Xen event channel interface for Mirage.
Event channels are the Xen equivalent of interrupts, used to signal when data (or space) is available for processing. There are 2 distinct implementations:
a Xen shared-memory + hypercall protocol for kernelspace
a binding to a set of libxc functions which access /dev/xen/evtchn for userspace
The mirage-platform/xen tree contains a custom set of C stubs which implements the simple parts of the protocol (eg mask, unmask, notify). These stubs are referenced from the Eventchn module. The choice of stubs (userspace or kernelspace) is performed at binary link-time by the 'mirage' command-line tool (or manually), avoiding the need for another functor for these cases.
The more 'Activations' signature which has blocking functions is implemented in OCaml in both the mirage-platform/xen tree (Activations) and here (Unix_activations). Libraries must be functorised and the functor must be instantiated in the final program.