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+===============================
+Industrial IIO configfs support
+===============================
+
+1. 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.rst for more information
+about how configfs works.
+
+2. 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.
+
+3. 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_sample_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.
+That attribute sets the polling frequency in Hz, with mHz precision.