Mika Westerberg
authored
When two hosts are connected over a Thunderbolt cable, there is a protocol they can use to communicate capabilities supported by the host. The discovery protocol uses automatically configured control channel (ring 0) and is build on top of request/response transactions using special XDomain primitives provided by the Thunderbolt base protocol. The capabilities consists of a root directory block of basic properties used for identification of the host, and then there can be zero or more directories each describing a Thunderbolt service and its capabilities. Once both sides have discovered what is supported the two hosts can setup high-speed DMA paths and transfer data to the other side using whatever protocol was agreed based on the properties. The software protocol used to communicate which DMA paths to enable is service specific. This patch adds support for the XDomain discovery protocol to the Thunderbolt bus. We model each remote host connection...