1. Overview¶

Configfs is a filesystem-based manager of kernel objects. IIO uses someobjects that could be easily configured using configfs (e.g.: devices,triggers).

See Documentation/filesystems/configfs.rst for more informationabout how configfs works.

2. Usage¶

In order to use configfs support in IIO we need to select it at compiletime via CONFIG_IIO_CONFIGFS config option.

Then, mount the configfs filesystem (usually under /config directory):

$ mkdir /config$ mount -t configfs none /config

At this point, all default IIO groups will be created and can be accessedunder /config/iio. Next chapters will describe available IIO configurationobjects.

3. Software triggers¶

One of the IIO default configfs groups is the “triggers” group. It isautomagically accessible when the configfs is mounted and can be foundunder /config/iio/triggers.

IIO software triggers implementation offers support for creating multipletrigger types. A new trigger type is usually implemented as a separatekernel module following the interface in include/linux/iio/sw_trigger.h:

/* * drivers/iio/trigger/iio-trig-sample.c * sample kernel module implementing a new trigger type */#include <linux/iio/sw_trigger.h>static struct iio_sw_trigger *iio_trig_sample_probe(const char *name){      /*       * This allocates and registers an IIO trigger plus other       * trigger type specific initialization.       */}static int iio_trig_hrtimer_remove(struct iio_sw_trigger *swt){      /*       * This undoes the actions in iio_trig_sample_probe       */}static const struct iio_sw_trigger_ops iio_trig_sample_ops = {      .probe          = iio_trig_sample_probe,      .remove         = iio_trig_sample_remove,};static struct iio_sw_trigger_type iio_trig_sample = {      .name = "trig-sample",      .owner = THIS_MODULE,      .ops = &iio_trig_sample_ops,};

module_iio_sw_trigger_driver(iio_trig_sample);

Each trigger type has its own directory under /config/iio/triggers. Loadingiio-trig-sample module will create ‘trig-sample’ trigger type directory/config/iio/triggers/trig-sample.

We support the following interrupt sources (trigger types):

• hrtimer, uses high resolution timers as interrupt source

$ mkdir /config/iio/triggers/hrtimer/instance1$ rmdir /config/iio/triggers/hrtimer/instance1