Google Summer of Code 2024: IIO Driver

Main GSoC Linux Foundation page: How to apply, deadlines, other workgroups, ...

The main purpose of the Industrial I/O subsystem (IIO) is to provide support for devices that in some sense perform either analog-to-digital conversion (ADC) or digital-to-analog conversion (DAC) or both. The aim is to fill the gap between the somewhat similar hwmon and input subsystems. Hwmon is directed at low sample rate sensors used to monitor and control the system itself, like fan speed control or temperature measurement. Input is, as its name suggests, focused on human interaction input devices (keyboard, mouse, touchscreen). In some cases there is considerable overlap between these and IIO.

Devices that fall into this category include: analog to digital converters (ADCs), accelerometers, capacitance to digital converters (CDCs), digital to analog converters (DACs), gyroscopes, inertial measurement units (IMUs), color and light sensors, magnetometers, pressure sensors, proximity sensors, temperature sensors, etc.

Usually these sensors are connected via SPI or I2C. A common use case of the sensors devices is to have combined functionality (e.g. light plus proximity sensor).

• ADI's Linux Industrial I/O Subsystem wiki page
• 10 Years of the Industrial I/O Kernel Subsystem
• Using Raspberry Pi With Connected Analog as Lab Instrumentation
• LibIIO - A Library for Interfacing with Linux IIO Devices
• Software Defined Radio - Sdr

Project Size: 1 contributor medium (175 hours), Level of difficulty: Intermediate

Desired knowledge: C, Bash, operating systems elementary concepts

The driver should be tested on the real hardware. The proposed setup is Raspberry Pi 3 Model B and EVAL-AD7294-2 evaluation board.

The goal of the project is to provide support for AD7294-2 chips within Linux which will require writing device tree documentation for AD7294-2 part and developing an IIO device driver. The desired final project state is to have AD7294-2 driver and associated device tree documentation merged with upstream IIO tree.

We are also open for suggestions for different ADI's component. If there won’t be suggestions, or they don’t make sense, we will choose one component for the accepted student.

Code repository: https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/

Code License: GPLv2

• Start with a section telling a bit about you with basic info such as name, summary of skills, email address, etc.
• Then provide a short bio and coding skills subsections.
• Next, add a section about your motivations for participating in the IIO driver GSoC project. This is a good opportunity to tell your experiences with the IIO subsystem if you have been involved with it before.
• If you made any contribution to the Linux kernel or any other open source project, you might list them in a section too.
• If you are very excited about participating GSoC and want to do more than the Linux driver you may add more sections describing additional ideas or plans.
• Finally, add a section about the project and the planned work schedule. Previous IIO driver GSoC project proposals have presented work schedules divided into weeks. For easy visualization of deadlines, we kindly ask participants to also display GSoC evaluation dates in their work schedules.
• Feel free to share your draft before submitting the final version.

• drivers/iio/accel/adxl355*
• drivers/iio/accel/adxl313*
• drivers/iio/adc/ad7292.c

Question: Will I have to buy the hardware (Raspberry Pi, evaluation board) for this project?

Answer: No, the hardware will be provided by Analog Devices. You don’t have to worry about this aspect.

Question: Are there any prerequisites for this project?

Answer: No, there are no hard prerequisites for participating in this project. However, it is expected that applicants be familiar with the C programming language, know how to use Linux shell command line interfaces, and understand elementary concepts of operating systems such as files, processes, and system call interface. Previous experience with Linux kernel development is not required although it is a plus for applicants who have it.

Question: I don`t know much about IIO. Where can I learn more about IIO? How can I get started with Linux kernel development for the IIO subsystem?

Answer: Aside from the presentations about IIO, you can follow the ADI instructions on the Building for Raspberry PI page or the official Raspberry Pi ones (using ADI repository and defconfig file).

The Linux Foundation offers a free introductory course for kernel development: A Beginner’s Guide to Linux Kernel Development (LFD103)

The Kernel Newbies website contains extensive material about Linux kernel development, including an IIO task page.

One can also find many kernel development tutorials on the Internet. For IIO development, I suggest some of FLUSP's tutorials 1, 2, 3, 4, 5.

Question: Is there any specific Linux distribution or patch to use for Linux kernel IIO development?

Answer: No, there is no specific distro or kernel version required for IIO development. Any distro should work. However, for testing on Raspberry Pi, one often uses a kernel that includes patches for the Raspberry Pi platform (such as the ADI kernel or the Raspberry Pi kernel). Kernels that don`t include those patches might not run on a Raspberry Pi board although may be used for testing in emulated environments.

Question: Is previous contributing to the Linux kernel a requirement for accepting a candidate?

Answer: No, although having a history of contribution often provides more visibility to a candidate.

Mailing list: https://lore.kernel.org/linux-iio/, http://vger.kernel.org/vger-lists.html#linux-iio

IRC: #linux-iio on OFTC

Mentors:

• Ciprian Hegbeli (ciprian dot hegbeli at analog.com)
• Marcelo Schmitt (marcelo dot schmitt at analog.com)
• Dragos Bogdan (dragos dot bogdan at analog.com)

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