1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>... And the Destructor?</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="pcm-interface.html" title="Chapter&#160;5.&#160;PCM Interface"><link rel="prev" href="pcm-interface-constructor.html" title="Constructor"><link rel="next" href="pcm-interface-runtime.html" title="Runtime Pointer - The Chest of PCM Information"></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">... And the Destructor?</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="pcm-interface-constructor.html">Prev</a>&#160;</td><th width="60%" align="center">Chapter&#160;5.&#160;PCM Interface</th><td width="20%" align="right">&#160;<a accesskey="n" href="pcm-interface-runtime.html">Next</a></td></tr></table><hr></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="pcm-interface-destructor"></a>... And the Destructor?</h2></div></div></div><p>
2        The destructor for a pcm instance is not always
3      necessary. Since the pcm device will be released by the middle
4      layer code automatically, you don't have to call the destructor
5      explicitly.
6      </p><p>
7        The destructor would be necessary if you created
8        special records internally and needed to release them. In such a
9        case, set the destructor function to
10        pcm-&gt;private_free: 
11
12        </p><div class="example"><a name="idp1094035556"></a><p class="title"><b>Example&#160;5.2.&#160;PCM Instance with a Destructor</b></p><div class="example-contents"><pre class="programlisting">
13
14  static void mychip_pcm_free(struct snd_pcm *pcm)
15  {
16          struct mychip *chip = snd_pcm_chip(pcm);
17          /* free your own data */
18          kfree(chip-&gt;my_private_pcm_data);
19          /* do what you like else */
20          ....
21  }
22
23  static int snd_mychip_new_pcm(struct mychip *chip)
24  {
25          struct snd_pcm *pcm;
26          ....
27          /* allocate your own data */
28          chip-&gt;my_private_pcm_data = kmalloc(...);
29          /* set the destructor */
30          pcm-&gt;private_data = chip;
31          pcm-&gt;private_free = mychip_pcm_free;
32          ....
33  }
34
35          </pre></div></div><p><br class="example-break">
36      </p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="pcm-interface-constructor.html">Prev</a>&#160;</td><td width="20%" align="center"><a accesskey="u" href="pcm-interface.html">Up</a></td><td width="40%" align="right">&#160;<a accesskey="n" href="pcm-interface-runtime.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Constructor&#160;</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">&#160;Runtime Pointer - The Chest of PCM Information</td></tr></table></div></body></html>
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