Re: [PATCH v8 5/5] iio: Documentation: Add IIO configfs documentation

[Daniel Baluta]

On Tue, Oct 20, 2015 at 2:50 PM, Crt Mori <cmo@xxxxxxxxxxx> wrote:
> On 20 October 2015 at 12:53, Daniel Baluta <daniel.baluta@xxxxxxxxx> wrote:
>> Signed-off-by: Daniel Baluta <daniel.baluta@xxxxxxxxx>
>> ---
>>  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@xxxxxxxxxxxxxxx
>> +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?

Automagically is more fun :).

http://www.urbandictionary.com/define.php?term=automagically


>> +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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