Add SMBus PEC byte to ec-test-lib serial transport

[dymk]

Summary

Adds SMBus PEC (Packet Error Code) byte computation on TX and verification on RX to ec-test-lib's serial transport, bringing it in line with the SMBus spec.

Motivation

embedded-services PR OpenDevicePartnership/embedded-services#852 makes uart-service's SmbusEspiMedium strictly spec-compliant: it now emits a PEC byte on every TX frame and requires one on every RX frame. Without a matching host-side change, ec-test-cli --source serial against any post-#852 uart-service consumer hangs — the EC waits for a PEC byte the host never sends, and the host waits for a PEC byte the EC includes but the host doesn't expect.

Changes

• ec/test-lib/Cargo.toml: add smbus-pec = "1.0.1" direct dependency
• ec/test-lib/src/serial.rs:
  • TX: append smbus_pec::pec() byte after the existing frame write
  • RX: read one extra byte after each response packet + verify against smbus_pec::pec() over the received frame; return Error::Protocol on mismatch

Validation

Test procedure

The goal was to validate that ec-test-cli --source serial works correctly against a dev-qemu EC firmware built with the post-#852 embedded-services (which emits and requires PEC bytes).

Environment: odp-platform-qemu-sbsa devcontainer (provides qemu-system-riscv32 v10.0.0).

Step 1 — Build dev-qemu with post-#852 embedded-services:

In odp-embedded-controller, temporarily patched platform/dev-qemu/Cargo.toml to:

• Pin uart-service to the dymk/phase-34-uart-service-generic branch of dymk/embedded-services (which contains PR #852's changes: generic Service<R, M>, spec-compliant SmbusEspiMedium with PEC emit/verify, frame_complete() requiring PEC byte)
• Add a [patch] section redirecting all embedded-services crates to the same fork branch (required for trait coherence since platform-common also depends on embedded-services)
• Locally swapped the medium from MctpSerialMedium (Phase 35's DSP0253 choice) to Service::default_smbusespi(relay) so the EC speaks the SmbusEspi wire format that ec-test-cli uses

Built inside the devcontainer:

cd platform/dev-qemu
cargo build --release --locked --config 'env.DEFMT_LOG="off"'

Step 2 — Build ec-test-cli with this PR's PEC changes:

In odp-platform-common/ec, applied this PR's changes to test-lib/Cargo.toml and test-lib/src/serial.rs, plus a temporary [patch] block in ec/Cargo.toml redirecting embedded-services to the same dymk fork branch (so the SerializableMessage trait + message types match between ec-test-cli and dev-qemu):

cd ec
cargo build --release -p ec-test-cli

The [patch] block is test-only — it is NOT part of this PR. In production, ec-test-cli's message struct shapes come from the upstream v0.2.0 branch which is wire-compatible.

Step 3 — Run the integration test:

Copied the built ec-test-cli binary into the devcontainer's PATH, then ran odp-embedded-controller's existing scripts/integration-test.sh (added by OpenDevicePartnership/odp-embedded-controller#14). This script:

1. Builds dev-qemu with cargo run-headless (QEMU with -serial pty)
2. Polls QEMU output for the allocated /dev/pts/N path
3. Runs 18 sequential ec-test-cli --port /dev/pts/N <service> <command> invocations

dev-qemu serial port: /dev/pts/2
Running thermal tests...
thermal get-temperature       → 19.950000000000045
thermal get-rpm               → 0.0
thermal get-min-rpm           → 0.0
thermal get-max-rpm           → 6000.0
thermal get-threshold on      → 24.950000000000045
thermal get-threshold ramping → 29.950000000000045
thermal get-threshold max     → 34.950000000000045
thermal set-rpm 1000
Running battery tests...
battery get-bst → BstReturn { battery_state: 2, battery_present_rate: 500, ... }
battery get-bix → BixFixedStrings { revision: 1, power_unit: 1, ... }
battery set-btp 50
Running RTC tests...
rtc get-capabilities          → TimeAlarmDeviceCapabilities { ... }
rtc get-real-time             → AcpiTimestamp { ... 1970-01-01 00:00:13 ... }
rtc get-wake-status ac        → TimerStatus { ... }
rtc get-wake-status dc        → TimerStatus { ... }
rtc get-expired-timer-wake-policy ac → AlarmExpiredWakePolicy(4294967295)
rtc get-expired-timer-wake-policy dc → AlarmExpiredWakePolicy(4294967295)
rtc get-timer-value ac        → AlarmTimerSeconds(4294967295)
rtc get-timer-value dc        → AlarmTimerSeconds(0)
SUCCESS: Integration test passed!

All 18 commands returned valid, non-error responses.

Step 4 — Verified the FAILURE case without this PR's changes:

Also ran the same test with an UNPATCHED ec-test-cli (no PEC changes) against the same post-#852 dev-qemu. Result: immediate timeout on the first command (thermal get-temperature), confirming the PEC mismatch is the root cause:

thermal get-temperature
Error: Io("Custom { kind: TimedOut, error: \"Operation timed out\" }")

Step 5 — Cleanup:

All temporary patches ([patch] blocks, medium swap in dev-qemu/src/main.rs, ec-test-cli binary in devcontainer) were reverted. Both repos' working trees verified clean.

Coordination note

This PR and embedded-services#852 must land in tight sequence. After #852 merges and odp-embedded-controller bumps its embedded-services pin past it, EC_TEST_CLI_REV in .github/workflows/check.yml must be bumped past this commit at the same time — otherwise the integration-test: CI job will fail.

Follow-up

A structural refactor to use mctp-rs directly in ec-test-lib::serial (eliminating the remaining hand-rolled MCTP framing) is planned as a separate followup PR.

[Copilot]

Pull request overview

This PR updates ec-test-lib’s serial transport to be SMBus-spec compliant by adding Packet Error Code (PEC) handling on both transmit (append) and receive (verify), aligning host behavior with updated uart-service expectations.

Changes:

• Add the smbus-pec crate as a direct dependency for PEC calculation.
• Append a computed PEC byte after each transmitted SMBus-framed request.
• Read and validate the trailing PEC byte on each received response packet, returning a protocol error on mismatch.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
ec/test-lib/src/serial.rs	Compute and append PEC on TX; read and verify PEC on RX for each packet.
ec/test-lib/Cargo.toml	Add smbus-pec = "1.0.1" dependency used by the serial transport.
ec/Cargo.lock	Lockfile update to include smbus-pec in the resolved dependency graph.

[kurtjd]

Looks good, thanks!

So should we wait for OpenDevicePartnership/embedded-services#852 to be merged, then odp-embedded-controller-updated, before we merge this?