iio: Documentation: Add IIO configfs documentation (4c3e2a40) · Commits · e / devices / android_kernel_teracube_2e

Documentation/ABI/testing/configfs-iio

0 → 100644

+21 −0

Original line number	Diff line number	Diff line
		What: /config/iio
		Date: October 2015
		KernelVersion: 4.4
		Contact: linux-iio@vger.kernel.org
		Description:
		This represents Industrial IO configuration entry point
		directory. It contains sub-groups corresponding to IIO
		objects.

		What: /config/iio/triggers
		Date: October 2015
		KernelVersion: 4.4
		Description:
		Industrial IO software triggers directory.

		What: /config/iio/triggers/hrtimers
		Date: October 2015
		KernelVersion: 4.4
		Description:
		High resolution timers directory. Creating a directory here
		will result in creating a hrtimer trigger in the IIO subsystem.

Documentation/iio/iio_configfs.txt

0 → 100644

+93 −0

Original line number	Diff line number	Diff line
		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/configfs.txt 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_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/triggers/hrtimer/instance1
		$ rmdir /config/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.