1 ===============================
2 Industrial IIO configfs support
3 ===============================
4
5 1. Overview
6 ===========
7
8 Configfs is a filesystem-based manager of kernel objects. IIO uses some
9 objects that could be easily configured using configfs (e.g.: devices,
10 triggers).
11
12 See Documentation/filesystems/configfs.rst for more information
13 about how configfs works.
14
15 2. Usage
16 ========
17
18 In order to use configfs support in IIO we need to select it at compile
19 time via CONFIG_IIO_CONFIGFS config option.
20
21 Then, mount the configfs filesystem (usually under /config directory)::
22
23 $ mkdir /config
24 $ mount -t configfs none /config
25
26 At this point, all default IIO groups will be created and can be accessed
27 under /config/iio. Next chapters will describe available IIO configuration
28 objects.
29
30 3. Software triggers
31 ====================
32
33 One of the IIO default configfs groups is the "triggers" group. It is
34 automagically accessible when the configfs is mounted and can be found
35 under /config/iio/triggers.
36
37 IIO software triggers implementation offers support for creating multiple
38 trigger types. A new trigger type is usually implemented as a separate
39 kernel 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
76 Each trigger type has its own directory under /config/iio/triggers. Loading
77 iio-trig-sample module will create 'trig-sample' trigger type directory
78 /config/iio/triggers/trig-sample.
79
80 We support the following interrupt sources (trigger types):
81
82 * hrtimer, uses high resolution timers as interrupt source
83
84 3.1 Hrtimer triggers creation and destruction
85 ---------------------------------------------
86
87 Loading iio-trig-hrtimer module will register hrtimer trigger types allowing
88 users to create hrtimer triggers under /config/iio/triggers/hrtimer.
89
90 e.g::
91
92 $ mkdir /config/iio/triggers/hrtimer/instance1
93 $ rmdir /config/iio/triggers/hrtimer/instance1
94
95 Each trigger can have one or more attributes specific to the trigger type.
96
97 3.2 "hrtimer" trigger types attributes
98 --------------------------------------
99
100 "hrtimer" trigger type doesn't have any configurable attribute from /config dir.
101 It does introduce the sampling_frequency attribute to trigger directory.
102 That attribute sets the polling frequency in Hz, with mHz precision.
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