openprot-pldm-service

Platform-independent PLDM-over-MCTP responder service.

Overview

This crate bridges openprot-mctp-api and pldm-interface so that firmware can receive and respond to PLDM messages transported over MCTP without depending on any particular MCTP implementation or OS.

┌──────────────────────────┐
│   Application / Firmware │  creates PldmResponder, calls run_once()
└───────────┬──────────────┘
            │
            ▼
┌──────────────────────────┐
│   openprot-pldm-service  │  dispatches to CmdInterface (this crate)
└───────────┬──────────────┘
            │ MctpListener / MctpRespChannel
            ▼
┌──────────────────────────┐
│   openprot-mctp-api      │  Stack<C: MctpClient>
└───────────┬──────────────┘
            │ IPC / transport
            ▼
┌──────────────────────────┐
│   MCTP Server            │
└──────────────────────────┘

Key types

TypeDescription
PldmResponder<'a>Holds a CmdInterface; call run_once() in a loop
PldmServiceErrorUnion of MCTP transport errors, PLDM handler errors, and overflow
PLDM_MSG_TYPEMCTP message-type constant for PLDM (0x01)

Usage

use openprot_pldm_service::PldmResponder;
use pldm-interface::control_context::ProtocolCapability;
use pldm-common::protocol::base::{PldmControlCmd, PldmSupportedType};

const CTRL_CMDS: [u8; 5] = [
    PldmControlCmd::SetTid as u8,
    PldmControlCmd::GetTid as u8,
    PldmControlCmd::GetPldmCommands as u8,
    PldmControlCmd::GetPldmVersion as u8,
    PldmControlCmd::GetPldmTypes as u8,
];

let caps = [
    ProtocolCapability::new(PldmSupportedType::Base, "1.1.0", &CTRL_CMDS).unwrap(),
];

let mut responder = PldmResponder::new(&caps);
let mut buf = [0u8; 1024];

// `stack` is a `Stack<impl MctpClient>` obtained from the platform MCTP client.
loop {
    if let Err(e) = responder.run_once(&stack, &mut buf, 0) {
        // handle or log error
    }
}

Buffer layout

run_once expects buf to be at least 2 bytes. Internally byte 0 is reserved for the MCTP message-type prefix (0x01); the PLDM payload is received into buf[1..] and the response is written back in-place:

buf[0]   : MCTP message-type byte (0x01) — managed by PldmResponder
buf[1..] : PLDM request / response bytes

Size the buffer to accommodate the largest PLDM message your application expects (typically ≤ 4096 bytes; smaller for embedded targets).

Build

bazel build //services/pldm:pldm_service

After adding pldm-common and pldm-interface to third_party/crates_io/Cargo.toml, re-pin the lock file:

CARGO_BAZEL_REPIN=1 bazel sync

Dependencies