cabletest/docs/state.md

Current state

Where the code is right now

The committed tree is the X520 product implementation: AF_PACKET datapath with read-time rate buckets and the backward excess-fill smear (nics/x520/ — rate is a headline, never a verdict; smearWindow 4 buckets = 64 ms display latency, resize after measuring the stall distribution: open-questions), the mixed FS+Wiitek diagnostics with the BCM ECD length path, testDriver = ixgbe. No hardware-timestamp machinery anywhere. The CX-5 is retired (nics/connectx-5/, "Status") and the E810 bit-bang investigation with it (nics/e810/).

Stashes

None. Every parked experiment is distilled into docs and its code dropped: the AF_XDP conversion in xdp.md, the CX-5 Wiitek-pair implementation in nics/connectx-5/ (including the MCIA gateway constants), the phydiag campaign across nics/e810/, nics/x710/, modules/fs/ and modules/fibergaga/. Remaining phydiag working copies: ~/work/phydiag-work/ (below).

The box

• Single usable PCIe slot (Gen4 x8): holds the X520-DA2 (dual SFP+). Verify 5 GT/s ×8 trained at bringup (lspci -vv). The ConnectX-5 is out of the box.
• X710 on a CPU x4 port (Gen3 x4, ~31.5 Gbps/dir — enough for 2×10G full duplex despite the driver's worst-case bandwidth warning).
• Many CPU cores; goroutine-heavy designs welcome.
• mstflint (AUR — not in the Arch repos) provides mstlink/mstreg/mstconfig for the CX-5, if it ever returns.

Interface	Device	Role (rules: hardware.md)
enp1s0f0 + second port	X520 (ixgbe)	Test pair — FS + Wiitek, dispatched by EEPROM PN so either port may hold either module. Stock ixgbe refuses the FS's honest EEPROM and its port has no netdev until ./load-ixgbe (allow_unsupported_sfp=1 + the sff_i2c/ETQF patches); the tool needs exactly 2 ixgbe interfaces
enp3s0f0np0 / enp3s0f1np1	X710 (i40e)	Unused by the tool (was the noise pair; alien crosstalk measured ineffective — measurement.md). Two Wiiteks still seated (has been enp4s0f* across reboots). The FS cannot live here (firmware rejects the honest EEPROM, no allow_unsupported_sfp in i40e)
enp88s0	igc	LAN uplink, default route; sibling enp89s0 is dark

Hardware

Item	Status	Notes
X520-DA2	Installed in the single PCIe slot — the product NIC (nics/x520/)	Unmediated bit-bang I2C (patched-ixgbe sff_i2c), <25 ms RollBall, FS links and the ECD length path is proven; the smoothed-bucket rate design removes the need for hardware RX stamps
ConnectX-5	Out of the box — retired	Ran the two-Wiitek pair at near line rate with dual-end SNR (MCIA transport, recorded with its gateway constants in nics/connectx-5/), but the firmware quantizes every module mailbox read to ~150 ms steps and the FS never links behind mlx5 — nics/connectx-5/, "Status"
FS SFP-10G-T-100 ×2	One in the X520 test pair, one on the shelf	BCM84891L, documented, robust; ixgbe-only (unlinkable behind mlx5 — host-interface deadlock, confirmed module-typed, nics/connectx-5/ — and rejected by the X710). The FS+Wiitek mixed pair (FS length via ECD + Wiitek SNR) is the product configuration
Replacement Wiiteks	One in the X520 test pair, two seated in the unused X710, rest on the shelf	Originals bricked by register exploration — modules/wiitek/ trap first. IEEE-standard registers only (modules/README.md safe set); VCT templates are single-shot candidates on a sacrificial unit only
Fibergaga SFP-10G-T-30M	On the shelf	Aquantia, RollBall, the documented oracle; the alternate length path if the pair mix ever changes
10Gtek	In hand	Claims SFP-10G-SR, still copper RJ45; filler, not in the test set
E810	Out of the box	Patched ice + sff_i2c remains useful only if it returns for read-side work

Diagnostics artifacts outside the repo

• Patched ixgbe, bench build (~/work/ixgbe-sff/) — out-of-tree module for the dev host: the product patch plus the bench-only extras (reg_ops value readback, ts_bench); ./load-ixgbe rebuilds + swaps the module with allow_unsupported_sfp=1. The product subset (raw I2C + sff_i2c, ETQF steering, FCoE slot guard) is versioned at kernel/ixgbe-sff.patch and applied by ./mkimage to every appliance kernel build — apply fails loudly when stable moves under it; port the patch then. Details: nics/x520/.
• Bench tools and clients (~/work/phydiag-work/) — etqfbench/, x520poke/, compound_test.py, bcm_mcia_emu.py, bcm_ixgbe.py, bcm_explore.py/bcm_eee_off.py, bcm_ecd_probe.py, bcm_phaselock_bench.py, rollball_ixgbe.py, rb_forensic.py. What each proved lives in modules/fs/, modules/wiitek/ and nics/x520/.

Every boot

1. ./load-ixgbe — until then the FS port has no netdev (stock driver, error -95) and driverPair("ixgbe") cannot find 2 interfaces. cabletest's BOOT check names the condition (patched ixgbe fails when any bound port lacks sff_i2c).
2. Re-apply host tuning (hardware.md) before trusting results.