>Output pad, relative to the entity. Output pads source data | |
135 | and are origins of links.</entry> | |
136 | </row> | |
137 | </tbody> | |
138 | </tgroup> | |
139 | </table> | |
140 | ||
141 | <table pgwide="1" frame="none" id="media-link-desc"> | |
142 | <title>struct <structname>media_links_desc</structname></title> | |
143 | <tgroup cols="3"> | |
144 | &cs-str; | |
145 | <tbody valign="top"> | |
146 | <row> | |
147 | <entry>struct &media-pad-desc;</entry> | |
148 | <entry><structfield>source</structfield></entry> | |
149 | <entry>Pad at the origin of this link.</entry> | |
150 | </row> | |
151 | <row> | |
152 | <entry>struct &media-pad-desc;</entry> | |
153 | <entry><structfield>sink</structfield></entry> | |
154 | <entry>Pad at the target of this link.</entry> | |
155 | </row> | |
156 | <row> | |
157 | <entry>__u32</entry> | |
158 | <entry><structfield>flags</structfield></entry> | |
159 | <entry>Link flags, see <xref linkend="media-link-flag" /> for more details.</entry> | |
160 | </row> | |
161 | </tbody> | |
162 | </tgroup> | |
163 | </table> | |
164 | ||
165 | <table frame="none" pgwide="1" id="media-link-flag"> | |
166 | <title>Media link flags</title> | |
167 | <tgroup cols="2"> | |
168 | <colspec colname="c1"/> | |
169 | <colspec colname="c2"/> | |
170 | <tbody valign="top"> | |
171 | <row> | |
172 | <entry><constant>MEDIA_LNK_FL_ENABLED</constant></entry> | |
173 | <entry>The link is enabled and can be used to transfer media data. | |
174 | When two or more links target a sink pad, only one of them can be | |
175 | enabled at a time.</entry> | |
176 | </row> | |
177 | <row> | |
178 | <entry><constant>MEDIA_LNK_FL_IMMUTABLE</constant></entry> | |
179 | <entry>The link enabled state can't be modified at runtime. An | |
180 | immutable link is always enabled.</entry> | |
181 | </row> | |
e02188c9 LP |
182 | <row> |
183 | <entry><constant>MEDIA_LNK_FL_DYNAMIC</constant></entry> | |
184 | <entry>The link enabled state can be modified during streaming. This | |
185 | flag is set by drivers and is read-only for applications.</entry> | |
186 | </row> | |
1651333b LP |
187 | </tbody> |
188 | </tgroup> | |
189 | </table> | |
190 | <para>One and only one of <constant>MEDIA_PAD_FL_SINK</constant> and | |
191 | <constant>MEDIA_PAD_FL_SOURCE</constant> must be set for every pad.</para> | |
192 | </refsect1> | |
193 | ||
194 | <refsect1> | |
195 | &return-value; | |
196 | ||
197 | <variablelist> | |
198 | <varlistentry> | |
199 | <term><errorcode>EINVAL</errorcode></term> | |
200 | <listitem> | |
201 | <para>The &media-links-enum; <structfield>id</structfield> references | |
202 | a non-existing entity.</para> | |
203 | </listitem> | |
204 | </varlistentry> | |
205 | </variablelist> | |
206 | </refsect1> | |
207 | </refentry> |