1======== 2Triggers 3======== 4 5* struct :c:type:`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_free` — Resource-managed iio_trigger_free 8* :c:func:`devm_iio_trigger_register` — Resource-managed iio_trigger_register 9* :c:func:`devm_iio_trigger_unregister` — Resource-managed 10 iio_trigger_unregister 11* :c:func:`iio_trigger_validate_own_device` — Check if a trigger and IIO 12 device belong to the same device 13 14In many situations it is useful for a driver to be able to capture data based 15on some external event (trigger) as opposed to periodically polling for data. 16An IIO trigger can be provided by a device driver that also has an IIO device 17based on hardware generated events (e.g. data ready or threshold exceeded) or 18provided by a separate driver from an independent interrupt source (e.g. GPIO 19line connected to some external system, timer interrupt or user space writing 20a specific file in sysfs). A trigger may initiate data capture for a number of 21sensors and also it may be completely unrelated to the sensor itself. 22 23IIO trigger sysfs interface 24=========================== 25 26There are two locations in sysfs related to triggers: 27 28* :file:`/sys/bus/iio/devices/trigger{Y}/*`, this file is created once an 29 IIO trigger is registered with the IIO core and corresponds to trigger 30 with index Y. 31 Because triggers can be very different depending on type there are few 32 standard attributes that we can describe here: 33 34 * :file:`name`, trigger name that can be later used for association with a 35 device. 36 * :file:`sampling_frequency`, some timer based triggers use this attribute to 37 specify the frequency for trigger calls. 38 39* :file:`/sys/bus/iio/devices/iio:device{X}/trigger/*`, this directory is 40 created once the device supports a triggered buffer. We can associate a 41 trigger with our device by writing the trigger's name in the 42 :file:`current_trigger` file. 43 44IIO trigger setup 45================= 46 47Let's see a simple example of how to setup a trigger to be used by a driver:: 48 49 struct iio_trigger_ops trigger_ops = { 50 .set_trigger_state = sample_trigger_state, 51 .validate_device = sample_validate_device, 52 } 53 54 struct iio_trigger *trig; 55 56 /* first, allocate memory for our trigger */ 57 trig = iio_trigger_alloc(dev, "trig-%s-%d", name, idx); 58 59 /* setup trigger operations field */ 60 trig->ops = &trigger_ops; 61 62 /* now register the trigger with the IIO core */ 63 iio_trigger_register(trig); 64 65IIO trigger ops 66=============== 67 68* struct :c:type:`iio_trigger_ops` — operations structure for an iio_trigger. 69 70Notice that a trigger has a set of operations attached: 71 72* :file:`set_trigger_state`, switch the trigger on/off on demand. 73* :file:`validate_device`, function to validate the device when the current 74 trigger gets changed. 75 76More details 77============ 78.. kernel-doc:: include/linux/iio/trigger.h 79.. kernel-doc:: drivers/iio/industrialio-trigger.c 80 :export: 81