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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>IEC958 (S/PDIF)</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="ch10.html" title="Chapter 10. Miscellaneous Devices" /><link rel="prev" href="ch10s02.html" title="Hardware-Dependent Devices" /><link rel="next" href="ch11.html" title="Chapter 11. Buffer and Memory Management" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">IEC958 (S/PDIF)</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch10s02.html">Prev</a> </td><th width="60%" align="center">Chapter 10. Miscellaneous Devices</th><td width="20%" align="right"> <a accesskey="n" href="ch11.html">Next</a></td></tr></table><hr /></div><div class="section" title="IEC958 (S/PDIF)"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="misc-devices-IEC958"></a>IEC958 (S/PDIF)</h2></div></div></div><p>
Usually the controls for IEC958 devices are implemented via
the control interface. There is a macro to compose a name string for
IEC958 controls, <code class="function">SNDRV_CTL_NAME_IEC958()</code>
defined in <code class="filename"><include/asound.h></code>.
</p><p>
There are some standard controls for IEC958 status bits. These
controls use the type <span class="type">SNDRV_CTL_ELEM_TYPE_IEC958</span>,
and the size of element is fixed as 4 bytes array
(value.iec958.status[x]). For the <em class="structfield"><code>info</code></em>
callback, you don't specify
the value field for this type (the count field must be set,
though).
</p><p>
<span class="quote">“<span class="quote">IEC958 Playback Con Mask</span>”</span> is used to return the
bit-mask for the IEC958 status bits of consumer mode. Similarly,
<span class="quote">“<span class="quote">IEC958 Playback Pro Mask</span>”</span> returns the bitmask for
professional mode. They are read-only controls, and are defined
as MIXER controls (iface =
<code class="constant">SNDRV_CTL_ELEM_IFACE_MIXER</code>).
</p><p>
Meanwhile, <span class="quote">“<span class="quote">IEC958 Playback Default</span>”</span> control is
defined for getting and setting the current default IEC958
bits. Note that this one is usually defined as a PCM control
(iface = <code class="constant">SNDRV_CTL_ELEM_IFACE_PCM</code>),
although in some places it's defined as a MIXER control.
</p><p>
In addition, you can define the control switches to
enable/disable or to set the raw bit mode. The implementation
will depend on the chip, but the control should be named as
<span class="quote">“<span class="quote">IEC958 xxx</span>”</span>, preferably using
the <code class="function">SNDRV_CTL_NAME_IEC958()</code> macro.
</p><p>
You can find several cases, for example,
<code class="filename">pci/emu10k1</code>,
<code class="filename">pci/ice1712</code>, or
<code class="filename">pci/cmipci.c</code>.
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