[avrdude-dev] suggest a "programmer"?

[Nicholas Flowers]

I have a couple old arduino boards floating around, and have been thinking
of reprogramming the on-board 16U2 to become first-class SPI programmers
for the on-board target chips.

Since I will be programming the 16U2, I'm pretty confident I can make them
conform to (just about) any programming "interface" of avrdude.

Still, after rummaging through the avrdude code for a few hours, I can't
decide the best way forward, and would like some advice.

Requirements:

- I'd like it to be a "usb" interface, not a serial (I want to keep my data
bridge clearly separate from the programming interface)

- I need to be able to specify my own vid/pid/serno.  (So that I can
clearly disambiguate which chip I am reprogramming, if I have multiple
plugged in.)

I can't find any programmers that seem to work:

- the stk500v2 have hard-coded vid/pid (can't read from config file).

- the usbtiny/usbasp will accept a vid/pid, but not a serno (like
usbdev_open seems to allow).

It looks like I can specify a "bus_name" and "dev_name" for usbtiny... but
I'm not sure how to query those given a serial number.

usbasp looks like you can filter by manufacturer/product strings, but
strangely not by serial.  I'd rather not disambiguate using one of those.

Can anyone suggest the best way forward?  Maybe I've overlooked a
programming interface that would fit?

Thanks,
Nick.