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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>Change Notification</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="Writing an ALSA Driver" /><link rel="up" href="ch06.html" title="Chapter 6. Control Interface" /><link rel="prev" href="ch06s06.html" title="Constructor" /><link rel="next" href="ch06s08.html" title="Metadata" /></head><body><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="ch06s06.html">Prev</a> </td><th width="60%" align="center">Chapter 6. Control Interface</th><td width="20%" align="right"> <a accesskey="n" href="ch06s08.html">Next</a></td></tr></table><hr /></div><div class="section" title="Change Notification"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="control-interface-change-notification"></a>Change Notification</h2></div></div></div><p>
If you need to change and update a control in the interrupt
routine, you can call <code class="function">snd_ctl_notify()</code>. For
example,
</p><div class="informalexample"><pre class="programlisting">
snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, id_pointer);
</pre></div><p>
This function takes the card pointer, the event-mask, and the
control id pointer for the notification. The event-mask
specifies the types of notification, for example, in the above
example, the change of control values is notified.
The id pointer is the pointer of struct <span class="structname">snd_ctl_elem_id</span>
to be notified.
You can find some examples in <code class="filename">es1938.c</code> or
<code class="filename">es1968.c</code> for hardware volume interrupts.
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