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Drop goals and open-questions docs, cut PTP from the appliance kernel

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flamingcow
2026-08-28 21:59:41 -07:00
parent 2166a456a3
commit b97893407e
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docs/nics/connectx-5/README.md
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@@ -57,12 +57,12 @@ The recipe (one SMI transaction = one MCIA SET, plus one MCIA GET for reads):
- SMI write of `devad.reg=val`: MCIA SET with `device_address=devad, size=4, dword[0]=reg<<16|val`.
- Live example: `mstreg -d 01:00.1 --reg_name MCIA --set "dword[0]=0x00020000" --indexes "module=1,i2c_device_address=0x56,page_number=0,device_address=0x21,size=2" --yes` then the GET → 0x3590.
## How cabletest reaches MCIA in production (`phy_mcia.go`)
## How cabletest reaches MCIA
There are two host paths to MCIA, and the split is decisive:
- **`/dev/fwctl` (the kernel's sanctioned firmware back-channel) is read-only for MCIA.** ACCESS_REG reads work at scope `DEBUG_READ_ONLY`; **writes are silently dropped** — the RPC returns success at every layer (`errno=0`, command status 0, MCIA status 0) yet the register never changes, at every scope including `DEBUG_WRITE_FULL`. The firmware honours the ACCESS_REG opcode under fwctl's restricted user context (uid 2, caps `0x04000000`) but no-ops the actual I2C write. Proven live with full pre/post op logging. Since a RollBall register **read** requires **writes** (set page/devad/command), fwctl cannot run RollBall at all.
- **The mstflint PCICONF path (VSC vendor capability → ICMD → FLASH_REG_ACCESS) can write**, so cabletest uses it. Per-dword gateway ops through the PCI config-space vendor capability reach ICMD space; a register-access command wrapped in operation+reg TLVs carries the MCIA transaction. Reimplemented in Go (`phy_mcia.go`), no mstflint dependency at runtime.
- **The mstflint PCICONF path (VSC vendor capability → ICMD → FLASH_REG_ACCESS) can write**, so cabletest uses it. Per-dword gateway ops through the PCI config-space vendor capability reach ICMD space; a register-access command wrapped in operation+reg TLVs carries the MCIA transaction. Reimplemented in Go, no mstflint dependency at runtime.
Two things that are not optional and one that is not needed: