Add Drop ALT support

[davewongillies]

Its working and I've managed to flash the keyboard but two smallish issues that may or may not matter:

• The keyboard identifies as Massdrop Inc. ALT Keyboard [VIA] Vial app but not vial.rocks. I can't figure out where the [VIA] bit is coming from.
• I followed the porting guide and enabled vialrgb mode but using the vial app the lighting tab doesn't show up in the app. It seems to somewhat work on vial.rocks, but color selection is broken with some errors such as Uncaught [object ErrorEvent] and Uncaught RuntimeError: memory access out of bounds. Is there anything else I should be enabling? Or is it possible that this keyboard might not be able to fully support vialrgb?

The regular keycodes for changing RGB lighting works though.

[xyzz]

The keyboard identifies as Massdrop Inc. ALT Keyboard [VIA] Vial app but not vial.rocks. I can't figure out where the [VIA] bit is coming from.

That happens because the atsam port doesn't support overriding the serial number which is what the desktop Vial application uses to detect Vial keyboards. I recall this line needs to be commented out for a usable Vial support:

vial-qmk/tmk_core/protocol/arm_atsam/usb/conf_usb.h

Line 75 in a2482e1

#define USB_DEVICE_SERIAL_USE_BOOTLOADER_SERIAL

[xyzz]

Closing because there's been no update for over a month.