1=============================== 2Industrial IIO configfs support 3=============================== 4 51. Overview 6=========== 7 8Configfs is a filesystem-based manager of kernel objects. IIO uses some 9objects that could be easily configured using configfs (e.g.: devices, 10triggers). 11 12See Documentation/filesystems/configfs.rst for more information 13about how configfs works. 14 152. Usage 16======== 17 18In order to use configfs support in IIO we need to select it at compile 19time via CONFIG_IIO_CONFIGFS config option. 20 21Then, mount the configfs filesystem (usually under /config directory):: 22 23 $ mkdir /config 24 $ mount -t configfs none /config 25 26At this point, all default IIO groups will be created and can be accessed 27under /config/iio. Next chapters will describe available IIO configuration 28objects. 29 303. Software triggers 31==================== 32 33One of the IIO default configfs groups is the "triggers" group. It is 34automagically accessible when the configfs is mounted and can be found 35under /config/iio/triggers. 36 37IIO software triggers implementation offers support for creating multiple 38trigger types. A new trigger type is usually implemented as a separate 39kernel module following the interface in include/linux/iio/sw_trigger.h:: 40 41 /* 42 * drivers/iio/trigger/iio-trig-sample.c 43 * sample kernel module implementing a new trigger type 44 */ 45 #include <linux/iio/sw_trigger.h> 46 47 48 static struct iio_sw_trigger *iio_trig_sample_probe(const char *name) 49 { 50 /* 51 * This allocates and registers an IIO trigger plus other 52 * trigger type specific initialization. 53 */ 54 } 55 56 static int iio_trig_sample_remove(struct iio_sw_trigger *swt) 57 { 58 /* 59 * This undoes the actions in iio_trig_sample_probe 60 */ 61 } 62 63 static const struct iio_sw_trigger_ops iio_trig_sample_ops = { 64 .probe = iio_trig_sample_probe, 65 .remove = iio_trig_sample_remove, 66 }; 67 68 static struct iio_sw_trigger_type iio_trig_sample = { 69 .name = "trig-sample", 70 .owner = THIS_MODULE, 71 .ops = &iio_trig_sample_ops, 72 }; 73 74 module_iio_sw_trigger_driver(iio_trig_sample); 75 76Each trigger type has its own directory under /config/iio/triggers. Loading 77iio-trig-sample module will create 'trig-sample' trigger type directory 78/config/iio/triggers/trig-sample. 79 80We support the following interrupt sources (trigger types): 81 82 * hrtimer, uses high resolution timers as interrupt source 83 843.1 Hrtimer triggers creation and destruction 85--------------------------------------------- 86 87Loading iio-trig-hrtimer module will register hrtimer trigger types allowing 88users to create hrtimer triggers under /config/iio/triggers/hrtimer. 89 90e.g:: 91 92 $ mkdir /config/iio/triggers/hrtimer/instance1 93 $ rmdir /config/iio/triggers/hrtimer/instance1 94 95Each trigger can have one or more attributes specific to the trigger type. 96 973.2 "hrtimer" trigger types attributes 98-------------------------------------- 99 100"hrtimer" trigger type doesn't have any configurable attribute from /config dir. 101It does introduce the sampling_frequency attribute to trigger directory. 102That attribute sets the polling frequency in Hz, with mHz precision. 103