DocBook/media_api/vidioc-g-output.html

<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="LINUX MEDIA INFRASTRUCTURE API"><link rel="up" href="user-func.html" title="Appendix&#160;A.&#160;Function Reference"><link rel="prev" href="vidioc-g-modulator.html" title="ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR"><link rel="next" href="vidioc-g-parm.html" title="ioctl VIDIOC_G_PARM, VIDIOC_S_PARM"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="vidioc-g-modulator.html">Prev</a>&#160;</td><th width="60%" align="center">Appendix&#160;A.&#160;Function Reference</th><td width="20%" align="right">&#160;<a accesskey="n" href="vidioc-g-parm.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="vidioc-g-output"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT &#8212; Query or select the current video output</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">ioctl</b>(</code></td><td>int <var class="pdparam">fd</var>, </td></tr><tr><td>&#160;</td><td>int <var class="pdparam">request</var>, </td></tr><tr><td>&#160;</td><td>int *<var class="pdparam">argp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1114868668"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>fd</code></em></span></dt><dd><p>File descriptor returned by <a class="link" href="func-open.html" title="V4L2 open()"><code class="function">open()</code></a>.</p></dd><dt><span class="term"><em class="parameter"><code>request</code></em></span></dt><dd><p>VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT</p></dd><dt><span class="term"><em class="parameter"><code>argp</code></em></span></dt><dd><p></p></dd></dl></div></div><div class="refsect1"><a name="idp1114872732"></a><h2>Description</h2><p>To query the current video output applications call the
<code class="constant">VIDIOC_G_OUTPUT</code> ioctl with a pointer to an integer
where the driver stores the number of the output, as in the
struct&#160;<a class="link" href="vidioc-enumoutput.html#v4l2-output" title="Table&#160;A.43.&#160;struct v4l2_output">v4l2_output</a> <em class="structfield"><code>index</code></em> field. This ioctl
will fail only when there are no video outputs, returning the
<span class="errorcode">EINVAL</span> error code.</p><p>To select a video output applications store the number of the
desired output in an integer and call the
<code class="constant">VIDIOC_S_OUTPUT</code> ioctl with a pointer to this integer.
Side effects are possible. For example outputs may support different
video standards, so the driver may implicitly switch the current
standard.
standard. Because of these possible side effects applications
must select an output before querying or negotiating any other parameters.</p><p>Information about video outputs is available using the
<a class="link" href="vidioc-enumoutput.html" title="ioctl VIDIOC_ENUMOUTPUT"><code class="constant">VIDIOC_ENUMOUTPUT</code></a> ioctl.</p></div><div class="refsect1"><a name="idp1114876268"></a><h2>Return Value</h2><p>On success <span class="returnvalue">0</span> is returned, on error <span class="returnvalue">-1</span> and the <code class="varname">errno</code> variable is set appropriately. The generic error codes are described at the <a class="link" href="gen_errors.html#gen-errors" title="Table&#160;19.1.&#160;Generic error codes">Generic Error Codes</a> chapter.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorcode">EINVAL</span></span></dt><dd><p>The number of the video output is out of bounds, or
there are no video outputs at all.</p></dd></dl></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="vidioc-g-modulator.html">Prev</a>&#160;</td><td width="20%" align="center"><a accesskey="u" href="user-func.html">Up</a></td><td width="40%" align="right">&#160;<a accesskey="n" href="vidioc-g-parm.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR&#160;</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">&#160;ioctl VIDIOC_G_PARM, VIDIOC_S_PARM</td></tr></table></div></body></html>