triggers.rst (2898B)
1======== 2Triggers 3======== 4 5* struct iio_trigger — industrial I/O trigger device 6* :c:func:`devm_iio_trigger_alloc` — Resource-managed iio_trigger_alloc 7* :c:func:`devm_iio_trigger_register` — Resource-managed iio_trigger_register 8 iio_trigger_unregister 9* :c:func:`iio_trigger_validate_own_device` — Check if a trigger and IIO 10 device belong to the same device 11 12In many situations it is useful for a driver to be able to capture data based 13on some external event (trigger) as opposed to periodically polling for data. 14An IIO trigger can be provided by a device driver that also has an IIO device 15based on hardware generated events (e.g. data ready or threshold exceeded) or 16provided by a separate driver from an independent interrupt source (e.g. GPIO 17line connected to some external system, timer interrupt or user space writing 18a specific file in sysfs). A trigger may initiate data capture for a number of 19sensors and also it may be completely unrelated to the sensor itself. 20 21IIO trigger sysfs interface 22=========================== 23 24There are two locations in sysfs related to triggers: 25 26* :file:`/sys/bus/iio/devices/trigger{Y}/*`, this file is created once an 27 IIO trigger is registered with the IIO core and corresponds to trigger 28 with index Y. 29 Because triggers can be very different depending on type there are few 30 standard attributes that we can describe here: 31 32 * :file:`name`, trigger name that can be later used for association with a 33 device. 34 * :file:`sampling_frequency`, some timer based triggers use this attribute to 35 specify the frequency for trigger calls. 36 37* :file:`/sys/bus/iio/devices/iio:device{X}/trigger/*`, this directory is 38 created once the device supports a triggered buffer. We can associate a 39 trigger with our device by writing the trigger's name in the 40 :file:`current_trigger` file. 41 42IIO trigger setup 43================= 44 45Let's see a simple example of how to setup a trigger to be used by a driver:: 46 47 struct iio_trigger_ops trigger_ops = { 48 .set_trigger_state = sample_trigger_state, 49 .validate_device = sample_validate_device, 50 } 51 52 struct iio_trigger *trig; 53 54 /* first, allocate memory for our trigger */ 55 trig = iio_trigger_alloc(dev, "trig-%s-%d", name, idx); 56 57 /* setup trigger operations field */ 58 trig->ops = &trigger_ops; 59 60 /* now register the trigger with the IIO core */ 61 iio_trigger_register(trig); 62 63IIO trigger ops 64=============== 65 66* struct iio_trigger_ops — operations structure for an iio_trigger. 67 68Notice that a trigger has a set of operations attached: 69 70* :file:`set_trigger_state`, switch the trigger on/off on demand. 71* :file:`validate_device`, function to validate the device when the current 72 trigger gets changed. 73 74More details 75============ 76.. kernel-doc:: include/linux/iio/trigger.h 77.. kernel-doc:: drivers/iio/industrialio-trigger.c 78 :export: