uboot/drivers/usb/emul/Kconfig
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   1config USB_EMUL
   2        bool "Support for USB device emulation"
   3        depends on DM_USB && SANDBOX
   4        help
   5          Since sandbox does not have access to a real USB bus, it is possible
   6          to use device emulators instead. This allows testing of the USB
   7          stack on sandbox without needing a real device, or any host machine
   8          USB resources.
   9