Re: [Qemu-devel] Internship idea: I2C passthrough

[Paolo Bonzini]

On 09/01/19 19:23, BALATON Zoltan wrote:
>> '''Summary:''' Implement I2C bus passthrough on Linux hosts so that
>> emulated Raspberry Pi or micro:bit boards can talk to real I2C
>> devices. 
>
> How about implementing USB for raspi boards instead? Or is there a
> project proposal (or even some code somewhere out of tree) for that
> already? Seems more useful to allow having emulated keyboard and mouse
> to use Raspbian for example or pass through USB devices. (I don't know
> anything about this was just reminded to a recent discussion by this
> message. If it's not relevant just disregard my comment and sorry for
> the noise.)

That's also a valid idea.  However, Stefan has misinterpreted the
reference to the raspi that I quickly made on IRC.  The idea of I2C
passthrough is that a single board computer like a Raspberry Pi can be
used to develop application for a microcontroller such as micro:bit,
without having to flash the firmware again and again, etc.

Real I2C devices---for example a GPIO extender, a temperature sensor or
a real-time clock---would be attached to the I2C bus on the single board
computer's GPIO headers, exposed as an I2C device through /dev/i2c, and
then driven by the emulated micro:bit through its own I2C controller (or
bitbanged).

(I've now updated the project idea).

Paolo