Hi Guys,

There are offline discussions going on to assess the possibility of re-using the Linux kernel Greybus framework for Virtio [1] use case, where we can control some of the controllers on the back-end (Host), like SPI, I2C, GPIO, etc, from front-end (VM), using the already well defined Greybus specification [2].

The Greybus specification and kernel source was initially developed for Google's Project ARA [3], and the source code was merged into mainline kernel long time back (in drivers/greybus/ and drivers/staging/greybus/). You can find more information about how Greybus works in this LWN article [4].

Greybus broadly provides two distinct features:

- Device discovery: at runtime, with the help of a manifest file (think of it like DT, though it has a different format). This helps the user of the hardware to identify the capabilities of the remote hardware, which it can use.

- Remote control/operation: of the IPs present on the remote hardware, using firmware/OS independent operations, these are already well defined for a lot of device types and can be extended if required.

We wanted to share this over email to get some discussion going, so it can be discussed later on the call.

Alex Elder (Cc'd) is one of the Maintainers of the Greybus core in Linux Kernel and I worked on a wide variety of stuff and maintain some of it. Both of us worked in project ARA and would like to see Greybus being used in other applications and would like to contribute towards it.