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<section id="asoc-platform-driver">
<h1>ASoC Platform Driver<a class="headerlink" href="#asoc-platform-driver" title="Link to this heading">¶</a></h1>
<p>An ASoC platform driver class can be divided into audio DMA drivers, SoC DAI
drivers and DSP drivers. The platform drivers only target the SoC CPU and must
have no board specific code.</p>
<section id="audio-dma">
<h2>Audio DMA<a class="headerlink" href="#audio-dma" title="Link to this heading">¶</a></h2>
<p>The platform DMA driver optionally supports the following ALSA operations:-</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>/* SoC audio ops */
struct snd_soc_ops {
int (*startup)(struct snd_pcm_substream *);
void (*shutdown)(struct snd_pcm_substream *);
int (*hw_params)(struct snd_pcm_substream *, struct snd_pcm_hw_params *);
int (*hw_free)(struct snd_pcm_substream *);
int (*prepare)(struct snd_pcm_substream *);
int (*trigger)(struct snd_pcm_substream *, int);
};
</pre></div>
</div>
<p>The platform driver exports its DMA functionality via <code class="xref c c-struct broken_xref docutils literal notranslate"><span class="pre">struct</span>
<span class="pre">snd_soc_component_driver</span></code>:-</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>struct snd_soc_component_driver {
const char *name;
...
int (*probe)(struct snd_soc_component *);
void (*remove)(struct snd_soc_component *);
int (*suspend)(struct snd_soc_component *);
int (*resume)(struct snd_soc_component *);
/* pcm creation and destruction */
int (*pcm_new)(struct snd_soc_pcm_runtime *);
void (*pcm_free)(struct snd_pcm *);
...
const struct snd_pcm_ops *ops;
const struct snd_compr_ops *compr_ops;
...
};
</pre></div>
</div>
<p>Please refer to the <a class="reference internal" href="../kernel-api/writing-an-alsa-driver.html"><span class="doc">ALSA driver documentation</span></a> for details of audio DMA.</p>
<p>An example DMA driver is soc/pxa/pxa2xx-pcm.c</p>
</section>
<section id="soc-dai-drivers">
<h2>SoC DAI Drivers<a class="headerlink" href="#soc-dai-drivers" title="Link to this heading">¶</a></h2>
<p>Each SoC DAI driver must provide the following features:-</p>
<ol class="arabic simple">
<li><p>Digital audio interface (DAI) description</p></li>
<li><p>Digital audio interface configuration</p></li>
<li><p>PCM’s description</p></li>
<li><p>SYSCLK configuration</p></li>
<li><p>Suspend and resume (optional)</p></li>
</ol>
<p>Please see <a class="reference internal" href="codec.html"><span class="doc">ASoC Codec Class Driver</span></a> for a description of items 1 - 4.</p>
</section>
<section id="soc-dsp-drivers">
<h2>SoC DSP Drivers<a class="headerlink" href="#soc-dsp-drivers" title="Link to this heading">¶</a></h2>
<p>Each SoC DSP driver usually supplies the following features :-</p>
<ol class="arabic simple">
<li><p>DAPM graph</p></li>
<li><p>Mixer controls</p></li>
<li><p>DMA IO to/from DSP buffers (if applicable)</p></li>
<li><p>Definition of DSP front end (FE) PCM devices.</p></li>
</ol>
<p>Please see DPCM.txt for a description of item 4.</p>
</section>
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