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     <section>
  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     </section>
  80
  81     <section>
  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     </section>
  89
  90     <para>Selection targets are documented in <xref
  91     linkend="v4l2-selections-common"/>.</para>
  92
  93     <table pgwide="1" frame="none" id="v4l2-subdev-selection-flags">
  94       <title>V4L2 subdev selection flags</title>
  95       <tgroup cols="3">
  96         &cs-def;
  97         <tbody valign="top">
  98           <row>
  99             <entry><constant>V4L2_SUBDEV_SEL_FLAG_SIZE_GE</constant></entry>
 100             <entry>(1 &lt;&lt; 0)</entry> <entry>Suggest the driver it
 101             should choose greater or equal rectangle (in size) than
 102             was requested. Albeit the driver may choose a lesser size,
 103             it will only do so due to hardware limitations. Without
 104             this flag (and
 105             <constant>V4L2_SUBDEV_SEL_FLAG_SIZE_LE</constant>) the
 106             behaviour is to choose the closest possible
 107             rectangle.</entry>
 108           </row>
 109           <row>
 110             <entry><constant>V4L2_SUBDEV_SEL_FLAG_SIZE_LE</constant></entry>
 111             <entry>(1 &lt;&lt; 1)</entry> <entry>Suggest the driver it
 112             should choose lesser or equal rectangle (in size) than was
 113             requested. Albeit the driver may choose a greater size, it
 114             will only do so due to hardware limitations.</entry>
 115           </row>
 116           <row>
 117             <entry><constant>V4L2_SUBDEV_SEL_FLAG_KEEP_CONFIG</constant></entry>
 118             <entry>(1 &lt;&lt; 2)</entry>
 119             <entry>The configuration should not be propagated to any
 120             further processing steps. If this flag is not given, the
 121             configuration is propagated inside the subdevice to all
 122             further processing steps.</entry>
 123           </row>
 124         </tbody>
 125       </tgroup>
 126     </table>
 127
 128     <table pgwide="1" frame="none" id="v4l2-subdev-selection">
 129       <title>struct <structname>v4l2_subdev_selection</structname></title>
 130       <tgroup cols="3">
 131         &cs-str;
 132         <tbody valign="top">
 133           <row>
 134             <entry>__u32</entry>
 135             <entry><structfield>which</structfield></entry>
 136             <entry>Active or try selection, from
 137             &v4l2-subdev-format-whence;.</entry>
 138           </row>
 139           <row>
 140             <entry>__u32</entry>
 141             <entry><structfield>pad</structfield></entry>
 142             <entry>Pad number as reported by the media framework.</entry>
 143           </row>
 144           <row>
 145             <entry>__u32</entry>
 146             <entry><structfield>target</structfield></entry>
 147             <entry>Target selection rectangle. See
 148             <xref linkend="v4l2-selections-common" />.</entry>
 149           </row>
 150           <row>
 151             <entry>__u32</entry>
 152             <entry><structfield>flags</structfield></entry>
 153             <entry>Flags. See
 154             <xref linkend="v4l2-subdev-selection-flags">.</xref></entry>
 155           </row>
 156           <row>
 157             <entry>&v4l2-rect;</entry>
 158             <entry><structfield>rect</structfield></entry>
 159             <entry>Selection rectangle, in pixels.</entry>
 160           </row>
 161           <row>
 162             <entry>__u32</entry>
 163             <entry><structfield>reserved</structfield>[8]</entry>
 164             <entry>Reserved for future extensions. Applications and drivers must
 165             set the array to zero.</entry>
 166           </row>
 167         </tbody>
 168       </tgroup>
 169     </table>
 170
 171   </refsect1>
 172
 173   <refsect1>
 174     &return-value;
 175
 176     <variablelist>
 177       <varlistentry>
 178         <term><errorcode>EBUSY</errorcode></term>
 179         <listitem>
 180           <para>The selection rectangle can't be changed because the
 181           pad is currently busy. This can be caused, for instance, by
 182           an active video stream on the pad. The ioctl must not be
 183           retried without performing another action to fix the problem
 184           first. Only returned by
 185           <constant>VIDIOC_SUBDEV_S_SELECTION</constant></para>
 186         </listitem>
 187       </varlistentry>
 188       <varlistentry>
 189         <term><errorcode>EINVAL</errorcode></term>
 190         <listitem>
 191           <para>The &v4l2-subdev-selection;
 192           <structfield>pad</structfield> references a non-existing
 193           pad, the <structfield>which</structfield> field references a
 194           non-existing format, or the selection target is not
 195           supported on the given subdev pad.</para>
 196         </listitem>
 197       </varlistentry>
 198     </variablelist>
 199   </refsect1>
 200 </refentry>