PLDM — Firmware & Monitoring

Platform Level Data Model (DMTF DSP0240/DSP0248/DSP0267)

PLDM handles the practical management tasks: updating firmware, reading sensors, and monitoring health.

PLDM Types

OpenPRoT has two separate PLDM implementations across its repositories:

`pldm-lib` — Standalone Library (OpenPRoT-native)

A 3-crate no_std workspace (pldm-lib / pldm-common / pldm-interface):

Type	Name	Status
Type 0	Base	Implemented — SetTid, GetTid, GetPldmVersion, GetPldmTypes, GetPldmCommands
Type 2	Platform Monitoring	Defined in enum only — not implemented
Type 5	Firmware Update	Implemented — Full state machine (v1.3.0, DSP0267)

`mctp-rs/pldm-fw` — Code Construct Implementation

Part of the mctp-rs workspace, provides both sides of the firmware update:

Module	Target	Role
`fd` (Firmware Device)	`no_std`	Responder state machine for embedded targets
`ua` (Update Agent)	`std`	Requester for Linux-based update tools
`pkg`	`alloc`	PLDM firmware package parser

Firmware Update State Machine

Both implementations follow the same PLDM FW Update specification state machine:

graph LR
    I["Idle"] --> LC["Learn<br/>Components"]
    LC --> RX["Ready<br/>Xfer"]
    RX --> DL["Download"]
    DL --> VR["Verify"]
    VR --> AP["Apply"]
    AP --> RX
    RX --> AC["Activate"]
    AC --> I

    style I fill:#509060,color:#fff
    style LC fill:#4a70a0,color:#fff
    style RX fill:#4a70a0,color:#fff
    style DL fill:#a09825,color:#fff
    style VR fill:#a09825,color:#fff
    style AP fill:#a09825,color:#fff
    style AC fill:#a05050,color:#fff

State transitions are enforced — each command handler validates the current state and returns appropriate completion codes (InvalidStateForCommand, AlreadyInUpdateMode, NotInUpdateMode).

Firmware Update Commands

Command	Code	Direction	Purpose
QueryDeviceIdentifiers	0x01	UA→FD	Discover device identity
GetFirmwareParameters	0x02	UA→FD	Query firmware capabilities
RequestUpdate	0x10	UA→FD	Initiate update session
PassComponentTable	0x13	UA→FD	Describe available components
UpdateComponent	0x14	UA→FD	Start component transfer
RequestFirmwareData	0x15	FD→UA	FD requests data chunks
TransferComplete	0x16	FD→UA	Transfer finished
VerifyComplete	0x17	FD→UA	Verification result
ApplyComplete	0x18	FD→UA	Apply result
ActivateFirmware	0x1A	UA→FD	Activate new firmware
GetStatus	0x1B	UA→FD	Query update status
CancelUpdate	0x1D	UA→FD	Abort update

CLI Tool

The pldm-fw-cli tool (from mctp-rs) provides a command-line interface for firmware management over Linux MCTP sockets:

# Query device firmware inventory
pldm-fw inventory <net>,<eid>

# Update firmware from a package file
pldm-fw update <net>,<eid> firmware-package.bin

# Inspect package contents
pldm-fw pkg-info firmware-package.bin

# Extract component images
pldm-fw extract firmware-package.bin 0 1

Code Patterns

Zero-copy serialization — #[repr(C, packed)] structs with zerocopy derives get automatic codec implementation
In-place message processing — Responses encoded into the same buffer as the decoded request
Pluggable device operations — FdOps struct provides hardware callbacks (verify, apply, activate)
No heap allocation — All data structures use fixed-size arrays with compile-time constants

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