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    Subject[RFC 5/9] iio: Documentation: Add IIO configfs documentation
    Date
    From: Daniel Baluta <daniel.baluta@intel.com>

    Signed-off-by: Daniel Baluta <daniel.baluta@intel.com>
    Acked-by: Crt Mori <cmo@melexis.com>
    ---
    Documentation/ABI/testing/configfs-iio | 21 ++++++++
    Documentation/iio/iio_configfs.txt | 93 ++++++++++++++++++++++++++++++++++
    2 files changed, 114 insertions(+)
    create mode 100644 Documentation/ABI/testing/configfs-iio
    create mode 100644 Documentation/iio/iio_configfs.txt

    diff --git a/Documentation/ABI/testing/configfs-iio b/Documentation/ABI/testing/configfs-iio
    new file mode 100644
    index 0000000..2483756
    --- /dev/null
    +++ b/Documentation/ABI/testing/configfs-iio
    @@ -0,0 +1,21 @@
    +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.
    diff --git a/Documentation/iio/iio_configfs.txt b/Documentation/iio/iio_configfs.txt
    new file mode 100644
    index 0000000..f0add35
    --- /dev/null
    +++ b/Documentation/iio/iio_configfs.txt
    @@ -0,0 +1,93 @@
    +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.
    --
    1.9.1


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