Documentation/DocBook/v4l/vidioc-enum-framesizes.xml

   1 <refentry id="vidioc-enum-framesizes">
   2
   3   <refmeta>
   4     <refentrytitle>ioctl VIDIOC_ENUM_FRAMESIZES</refentrytitle>
   5     &manvol;
   6   </refmeta>
   7
   8   <refnamediv>
   9     <refname>VIDIOC_ENUM_FRAMESIZES</refname>
  10     <refpurpose>Enumerate frame sizes</refpurpose>
  11   </refnamediv>
  12
  13   <refsynopsisdiv>
  14     <funcsynopsis>
  15       <funcprototype>
  16         <funcdef>int <function>ioctl</function></funcdef>
  17         <paramdef>int <parameter>fd</parameter></paramdef>
  18         <paramdef>int <parameter>request</parameter></paramdef>
  19         <paramdef>struct v4l2_frmsizeenum *<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_ENUM_FRAMESIZES</para>
  38         </listitem>
  39       </varlistentry>
  40       <varlistentry>
  41         <term><parameter>argp</parameter></term>
  42         <listitem>
  43           <para>Pointer to a &v4l2-frmsizeenum; that contains an index
  44 and pixel format and receives a frame width and height.</para>
  45         </listitem>
  46       </varlistentry>
  47     </variablelist>
  48   </refsect1>
  49
  50   <refsect1>
  51     <title>Description</title>
  52
  53     <note>
  54       <title>Experimental</title>
  55
  56       <para>This is an <link linkend="experimental">experimental</link>
  57 interface and may change in the future.</para>
  58     </note>
  59
  60     <para>This ioctl allows applications to enumerate all frame sizes
  61 (&ie; width and height in pixels) that the device supports for the
  62 given pixel format.</para>
  63     <para>The supported pixel formats can be obtained by using the
  64 &VIDIOC-ENUM-FMT; function.</para>
  65     <para>The return value and the content of the
  66 <structfield>v4l2_frmsizeenum.type</structfield> field depend on the
  67 type of frame sizes the device supports. Here are the semantics of the
  68 function for the different cases:</para>
  69
  70     <itemizedlist>
  71       <listitem>
  72         <para><emphasis role="bold">Discrete:</emphasis> The function
  73 returns success if the given index value (zero-based) is valid. The
  74 application should increase the index by one for each call until
  75 <constant>EINVAL</constant> is returned. The
  76 <structfield>v4l2_frmsizeenum.type</structfield> field is set to
  77 <constant>V4L2_FRMSIZE_TYPE_DISCRETE</constant> by the driver. Of the
  78 union only the <structfield>discrete</structfield> member is
  79 valid.</para>
  80       </listitem>
  81       <listitem>
  82         <para><emphasis role="bold">Step-wise:</emphasis> The function
  83 returns success if the given index value is zero and
  84 <constant>EINVAL</constant> for any other index value. The
  85 <structfield>v4l2_frmsizeenum.type</structfield> field is set to
  86 <constant>V4L2_FRMSIZE_TYPE_STEPWISE</constant> by the driver. Of the
  87 union only the <structfield>stepwise</structfield> member is
  88 valid.</para>
  89       </listitem>
  90       <listitem>
  91         <para><emphasis role="bold">Continuous:</emphasis> This is a
  92 special case of the step-wise type above. The function returns success
  93 if the given index value is zero and <constant>EINVAL</constant> for
  94 any other index value. The
  95 <structfield>v4l2_frmsizeenum.type</structfield> field is set to
  96 <constant>V4L2_FRMSIZE_TYPE_CONTINUOUS</constant> by the driver. Of
  97 the union only the <structfield>stepwise</structfield> member is valid
  98 and the <structfield>step_width</structfield> and
  99 <structfield>step_height</structfield> values are set to 1.</para>
 100       </listitem>
 101     </itemizedlist>
 102
 103     <para>When the application calls the function with index zero, it
 104 must check the <structfield>type</structfield> field to determine the
 105 type of frame size enumeration the device supports. Only for the
 106 <constant>V4L2_FRMSIZE_TYPE_DISCRETE</constant> type does it make
 107 sense to increase the index value to receive more frame sizes.</para>
 108     <para>Note that the order in which the frame sizes are returned
 109 has no special meaning. In particular does it not say anything about
 110 potential default format sizes.</para>
 111     <para>Applications can assume that the enumeration data does not
 112 change without any interaction from the application itself. This means
 113 that the enumeration data is consistent if the application does not
 114 perform any other ioctl calls while it runs the frame size
 115 enumeration.</para>
 116   </refsect1>
 117
 118   <refsect1>
 119     <title>Structs</title>
 120
 121     <para>In the structs below, <emphasis>IN</emphasis> denotes a
 122 value that has to be filled in by the application,
 123 <emphasis>OUT</emphasis> denotes values that the driver fills in. The
 124 application should zero out all members except for the
 125 <emphasis>IN</emphasis> fields.</para>
 126
 127     <table pgwide="1" frame="none" id="v4l2-frmsize-discrete">
 128       <title>struct <structname>v4l2_frmsize_discrete</structname></title>
 129       <tgroup cols="3">
 130         &cs-str;
 131         <tbody valign="top">
 132           <row>
 133             <entry>__u32</entry>
 134             <entry><structfield>width</structfield></entry>
