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

Indices shift as stashes are pushed/popped — match by message, not number.

"CX-5 Wiitek: MCIA transport…" (currently stash@{0}) — the whole Wiitek-pair rewrite for the CX-5, kept as a parts bin: phy_mcia.go (VSC/ICMD MCIA transport), transport-interface phy.go (the same RollBall logic over either patched-ixgbe sff_i2c or MCIA), dual-end per-pair SNR from both modules (headline: worst pair across both ends), mlx5 ntuple steering + PHY RMON counters, test interfaces at MTU 9000 with a 9018-byte jumbo in the size mix; BCM/ECD/length dropped. Technical record: nics/connectx-5/. Carries live debug instrumentation and rbCmdPoll lowered to 2 ms from the mailbox-latency investigation — not shippable as-is, clean it before committing — plus the pre-existing uncommitted ui.go/ui_test.go edits that were entangled in the same files.
"AF_XDP both directions…" (currently stash@{1}) — AF_XDP conversion (hand-rolled XSK + XDP program, per-frame MAC-stamp buckets via rx metadata). Built for the E810-era datapath. An experiment, not a requirement.
"phydiag campaign…" (currently stash@{2}) — python transport clients (i40e_aq.py, rollball_i40e.py, sff.py), scanners, campaign log. Working copies live in ~/work/phydiag-work/; the knowledge is in these docs; the code should eventually move into the repo properly.

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)	Noise pair (has been `enp4s0f*` across reboots) — two Wiiteks, both qualified by the X710. 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 (stashed `phy_mcia.go` MCIA transport), 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 in the X710 noise pair, 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

In ~/work/, ready to fold into the repo's kernel/:

Patched ixgbe (~/work/ixgbe-sff/) — the sff_i2c raw-I2C debugfs transport, ETQF steering, reg_ops/ts_bench; ./load-ixgbe rebuilds + swaps the module with allow_unsupported_sfp=1. 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

./load-ixgbe — until then the FS port has no netdev (stock driver, error -95) and driverPair("ixgbe") cannot find 2 interfaces. Verify sff_i2c present for both ports.
Re-apply host tuning (hardware.md) before trusting results.

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