tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1===============================
2Industrial IIO configfs support
3===============================
4
51. Overview
6===========
7
8Configfs is a filesystem-based manager of kernel objects. IIO uses some
9objects that could be easily configured using configfs (e.g.: devices,
10triggers).
11
12See Documentation/filesystems/configfs.rst for more information
13about how configfs works.
14
152. Usage
16========
17
18In order to use configfs support in IIO we need to select it at compile
19time via CONFIG_IIO_CONFIGFS config option.
20
21Then, mount the configfs filesystem (usually under /config directory)::
22
23 $ mkdir /config
24 $ mount -t configfs none /config
25
26At this point, all default IIO groups will be created and can be accessed
27under /config/iio. Next chapters will describe available IIO configuration
28objects.
29
303. Software triggers
31====================
32
33One of the IIO default configfs groups is the "triggers" group. It is
34automagically accessible when the configfs is mounted and can be found
35under /config/iio/triggers.
36
37IIO software triggers implementation offers support for creating multiple
38trigger types. A new trigger type is usually implemented as a separate
39kernel module following the interface in include/linux/iio/sw_trigger.h::
40
41 /*
42 * drivers/iio/trigger/iio-trig-sample.c
43 * sample kernel module implementing a new trigger type
44 */
45 #include <linux/iio/sw_trigger.h>
46
47
48 static struct iio_sw_trigger *iio_trig_sample_probe(const char *name)
49 {
50 /*
51 * This allocates and registers an IIO trigger plus other
52 * trigger type specific initialization.
53 */
54 }
55
56 static int iio_trig_sample_remove(struct iio_sw_trigger *swt)
57 {
58 /*
59 * This undoes the actions in iio_trig_sample_probe
60 */
61 }
62
63 static const struct iio_sw_trigger_ops iio_trig_sample_ops = {
64 .probe = iio_trig_sample_probe,
65 .remove = iio_trig_sample_remove,
66 };
67
68 static struct iio_sw_trigger_type iio_trig_sample = {
69 .name = "trig-sample",
70 .owner = THIS_MODULE,
71 .ops = &iio_trig_sample_ops,
72 };
73
74 module_iio_sw_trigger_driver(iio_trig_sample);
75
76Each trigger type has its own directory under /config/iio/triggers. Loading
77iio-trig-sample module will create 'trig-sample' trigger type directory
78/config/iio/triggers/trig-sample.
79
80We support the following interrupt sources (trigger types):
81
82 * hrtimer, uses high resolution timers as interrupt source
83
843.1 Hrtimer triggers creation and destruction
85---------------------------------------------
86
87Loading iio-trig-hrtimer module will register hrtimer trigger types allowing
88users to create hrtimer triggers under /config/iio/triggers/hrtimer.
89
90e.g::
91
92 $ mkdir /config/iio/triggers/hrtimer/instance1
93 $ rmdir /config/iio/triggers/hrtimer/instance1
94
95Each trigger can have one or more attributes specific to the trigger type.
96
973.2 "hrtimer" trigger types attributes
98--------------------------------------
99
100"hrtimer" trigger type doesn't have any configurable attribute from /config dir.
101It does introduce the sampling_frequency attribute to trigger directory.
102That attribute sets the polling frequency in Hz, with mHz precision.