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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>... And the Destructor?</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="ch05.html" title="Chapter 5. PCM Interface" /><link rel="prev" href="ch05s03.html" title="Constructor" /><link rel="next" href="ch05s05.html" title="Runtime Pointer - The Chest of PCM Information" /></head><body><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="ch05s03.html">Prev</a> </td><th width="60%" align="center">Chapter 5. PCM Interface</th><td width="20%" align="right"> <a accesskey="n" href="ch05s05.html">Next</a></td></tr></table><hr /></div><div class="section" title="... And the Destructor?"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="pcm-interface-destructor"></a>... And the Destructor?</h2></div></div></div><p>
The destructor for a pcm instance is not always
necessary. Since the pcm device will be released by the middle
layer code automatically, you don't have to call the destructor
explicitly.
</p><p>
The destructor would be necessary if you created
special records internally and needed to release them. In such a
case, set the destructor function to
pcm->private_free:
</p><div class="example"><a id="id2946633"></a><p class="title"><b>Example 5.2. PCM Instance with a Destructor</b></p><div class="example-contents"><pre class="programlisting">
static void mychip_pcm_free(struct snd_pcm *pcm)
{
struct mychip *chip = snd_pcm_chip(pcm);
/* free your own data */
kfree(chip->my_private_pcm_data);
/* do what you like else */
....
}
static int __devinit snd_mychip_new_pcm(struct mychip *chip)
{
struct snd_pcm *pcm;
....
/* allocate your own data */
chip->my_private_pcm_data = kmalloc(...);
/* set the destructor */
pcm->private_data = chip;
pcm->private_free = mychip_pcm_free;
....
}
</pre></div></div><p><br class="example-break" />
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