Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
1 Industrial IIO configfs support 2 3 1. Overview 4 5 Configfs is a filesystem-based manager of kernel objects. IIO uses some 6 objects that could be easily configured using configfs (e.g.: devices, 7 triggers). 8 9 See Documentation/filesystems/configfs/configfs.txt for more information 10 about how configfs works. 11 12 2. Usage 13 14 In order to use configfs support in IIO we need to select it at compile 15 time via CONFIG_IIO_CONFIGFS config option. 16 17 Then, mount the configfs filesystem (usually under /config directory): 18 19 $ mkdir /config 20 $ mount -t configfs none /config 21 22 At this point, all default IIO groups will be created and can be accessed 23 under /config/iio. Next chapters will describe available IIO configuration 24 objects. 25 26 3. Software triggers 27 28 One of the IIO default configfs groups is the "triggers" group. It is 29 automagically accessible when the configfs is mounted and can be found 30 under /config/iio/triggers. 31 32 IIO software triggers implementation offers support for creating multiple 33 trigger types. A new trigger type is usually implemented as a separate 34 kernel module following the interface in include/linux/iio/sw_trigger.h: 35 36 /* 37 * drivers/iio/trigger/iio-trig-sample.c 38 * sample kernel module implementing a new trigger type 39 */ 40 #include <linux/iio/sw_trigger.h> 41 42 43 static struct iio_sw_trigger *iio_trig_sample_probe(const char *name) 44 { 45 /* 46 * This allocates and registers an IIO trigger plus other 47 * trigger type specific initialization. 48 */ 49 } 50 51 static int iio_trig_hrtimer_remove(struct iio_sw_trigger *swt) 52 { 53 /* 54 * This undoes the actions in iio_trig_sample_probe 55 */ 56 } 57 58 static const struct iio_sw_trigger_ops iio_trig_sample_ops = { 59 .probe = iio_trig_sample_probe, 60 .remove = iio_trig_sample_remove, 61 }; 62 63 static struct iio_sw_trigger_type iio_trig_sample = { 64 .name = "trig-sample", 65 .owner = THIS_MODULE, 66 .ops = &iio_trig_sample_ops, 67 }; 68 69 module_iio_sw_trigger_driver(iio_trig_sample); 70 71 Each trigger type has its own directory under /config/iio/triggers. Loading 72 iio-trig-sample module will create 'trig-sample' trigger type directory 73 /config/iio/triggers/trig-sample. 74 75 We support the following interrupt sources (trigger types): 76 * hrtimer, uses high resolution timers as interrupt source 77 78 3.1 Hrtimer triggers creation and destruction 79 80 Loading iio-trig-hrtimer module will register hrtimer trigger types allowing 81 users to create hrtimer triggers under /config/iio/triggers/hrtimer. 82 83 e.g: 84 85 $ mkdir /config/iio/triggers/hrtimer/instance1 86 $ rmdir /config/iio/triggers/hrtimer/instance1 87 88 Each trigger can have one or more attributes specific to the trigger type. 89 90 3.2 "hrtimer" trigger types attributes 91 92 "hrtimer" trigger type doesn't have any configurable attribute from /config dir. 93 It does introduce the sampling_frequency attribute to trigger directory.