1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>Change Notification</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="Writing an ALSA Driver"><link rel="up" href="control-interface.html" title="Chapter&#160;6.&#160;Control Interface"><link rel="prev" href="control-interface-constructor.html" title="Constructor"><link rel="next" href="control-interface-tlv.html" title="Metadata"></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">Change Notification</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="control-interface-constructor.html">Prev</a>&#160;</td><th width="60%" align="center">Chapter&#160;6.&#160;Control Interface</th><td width="20%" align="right">&#160;<a accesskey="n" href="control-interface-tlv.html">Next</a></td></tr></table><hr></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="control-interface-change-notification"></a>Change Notification</h2></div></div></div><p>
2        If you need to change and update a control in the interrupt
3      routine, you can call <code class="function">snd_ctl_notify()</code>. For
4      example, 
5
6        </p><div class="informalexample"><pre class="programlisting">
7
8  snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, id_pointer);
9
10          </pre></div><p>
11
12        This function takes the card pointer, the event-mask, and the
13      control id pointer for the notification. The event-mask
14      specifies the types of notification, for example, in the above
15      example, the change of control values is notified.
16      The id pointer is the pointer of struct <span class="structname">snd_ctl_elem_id</span>
17      to be notified.
18      You can find some examples in <code class="filename">es1938.c</code> or
19      <code class="filename">es1968.c</code> for hardware volume interrupts. 
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