Greybus is the name for a new application layer protocol on top of Unipro that controls the Ara Phone from Google. This protocol turns a phone into a modular device, allowing any part of the system to be hotplugged while the phone is running.
This talk will describe what this protocol is, why it was designed, and give the basics for how it works. It will discuss how this is implemented in the Linux kernel, and how it easily bridges existing hardware like USB, I2C, GPIO and others with little to no changes needed to existing kernel drivers.
Greg KH, Linux Foundation