ColorHug Support
================

Introduction
------------

The ColorHug is an affordable open source display colorimeter built by
Hughski Limited. The USB device allows you to calibrate your screen for
accurate color matching.

ColorHug versions 1 and 2 support a custom HID-based flashing protocol, but
version 3 (ColorHug+) has now switched to DFU.

Firmware Format
---------------

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

This plugin supports the following protocol ID:

 * com.hughski.colorhug

GUID Generation
---------------

These devices use the standard USB DeviceInstanceId values, e.g.

 * `USB\VID_273F&PID_1001&REV_0001`
 * `USB\VID_273F&PID_1001`
 * `USB\VID_273F`

Update Behavior
---------------

The device usually presents in runtime mode, but on detach re-enumerates with a
different USB PID in a bootloader mode. On attach the device again re-enumerates
back to the runtime mode.

For this reason the `REPLUG_MATCH_GUID` internal device flag is used so that
the bootloader and runtime modes are treated as the same device.

Vendor ID Security
------------------

The vendor ID is set from the USB vendor, in this instance set to `USB:0x273F`

External interface access
-------------------------
This plugin requires read/write access to `/dev/bus/usb`.