#### Plugin: Synaptics MST

## Introduction

This plugin supports querying and flashing Synaptics MST hubs used in Dell systems and docks.

## Firmware Format

The daemon will decompress the cabinet archive and extract a firmware blob in an unspecified binary file format.

This plugin supports the following protocol ID:

- `com.synaptics.mst`

## GUID Generation

These devices use custom GUID values, e.g.

- `MST-$(board-ID)`
- `MST-$(device_kind)-$(chip-ID)-$(board-ID)`
- `MST-$(device_kind)-$(board-ID)`
- `MST-$(device_kind)`

Please refer to the plugin source for more details about how the GUID is constructed for specific hardware.

## 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 MST 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 example set to `DRM_DP_AUX_DEV:0x$(vid)`

## Quirk Use

This plugin uses the following plugin-specific quirks:

### Flags:manual-restart-required

The device must be restarted manually after the update has completed.

### Flags:ignore-board-id

Ignore board ID firmware mismatch.

## Requirements

### (Kernel) DP Aux Interface

Kernel 4.6 introduced an DRM DP Aux interface for manipulation of the registers needed to access an MST hub. This patch can be backported to earlier kernels: https://github.com/torvalds/linux/commit/e94cb37b34eb8a88fe847438dba55c3f18bf024a

## Usage

Supported devices will be displayed in `# fwupdmgr get-devices` output.

Here is an example output from a Dell WD15 dock:

    Dell WD15/TB16 wired Dock Synaptics VMM3332
      Guid:                 653cd006-5433-57db-8632-0413af4d3fcc
      DeviceID:             MST-1-1-0-0
      Plugin:               synaptics_mst
      Flags:                allow-online
      Version:              3.10.002
      Created:              2017-01-13
      Modified:             2017-01-13
      Trusted:              none

Payloads can be flashed just like any other plugin from LVFS.

## Supported devices

Not all Dell systems or accessories contain MST hubs. Here is a sample list of systems known to support them however:

- Dell WD15 dock
- Dell TB16 dock
- Dell TB18DC
- Latitude E5570
- Latitude E5470
- Latitude E5270
- Latitude E7470
- Latitude E7270
- Latitude E7450
- Latitude E7250
- Latitude E5550
- Latitude E5450
- Latitude E5250
- Latitude Rugged 5414
- Latitude Rugged 7214
- Latitude Rugged 7414

## External Interface Access

This plugin requires read/write access to `/dev/drm_dp_aux*`.

## Version Considerations

This plugin has been available since fwupd version `1.3.6`.

## Data Flow

      flowchart LR
          subgraph MST Controller
            MST(Controller)
            SPI[(SPI)]
          end
          subgraph Kernel
            gpu(GPU\ndriver)
          end
          subgraph fwupd Process
            fwupdengine(FuEngine)
            mst_plugin(Synaptics MST\nPlugin)
          end
          fwupdengine-->mst_plugin
          mst_plugin<--/dev/drm_dp_aux-->gpu
          gpu<--DDC/I2C-->MST
          MST---SPI

## Owners

Anyone can submit a pull request to modify this plugin, but the following people should be consulted before making major or functional changes:

- Apollo Ling: `ApolloLing`