Documentation/DocBook/media/v4l/vidioc-subdev-g-selection.xml

   1 <refentry id="vidioc-subdev-g-selection">
   2   <refmeta>
   3     <refentrytitle>ioctl VIDIOC_SUBDEV_G_SELECTION, VIDIOC_SUBDEV_S_SELECTION</refentrytitle>
   4     &manvol;
   5   </refmeta>
   6
   7   <refnamediv>
   8     <refname>VIDIOC_SUBDEV_G_SELECTION</refname>
   9     <refname>VIDIOC_SUBDEV_S_SELECTION</refname>
  10     <refpurpose>Get or set selection rectangles on a subdev pad</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_subdev_selection *<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_G_SELECTION, VIDIOC_SUBDEV_S_SELECTION</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>The selections are used to configure various image
  59     processing functionality performed by the subdevs which affect the
  60     image size. This currently includes cropping, scaling and
  61     composition.</para>
  62
  63     <para>The selection API replaces <link
  64     linkend="vidioc-subdev-g-crop">the old subdev crop API</link>. All
  65     the function of the crop API, and more, are supported by the
  66     selections API.</para>
  67
  68     <para>See <xref linkend="subdev"></xref> for
  69     more information on how each selection target affects the image
  70     processing pipeline inside the subdevice.</para>
  71
  72     <refsect2>
  73       <title>Types of selection targets</title>
  74
  75       <para>There are two types of selection targets: actual and bounds. The
  76       actual targets are the targets which configure the hardware. The BOUNDS
  77       target will return a rectangle that contain all possible actual
  78       rectangles.</para>
  79     </refsect2>
  80
  81     <refsect2>
  82       <title>Discovering supported features</title>
  83
  84       <para>To discover which targets are supported, the user can
  85       perform <constant>VIDIOC_SUBDEV_G_SELECTION</constant> on them.
  86       Any unsupported target will return
  87       <constant>EINVAL</constant>.</para>
  88
  89     <para>Selection targets and flags are documented in <xref
  90     linkend="v4l2-selections-common"/>.</para>
  91
  92     <table pgwide="1" frame="none" id="v4l2-subdev-selection">
  93       <title>struct <structname>v4l2_subdev_selection</structname></title>
  94       <tgroup cols="3">
  95         &cs-str;
  96         <tbody valign="top">
  97           <row>
  98             <entry>__u32</entry>
  99             <entry><structfield>which</structfield></entry>
 100             <entry>Active or try selection, from
 101             &v4l2-subdev-format-whence;.</entry>
 102           </row>
 103           <row>
 104             <entry>__u32</entry>
 105             <entry><structfield>pad</structfield></entry>
 106             <entry>Pad number as reported by the media framework.</entry>
 107           </row>
 108           <row>
 109             <entry>__u32</entry>
 110             <entry><structfield>target</structfield></entry>
 111             <entry>Target selection rectangle. See
 112             <xref linkend="v4l2-selections-common" />.</entry>
 113           </row>
 114           <row>
 115             <entry>__u32</entry>
 116             <entry><structfield>flags</structfield></entry>
 117             <entry>Flags. See
 118             <xref linkend="v4l2-selection-flags" />.</entry>
 119           </row>
 120           <row>
 121             <entry>&v4l2-rect;</entry>
 122             <entry><structfield>r</structfield></entry>
 123             <entry>Selection rectangle, in pixels.</entry>
 124           </row>
 125           <row>
 126             <entry>__u32</entry>
 127             <entry><structfield>reserved</structfield>[8]</entry>
 128             <entry>Reserved for future extensions. Applications and drivers must
 129             set the array to zero.</entry>
 130           </row>
 131         </tbody>
 132       </tgroup>
 133     </table>
 134     </refsect2>
 135
 136   </refsect1>
 137
 138   <refsect1>
 139     &return-value;
 140
 141     <variablelist>
 142       <varlistentry>
 143         <term><errorcode>EBUSY</errorcode></term>
 144         <listitem>
 145           <para>The selection rectangle can't be changed because the
 146           pad is currently busy. This can be caused, for instance, by
 147           an active video stream on the pad. The ioctl must not be
 148           retried without performing another action to fix the problem
 149           first. Only returned by
 150           <constant>VIDIOC_SUBDEV_S_SELECTION</constant></para>
 151         </listitem>
 152       </varlistentry>
 153       <varlistentry>
 154         <term><errorcode>EINVAL</errorcode></term>
 155         <listitem>
 156           <para>The &v4l2-subdev-selection;
 157           <structfield>pad</structfield> references a non-existing
 158           pad, the <structfield>which</structfield> field references a
 159           non-existing format, or the selection target is not
 160           supported on the given subdev pad.</para>
 161         </listitem>
 162       </varlistentry>
 163     </variablelist>
 164   </refsect1>
 165 </refentry>