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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>snd_ctl_add_slave</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="The ALSA Driver API" /><link rel="up" href="ch03s03.html" title="Virtual Master Control API" /><link rel="prev" href="re92.html" title="snd_ctl_make_virtual_master" /><link rel="next" href="re94.html" title="snd_ctl_add_slave_uncached" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>snd_ctl_add_slave</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re92.html">Prev</a> </td><th width="60%" align="center">Virtual Master Control API</th><td width="20%" align="right"> <a accesskey="n" href="re94.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="snd_ctl_add_slave"><a id="API-snd-ctl-add-slave"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>snd_ctl_add_slave —
Add a virtual slave control
</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">snd_ctl_add_slave </b>(</code></td><td>struct snd_kcontrol * <var class="pdparam">master</var>, </td></tr><tr><td> </td><td>struct snd_kcontrol * <var class="pdparam">slave</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2957886"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>master</code></em></span></dt><dd><p>
vmaster element
</p></dd><dt><span class="term"><em class="parameter"><code>slave</code></em></span></dt><dd><p>
slave element to add
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2957928"></a><h2>Description</h2><p>
Add a virtual slave control to the given master element created via
<code class="function">snd_ctl_create_virtual_master</code> beforehand.
Returns zero if successful or a negative error code.
</p><p>
All slaves must be the same type (returning the same information
via info callback). The fucntion doesn't check it, so it's your
responsibility.
</p><p>
Also, some additional limitations:
at most two channels,
logarithmic volume control (dB level) thus no linear volume,
master can only attenuate the volume without gain
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