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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Industrial I/O triggers</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="Industrial I/O driver developer's guide"><link rel="up" href="iiosubsys.html" title="Chapter 2. Industrial I/O core"><link rel="prev" href="API-iio-buffer-put.html" title="iio_buffer_put"><link rel="next" href="API-struct-iio-trigger.html" title="struct iio_trigger"></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"> Industrial I/O triggers </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-iio-buffer-put.html">Prev</a> </td><th width="60%" align="center">Chapter 2. Industrial I/O core</th><td width="20%" align="right"> <a accesskey="n" href="API-struct-iio-trigger.html">Next</a></td></tr></table><hr></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="iiotrigger"></a> Industrial I/O triggers </h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="refentrytitle"><a href="API-struct-iio-trigger.html"><span class="phrase">struct iio_trigger</span></a></span><span class="refpurpose"> —
industrial I/O trigger device
</span></dt><dt><span class="refentrytitle"><a href="API-devm-iio-trigger-alloc.html"><span class="phrase">devm_iio_trigger_alloc</span></a></span><span class="refpurpose"> —
Resource-managed <code class="function">iio_trigger_alloc</code>
</span></dt><dt><span class="refentrytitle"><a href="API-devm-iio-trigger-free.html"><span class="phrase">devm_iio_trigger_free</span></a></span><span class="refpurpose"> —
Resource-managed <code class="function">iio_trigger_free</code>
</span></dt><dt><span class="sect2"><a href="iiotrigger.html#iiotrigsysfs"> IIO trigger sysfs interface </a></span></dt><dt><span class="sect2"><a href="iiotrigger.html#iiotrigattr"> IIO trigger setup</a></span></dt><dt><span class="sect2"><a href="iiotrigger.html#iiotrigsetup"> IIO trigger ops</a></span></dt></dl></div><p>
In many situations it is useful for a driver to be able to
capture data based on some external event (trigger) as opposed
to periodically polling for data. An IIO trigger can be provided
by a device driver that also has an IIO device based on hardware
generated events (e.g. data ready or threshold exceeded) or
provided by a separate driver from an independent interrupt
source (e.g. GPIO line connected to some external system, timer
interrupt or user space writing a specific file in sysfs). A
trigger may initiate data capture for a number of sensors and
also it may be completely unrelated to the sensor itself.
</p><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="iiotrigsysfs"></a> IIO trigger sysfs interface </h3></div></div></div>
There are two locations in sysfs related to triggers:
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><code class="filename">/sys/bus/iio/devices/triggerY</code>,
this file is created once an IIO trigger is registered with
the IIO core and corresponds to trigger with index Y. Because
triggers can be very different depending on type there are few
standard attributes that we can describe here:
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><span class="emphasis"><em>name</em></span>, trigger name that can be later
used for association with a device.
</li><li class="listitem"><span class="emphasis"><em>sampling_frequency</em></span>, some timer based
triggers use this attribute to specify the frequency for
trigger calls.
</li></ul></div></li><li class="listitem"><code class="filename">/sys/bus/iio/devices/iio:deviceX/trigger/</code>, this
directory is created once the device supports a triggered
buffer. We can associate a trigger with our device by writing
the trigger's name in the <code class="filename">current_trigger</code> file.
</li></ul></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="iiotrigattr"></a> IIO trigger setup</h3></div></div></div><p>
Let's see a simple example of how to setup a trigger to be used
by a driver.
</p><pre class="programlisting">
struct iio_trigger_ops trigger_ops = {
.set_trigger_state = sample_trigger_state,
.validate_device = sample_validate_device,
}
struct iio_trigger *trig;
/* first, allocate memory for our trigger */
trig = iio_trigger_alloc(dev, "trig-%s-%d", name, idx);
/* setup trigger operations field */
trig->ops = &trigger_ops;
/* now register the trigger with the IIO core */
iio_trigger_register(trig);
</pre><p>
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="iiotrigsetup"></a> IIO trigger ops</h3></div></div></div><div class="toc"><dl class="toc"><dt><span class="refentrytitle"><a href="API-struct-iio-trigger-ops.html"><span class="phrase">struct iio_trigger_ops</span></a></span><span class="refpurpose"> —
operations structure for an iio_trigger.
</span></dt></dl></div><p>
Notice that a trigger has a set of operations attached:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><code class="function">set_trigger_state</code>, switch the trigger on/off
on demand.
</li><li class="listitem"><code class="function">validate_device</code>, function to validate the
device when the current trigger gets changed.
</li></ul></div><p>
</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="API-iio-buffer-put.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="iiosubsys.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="API-struct-iio-trigger.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="phrase">iio_buffer_put</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span class="phrase">struct iio_trigger</span></td></tr></table></div></body></html>