Present the NetMD.Simulator brain as a real USB NetMD device.

Where NetMD.Simulator implements a NetMD.Transport for in-process use, this wires the same device brain to a Linux USB gadget over BodgeUSBGadget and BodgeUSBGadget.FunctionFs. The vendor control protocol (reply-length poll, command, read-reply, factory) arrives as FunctionFS SETUP events; the bulk OUT endpoint (track download) is read by a task. The result is an actual USB device on the bus.

With dummy_hcd loaded, the gadget and a host driving it with the real NetMD.Transport.Usb can run in the same machine, so the whole stack is exercised over usbfs without any external hardware. This is the "both sides in one VM" setup; see vm/ and README_VM.md.

Requirements (root)

configfs and functionfs mounted, libcomposite and usb_f_fs loaded, a UDC available (dummy_hcd provides dummy_udc.0). It does nothing useful off a Linux gadget host, so it is not started by the library.

Use

{:ok, g} = NetMD.Simulator.Gadget.start_link(udc: "dummy_udc.0")
# ... a host now enumerates a Sony NetMD device and can be driven
# with NetMD.open() (real transport) from another process/VM ...
:ok = NetMD.Simulator.Gadget.stop(g)

Pass disc: to start from a custom NetMD.Simulator.Disc.