Industrial IIO configfs support
- Overview
Configfs is a filesystem-based manager of kernel objects. IIO uses some
objects that could be easily configured using configfs (e.g.: devices,
triggers).
See Documentation/filesystems/configfs/configfs.txt for more information
about how configfs works.
- Usage
In order to use configfs support in IIO we need to select it at compile
time 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 accessed
under /config/iio. Next chapters will describe available IIO configuration
objects.
- Software triggers
One of the IIO default configfs groups is the “triggers” group. It is
automagically accessible when the configfs is mounted and can be found
under /config/iio/triggers.
IIO software triggers implementation offers support for creating multiple
trigger types. A new trigger type is usually implemented as a separate
kernel 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. Loading
iio-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
3.1 Hrtimer triggers creation and destruction
Loading iio-trig-hrtimer module will register hrtimer trigger types allowing
users to create hrtimer triggers under /config/iio/triggers/hrtimer.
e.g:
$ mkdir /config/iio/triggers/hrtimer/instance1
$ rmdir /config/iio/triggers/hrtimer/instance1
Each trigger can have one or more attributes specific to the trigger type.
3.2 “hrtimer” trigger types attributes
“hrtimer” trigger type doesn’t have any configurable attribute from /config dir.
It does introduce the sampling_frequency attribute to trigger directory.
