linux-kernel - Re: [PATCH v7 5/5] iio: Documentation: Add IIO configfs documentation

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Date:	Mon, 17 Aug 2015 15:01:57 +0300
From:	Vladimir Barinov <vladimir.barinov@...entembedded.com>
To:	Daniel Baluta <daniel.baluta@...el.com>, jic23@...nel.org,
	jlbec@...lplan.org, linux-iio@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
CC:	lars@...afoo.de, 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.opriceana@...il.com, pmeerw@...erw.net, hch@....de,
	viro@...iv.linux.org.uk, akpm@...ux-foundation.org
Subject: Re: [PATCH v7 5/5] iio: Documentation: Add IIO configfs documentation

Hi Daniel,

Find minor comments.

Regards,
Vladimir

On 11.08.2015 01:42, Daniel Baluta wrote:
> Signed-off-by: Daniel Baluta <daniel.baluta@...el.com>
> ---
>   Documentation/ABI/testing/configfs-iio | 20 ++++++++++++
>   Documentation/iio/iio_configfs.txt     | 57 ++++++++++++++++++++++++++++++++++
>   2 files changed, 77 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..1fd7cf4
> --- /dev/null
> +++ b/Documentation/ABI/testing/configfs-iio
> @@ -0,0 +1,20 @@
> +What:		/config/iio
> +Date:		May 2015
> +KernelVersion:	4.2
> +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:		August 2015
> +KernelVersion:	4.2
> +Description:
> +		Industrial IO software triggers directory.
> +
> +What:		/config/iio/triggers/hrtimer
> +Date:		August 2015
> +KernelVersion:	4.2
> +Description:
> +		Industrial IO hrtimer based software triggers directory.
> diff --git a/Documentation/iio/iio_configfs.txt b/Documentation/iio/iio_configfs.txt
> new file mode 100644
> index 0000000..7c56997
> --- /dev/null
> +++ b/Documentation/iio/iio_configfs.txt
> @@ -0,0 +1,57 @@
> +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" groups. It is
> +automagically accessible when the configfs is mounted and can be found
> +under /config/iio/triggers.
> +
> +Software triggers are created under /config/iio/triggers directory. There
> +must exist an associated kernel module that implements a software trigger type.
> +
> +We support now the following software trigger types:
> +	* hrtimer, uses high resolution timers as interrupt source implemened
> +	by the iio-trig-hrtimer.c module.
> +
> +3.1 Software triggers creation and destruction
> +
> +As simply as:
> +
> +$ insmod iio-trig-hrtimer.ko
> +$ ls /config/triggers
ls /config/iio/triggers/

> +hrtimer
> +$ mkdir /config/triggers/hrtimer/trig1
mkdir /config/iio/triggers/hrtimer/trig1

This is confusing:
$ cat /sys/bus//iio/devices/trigger0/name
trig1

How may I know that this is a hrtimer trigger in case I've enabled
couple of triggers or when sw_trigger support extends with other
then hrtimer trigger?

> +
> +$ rmdir /config/triggers/hrtimer/trig1
ditto


> +$ rmmod iio-trig-hrtimer
> +
> +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,
> +but hrtimer triggers have the sampling_frequency attribute under /sys/bus/iio/devices/triggerX
> +directory.

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