Internships/ProjectIdeas/I2CPassthrough

I2C Passthrough

Summary: Implement I2C device passthrough on Linux hosts so that a single board computer like a Raspberry Pi can be used to develop applications for microcontrollers like the micro:bit.

QEMU emulates I2C devices in software but currently cannot pass through real I2C devices from the host to the guest. It would be useful to access real I2C devices from inside the guest, for example for developers writing and testing software under QEMU on their computer.

The project consists of the following tasks:

• Write tests for one or more I2C emulated controllers using the qtest framework
• Implement -device i2c-passthrough,device=/dev/i2c-N (another possibility is to implement Linux I2C device support as a character device, like -chardev linux-i2c,device=/dev/i2c-N,id=i2c-chardev -device i2c-passthrough,chardev=i2c-chardev; this enables testing even without actual I2C devices available)
• Add clock stretching support to i2c-passthrough support, and implement it in at least one emulated controller
• Implement micro:bit TWI controller emulation on the nRF51 system-on-chip

This project will allow you to learn about the I2C bus and how to write device emulation code in QEMU. You will enjoy it if you like working with physical hardware.

Links:

• I2C wikipedia page
• Overview of Linux I2C programming interfaces
• Linux I2C userspace interface documentation

Details:

• Skill level: advanced (the project is not very difficult, but it is larger than usual)
• Language: C
• Mentor: Paolo Bonzini <pbonzini@redhat.com> ("bonzini" on IRC), Stefan Hajnoczi <stefanha@redhat.com> ("stefanha" on IRC)