Date:	Tue, 20 Oct 2015 13:50:07 +0200
From:	Crt Mori <cmo@...exis.com>
To:	Daniel Baluta <daniel.baluta@...el.com>
Cc:	Johnathan Iain Cameron <jic23@...nel.org>, jlbec@...lplan.org,
	linux-iio@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Lars-Peter Clausen <lars@...afoo.de>,
	Hartmut Knaack <knaack.h@....de>, linux-kernel@...r.kernel.org,
	octavian.purdila@...el.com, pebolle@...cali.nl,
	patrick.porlan@...el.com, adriana.reus@...el.com,
	constantin.musca@...el.com, marten@...uitiveaerial.com,
	Cristina Georgiana Opriceana <cristina.opriceana@...il.com>,
	Peter Meerwald <pmeerw@...erw.net>, hch@....de,
	viro@...iv.linux.org.uk, akpm@...ux-foundation.org
Subject: Re: [PATCH v8 5/5] iio: Documentation: Add IIO configfs documentation

On 20 October 2015 at 12:53, Daniel Baluta <daniel.baluta@...el.com> wrote:
> Signed-off-by: Daniel Baluta <daniel.baluta@...el.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@...r.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
automagically is probably automatically?
> +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.
> --
--
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