= Welcome to IIO tasks page =

This page is dedicated to students applying for GSoC/Outreachy programs.

It also aims to help newcomers getting started with the Industrial IO subsystem, offering pointers to documentation and small tasks.

For GSoC/Outreachy students:

Please use a single email thread for communication. During the application always reply to this thread if you have
a question or sending the solution for a task. The email should have the following format:

subject: GSoC IIO project: Your Name

body:
<short description of content: e.g Task 01 / Question about the schedule / etc>
<the actual email body>


= Experimenting with IIO subsystem =

For this we will use two kernel modules found in {{{drivers/iio/dummy}}}:

 * {{{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}}}
 * {{{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}}}
 
== Dummy modules compilation ==

You need to select the following config options:
 * {{{CONFIG_IIO_CONFIGFS}}} - for creating the dummy device under configfs
 * {{{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.
 * {{{CONFIG_IIO_DUMMY_EVGEN}}} - for building {{{iio_dummy_evgen}}} kernel module
 * Mount the configfs filesystem: read Documentation/iio/iio_configfs.txt

Use the following commands for modules compilation:
 * {{{$ make drivers/iio/dummy/iio_dummy_evgen.ko}}}
 * {{{$ make drivers/iio/dummy/iio_dummy.ko}}}

Use the following commands for module loading:
 * {{{$ insmod iio_dummy_evgen.ko}}}
 * {{{$ insmod iio_dummy.ko}}}

Use the following command to create your dummy device under the configfs filesystem:
 *  {{{$  mkdir /config/iio/devices/dummy/my_dummy_device}}}

Task 01:
 * Show that config options for IIO dummy modules were correctly selected
   * send the content of the following command grep IIO .config

Task 02:
 * Show that the modules were successfully loaded.
   * lsmod | grep dummy
   * ls -l /config/iio/devices/dummy/
   * ls -l /sys/bus/iio/devices/iio:device0/
   * ls -l /sys/bus/iio/devices/iio_evgen/

Task 03:
 * Add channels for a 3-axis compass to iio_simple_dummy module.
 * Show that channels were successfully added
    * ls -l /sys/bus/iio/devices/iio:device0/
    * ls -l /sys/bus/iio/devices/iio:device0/scan_elements
    * create a patch with your changes
 * '''Hints''':
    * channel type for a compass is IIO_MAGN
    * users should be able to read raw readings from each axis
    * users should be able to read a shared scale
    * users should be able to access data via a buffer
      * data is unsigned, resolution is 16 bits, storage is 16 bits
    * compass doesn't support events

== 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 {{{tools/iio/}}}. <<BR>>

Task 04:

Compile iio_event_monitor:

    * compile {{{iio_event_monitor.c}}} to obtain an executable called {{{iio_event_monitor}}}.
    * send us the command(s) used to successfully compile iio_event_monitor.c

Task 05:

Read events using iio_event_monitor
    * run iio_event_monitor without arguments to figure out how it should be used
    * read events from iio_dummy module
    * '''Hints'''
       * Events are generated by iio_dummy_evgen via sysfs (look inside /sys/bus/iio/devices/iio_evgen/)
    * send us the commands used to read/generate the events

== Generic buffer ==

Task 06:

Create triggers using configfs interface.
    * read Documentation/iio/iio_configfs.txt in order to create an hrtimer software trigger named t1.
    * where in the sysfs hierarchy does the trigger resides?
    * sends us the commands used to create the trigger

Task 07:

Read samples from buffer generated by the iio_dummy module.
    * compile iio_generic_buffer.c from tools/iio. This program will be used to read data from buffer.
    * have a look at ./iio_generic_buffer -h options. You will use the trigger ''t1'' created with the previous tasks and ''iio_dummy_part_no'' for IIO device.
    * send us the full command history

= Coding Tasks =

== Coding Task 1  ==

Send 2 cleanup patches to the linux kernel.

Important:

 * patches should be for code in drivers/staging/
 * use tools like checkpatch.pl, sparse or coccinelle to find cleanups.

Useful links:
 * [[https://kernelnewbies.org/Outreachyfirstpatch | Outreachy First Patch]]
 * [[https://www.youtube.com/watch?v=LLBrBBImJt4 | Greg KH presentation - Send your first patch]]

== Coding Task 2 ==

drivers/staging directory is the place where drivers that aren't yet fit to be merged into the main portion of the kernel for various reasons: code quality, non standard interfaces, etc. Grab a driver from drivers/staging/iio and try to move it into drivers/iio.

Important:

 * read IIO documentation and try to understand why the driver you picked is not yet ready to be merged into drivers/iio.
 * send an email to linux-iio mailing list with your idea for changes to be done in order to move the driver out of staging

== Coding Task 3 ==

Each driver that supports both SPI and I2C has the following structure:
 * common part
 * I2C part
 * SPI part

It seems that there is a lot of duplicate/similar code for I2C/SPI parts. Have a look at the following drivers:
 * drivers/iio/accel/mma7455_{core,spi,i2c}.c
 * drivers/iio/pressure/st_pressure{core,spi,i2c}.c
 * drivers/iio/magnetometer/hmc5843{core,spi,i2c}.c

We want to create a common framework for I2C/SPI parts and reuse it for each driver to avoid code duplication.

Important:

* before starting writing the code send an email to linux-iio list presenting your idea on how do you want
to solve this in order to get some feedback.

= Resources =

 * [[http://vger.kernel.org/vger-lists.html#linux-iio | linux-iio]] mailing list.
 * [[https://www.kernel.org/doc/html/v4.12/driver-api/iio/index.html | IIO documentation]]
 * [[https://events.static.linuxfound.org/sites/events/files/slides/lceu15_baluta.pdf | IIO presentation]] 

For questions please send questions in the format mentioned above to daniel.baluta at nxp dot com or the #linux-iio IRC channel (server irc.oftc.net).