gazagnaire.org
RPMsg inter-partition messaging
1# rpmsg
2
3OCaml bindings to the Linux RPMsg character device interface for inter-partition messaging.
4
5RPMsg (Remote Processor Messaging) provides message-based IPC between
6partitions on asymmetric multiprocessing platforms. This library wraps the
7`/dev/rpmsg_ctrl*` and `/dev/rpmsg*` character devices, encoding the
8`rpmsg_endpoint_info` struct via Wire codecs instead of manual C struct packing.
9It is used for communication between the Linux host and co-processor partitions
10via virtio vrings on Jailhouse, Xen, and Zynq UltraScale+ platforms.
11
12Endpoint IO is built on Eio flows, so it integrates directly with the Eio
13event loop.
14
15## Installation
16
17```
18opam install rpmsg
19```
20
21## Usage
22
23```ocaml
24(* Create an endpoint and exchange messages *)
25let () =
26 let ctrl = Rpmsg.Ctrl.open_ () in
27 let idx = Rpmsg.Ctrl.create_endpoint ctrl ~name:"my-ep" ~src:1024 ~dst:1025 in
28 let fd = Rpmsg.Endpoint.open_ idx in
29 (* wrap the fd with Eio flows, then: *)
30 (* let ep = Rpmsg.Endpoint.of_source_sink ~source ~sink in *)
31 (* Rpmsg.Endpoint.send ep "hello"; *)
32 Unix.close fd;
33 Rpmsg.Ctrl.close ctrl
34```
35
36## API
37
38- `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.
39- `Rpmsg.endpoint_info_codec` -- Wire codec for serializing and deserializing the endpoint info struct (40 bytes).
40- `Rpmsg.Ctrl` -- Control device handle (`/dev/rpmsg_ctrl*`). Create and destroy RPMsg endpoints via ioctl.
41- `Rpmsg.Endpoint` -- Message endpoint backed by Eio flows. Send and receive messages up to 496 bytes (512 minus the 16-byte virtio header).
42
43## References
44
45- [Linux RPMsg documentation](https://docs.kernel.org/staging/rpmsg.html)
46- [Jailhouse hypervisor](https://github.com/siemens/jailhouse)
47- [Xilinx OpenAMP / RPMsg on Zynq UltraScale+](https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/18842073/OpenAMP)