1 ======== 1 ========
2 Triggers 2 Triggers
3 ======== 3 ========
4 4
5 * struct iio_trigger — industrial I/O trigge 5 * struct iio_trigger — industrial I/O trigger device
6 * :c:func:`devm_iio_trigger_alloc` — Resourc 6 * :c:func:`devm_iio_trigger_alloc` — Resource-managed iio_trigger_alloc
7 * :c:func:`devm_iio_trigger_register` — Reso 7 * :c:func:`devm_iio_trigger_register` — Resource-managed iio_trigger_register
8 iio_trigger_unregister 8 iio_trigger_unregister
9 * :c:func:`iio_trigger_validate_own_device` †9 * :c:func:`iio_trigger_validate_own_device` — Check if a trigger and IIO
10 device belong to the same device 10 device belong to the same device
11 11
12 In many situations it is useful for a driver t 12 In many situations it is useful for a driver to be able to capture data based
13 on some external event (trigger) as opposed to 13 on some external event (trigger) as opposed to periodically polling for data.
14 An IIO trigger can be provided by a device dri 14 An IIO trigger can be provided by a device driver that also has an IIO device
15 based on hardware generated events (e.g. data 15 based on hardware generated events (e.g. data ready or threshold exceeded) or
16 provided by a separate driver from an independ 16 provided by a separate driver from an independent interrupt source (e.g. GPIO
17 line connected to some external system, timer 17 line connected to some external system, timer interrupt or user space writing
18 a specific file in sysfs). A trigger may initi 18 a specific file in sysfs). A trigger may initiate data capture for a number of
19 sensors and also it may be completely unrelate 19 sensors and also it may be completely unrelated to the sensor itself.
20 20
21 IIO trigger sysfs interface 21 IIO trigger sysfs interface
22 =========================== 22 ===========================
23 23
24 There are two locations in sysfs related to tr 24 There are two locations in sysfs related to triggers:
25 25
26 * :file:`/sys/bus/iio/devices/trigger{Y}/*`, t 26 * :file:`/sys/bus/iio/devices/trigger{Y}/*`, this file is created once an
27 IIO trigger is registered with the IIO core 27 IIO trigger is registered with the IIO core and corresponds to trigger
28 with index Y. 28 with index Y.
29 Because triggers can be very different depen 29 Because triggers can be very different depending on type there are few
30 standard attributes that we can describe her 30 standard attributes that we can describe here:
31 31
32 * :file:`name`, trigger name that can be lat 32 * :file:`name`, trigger name that can be later used for association with a
33 device. 33 device.
34 * :file:`sampling_frequency`, some timer bas 34 * :file:`sampling_frequency`, some timer based triggers use this attribute to
35 specify the frequency for trigger calls. 35 specify the frequency for trigger calls.
36 36
37 * :file:`/sys/bus/iio/devices/iio:device{X}/tr 37 * :file:`/sys/bus/iio/devices/iio:device{X}/trigger/*`, this directory is
38 created once the device supports a triggered 38 created once the device supports a triggered buffer. We can associate a
39 trigger with our device by writing the trigg 39 trigger with our device by writing the trigger's name in the
40 :file:`current_trigger` file. 40 :file:`current_trigger` file.
41 41
42 IIO trigger setup 42 IIO trigger setup
43 ================= 43 =================
44 44
45 Let's see a simple example of how to setup a t 45 Let's see a simple example of how to setup a trigger to be used by a driver::
46 46
47 struct iio_trigger_ops trigger_ops = { 47 struct iio_trigger_ops trigger_ops = {
48 .set_trigger_state = sample_trigger_ 48 .set_trigger_state = sample_trigger_state,
49 .validate_device = sample_validate_d 49 .validate_device = sample_validate_device,
50 } 50 }
51 51
52 struct iio_trigger *trig; 52 struct iio_trigger *trig;
53 53
54 /* first, allocate memory for our trigge 54 /* first, allocate memory for our trigger */
55 trig = iio_trigger_alloc(dev, "trig-%s-% 55 trig = iio_trigger_alloc(dev, "trig-%s-%d", name, idx);
56 56
57 /* setup trigger operations field */ 57 /* setup trigger operations field */
58 trig->ops = &trigger_ops; 58 trig->ops = &trigger_ops;
59 59
60 /* now register the trigger with the IIO 60 /* now register the trigger with the IIO core */
61 iio_trigger_register(trig); 61 iio_trigger_register(trig);
62 62
63 IIO trigger ops 63 IIO trigger ops
64 =============== 64 ===============
65 65
66 * struct iio_trigger_ops — operations struct 66 * struct iio_trigger_ops — operations structure for an iio_trigger.
67 67
68 Notice that a trigger has a set of operations 68 Notice that a trigger has a set of operations attached:
69 69
70 * :file:`set_trigger_state`, switch the trigge 70 * :file:`set_trigger_state`, switch the trigger on/off on demand.
71 * :file:`validate_device`, function to validat 71 * :file:`validate_device`, function to validate the device when the current
72 trigger gets changed. 72 trigger gets changed.
73 73
74 More details 74 More details
75 ============ 75 ============
76 .. kernel-doc:: include/linux/iio/trigger.h 76 .. kernel-doc:: include/linux/iio/trigger.h
77 .. kernel-doc:: drivers/iio/industrialio-trigg 77 .. kernel-doc:: drivers/iio/industrialio-trigger.c
78 :export: 78 :export:
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