This ACPI device exposed by the Chrome EC reports when a laptop-tablet convertible Chromebook (e.g., Google Pixelbook) is switched to tablet mode. Like on Linux, the reporting is via evdev:
-event3 SWITCH_TOGGLE +3.27s switch tablet-mode state 1 event3 SWITCH_TOGGLE +8.63s switch tablet-mode state 0
though I can add more ways of notification (devd events I guess).
Google will eventually replace this device with Intel Virtual Buttons (used by other convertibles), but for now this exists. When I get my debug cable, I'll build firmware with that patch and write a driver for vbtn too.
Is there a good way to autoload such things? (I guess not, since I've had to load acpi_ibm manually on Thinkpads)