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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>spi_async</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="Linux Device Drivers" /><link rel="up" href="ch09.html" title="Chapter 9. Serial Peripheral Interface (SPI)" /><link rel="prev" href="re750.html" title="spi_setup" /><link rel="next" href="re752.html" title="spi_sync" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>spi_async</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re750.html">Prev</a> </td><th width="60%" align="center">Chapter 9. Serial Peripheral Interface (SPI)</th><td width="20%" align="right"> <a accesskey="n" href="re752.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="spi_async"><a id="API-spi-async"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>spi_async —
asynchronous SPI transfer
</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">spi_async </b>(</code></td><td>struct spi_device * <var class="pdparam">spi</var>, </td></tr><tr><td> </td><td>struct spi_message * <var class="pdparam">message</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2707627"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>spi</code></em></span></dt><dd><p>
device with which data will be exchanged
</p></dd><dt><span class="term"><em class="parameter"><code>message</code></em></span></dt><dd><p>
describes the data transfers, including completion callback
</p></dd></dl></div></div><div class="refsect1" title="Context"><a id="id2707671"></a><h2>Context</h2><p>
any (irqs may be blocked, etc)
</p></div><div class="refsect1" title="Description"><a id="id2707682"></a><h2>Description</h2><p>
This call may be used in_irq and other contexts which can't sleep,
as well as from task contexts which can sleep.
</p><p>
The completion callback is invoked in a context which can't sleep.
Before that invocation, the value of message->status is undefined.
When the callback is issued, message->status holds either zero (to
indicate complete success) or a negative error code. After that
callback returns, the driver which issued the transfer request may
deallocate the associated memory; it's no longer in use by any SPI
core or controller driver code.
</p><p>
Note that although all messages to a spi_device are handled in
FIFO order, messages may go to different devices in other orders.
Some device might be higher priority, or have various <span class="quote">“<span class="quote">hard</span>”</span> access
time requirements, for example.
</p><p>
On detection of any fault during the transfer, processing of
the entire message is aborted, and the device is deselected.
Until returning from the associated message completion callback,
no other spi_message queued to that device will be processed.
(This rule applies equally to all the synchronous transfer calls,
which are wrappers around this core asynchronous primitive.)
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re750.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch09.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re752.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>spi_setup</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>spi_sync</span></td></tr></table></div></body></html>
