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4c3e2a40 DB |
1 | Industrial IIO configfs support |
2 | ||
3 | 1. Overview | |
4 | ||
5 | Configfs is a filesystem-based manager of kernel objects. IIO uses some | |
6 | objects that could be easily configured using configfs (e.g.: devices, | |
7 | triggers). | |
8 | ||
9 | See Documentation/filesystems/configfs/configfs.txt for more information | |
10 | about how configfs works. | |
11 | ||
12 | 2. Usage | |
13 | ||
14 | In order to use configfs support in IIO we need to select it at compile | |
15 | time via CONFIG_IIO_CONFIGFS config option. | |
16 | ||
17 | Then, mount the configfs filesystem (usually under /config directory): | |
18 | ||
19 | $ mkdir /config | |
20 | $ mount -t configfs none /config | |
21 | ||
22 | At this point, all default IIO groups will be created and can be accessed | |
23 | under /config/iio. Next chapters will describe available IIO configuration | |
24 | objects. | |
25 | ||
26 | 3. Software triggers | |
27 | ||
28 | One of the IIO default configfs groups is the "triggers" group. It is | |
29 | automagically accessible when the configfs is mounted and can be found | |
30 | under /config/iio/triggers. | |
31 | ||
32 | IIO software triggers implementation offers support for creating multiple | |
33 | trigger types. A new trigger type is usually implemented as a separate | |
34 | kernel module following the interface in include/linux/iio/sw_trigger.h: | |
35 | ||
36 | /* | |
37 | * drivers/iio/trigger/iio-trig-sample.c | |
38 | * sample kernel module implementing a new trigger type | |
39 | */ | |
40 | #include <linux/iio/sw_trigger.h> | |
41 | ||
42 | ||
43 | static struct iio_sw_trigger *iio_trig_sample_probe(const char *name) | |
44 | { | |
45 | /* | |
46 | * This allocates and registers an IIO trigger plus other | |
47 | * trigger type specific initialization. | |
48 | */ | |
49 | } | |
50 | ||
51 | static int iio_trig_hrtimer_remove(struct iio_sw_trigger *swt) | |
52 | { | |
53 | /* | |
54 | * This undoes the actions in iio_trig_sample_probe | |
55 | */ | |
56 | } | |
57 | ||
58 | static const struct iio_sw_trigger_ops iio_trig_sample_ops = { | |
59 | .probe = iio_trig_sample_probe, | |
60 | .remove = iio_trig_sample_remove, | |
61 | }; | |
62 | ||
63 | static struct iio_sw_trigger_type iio_trig_sample = { | |
64 | .name = "trig-sample", | |
65 | .owner = THIS_MODULE, | |
66 | .ops = &iio_trig_sample_ops, | |
67 | }; | |
68 | ||
69 | module_iio_sw_trigger_driver(iio_trig_sample); | |
70 | ||
71 | Each trigger type has its own directory under /config/iio/triggers. Loading | |
72 | iio-trig-sample module will create 'trig-sample' trigger type directory | |
73 | /config/iio/triggers/trig-sample. | |
74 | ||
75 | We support the following interrupt sources (trigger types): | |
76 | * hrtimer, uses high resolution timers as interrupt source | |
77 | ||
78 | 3.1 Hrtimer triggers creation and destruction | |
79 | ||
80 | Loading iio-trig-hrtimer module will register hrtimer trigger types allowing | |
81 | users to create hrtimer triggers under /config/iio/triggers/hrtimer. | |
82 | ||
83 | e.g: | |
84 | ||
85 | $ mkdir /config/triggers/hrtimer/instance1 | |
86 | $ rmdir /config/triggers/hrtimer/instance1 | |
87 | ||
88 | Each trigger can have one or more attributes specific to the trigger type. | |
89 | ||
90 | 3.2 "hrtimer" trigger types attributes | |
91 | ||
92 | "hrtimer" trigger type doesn't have any configurable attribute from /config dir. | |
93 | It does introduce the sampling_frequency attribute to trigger directory. |