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Date: Wed, 25 Mar 2015 19:00:32 +0200 From: Daniel Baluta <daniel.baluta@...el.com> To: jic23@...nel.org Cc: jlbec@...lplan.org, lars@...afoo.de, knaack.h@....de, pmeerw@...erw.net, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, octavian.purdila@...el.com, daniel.baluta@...el.com Subject: [PATCH 3/3] iio: Documentation: Add initial documentaton for IIO This file wants to be a starting point document for anyone wanting to use IIO configfs support or adding new IIO configfs functionality. Signed-off-by: Daniel Baluta <daniel.baluta@...el.com> --- Documentation/iio/iio_configfs.txt | 74 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) create mode 100644 Documentation/iio/iio_configfs.txt diff --git a/Documentation/iio/iio_configfs.txt b/Documentation/iio/iio_configfs.txt new file mode 100644 index 0000000..494f4ff --- /dev/null +++ b/Documentation/iio/iio_configfs.txt @@ -0,0 +1,74 @@ +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 creatd and can be accessed under +/config/iio. Next chapters will describe available IIO configurable objects. + +2.1. Software triggers creation and destruction + +One of the IIO default configfs groups is the "triggers" groups. It is +automagically accessible when the configfs is mounted and can be found under +/config/iio/triggers. + +2.1.1. Trigger creation + +As simply as: + +$ mkdir /config/triggers/my_trigger + +This will create a directory associated with a trigger. To understand how this +works we first need to see "my_triggers"'s attributes: + +$ ls /config/triggers/my_trigger +activate sampling_frequency type + +Available types for triggers are: + * none, this is a default dummy trigger that does nothing. + * hrtimer, this is trigger based on high resolution timer. + +Order of operations in order to create a "hrtimer" trigger: + +$ echo hrtimer > /config/triggers/my_trigger/type +$ echo 1 > /config/triggers/my_trigger/activate +$ echo 100 > /config/triggers/my_trigger/sampling_frequency + +At this point the trigger can be used by an IIO device. + +2.1.2 Trigger destruction + +$ echo 1 > /config/triggers/my_trigger/activate + +3. Misc + +In order to add a new trigger type, one need to implement a driver that creates +an instance of struct iio_configfs_ops (see iio_configfs_trigger.h header file +in include/linux/iio) and then support it in iio_trigger_set_configfs_ops +function from industrialiio-configfs.c file. + +These are the existing drivers implementing new trigger types: + * hrtimer => iio/trigger/iio-trig-hrtimer.c + +4. Further work + +* IIO dummy device creation +* Mappings to 'soft' in kernel users such as iio_input and iio_hwmon +* IIO on IIO drivers + -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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