Mentors: [http://kernelnewbies.org/OctavianPurdila Octavian Purdila], [http://kernelnewbies.org/DanielBaluta Daniel Baluta]
Experimenting with IIO subsystem
For this we will use two kernel modules found in drivers/staging/iio:
iio_dummy_evgen.ko - generates fake events interrupts to be used by the iio_dummy example driver
implementation for this module is in iio_dummy_evgen.c
iio_dummy.ko - example IIO driver to demonstrate existing functionality
core implementation can be found in iio_simple_dummy.c
buffer functionality is implemented in iio_simple_dummy_buffer.c
events functionality is implemented in iio_simple_dummy_events.c
Dummy modules compilation
You need to select the following config options:
CONFIG_IIO_DUMMY_EVGEN - for building iio_dummy_evgen kernel module
CONFIG_IIO_SIMPLE_DUMMY - for building iio_dummy kernel module
CONFIG_IIO_SIMPLE_DUMMY_EVENTS, CONFIG_IIO_SIMPLE_DUMMY_BUFFER should be selected for events and buffer functionality.
Use the following commands for modules compilation:
$ make drivers/staging/iio/iio_dummy_evgen.ko
$ make drivers/staging/iio/iio_dummy.ko
Use the following commands for module loading:
$ insmod iio_dummy_evgen.ko
$ insmod iio_dummy.ko
Task 01:
- Show that the modules were successfully loaded . Send an email to mentors listed at the top of the page, with the output of the following commands
- lsmod
- ls -l /sys/bus/iio/devices/
- ls -l /sys/bus/iio/devices/iio:device0/
- ls -l /sys/bus/iio/devices/iio_evgen/
IIO event monitor
IIO event monitor is an user space example application which reads events from IIO layer and pretty prints the results. Implementation can be found in iio_event_monitor.c under iio/drivers/staging/iio/Documentation. BR
Task 02:
compile iio_event_monitor.c to obtain an executable called iio_event_monitor. Send an email with the command used for compilation to mentors listed at the top of the page.
IIO sysfs attributes
IIO sysfs attributes should all be documented in Documentation/ABI/testing/sysfs-bus-iio. Have a look at this file, with a focus on the following entries:
- /sys/bus/iio/devices/iio:deviceX
- /sys/bus/iio/devices/triggerX
- /sys/bus/iio/devices/iio:deviceX/buffer
- /sys/bus/iio/devices/iio:deviceX/events
Task 03: Add missing ABI Documentation
this task asks you to find missing ABI documentation in Documentation/ABI/testing/sysfs-bus-iio (for example look at this [http://www.spinics.net/lists/linux-iio/msg15203.html patch])
the key structure to be analyzed is [http://lxr.free-electrons.com/source/include/linux/iio/iio.h#L217 struct iio_chan_spec]
use drivers/staging/iio/iio_simple_dummy.c for testing adding new channels to iio_dummy_channels[] array. Then look for the attributes names in /sys/bus/iio/devices/iio:device0 and check to see if they
are documented in Documentation/ABI/testing/sysfs-bus-iio
make sure that the undocumented ABI has at least one user driver in drivers/iio/ or drivers/staging/iio/