TLV Writer Documentation

Dependencies

To ensure all required dependencies are installed, run:

sudo apt update
sudo apt install python3 python3-smbus

this will:

Install Python 3 if it is not already installed.
Install smbus for I2C communication.

Usage

python3 TLV_write.py <i2c_bus> <eeprom_address> [--yes] [-b] <key> <value> <key> <value> ...

Arguments

Argument	Description
i2c_bus	The I2C bus number.
eeprom_address	The EEPROM address (hex or decimal).
--yes -y --force	Automatically confirms the operation (skips user confirmation).
-b	Writes the TLV data to a binary file (`/tmp/eeprom_tlv.bin`) without writing to the EEPROM. You can later write it manually using `dd`.
<key> <value>	One or more key-value pairs to write to EEPROM.

Example Usage

For example if we want the following data to appear in DMI:

Handle 0xXXXX, DMI type 1, XX bytes
System Information
	Manufacturer: XXXXX
	Product Name: MySystem
	Version: 1.0
	Serial Number: XXXXXX
	UUID: XXXXXX-XXXXX-XXXXX-XXXXX-XXXXX
	Wake-up Type: XXXXXXXXXXXX
	SKU Number: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
	Family: XXXXXXXXXXXXXXXXXXXXXXX

We want to run the following command (Note that bus 3 address 0X50 is used in this example):

python3 TLVwriter.py 3 0x50 TLV_CODE_SYS_NAME "MySystem" TLV_CODE_SYS_VERSION "1.0"

eeprom example for this :

python3 TLVwriter.py 3 0x50 TLV_CODE_SYS_NAME "EmbeddedDevice" \
      TLV_CODE_SYS_SKU "ED-2024" \
      TLV_CODE_SYS_SERIAL_NUMBER "SN123456789" \
      TLV_CODE_SYS_VERSION "01.02" \
      TLV_CODE_FAMILY "Industrial" \
      TLV_CODE_MANUF_NAME "Solid-Run" \
      TLV_CODE_MANUF_DATE "2024-03-11" \
      TLV_CODE_PLATFORM_NAME "Bedrock-IPC"

00: 54 6c 76 49 6e 66 6f 00 01 65 00 30 0e 45 6d 62 TlvInfo.?e.0?Emb
10: 65 64 64 65 64 44 65 76 69 63 65 31 07 45 44 2d eddedDevice1?ED-
20: 32 30 32 34 32 0b 53 4e 31 32 33 34 35 36 37 38 20242?SN12345678
30: 39 33 05 30 31 2E 30 32 20 0a 49 6e 64 75 73 74 93?01.02 ?Indust
40: 72 69 61 6c 25 09 73 6f 6c 69 64 2d 72 75 6e 23 rial%.solid-run#
50: 0a 32 30 32 34 2d 30 33 2d 31 31 24 0b 42 65 64 .2024-03-11$.Bed
60: 72 6f 63 6b 2d 49 50 43 fe 04 6e 7e c0 fd 00 00 rock-IPC??n~??
70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
80: ……

header

version

Total Payload Length (little endian)

Type

Length

Value

crc checksum TLV

Finding the I2C Bus Number

To determine the correct I2C bus number, run the following command:

sudo i2cdetect -y 1

If no EEPROM device is found, repeat the command with different bus numbers (e.g., 2, 3, 4, etc.) until you detect an address 0x50 or 0x56. Once found, use the corresponding bus number in the script.

Example:

sudo i2cdetect -y 2

If the output shows:

     0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

Then bus 2 and address 0x50 should be used in the script.

Supported TLV Keys

Each TLV Key has a Hex Code, Max Length, and belongs to a DMIDecode Type.

System Information (SMBUS Type 1)

TLV Key	Max Length (bytes)	BIOS path
TLV_CODE_FAMILY	20	-
TLV_CODE_MANUF_DATE	10	-
TLV_CODE_PLATFORM_NAME	20	-
TLV_CODE_MANUF_NAME	20	-
TLV_CODE_VENDOR_NAME	20	-
TLV_CODE_SYS_NAME	20	Main → Detailed Configuration Information → Model
TLV_CODE_SYS_SKU	20	Main screen
TLV_CODE_SYS_SERIAL_NUMBER	24	Main screen
TLV_CODE_SYS_VERSION	5	-

NIO Information (SMBUS Type 2)

TLV Key	Max Length (bytes)
TLV_CODE_NIO_NAME	20
TLV_CODE_NIO_SERIAL_NUMBER	24
TLV_CODE_NIO_VERSION	5

Chassis Information (SMBUS Type 3)

TLV Key	Max Length (bytes)
TLV_CODE_CHS_SERIAL_NUMBER	24
TLV_CODE_CHS_VERSION	5

TLV Key	Max Length (bytes)	BIOS path
TLV_CODE_CONFIG_CODE	200	Main → Detailed Configuration Information → Configuration String

Error Handling

If invalid input is provided, the script will:

Print an error message.
Exit without modifying EEPROM contents.

Possible Errors

Error Message	Cause
`Error: Unknown key`	Provided TLV key is not in the supported list.
`Error: Value for key 'X' is too long`	Input exceeds the maximum allowed length.
`Error: MAC address must have 6 parts`	Incorrect MAC format.
`Error: I2C write error`	I2C communication issue during EEPROM write.
`Error: Total TLV data length exceeds EEPROM capacity`	Data is too large for EEPROM storage.

Table of Contents

where to get

Overview