Signed-off-by: Daniel Baluta <daniel.baluta@xxxxxxxxx> --- Changes since v1: * addressed feedback for v1: * https://lkml.org/lkml/2015/3/25/648 * adapted to match the changes in patches 1 and 2 * fixed some typos and clarified further work Documentation/iio/iio_configfs.txt | 82 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) create mode 100644 Documentation/iio/iio_configfs.txt diff --git a/Documentation/iio/iio_configfs.txt b/Documentation/iio/iio_configfs.txt new file mode 100644 index 0000000..a49d5a1 --- /dev/null +++ b/Documentation/iio/iio_configfs.txt @@ -0,0 +1,82 @@ +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/configfs.txt 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" groups. It is +automagically accessible when the configfs is mounted and can be found +under /config/iio/triggers. + +Under /config/iio/triggers we will create trigger types. For the moment +we have "hrtimer" trigger time and we plan to add at least one more +"sysfs" trigger type. + +3.1 Trigger types + +Represent a specific type of trigger. For now we have an implementation +for "hrtimer" trigger type. + +3.2. Trigger creation and destruction + +As simply as: + +$ mkdir /config/triggers/hrtimer/my_trigger + +Creating my_trigger directory will result in creation of "my_trigger" +trigger of "hrtimer" type. Destruction happens when my_trigger directory +is removed. + +Each trigger can have one or more attributes specific to the trigger type. + +3.3 "hrtimer" trigger types attributes + +"hrtimer" trigger type has only one attribute: + +$ ls /config/triggers/hrtimer/my_trigger delay + +delay - represents the amount of time in nanoseconds between two +consecutive iio_trigger_poll calls. By default it is set to 100000000, +that is the equivalent of a 100Hz frequency. + +3.4. Adding a new trigger type + +In order to add a new trigger type, one needs to: + +* [iio_configfs_trigger.h] + ** add a new IIO_TRIGGER_TYPE +* [iio-trig-<type>.c] + ** declare and initialize a structure of type + iio_configfs_trigger_type + ** implement needed iio_configfs_trigger_ops + ** register/unregister the new trigger + type with the IIO configfs core +* [industrialiio-configfs.c] + ** create a new group type and add it in the default group of + trigger types. + ** create new attributes and them to the IIO configfs core. + +4. Further work + +* add "sysfs" trigger type + -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