 135             <entry>Width of the frame [pixel].</entry>
 136           </row>
 137           <row>
 138             <entry>__u32</entry>
 139             <entry><structfield>height</structfield></entry>
 140             <entry>Height of the frame [pixel].</entry>
 141           </row>
 142         </tbody>
 143       </tgroup>
 144     </table>
 145
 146     <table pgwide="1" frame="none" id="v4l2-frmsize-stepwise">
 147       <title>struct <structname>v4l2_frmsize_stepwise</structname></title>
 148       <tgroup cols="3">
 149         &cs-str;
 150         <tbody valign="top">
 151           <row>
 152             <entry>__u32</entry>
 153             <entry><structfield>min_width</structfield></entry>
 154             <entry>Minimum frame width [pixel].</entry>
 155           </row>
 156           <row>
 157             <entry>__u32</entry>
 158             <entry><structfield>max_width</structfield></entry>
 159             <entry>Maximum frame width [pixel].</entry>
 160           </row>
 161           <row>
 162             <entry>__u32</entry>
 163             <entry><structfield>step_width</structfield></entry>
 164             <entry>Frame width step size [pixel].</entry>
 165           </row>
 166           <row>
 167             <entry>__u32</entry>
 168             <entry><structfield>min_height</structfield></entry>
 169             <entry>Minimum frame height [pixel].</entry>
 170           </row>
 171           <row>
 172             <entry>__u32</entry>
 173             <entry><structfield>max_height</structfield></entry>
 174             <entry>Maximum frame height [pixel].</entry>
 175           </row>
 176           <row>
 177             <entry>__u32</entry>
 178             <entry><structfield>step_height</structfield></entry>
 179             <entry>Frame height step size [pixel].</entry>
 180           </row>
 181         </tbody>
 182       </tgroup>
 183     </table>
 184
 185     <table pgwide="1" frame="none" id="v4l2-frmsizeenum">
 186       <title>struct <structname>v4l2_frmsizeenum</structname></title>
 187       <tgroup cols="4">
 188         <colspec colname="c1" />
 189         <colspec colname="c2" />
 190         <colspec colname="c3" />
 191         <colspec colname="c4" />
 192         <tbody valign="top">
 193           <row>
 194             <entry>__u32</entry>
 195             <entry><structfield>index</structfield></entry>
 196             <entry></entry>
 197             <entry>IN: Index of the given frame size in the enumeration.</entry>
 198           </row>
 199           <row>
 200             <entry>__u32</entry>
 201             <entry><structfield>pixel_format</structfield></entry>
 202             <entry></entry>
 203             <entry>IN: Pixel format for which the frame sizes are enumerated.</entry>
 204           </row>
 205           <row>
 206             <entry>__u32</entry>
 207             <entry><structfield>type</structfield></entry>
 208             <entry></entry>
 209             <entry>OUT: Frame size type the device supports.</entry>
 210           </row>
 211           <row>
 212             <entry>union</entry>
 213             <entry></entry>
 214             <entry></entry>
 215             <entry>OUT: Frame size with the given index.</entry>
 216           </row>
 217           <row>
 218             <entry></entry>
 219             <entry>&v4l2-frmsize-discrete;</entry>
 220             <entry><structfield>discrete</structfield></entry>
 221             <entry></entry>
 222           </row>
 223           <row>
 224             <entry></entry>
 225             <entry>&v4l2-frmsize-stepwise;</entry>
 226             <entry><structfield>stepwise</structfield></entry>
 227             <entry></entry>
 228           </row>
 229           <row>
 230             <entry>__u32</entry>
 231             <entry><structfield>reserved[2]</structfield></entry>
 232             <entry></entry>
 233             <entry>Reserved space for future use.</entry>
 234           </row>
 235         </tbody>
 236       </tgroup>
 237     </table>
 238   </refsect1>
 239
 240   <refsect1>
 241     <title>Enums</title>
 242
 243     <table pgwide="1" frame="none" id="v4l2-frmsizetypes">
 244       <title>enum <structname>v4l2_frmsizetypes</structname></title>
 245       <tgroup cols="3">
 246         &cs-def;
 247         <tbody valign="top">
 248           <row>
 249             <entry><constant>V4L2_FRMSIZE_TYPE_DISCRETE</constant></entry>
 250             <entry>1</entry>
 251             <entry>Discrete frame size.</entry>
 252           </row>
 253           <row>
 254             <entry><constant>V4L2_FRMSIZE_TYPE_CONTINUOUS</constant></entry>
 255             <entry>2</entry>
 256             <entry>Continuous frame size.</entry>
 257           </row>
 258           <row>
 259             <entry><constant>V4L2_FRMSIZE_TYPE_STEPWISE</constant></entry>
 260             <entry>3</entry>
 261             <entry>Step-wise defined frame size.</entry>
 262           </row>
 263         </tbody>
 264       </tgroup>
 265     </table>
 266   </refsect1>
 267
 268   <refsect1>
 269     &return-value;
 270
 271     <para>See the description section above for a list of return
 272 values that <varname>errno</varname> can have.</para>
 273   </refsect1>
 274 </refentry>
 275
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