> In the case of dib0700, it was clear from the source code that the 
> driver uses USB Control transfers to tell the hardware about I2C 
> messages.  I don't know if other bridges work in the same way.  In 
> theory a bridge could use USB Bulk transfers instead; they aren't 
> subject to this restriction on length-0 reads.  Or a bridge could use a 
> Control read transfer but include extra header material along with the 
> actual data, so that a length-0 message wouldn't end up generating a 
> length-0 read.

Fully understood, thanks for your explanation.

> So the short answer is that you would need to find someone who really 
> understands what's going on here -- which I don't.  Sorry.

No worries. There are only 5 drivers or so, I will manually check if
they use a control_read and have no own header. Doesn't sound hard.