This host controller driver emulates USB, looping all data transfer
requests back to a USB "gadget driver" in the same host. The host
side is the master; the gadget side is the slave. Gadget drivers
can be high, full, or low speed; and they have access to endpoints
like those from NET2280, PXA2xx, or SA1100 hardware.

This may help in some stages of creating a driver to embed in a
Linux device, since it lets you debug several parts of the gadget
driver without its hardware or drivers being involved.

Since such a gadget side driver needs to interoperate with a host
side Linux-USB device driver, this may help to debug both sides
of a USB protocol stack.

Say "y" to link the driver statically, or "m" to build a
dynamically linked module called "dummy_hcd" and force all
gadget drivers to also be dynamically linked.

source code:

drivers/usb/gadget/dummy_hcd.c