Kernel fixup for Cotsworks SFF modules with invalid EEPROM identity bytes and a bad base checksum

Question

Some Cotsworks SFF fibre modules ship with invalid data in the first EEPROM bytes (physical ID, extended physical ID, connector type) and with checksums programmed before the fields were finalised, so the Linux phy/sfp driveer does not detect them as valid modules. A kernel fixup rewrites the three bad bytes with the correct values, inserting a 50 ms delay between writes as these modules require, and recalculates the base-structure checksum.

Hardware: Linux host with sfp cage
Transceivers: Cotsworks SFF modules
Form factor: SFP

Symptoms / messages:

invalid identity bytes
module not detected as valid
bad base checksum

netadmin · Accepted Answer

The fixup matches specific Cotsworks part numbers, rewrites the corrupted bytes with a 50 ms inter-write delay and updates the base checksum; the extended checksum is intentionally left, so its warning may persist.

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