fwupd/plugins/cros-ec/README.md
Richard Hughes 078beafb2d Add a new internal flag to opt-in to GUID matching
It is far too easy to forget to set FWUPD_DEVICE_FLAG_NO_GUID_MATCHING for new
plugins, and without it it all works really well *until* a user has two devices
of the same type installed at the same time and then one 'disappears' for hard
to explain reasons. Typically we only need it for replug anyway!

Explicitly opt-in to this rarely-required behaviour, with the default to just
use the physical and logical IDs. Also document the update behavior for each
plugin to explain why the flag is being used.

This allows you to have two identical Unifying plugged in without one of them
being hidden from the user, at the same time allowing a HIDRAW<->USB transition
when going to and from bootloader and runtime modes.

This removes the workaround added in 99eb3f06b6.

Fixes https://github.com/fwupd/fwupd/issues/2915
2021-02-25 15:47:25 +00:00

1.7 KiB

Chrome OS EC Support

Introduction

This plugin provides support for the firmware updates for Chrome OS EC project based devices.

Initially, it supports the USB endpoint updater, but lays the groundwork for future updaters which use other update methods other than the USB endpoint.

This is based on the chromeos ec project's usb_updater2 application [1].

Information about the USB update protocol is available at [2].

Firmware Format

The daemon will decompress the cabinet archive and extract a firmware blob in the Google fmap [3] file format.

This plugin supports the following protocol ID:

  • com.google.usb.crosec

GUID Generation

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

  • USB\VID_18D1&PID_501A

Update Behavior

The device usually presents in runtime mode, but on detach re-enumerates with the same USB PID in an unlocked mode. On attach the device again re-enumerates back to the runtime locked 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, which is set to various different values depending on the model and device mode. The list of USB VIDs used is:

  • USB:0x18D1

External interface access

This plugin requires read/write access to /dev/bus/usb.

[1] https://chromium.googlesource.com/chromiumos/platform/ec/+/master/extra/usb_updater/usb_updater2.c [2] https://chromium.googlesource.com/chromiumos/platform/ec/+/master/docs/usb_updater.md [3] https://www.chromium.org/chromium-os/firmware-porting-guide/fmap