Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / Documentation / DocBook / media / v4l / vidioc-g-crop.xml

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+<refentry id="vidioc-g-crop">
+  <refmeta>
+    <refentrytitle>ioctl VIDIOC_G_CROP, VIDIOC_S_CROP</refentrytitle>
+    &manvol;
+  </refmeta>
+
+  <refnamediv>
+    <refname>VIDIOC_G_CROP</refname>
+    <refname>VIDIOC_S_CROP</refname>
+    <refpurpose>Get or set the current cropping rectangle</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcprototype>
+       <funcdef>int <function>ioctl</function></funcdef>
+       <paramdef>int <parameter>fd</parameter></paramdef>
+       <paramdef>int <parameter>request</parameter></paramdef>
+       <paramdef>struct v4l2_crop *<parameter>argp</parameter></paramdef>
+      </funcprototype>
+    </funcsynopsis>
+    <funcsynopsis>
+      <funcprototype>
+       <funcdef>int <function>ioctl</function></funcdef>
+       <paramdef>int <parameter>fd</parameter></paramdef>
+       <paramdef>int <parameter>request</parameter></paramdef>
+       <paramdef>const struct v4l2_crop *<parameter>argp</parameter></paramdef>
+      </funcprototype>
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Arguments</title>
+
+    <variablelist>
+      <varlistentry>
+       <term><parameter>fd</parameter></term>
+       <listitem>
+         <para>&fd;</para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term><parameter>request</parameter></term>
+       <listitem>
+         <para>VIDIOC_G_CROP, VIDIOC_S_CROP</para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term><parameter>argp</parameter></term>
+       <listitem>
+         <para></para>
+       </listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para>To query the cropping rectangle size and position
+applications set the <structfield>type</structfield> field of a
+<structname>v4l2_crop</structname> structure to the respective buffer
+(stream) type and call the <constant>VIDIOC_G_CROP</constant> ioctl
+with a pointer to this structure. The driver fills the rest of the
+structure or returns the &EINVAL; if cropping is not supported.</para>
+
+    <para>To change the cropping rectangle applications initialize the
+<structfield>type</structfield> and &v4l2-rect; substructure named
+<structfield>c</structfield> of a v4l2_crop structure and call the
+<constant>VIDIOC_S_CROP</constant> ioctl with a pointer to this
+structure.</para>
+
+<para>Do not use the multiplanar buffer types.  Use <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>
+instead of <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant>
+and use <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> instead of
+<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant>.</para>
+
+    <para>The driver first adjusts the requested dimensions against
+hardware limits, &ie; the bounds given by the capture/output window,
+and it rounds to the closest possible values of horizontal and
+vertical offset, width and height. In particular the driver must round
+the vertical offset of the cropping rectangle to frame lines modulo
+two, such that the field order cannot be confused.</para>
+
+    <para>Second the driver adjusts the image size (the opposite
+rectangle of the scaling process, source or target depending on the
+data direction) to the closest size possible while maintaining the
+current horizontal and vertical scaling factor.</para>
+
+    <para>Finally the driver programs the hardware with the actual
+cropping and image parameters. <constant>VIDIOC_S_CROP</constant> is a
+write-only ioctl, it does not return the actual parameters. To query
+them applications must call <constant>VIDIOC_G_CROP</constant> and
+&VIDIOC-G-FMT;. When the parameters are unsuitable the application may
+modify the cropping or image parameters and repeat the cycle until
+satisfactory parameters have been negotiated.</para>
+
+    <para>When cropping is not supported then no parameters are
+changed and <constant>VIDIOC_S_CROP</constant> returns the
+&EINVAL;.</para>
+
+    <table pgwide="1" frame="none" id="v4l2-crop">
+      <title>struct <structname>v4l2_crop</structname></title>
+      <tgroup cols="3">
+       &cs-str;
+       <tbody valign="top">
+         <row>
+           <entry>__u32</entry>
+           <entry><structfield>type</structfield></entry>
+           <entry>Type of the data stream, set by the application.
+Only these types are valid here: <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>,
+<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> and
+<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>. See <xref linkend="v4l2-buf-type" />.</entry>
+         </row>
+         <row>
+           <entry>&v4l2-rect;</entry>
+           <entry><structfield>c</structfield></entry>
+           <entry>Cropping rectangle. The same co-ordinate system as
+for &v4l2-cropcap; <structfield>bounds</structfield> is used.</entry>
+         </row>
+       </tbody>
+      </tgroup>
+    </table>
+  </refsect1>
+
+  <refsect1>
+    &return-value;
+  </refsect1>
+</refentry>