libusb-gadget

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• What's this?

libusb-gadget is a simple wrapper around Linux USB GadgetFS[1], which enables USB target development in userspace. It allows developers to write a trivial gadget in ~200 lines, while the original GadgetFS example[2] is ~1700 lines.

• Requirements

• linux 2.6.XX

• Quick start

I assume that you are using Debian GNU/Linux. Since the USB gadget framework is not compiled in the stock kernel (as of 2.6.29-1), you will need to generate a couple of kernel modules by hand:

$ sudo apt-get install linux-source-2.6.XX linux-headers-2.6.XX $ cd /usr/src $ tar xf linux-source-2.6.XX.tar.bz2 $ cd libusb-gadget/scripts $ ./generate-kernel-modules /usr/src/linux-source-2.6.XX

After successful build, you will find "dummy_hcd.ko" and "gadgetfs.ko" in the current working directory. You can load them with:

$ sudo insmod dummy_hcd.ko $ sudo insmod gadgetfs.ko

and mount the GadgetFS:

$ sudo mkdir /dev/gadget $ sudo mount -t gadgetfs none /dev/gadget

Now you can try libusb-gadget.

$ cd libusb-gadget $ ./configure $ make

tests/ contains an example gadget.

$ cd tests $ sudo ./loopback 00FF:0000 # VEND:PROD

On another terminal:

$ cd libusb-gadget/tests $ sudo ./loopback-test 00FF:0000 # VEND:PROD

• Limitations

• Multithreading is necessary since /dev/gadget/$ENDPOINT (except for ep0) do not support polling.

• The endpoint number in the endpoint descriptor must be specified explicitly, while the kernel space API assigns them automatically.

• The max packet size is also mandatory in that descriptor.

• License

LGPLv3+. See COPYING.LESSER for detail.

Footnotes: [1] http://www.linux-usb.org/gadget/ [2] http://www.linux-usb.org/gadget/usb.c

• Copyright

All files are under the copyright of:

Copyright (C) 2009 Daiki Ueno [email protected]

except src/usbstring.[ch] which are based on the version by David Brownell and under the copyright of:

Copyright (C) 2003 David Brownell