1<refentry id="vidioc-subdev-enum-frame-interval">
2  <refmeta>
3    <refentrytitle>ioctl VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL</refentrytitle>
4    &manvol;
5  </refmeta>
6
7  <refnamediv>
8    <refname>VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL</refname>
9    <refpurpose>Enumerate frame intervals</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 v4l2_subdev_frame_interval_enum *
19	<parameter>argp</parameter></paramdef>
20      </funcprototype>
21    </funcsynopsis>
22  </refsynopsisdiv>
23
24  <refsect1>
25    <title>Arguments</title>
26
27    <variablelist>
28      <varlistentry>
29	<term><parameter>fd</parameter></term>
30	<listitem>
31	  <para>&fd;</para>
32	</listitem>
33      </varlistentry>
34      <varlistentry>
35	<term><parameter>request</parameter></term>
36	<listitem>
37	  <para>VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL</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    <note>
53      <title>Experimental</title>
54      <para>This is an <link linkend="experimental">experimental</link>
55      interface and may change in the future.</para>
56    </note>
57
58    <para>This ioctl lets applications enumerate available frame intervals on a
59    given sub-device pad. Frame intervals only makes sense for sub-devices that
60    can control the frame period on their own. This includes, for instance,
61    image sensors and TV tuners.</para>
62
63    <para>For the common use case of image sensors, the frame intervals
64    available on the sub-device output pad depend on the frame format and size
65    on the same pad. Applications must thus specify the desired format and size
66    when enumerating frame intervals.</para>
67
68    <para>To enumerate frame intervals applications initialize the
69    <structfield>index</structfield>, <structfield>pad</structfield>,
70    <structfield>which</structfield>, <structfield>code</structfield>,
71    <structfield>width</structfield> and <structfield>height</structfield>
72    fields of &v4l2-subdev-frame-interval-enum; and call the
73    <constant>VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL</constant> ioctl with a pointer
74    to this structure. Drivers fill the rest of the structure or return
75    an &EINVAL; if one of the input fields is invalid. All frame intervals are
76    enumerable by beginning at index zero and incrementing by one until
77    <errorcode>EINVAL</errorcode> is returned.</para>
78
79    <para>Available frame intervals may depend on the current 'try' formats
80    at other pads of the sub-device, as well as on the current active links. See
81    &VIDIOC-SUBDEV-G-FMT; for more information about the try formats.</para>
82
83    <para>Sub-devices that support the frame interval enumeration ioctl should
84    implemented it on a single pad only. Its behaviour when supported on
85    multiple pads of the same sub-device is not defined.</para>
86
87    <table pgwide="1" frame="none" id="v4l2-subdev-frame-interval-enum">
88      <title>struct <structname>v4l2_subdev_frame_interval_enum</structname></title>
89      <tgroup cols="3">
90	&cs-str;
91	<tbody valign="top">
92	  <row>
93	    <entry>__u32</entry>
94	    <entry><structfield>index</structfield></entry>
95	    <entry>Number of the format in the enumeration, set by the
96	    application.</entry>
97	  </row>
98	  <row>
99	    <entry>__u32</entry>
100	    <entry><structfield>pad</structfield></entry>
101	    <entry>Pad number as reported by the media controller API.</entry>
102	  </row>
103	  <row>
104	    <entry>__u32</entry>
105	    <entry><structfield>code</structfield></entry>
106	    <entry>The media bus format code, as defined in
107	    <xref linkend="v4l2-mbus-format" />.</entry>
108	  </row>
109	  <row>
110	    <entry>__u32</entry>
111	    <entry><structfield>width</structfield></entry>
112	    <entry>Frame width, in pixels.</entry>
113	  </row>
114	  <row>
115	    <entry>__u32</entry>
116	    <entry><structfield>height</structfield></entry>
117	    <entry>Frame height, in pixels.</entry>
118	  </row>
119	  <row>
120	    <entry>&v4l2-fract;</entry>
121	    <entry><structfield>interval</structfield></entry>
122	    <entry>Period, in seconds, between consecutive video frames.</entry>
123	  </row>
124	  <row>
125	    <entry>__u32</entry>
126	    <entry><structfield>which</structfield></entry>
127	    <entry>Frame intervals to be enumerated, from &v4l2-subdev-format-whence;.</entry>
128	  </row>
129	  <row>
130	    <entry>__u32</entry>
131	    <entry><structfield>reserved</structfield>[8]</entry>
132	    <entry>Reserved for future extensions. Applications and drivers must
133	    set the array to zero.</entry>
134	  </row>
135	</tbody>
136      </tgroup>
137    </table>
138  </refsect1>
139
140  <refsect1>
141    &return-value;
142
143    <variablelist>
144      <varlistentry>
145	<term><errorcode>EINVAL</errorcode></term>
146	<listitem>
147	  <para>The &v4l2-subdev-frame-interval-enum;
148	  <structfield>pad</structfield> references a non-existing pad, one of
149	  the <structfield>code</structfield>, <structfield>width</structfield>
150	  or <structfield>height</structfield> fields are invalid for the given
151	  pad or the <structfield>index</structfield> field is out of bounds.
152	  </para>
153	</listitem>
154      </varlistentry>
155    </variablelist>
156  </refsect1>
157</refentry>
158