=============================== Industrial IIO configfs support =============================== 1. Overview =========== Configfs is a filesystem-based manager of kernel objects. IIO uses some objects that could be easily configured using configfs (e.g.: devices, triggers). See Documentation/filesystems/configfs.rst for more information about how configfs works. 2. Usage ======== In order to use configfs support in IIO we need to select it at compile time via CONFIG_IIO_CONFIGFS config option. Then, mount the configfs filesystem (usually under /config directory):: $ mkdir /config $ mount -t configfs none /config At this point, all default IIO groups will be created and can be accessed under /config/iio. Next chapters will describe available IIO configuration objects. 3. Software triggers ==================== One of the IIO default configfs groups is the "triggers" group. It is automagically accessible when the configfs is mounted and can be found under /config/iio/triggers. IIO software triggers implementation offers support for creating multiple trigger types. A new trigger type is usually implemented as a separate kernel module following the interface in include/linux/iio/sw_trigger.h:: /* * drivers/iio/trigger/iio-trig-sample.c * sample kernel module implementing a new trigger type */ #include static struct iio_sw_trigger *iio_trig_sample_probe(const char *name) { /* * This allocates and registers an IIO trigger plus other * trigger type specific initialization. */ } static int iio_trig_sample_remove(struct iio_sw_trigger *swt) { /* * This undoes the actions in iio_trig_sample_probe */ } static const struct iio_sw_trigger_ops iio_trig_sample_ops = { .probe = iio_trig_sample_probe, .remove = iio_trig_sample_remove, }; static struct iio_sw_trigger_type iio_trig_sample = { .name = "trig-sample", .owner = THIS_MODULE, .ops = &iio_trig_sample_ops, }; module_iio_sw_trigger_driver(iio_trig_sample); Each trigger type has its own directory under /config/iio/triggers. Loading iio-trig-sample module will create 'trig-sample' trigger type directory /config/iio/triggers/trig-sample. We support the following interrupt sources (trigger types): * hrtimer, uses high resolution timers as interrupt source 3.1 Hrtimer triggers creation and destruction --------------------------------------------- Loading iio-trig-hrtimer module will register hrtimer trigger types allowing users to create hrtimer triggers under /config/iio/triggers/hrtimer. e.g:: $ mkdir /config/iio/triggers/hrtimer/instance1 $ rmdir /config/iio/triggers/hrtimer/instance1 Each trigger can have one or more attributes specific to the trigger type. 3.2 "hrtimer" trigger types attributes -------------------------------------- "hrtimer" trigger type doesn't have any configurable attribute from /config dir. It does introduce the sampling_frequency attribute to trigger directory. That attribute sets the polling frequency in Hz, with mHz precision.