Hi Rob,
Thanks for the patch. I've just glimpsed to them. I will provide a thorough review in a near future (next week probably).
This patch contains an implementation of the fastboot protocol on the device side and a little of documentation. The gadget expects the new-style gadget framework.
What do you mean by that? To which version of gadget framework from linux does it correspond? The u-boot's gadget infrastructure, used by UMS, DFU and THOR gadgets [*], is based on linux 2.6.36.
The gadget implements the getvar, reboot, download and reboot commands. What is missing is the flash handling i.e. writting the image to media.
For the three above gadgets [*] one "flashing" backend is used. It is done by dfu_write() function defined at ./drivers/dfu/dfu.c.
Additionally some common gadget handling code is already in the u-boot tree. It is called g_dnl.c at drivers/usb/gadget, and is used by [*] gadgets. Maybe fastboot gadget could reuse its code?