gazagnaire.org / ocaml-rpmsg
RPMsg inter-partition messaging
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README.md

rpmsg#

OCaml bindings to the Linux RPMsg character device interface for inter-partition messaging.

RPMsg (Remote Processor Messaging) provides message-based IPC between partitions on asymmetric multiprocessing platforms. This library wraps the /dev/rpmsg_ctrl* and /dev/rpmsg* character devices, encoding the rpmsg_endpoint_info struct via Wire codecs instead of manual C struct packing. It is used for communication between the Linux host and co-processor partitions via virtio vrings on Jailhouse, Xen, and Zynq UltraScale+ platforms.

Endpoint IO is built on Eio flows, so it integrates directly with the Eio event loop.

Installation#

opam install rpmsg

Usage#

(* Create an endpoint and exchange messages *)
let () =
  let ctrl = Rpmsg.Ctrl.open_ () in
  let idx = Rpmsg.Ctrl.create_endpoint ctrl ~name:"my-ep" ~src:1024 ~dst:1025 in
  let fd = Rpmsg.Endpoint.open_ idx in
  (* wrap the fd with Eio flows, then: *)
  (* let ep = Rpmsg.Endpoint.of_source_sink ~source ~sink in *)
  (* Rpmsg.Endpoint.send ep "hello"; *)
  Unix.close fd;
  Rpmsg.Ctrl.close ctrl

API#

  • Rpmsg.endpoint_info -- The rpmsg_endpoint_info record type matching the Linux kernel struct: a 32-byte name, 32-bit source address, and 32-bit destination address.
  • Rpmsg.endpoint_info_codec -- Wire codec for serializing and deserializing the endpoint info struct (40 bytes).
  • Rpmsg.Ctrl -- Control device handle (/dev/rpmsg_ctrl*). Create and destroy RPMsg endpoints via ioctl.
  • Rpmsg.Endpoint -- Message endpoint backed by Eio flows. Send and receive messages up to 496 bytes (512 minus the 16-byte virtio header).

References#