#### Plugin: Mediatek Display Controller

## Introduction

This plugin updates the firmware of DisplayPort device made by Mediatek.

These devices communicate over I²C, via the DisplayPort aux channel. Devices are declared by kernel graphic driver, and queried with custom DDC/CI command to ensure the target devie.

This plugin polls every drm dp aux device to find out the `i2c-dev` that is being used for DDC/CI communication. Devices should respond to a vendor specific command otherwise the display controller is ignored as unsupported.

## Firmware Format

The daemon will decompress the cabinet archive and extract a firmware blob in an unspecified binary file format, which is written to the partition of the device flash that is not currently running.

This plugin supports the following protocol ID:

- `com.mediatek.scaler`

## GUID Generation

Devices use instance ID and the ingredients are vary according to fwupd version.

### fwupd 1.9.6

Devices use instance ID that is composed of `Subsystem ID`, `Subsystem Model`, and the `Hardware Version`. The hardware version is read from the device.

- `DISPLAY\VID_1028&PID_0C88&HWVER_2.1.2.1` (metadata)
- `DISPLAY\VID_1028&PID_0C8A&HWVER_2.1.2.1` (metadata)

### fwupd 1.9.10

The DDC/CI commands used to test the target device have been restricted to run on specific hardware only. Typically by adding a quirk file to match the system `VID` and `PID` from the `PCI` bus.

- `DISPLAY\VID_1028&PID_0C88&HWVER_2.1.2.1` (metadata)
- `DISPLAY\VID_1028&PID_0C8A&HWVER_2.1.2.1` (metadata)
- `PCI\VID_1028&PID_0C88` (only-quirks)
- `PCI\VID_1028&PID_0C8A` (only-quirks)

### fwupd 2.0.0

The enumeration of `i2c` devices has been centralized to daemon libfwupdplugin and declared as a `proxy` device for the `drm` subsystem device. The instance ID will be composed of `VEN`, `DEV` and the `HWVER`.

The instance ID `VEN` is equivalent to the `mfg id` in device `EDID` while `DEV` is the `product code`.

- `DRM\VEN_DEL&DEV_4340&HWVER_2.1.2.1` (quirks and metadata)
- `DRM\VEN_DEL&DEV_7430&HWVER_3.1.5.1` (quirks and metadata)

Example below for the information in EDID:

    $ sudo apt install ddcutil
    $ sudo ddcutil detect
    Display 1
       I2C bus:  /dev/i2c-14
       DRM connector:           card1-DP-2
       EDID synopsis:
          Mfg id:               DEL - Dell Inc.
          Model:                OptiPlex AIO
          Product code:         17216  (0x4340)
          Serial number:
          Binary serial number: 1145581640 (0x44483048)
          Manufacture year:     2023,  Week: 30
       VCP version:         2.1

## Update Behavior

The firmware is deployed when the device is in normal runtime mode, and the device will reset when the new firmware has been written. On some hardware the DRM device may not enumerate if there is no monitor actually plugged in.

## Vendor ID security

The vendor ID is set from the PCI vendor, for instance `PCI:0x1028` on Dell systems.

## Quirk Use

This plugin uses the following plugin-specific quirks:

### `bank2-only`

Install firmware to bank 2 only.

Since: 2.0.0

## External Interface Access

This plugin requires access to i2c buses associated with the specified DisplayPort aux channel, for instance `/dev/i2c-5` and `/dev/drm_dp_aux3`. Note that the device number changes in various situations.

## Version Considerations

This plugin has been available since fwupd version `1.9.6`.