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