spdr

A read-only, zero-copy DDR5 SPD content decoder plus a semantic linter that validates beyond the CRC. Input is a raw 1024-byte SPD image; output is a fully typed decode and a structured lint report. The crate never writes SPD, never touches hardware, and performs no network I/O. Because JESD400-5 is paywalled, the decoder doubles as an open reference: every field decoder is explicit and documented rather than table-driven.

This is the library crate. The spdr command-line tool lives in the companion spdr-cli crate.

Install

cargo add spdr

spdr is #![no_std] and allocation-free by default, so it stays embeddable in firmware and UEFI contexts. It is #![forbid(unsafe_code)], and every slice access is bounds-checked, so malformed input returns an Err rather than panicking.

An optional serde feature derives Serialize (only) on the public decoded types for JSON output; it is off by default, so the default build stays no_std and serde-free:

cargo add spdr --features serde

What it decodes

• The JESD400-5 base content: identity and base configuration, the base configuration CRC (reported, never a gate on decoding), the base JEDEC timings, the unbuffered (UDIMM) module-specific block, and the manufacturing block.
• The vendor overclocking profiles, Intel XMP 3.0 and AMD EXPO, each anchored by its own section CRC so an unconfirmed region is never presented as authoritative.

The linter (the lint function and the Finding / Severity types) goes past the CRC: the CRC only proves the bytes survived transit, while the linter reports values that are internally inconsistent even in a CRC-valid SPD. It covers four rule families: capacity math, JEDEC timing relationships and speed-bin recognition, reference-declared reserved bits, and cross-field consistency.

Scope

Unbuffered (UDIMM) is complete. SODIMM, RDIMM, and LRDIMM module-specific decoding is deferred and gated on real fixtures of each type; those types resolve to an explicit not-yet-decoded result rather than a guess. Full JEDEC sub-grade-table conformance and the tFAW >= 4 x tRRD_S ordering are likewise deferred. The no-panic contract is property-tested (a cargo-fuzz harness is committed but not yet deep-run, so this is "property-tested," not "fuzzed"). The decoder is confirmed correct against one real module so far, a TEAMGROUP T-Create Expert 6000 (UD5-6000); see docs/validated-against.md in the repository.

License

Apache-2.0.