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.
  76       The ACTUAL targets are the targets which configure the hardware.
  77       The BOUNDS target will return a rectangle that contain all
  78       possible ACTUAL 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     <table pgwide="1" frame="none" id="v4l2-subdev-selection-targets">
  91       <title>V4L2 subdev selection targets</title>
  92       <tgroup cols="3">
  93         &cs-def;
  94         <tbody valign="top">
  95           <row>
  96             <entry><constant>V4L2_SUBDEV_SEL_TGT_CROP_ACTUAL</constant></entry>
  97             <entry>0x0000</entry>
  98             <entry>Actual crop. Defines the cropping
  99             performed by the processing step.</entry>
 100           </row>
 101           <row>
 102             <entry><constant>V4L2_SUBDEV_SEL_TGT_CROP_BOUNDS</constant></entry>
 103             <entry>0x0002</entry>
 104             <entry>Bounds of the crop rectangle.</entry>
 105           </row>
 106           <row>
 107             <entry><constant>V4L2_SUBDEV_SEL_TGT_COMPOSE_ACTUAL</constant></entry>
 108             <entry>0x0100</entry>
 109             <entry>Actual compose rectangle. Used to configure scaling
 110             on sink pads and composition on source pads.</entry>
 111           </row>
 112           <row>
 113             <entry><constant>V4L2_SUBDEV_SEL_TGT_COMPOSE_BOUNDS</constant></entry>
 114             <entry>0x0102</entry>
 115             <entry>Bounds of the compose rectangle.</entry>
 116           </row>
 117         </tbody>
 118       </tgroup>
 119     </table>
 120
 121     <table pgwide="1" frame="none" id="v4l2-subdev-selection-flags">
 122       <title>V4L2 subdev selection flags</title>
 123       <tgroup cols="3">
 124         &cs-def;
 125         <tbody valign="top">
 126           <row>
 127             <entry><constant>V4L2_SUBDEV_SEL_FLAG_SIZE_GE</constant></entry>
 128             <entry>(1 &lt;&lt; 0)</entry> <entry>Suggest the driver it
 129             should choose greater or equal rectangle (in size) than
 130             was requested. Albeit the driver may choose a lesser size,
 131             it will only do so due to hardware limitations. Without
 132             this flag (and
 133             <constant>V4L2_SUBDEV_SEL_FLAG_SIZE_LE</constant>) the
 134             behaviour is to choose the closest possible
 135             rectangle.</entry>
 136           </row>
 137           <row>
 138             <entry><constant>V4L2_SUBDEV_SEL_FLAG_SIZE_LE</constant></entry>
 139             <entry>(1 &lt;&lt; 1)</entry> <entry>Suggest the driver it
 140             should choose lesser or equal rectangle (in size) than was
 141             requested. Albeit the driver may choose a greater size, it
 142             will only do so due to hardware limitations.</entry>
 143           </row>
 144           <row>
 145             <entry><constant>V4L2_SUBDEV_SEL_FLAG_KEEP_CONFIG</constant></entry>
 146             <entry>(1 &lt;&lt; 2)</entry>
 147             <entry>The configuration should not be propagated to any
 148             further processing steps. If this flag is not given, the
 149             configuration is propagated inside the subdevice to all
 150             further processing steps.</entry>
 151           </row>
 152         </tbody>
 153       </tgroup>
 154     </table>
 155
 156     <table pgwide="1" frame="none" id="v4l2-subdev-selection">
 157       <title>struct <structname>v4l2_subdev_selection</structname></title>
 158       <tgroup cols="3">
 159         &cs-str;
 160         <tbody valign="top">
 161           <row>
 162             <entry>__u32</entry>
 163             <entry><structfield>which</structfield></entry>
 164             <entry>Active or try selection, from
 165             &v4l2-subdev-format-whence;.</entry>
 166           </row>
 167           <row>
 168             <entry>__u32</entry>
 169             <entry><structfield>pad</structfield></entry>
 170             <entry>Pad number as reported by the media framework.</entry>
 171           </row>
 172           <row>
 173             <entry>__u32</entry>
 174             <entry><structfield>target</structfield></entry>
 175             <entry>Target selection rectangle. See
 176             <xref linkend="v4l2-subdev-selection-targets">.</xref>.</entry>
 177           </row>
 178           <row>
 179             <entry>__u32</entry>
 180             <entry><structfield>flags</structfield></entry>
 181             <entry>Flags. See
 182             <xref linkend="v4l2-subdev-selection-flags">.</xref></entry>
 183           </row>
 184           <row>
 185             <entry>&v4l2-rect;</entry>
 186             <entry><structfield>rect</structfield></entry>
 187             <entry>Selection rectangle, in pixels.</entry>
 188           </row>
 189           <row>
 190             <entry>__u32</entry>
 191             <entry><structfield>reserved</structfield>[8]</entry>
 192             <entry>Reserved for future extensions. Applications and drivers must
 193             set the array to zero.</entry>
 194           </row>
 195         </tbody>
 196       </tgroup>
 197     </table>
 198
 199   </refsect1>
 200
 201   <refsect1>
 202     &return-value;
 203
 204     <variablelist>
 205       <varlistentry>
 206         <term><errorcode>EBUSY</errorcode></term>
 207         <listitem>
 208           <para>The selection rectangle can't be changed because the
 209           pad is currently busy. This can be caused, for instance, by
 210           an active video stream on the pad. The ioctl must not be
 211           retried without performing another action to fix the problem
 212           first. Only returned by
 213           <constant>VIDIOC_SUBDEV_S_SELECTION</constant></para>
 214         </listitem>
 215       </varlistentry>
 216       <varlistentry>
 217         <term><errorcode>EINVAL</errorcode></term>
 218         <listitem>
 219           <para>The &v4l2-subdev-selection;
 220           <structfield>pad</structfield> references a non-existing
 221           pad, the <structfield>which</structfield> field references a
 222           non-existing format, or the selection target is not
 223           supported on the given subdev pad.</para>
 224         </listitem>
 225       </varlistentry>
 226     </variablelist>
 227   </refsect1>
 228 </refentry>