cabletest/docs/state.md

Current state

Committed tree

AF_PACKET raw sockets everywhere (sock.go), flow-director steering, read-time-stamped rate buckets, framebuffer UI, harness. The zero-copy AF_XDP conversion (both directions, hand-rolled XSK + hand-assembled XDP program, per-frame MAC-stamp buckets via rx metadata) lives uncommitted in stash@{0}; it was built for the era when the test path ran on the E810, whose datapath delivers per-packet MAC timestamps. It is an experiment, not a requirement.

stash@{1} holds the phydiag campaign: python transport clients (i40e_aq.py, rollball_i40e.py, sff.py), scanners, and a STATUS.md campaign log. Working copies extracted to ~/work/phydiag-work/ during the module work. The knowledge from that campaign is now in these docs; the code should eventually move into the repo properly.

Hardware in flight

• Intel X520-DA2 ordered — replaces the E810 in the box's single PCIe slot. Chosen because ixgbe bit-bangs module I2C from the host (no firmware policy layer), enabling in-product module-PHY diagnostics; see transports.md.
• Replacement Wiitek (Marvell CUX3610) modules ordered. Both original units were bricked by register exploration — see modules.md for the trap before ever touching one.
• In hand (all copper RJ45 10GBASE-T modules with cloned/lying fiber EEPROMs — see hardware.md; none are actually fiber):
  • 2× FS SFP-10G-T-100 (Broadcom BCM84891L, fully documented diagnostics).
  • 1× Fibergaga SFP-10G-T-30M (Aquantia, RollBall, the proven oracle module).
  • 1× 10Gtek, EEPROM claims SFP-10G-SR — still a copper RJ45 module; filler, not part of the test set.

Bringup plan when the X520 arrives

1. ixgbe debugfs patch exposing raw I2C transactions (model: the ice sff_i2c patch in kernel/; ixgbe has no firmware to refuse, so arbitrary framing works).
2. FS/BCM modules first: prove the SMI transport against known-value registers, then the command handler (CMD_GET_SNR vs IEEE registers), on the test cable set.
3. Replacement Wiiteks: IEEE-standard registers only (SNR, latches) unless/until a documented recipe exists for more; the VCT templates in modules.md are candidates for single-shot targeted probes on a sacrificial unit only.
4. Re-derive host tuning on ixgbe (coalescing/ring syntax differs) and re-verify the rxnfc flow-steering code against ixgbe's fdir.

Open items

• ECD register chapter: the one missing document for BCM cable length. FS has been responsive; the narrow ask is "which registers invoke ECD / report the DSP cable-length estimate, and does it run with link up?"
• Pre-FEC classification on the Aquantia (3.e820): needs a marginal channel; cabletest's noise stress will provide one once diagnostics are integrated.
• X710 PTP path-delay length measurement: viable fallback for linked-cable length (PTP-latch timestamps both ports, same oscillator, 1 ft calibration cancels PHY latency); scoped but unbuilt. Superseded for the product if BCM ECD/DSP length pans out.
• E810 leaves the box when the X520 arrives; the patched ice + sff_i2c remains useful only if an E810 returns for read-side work.