mirror of
https://github.com/torvalds/linux.git
synced 2024-12-05 02:23:16 +00:00
dafcf4ed83
Allow setting frequency below 1Hz or sub 1Hz precision. Useful for slow sensors like ALS. Test frequency is set properly: modprobe iio-trig-hrtimer && \ mkdir /sys/kernel/config/iio/triggers/hrtimer/t1 && \ cd /sys/bus/iio/devices/triggerX ; for i in 1 .1 .01 .001 ; do echo $i > sampling_frequency cat sampling_frequency done Signed-off-by: Gwendal Grignou <gwendal@chromium.org> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Link: https://lore.kernel.org/r/20210226014733.2108544-1-gwendal@chromium.org Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
103 lines
3.0 KiB
ReStructuredText
103 lines
3.0 KiB
ReStructuredText
===============================
|
|
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.rst 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_sample_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/iio/triggers/hrtimer/instance1
|
|
$ rmdir /config/iio/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.
|
|
That attribute sets the polling frequency in Hz, with mHz precision.
|