embedded hardware choices with good usb slave support?

Most will have a USB OTG ( On The Go ) port.

" Use of USB OTG allows those devices to switch back and forth between the roles of host and client."

The USB OTG port is often used to reflash devices.

Thanks for your answer, Les. You're right, it seems that OTG is available pretty much on all systems, with the exception RaspberryPI B models, as far as I could make it out. And GadgetFS is what I was looking for in terms of implementing device protocols; I guess I'm all set.

Cheers Dietmar

Don't relax just yet.

Dig a little deeper and make sure there is software support for it to be used as you expect it to work. Unfortunately, this is a ragged process.

Using the OTG to reflash is critical; other uses are not.

Devil's in the details, to be sure.

That said I'm actually fairly confident now I can build upon the code examp les accompanying the GadgetFS API [essentially a generic USB kernel driver that maps packet streams, descriptors and endpoint configuration to user sp ace via the file system] in order to do what I want to do. Particularly so because my needs are more in the line of a simple FIFO rather than implemen ting the mass storage protocol implied by reflashing.

Cheers, Dietmar