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Q(SFP) Module EEPROM Reading and Writing

This repository contains a kernel patch and a user space program to read and write arbitrary Bytes from and into the EEPROM of SFP or QSFP modules.


Kernel Patch

Kernel patches are for Linux Kernel 6.6 and 6.12 and can be found inside patches/.

The writing is done by implementing a new ethtool netlink message ETHTOOL_MSG_MODULE_EEPROM_SET. Such a message contains the following attributes:

Field Type Description
ETHTOOL_A_MODULE_EEPROM_HEADER nested request header
ETHTOOL_A_MODULE_EEPROM_OFFSET u32 offset within a page
ETHTOOL_A_MODULE_EEPROM_LENGTH u32 amount of bytes to write
ETHTOOL_A_MODULE_EEPROM_PAGE u8 page number
ETHTOOL_A_MODULE_EEPROM_I2C_ADDRESS u8 page I2C address
ETHTOOL_A_MODULE_EEPROM_BANK u8 bank number (optional)
ETHTOOL_A_MODULE_EEPROM_DATA nested array of bytes for module EEPROM write

Compiling

To compile the user space program, switch to the src/ directory and execute make. The module_eeprom binary will be located inside src/bin/.

cd src/
make

Running

The user space program can be run using the following options:

Usage: ./module_eeprom <iface> [options]

Options:
  -a, --address    EEPROM I²C address (Default: 0x50)
  -l, --length     EEPROM byte read length
  -o, --offset     EEPROM byte offset
  -p, --page       EEPROM page number
  -r, --raw        Raw mode, don't convert to hex
  -w, --write      Bytes to write to EEPROM

If -l is passed, the program will try to read from the EEPROM.
If -w is passed, the program will try to write to the EEPROM.
Both options cannot be passed together.