m1n1 is an open early-stage bootloader for Apple Silicon macs. It is designed to take the place of a XNU kernel in the Mac boot process and present a standard Linux devicetree boot environment to downstream software, such as U-Boot and Linux kernels.
m1n1 also serves as a hardware reverse engineering and experimentation platform, providing a terminal and remote control interface over UART and USB that can be used to interactively research the device’s hardware from a host machine, load kernels remotely, run macOS as a VM guest, and more.
This USB device is the USB gadget mode device presented by m1n1 using the USB device controller built into these SoCs, which implements the CDC-ACM class and serves as both an ASCII tty and a binary proxy protocol to issue requests and receive events for remote control. It can be used from any host that can run Python scripts. The same protocol is also exposed over the UART, but this requires a special cable or host device.
Note: idProduct 0x316D is ‘m1’ in little-endian ASCII.