ddcci

A small Linux I2C/DDC/CI utility that scans local monitor devices, reads monitor EDID information, and, when a Dell monitor is detected, tries to reconstruct its firmware version.

The executable currently built by this repository is named DellDevice, and the program entry point is main.c.

Feature Overview

• Scan /dev/iic* and /dev/i2c* on the system
• Read monitor EDID
• Detect whether the monitor vendor is Dell
• Extract the monitor model and serial number
• For Dell monitors, read DDC/CI control codes 0xC8, 0xC9, and 0xFD
• For Dell monitors, combine those values into a firmware version string

Project Structure

• main.c: main program containing EDID reading, Dell detection, DDC/CI communication, and firmware version parsing logic
• i2c-dev.h: locally included header for I2C ioctl definitions
• Makefile: build script
• DellDevice: prebuilt binary currently present in the repository

Build

The project has very few dependencies and can be built directly with gcc.

make

Generated binary:

./DellDevice

Clean build artifacts:

make clean

Runtime Environment

It is recommended to run this on Linux with the following conditions met:

• The system exposes accessible /dev/i2c-* or /dev/iic* device nodes
• The current user has read and write permission for the corresponding I2C devices
• The monitor and GPU connection support DDC/CI
• To read firmware versions, the target monitor must be a Dell display whose DDC/CI responses match the assumptions in the current implementation

If permission is denied, you usually need to run it as root or adjust device access permissions first.

Usage

Run the program directly:

./DellDevice

The program automatically enumerates I2C devices on the system and tries to read monitor information from each one.

For non-Dell monitors, it only reads and prints the model and serial number from EDID, and shows the firmware version as N/A.

Example successful output:

/dev/i2c-3: Model = P2424HEB, Serial = XXXXXXXX, Firmware Version = M3T102

Example output for a non-Dell monitor:

/dev/i2c-4: Model = VG27A, Serial = XXXXXXXX, Firmware Version = N/A

On failure, the program prints an error message for the corresponding device, for example:

Failed to get monitor info from /dev/i2c-3

Implementation Notes

The core flow of the program is:

1. Enumerate /dev/iic* and /dev/i2c*
2. Read EDID from address 0x50 for each device
3. Parse the vendor ID, model, and serial number from EDID
4. Check whether the vendor ID is DEL
5. If it is Dell, send a presence check to DDC/CI address 0x37
6. For Dell devices, continue reading control codes:
   • 0xC8
   • 0xC9
   • 0xFD
7. Map those values into a firmware version string; non-Dell devices keep EDID-only information

The model is taken from the EDID 0xFC descriptor, and the serial number is taken from the 0xFF descriptor.

Known Limitations

• Non-Dell monitors only use EDID parsing and do not attempt to read firmware versions through DDC/CI
• Device scanning depends on ls /dev/iic* /dev/i2c* 2>/dev/null
• The Makefile uses a minimal gcc -o DellDevice main.c build and does not explicitly add extra compiler flags
• The firmware version parsing logic is hard-coded for specific Dell model behavior and may not work for all models
• The program prints a large amount of debug output, including full EDID dumps and control code read traces
• There are currently no command-line options, unit tests, or installation scripts

Possible Improvements

• Add command-line options to target a single I2C device
• Add a quiet mode or structured output mode such as JSON
• Improve device enumeration to avoid depending on shell commands
• Separate debug logs from normal output
• Add firmware version parsing rules for more models
• Add error codes and more reliable retry logic

License Notes

The header comment in i2c-dev.h says it comes from Linux I2C-related code and includes GPL license text. If you plan to distribute this repository or use it in a formal project, you should verify the overall license boundaries and compatibility more carefully.