RPMsg inter-partition messaging
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# rpmsg
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OCaml bindings to the Linux RPMsg character device interface for inter-partition messaging.
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RPMsg (Remote Processor Messaging) provides message-based IPC between
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partitions on asymmetric multiprocessing platforms. This library wraps the
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`/dev/rpmsg_ctrl*` and `/dev/rpmsg*` character devices, encoding the
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`rpmsg_endpoint_info` struct via Wire codecs instead of manual C struct packing.
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It is used for communication between SpaceOS (Linux) and co-processor
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partitions via virtio vrings on Jailhouse, Xen, and Zynq UltraScale+
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platforms.
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Endpoint IO is built on Eio flows, so it integrates directly with the Eio
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event loop.
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## Installation
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```
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opam install rpmsg
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```
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## Usage
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```ocaml
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(* Create an endpoint and exchange messages *)
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let () =
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let ctrl = Rpmsg.Ctrl.open_ () in
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let idx = Rpmsg.Ctrl.create_endpoint ctrl ~name:"my-ep" ~src:1024 ~dst:1025 in
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let fd = Rpmsg.Endpoint.open_ idx in
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(* wrap the fd with Eio flows, then: *)
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(* let ep = Rpmsg.Endpoint.of_source_sink ~source ~sink in *)
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(* Rpmsg.Endpoint.send ep "hello"; *)
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Unix.close fd;
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Rpmsg.Ctrl.close ctrl
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```
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## API
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- `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.
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- `Rpmsg.endpoint_info_codec` -- Wire codec for serializing and deserializing the endpoint info struct (40 bytes).
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- `Rpmsg.Ctrl` -- Control device handle (`/dev/rpmsg_ctrl*`). Create and destroy RPMsg endpoints via ioctl.
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- `Rpmsg.Endpoint` -- Message endpoint backed by Eio flows. Send and receive messages up to 496 bytes (512 minus the 16-byte virtio header).
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## References
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- [Linux RPMsg documentation](https://docs.kernel.org/staging/rpmsg.html)
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- [Jailhouse hypervisor](https://github.com/siemens/jailhouse)
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- [Xilinx OpenAMP / RPMsg on Zynq UltraScale+](https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/18842073/OpenAMP)